WorldWideScience

Sample records for black-containing elastomers decomposition

  1. Effect of nanoclay loading on the thermal decomposition of nanoclay polyurethane elastomers obtained by bulk polymerization

    Science.gov (United States)

    Quagliano, Javier; Bocchio, Javier

    2014-08-01

    Thermoplastic urethane (TPU) nanocomposite was prepared successfully by dispersion at high shear stress of the nanoclay in polyol and further bulk polymerization. Our results from DSC studies showed an increase in decomposition temperature when nanoclay was loaded at 3,5% on elastomeric PU made from TDI, PTMEG and BDO, while not when nanoclay content was lower (1,5%). The exotherms at 370-375°C could be adscribed to the decomposition of the hard segments according to previous work.

  2. Elastomers Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Primary capabilities include: elastomer compounding in various sizes (micro, 3x5, 8x12, 8x15 rubber mills); elastomer curing and post curing (two 50-ton presses, one...

  3. Bimodal condensation silicone elastomers as dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    elastomers were prepared by mixing different mass ratios between long polydimethylsiloxane (PDMS) chains and short PDMS chains. The resulting elastomers were investigated with respect to their rheology, dielectric properties, tensile strength, electrical breakdown, thermal stability, as well...

  4. Perfluroether triazine elastomers

    Science.gov (United States)

    Korus, R. A.

    1980-01-01

    In order to obtain high performance elastomers with the high thermal stability and chemical inertness of perfluoroalkylene triazine and a low glass transition temperature, perfluoroether triazine elastomers were synthesized. The procedure for elastomer synthesis is described as well as general experimental methods. Results are presented and discussed. The screening of catalysts for the dehydration of perfluoroether diamide is also considered.

  5. Elastomers with Reversible Nanoporosity

    DEFF Research Database (Denmark)

    Szewczykowski, Piotr Przemyslaw; Andersen, K.; Schulte, Lars;

    2009-01-01

    An elastomer was created via cross-linking a diene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) block copolymer in the ordered state of hexagonal morphology, followed by the quantitative removal of the PDMS component. The elastomer material collapsed following etching of the PDMS...

  6. Mechanical Design Handbook for Elastomers

    Science.gov (United States)

    Darlow, M.; Zorzi, E.

    1986-01-01

    Mechanical Design Handbook for Elastomers reviews state of art in elastomer-damper technology with particular emphasis on applications of highspeed rotor dampers. Self-contained reference but includes some theoretical discussion to help reader understand how and why dampers used for rotating machines. Handbook presents step-by-step procedure for design of elastomer dampers and detailed examples of actual elastomer damper applications.

  7. Bimodal condensation silicone elastomers as dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    unimodal refers to that there is one polymer only in the system. As an alternative to unimodal networks there are the bimodal networks where two polymers with significantly different molecular weights are mixed with one crosslinker. [2]Silicone rubber can be divided into condensation type and addition type...... according to the curing reaction. The advantages of condensation silicones compared to addition are the relatively low cost, the curing rate largely being independent of temperature, the excellent adhesion, and the catalyst being nontoxic. [3]In this work, a series of bimodal condensation silicone......, the top and bottom surfaces of the elastomer (7:3) prepared at 23oC and 50% humidity were tested by water contact angle and optical microscope. The results show the bimodal condensation elastomer possesses structural heterogeneity, which may lead to favourable properties for DE applications....

  8. Bonding Elastomers To Metal Substrates

    Science.gov (United States)

    Dickerson, George E.; Kelley, Henry L.

    1990-01-01

    Improved, economical method for bonding elastomers to metals prevents failures caused by debonding. In new technique, vulcanization and curing occur simultaneously in specially designed mold that acts as form for desired shape of elastomer and as container that positions and supports metal parts. Increases interface adhesion between metal, adhesive, and elastomer.

  9. Dielectric elastomer memory

    Science.gov (United States)

    O'Brien, Benjamin M.; McKay, Thomas G.; Xie, Sheng Q.; Calius, Emilio P.; Anderson, Iain A.

    2011-04-01

    Life shows us that the distribution of intelligence throughout flexible muscular networks is a highly successful solution to a wide range of challenges, for example: human hearts, octopi, or even starfish. Recreating this success in engineered systems requires soft actuator technologies with embedded sensing and intelligence. Dielectric Elastomer Actuator(s) (DEA) are promising due to their large stresses and strains, as well as quiet flexible multimodal operation. Recently dielectric elastomer devices were presented with built in sensor, driver, and logic capability enabled by a new concept called the Dielectric Elastomer Switch(es) (DES). DES use electrode piezoresistivity to control the charge on DEA and enable the distribution of intelligence throughout a DEA device. In this paper we advance the capabilities of DES further to form volatile memory elements. A set reset flip-flop with inverted reset line was developed based on DES and DEA. With a 3200V supply the flip-flop behaved appropriately and demonstrated the creation of dielectric elastomer memory capable of changing state in response to 1 second long set and reset pulses. This memory opens up applications such as oscillator, de-bounce, timing, and sequential logic circuits; all of which could be distributed throughout biomimetic actuator arrays. Future work will include miniaturisation to improve response speed, implementation into more complex circuits, and investigation of longer lasting and more sensitive switching materials.

  10. Sustainable Elastomers from Renewable Biomass.

    Science.gov (United States)

    Wang, Zhongkai; Yuan, Liang; Tang, Chuanbing

    2017-07-18

    Sustainable elastomers have undergone explosive growth in recent years, partly due to the resurgence of biobased materials prepared from renewable natural resources. However, mounting challenges still prevail: How can the chemical compositions and macromolecular architectures of sustainable polymers be controlled and broadened? How can their processability and recyclability be enabled? How can they compete with petroleum-based counterparts in both cost and performance? Molecular-biomass-derived polymers, such as polymyrcene, polymenthide, and poly(ε-decalactone), have been employed for constructing thermoplastic elastomers (TPEs). Plant oils are widely used for fabricating thermoset elastomers. We use abundant biomass, such as plant oils, cellulose, rosin acids, and lignin, to develop elastomers covering a wide range of structure-property relationships in the hope of delivering better performance. In this Account, recent progress in preparing monomers and TPEs from biomass is first reviewed. ABA triblock copolymer TPEs were obtained with a soft middle block containing a soybean-oil-based monomer and hard outer blocks containing styrene. In addition, a combination of biobased monomers from rosin acids and soybean oil was formulated to prepare triblock copolymer TPEs. Together with the above-mentioned approaches based on block copolymers, multigraft copolymers with a soft backbone and rigid side chains are recognized as the first-generation and second-generation TPEs, respectively. It has been recently demonstrated that multigraft copolymers with a rigid backbone and elastic side chains can also be used as a novel architecture of TPEs. Natural polymers, such as cellulose and lignin, are utilized as a stiff, macromolecular backbone. Cellulose/lignin graft copolymers with side chains containing a copolymer of methyl methacrylate and butyl acrylate exhibited excellent elastic properties. Cellulose graft copolymers with biomass-derived polymers as side chains were

  11. Self-healing elastomer system

    Science.gov (United States)

    Keller, Michael W. (Inventor); Sottos, Nancy R. (Inventor); White, Scott R. (Inventor)

    2009-01-01

    A composite material includes an elastomer matrix, a set of first capsules containing a polymerizer, and a set of second capsules containing a corresponding activator for the polymerizer. The polymerizer may be a polymerizer for an elastomer. The composite material may be prepared by combining a first set of capsules containing a polymerizer, a second set of capsules containing a corresponding activator for the polymerizer, and a matrix precursor, and then solidifying the matrix precursor to form an elastomeric matrix.

  12. Mechanical design handbook for elastomers. [the design of elastomer dampers for application in rotating machinery

    Science.gov (United States)

    Darlow, M.; Zorzi, E.

    1981-01-01

    A comprehensive guide for the design of elastomer dampers for application in rotating machinery is presented. Theoretical discussions, a step by step procedure for the design of elastomer dampers, and detailed examples of actual elastomer damper applications are included. Dynamic and general physical properties of elastomers are discussed along with measurement techniques.

  13. Artificial muscle using nonlinear elastomers

    Science.gov (United States)

    Ratna, Banahalli

    2002-03-01

    Anisotropic freestanding films or fibers of nematic elastomers from laterally attached side-chain polymers show muscle-like mechanical properties. The orientational order of the liquid crystal side groups imposes a conformational anisotropy in the polymer backbone. When a large change in the order parameter occurs, as at the nematic-isotropic phase transition, there is a concomitant loss of order in the backbone which results in a contraction of the film in the direction of the director orientation. The crosslinked network imposes a symmetry-breaking field on the nematic and drives the nematic-isotropic transition towards a critical point with the application of external stress. Isostrain studies on these nonlinear elastomers, show that there are large deviations from ideal classical rubber elasticity and the contributions from total internal energy to the elastic restoring force cannot be ignored. The liquid crystal elastomers exhibiting anisoptopic contraction/extension coupled with a graded strain response to an applied external stimulus provide an excellent framework for mimicking muscular action. Liquid crystal elastomers by their very chemical nature have a number of ‘handles’ such as the liquid crystalline phase range, density of crosslinking, flexibility of the backbone, coupling between the backbone and the mesogen and the coupling between the mesogen and the external stimulus, that can be tuned to optimize the mechanical properties. We have demonstrated actuation in nematic elastomers under thermal and optical stimuli. We have been able to dope the elastomers with dyes to make them optically active. We have also doped them with carbon nanotubes in order to increase the thermal and electrical conductivity of the elastomer.

  14. 21 CFR 177.1590 - Polyester elastomers.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Polyester elastomers. 177.1590 Section 177.1590... Components of Single and Repeated Use Food Contact Surfaces § 177.1590 Polyester elastomers. The polyester...) For the purpose of this section, polyester elastomers are those produced by the ester...

  15. Elastomer Reinforced with Carbon Nanotubes

    Science.gov (United States)

    Hudson, Jared L.; Krishnamoorti, Ramanan

    2009-01-01

    Elastomers are reinforced with functionalized, single-walled carbon nanotubes (SWNTs) giving them high-breaking strain levels and low densities. Cross-linked elastomers are prepared using amine-terminated, poly(dimethylsiloxane) (PDMS), with an average molecular weight of 5,000 daltons, and a functionalized SWNT. Cross-link densities, estimated on the basis of swelling data in toluene (a dispersing solvent) indicated that the polymer underwent cross-linking at the ends of the chains. This thermally initiated cross-linking was found to occur only in the presence of the aryl alcohol functionalized SWNTs. The cross-link could have been via a hydrogen-bonding mechanism between the amine and the free hydroxyl group, or via attack of the amine on the ester linage to form an amide. Tensile properties examined at room temperature indicate a three-fold increase in the tensile modulus of the elastomer, with rupture and failure of the elastomer occurring at a strain of 6.5.

  16. Polyurethane elastomers in armour applications

    NARCIS (Netherlands)

    Carton, E.P.; Broos, J.P.F.

    2012-01-01

    The use of elastomers in ballistic protection products (armour) is limited to low threat levels and transparent armour solution components. Often armor is considered a parasitic mass that increases with increasing threat levels. Therefore, low weight solutions are welcomed and bulk polymers,

  17. Entirely soft dielectric elastomer robots

    Science.gov (United States)

    Henke, E.-F. Markus; Wilson, Katherine E.; Anderson, Iain A.

    2017-04-01

    Multifunctional Dielectric Elastomer (DE) devices are well established as actuators, sensors and energy har- vesters. Since the invention of the Dielectric Elastomer Switch (DES), a piezoresistive electrode that can directly switch charge on and off, it has become possible to expand the wide functionality of DE structures even more. We show the application of fully soft DE subcomponents in biomimetic robotic structures. It is now possible to couple arrays of actuator/switch units together so that they switch charge between them- selves on and off. One can then build DE devices that operate as self-controlled oscillators. With an oscillator one can produce a periodic signal that controls a soft DE robot - a DE device with its own DE nervous system. DESs were fabricated using a special electrode mixture, and imprinting technology at an exact pre-strain. We have demonstrated six orders of magnitude change in conductivity within the DES over 50% strain. The control signal can either be a mechanical deformation from another DE or an electrical input to a connected dielectric elastomer actuator (DEA). We have demonstrated a variety of fully soft multifunctional subcomponents that enable the design of autonomous soft robots without conventional electronics. The combination of digital logic structures for basic signal processing, data storage in dielectric elastomer flip-flops and digital and analogue clocks with adjustable frequencies, made of dielectric elastomer oscillators (DEOs), enables fully soft, self-controlled and electronics-free robotic structures. DE robotic structures to date include stiff frames to maintain necessary pre-strains enabling sufficient actuation of DEAs. Here we present a design and production technology for a first robotic structure consisting only of soft silicones and carbon black.

  18. Silicone elastomers with aromatic voltage stabilizers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    breakdown strength, the storage modulus and the loss modulus of the elastomer were investigated, as well as the excitation energy from the collision between electron carriers and benzene rings in PDMS-PPMS copolymer was measured by UV-vis spectroscopy. The developed elastomers were inherently soft...

  19. Novel silicone elastomer formulations for DEAPs

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard; Vudayagiri, Sindhu; Benslimane, Mohamed

    2013-01-01

    We demonstrate that the force output and work density of polydimethylsiloxane (PDMS) based dielectric elastomer transducers can be significantly enhanced by the addition of high permittivity titanium dioxide nanoparticles which was also shown by Stoyanov et al[1] for pre-stretched elastomers...

  20. Role of catalysis in sustainable production of synthetic elastomers

    Indian Academy of Sciences (India)

    Vivek K Srivastava; Madhuchhanda Maiti; Ganesh C Basak; Raksh V Jasra

    2014-03-01

    Elastomer business plays a significant role in the transportation industry. In fact, elastomers make the world move. Due to limited availability of natural rubber, synthetic elastomers bridge the gap between demand and supply in today’s growing tyre and automobile industry.With more than ∼10000 KTA total world productions, the impact of synthetic elastomer business cannot be overlooked. The need of synthetic elastomers for tyre and automobile industries is stringently specific. Catalysis plays an inevitable role in achieving the growing demand of specific synthetic elastomers. The present study will describe how catalysis plays a significant role in the sustainable development of elastomers with special reference to polybutadiene rubber.

  1. Magnetostriction of engineered magnetorheological elastomers

    Science.gov (United States)

    Rieger, William; Kassner, Chris; von Lockette, Paris; Lofland, Samuel

    2012-02-01

    We have completed a study of the magnetostriction and poison ratio of several types of magnetorheological elastomers (MREs), including both hard and soft magnetic materials in silicone rubber matrices. While both random and aligned soft magnetic particles gave large (˜1%) magnetostriction, hard magnetic powders provided minimal actuation, regardless of whether they were aligned or not. In addition, we have created engineered lattices of magnetic wires and find the actuation highly dependent on the sample shape, and the angle of the magnetic field with respect to the alginment axis. We also propose some new structures based on hard magnetic wires which should provide piezomagnetic response.

  2. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Mateiu, Ramona Valentina; Skov, Anne Ladegaard

    years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we focus on the chloro propyl functionalized silicone elastomers prepared in Madsen et al[2] and we investigate the electrical...... breakdown patterns of two similar chloro propyl functionalized silicone elastomers which break down electrically in a rather different way as well as we compare them to a silicone based reference. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) are used to evaluate...... the elastomers after electrical breakdown....

  3. Modeling of a Dielectric Elastomer Bender Actuator

    Directory of Open Access Journals (Sweden)

    Paul White

    2014-07-01

    Full Text Available The current smallest self-contained modular robot uses a shape memory alloy, which is inherently inefficient, slow and difficult to control. We present the design, fabrication and demonstration of a module based on dielectric elastomer actuation. The module uses a pair of bowtie dielectric elastomer actuators in an agonist-antagonist configuration and is seven times smaller than previously demonstrated. In addition, we present an intuitive model for the bowtie configuration that predicts the performance with experimental verification. Based on this model and the experimental analysis, we address the theoretical limitations and advantages of this antagonistic bender design relative to other dielectric elastomer actuators.

  4. Hencky's model for elastomer forming process

    Science.gov (United States)

    Oleinikov, A. A.; Oleinikov, A. I.

    2016-08-01

    In the numerical simulation of elastomer forming process, Henckys isotropic hyperelastic material model can guarantee relatively accurate prediction of strain range in terms of large deformations. It is shown, that this material model prolongate Hooke's law from the area of infinitesimal strains to the area of moderate ones. New representation of the fourth-order elasticity tensor for Hencky's hyperelastic isotropic material is obtained, it possesses both minor symmetries, and the major symmetry. Constitutive relations of considered model is implemented into MSC.Marc code. By calculating and fitting curves, the polyurethane elastomer material constants are selected. Simulation of equipment for elastomer sheet forming are considered.

  5. Thermoset elastomers derived from carvomenthide.

    Science.gov (United States)

    Yang, Jinyoung; Lee, Sangjun; Choi, Woo Jin; Seo, Howon; Kim, Pilhan; Kim, Geon-Joong; Kim, Young-Wun; Shin, Jihoon

    2015-01-12

    Renewable thermoset elastomers were prepared using the plant-based monomer carvomenthide. Controlled ring-opening transesterification polymerization of carvomenthide using diethylene glycol as an initiator gave α,ω-dihydroxyl poly(carvomenthide) (HO-PCM-OH), which was subsequently converted to carboxy-telechelic poly(carvomenthide) (HOOC-PCM-COOH) by esterification with excess succinic anhydride through a one-pot, two-step process, leading to no crystallinity, high viscosity, strong thermal resistance, and low glass transition temperature of the resulting functionalized polyester. Thermal curing processes of the resulting 3, 6, and 12 kg mol(-1) prepolymers were achieved with trifunctional aziridine to give cross-linked PCM elastomers. The thermal properties, mechanical behavior, and biocompatibility of the rubbery thermoset products were investigated by differential scanning calorimetry, thermal gravimetric analysis, dynamic mechanical analysis, tensile tests under static and cyclic loads, and cell adherence. These new materials are useful candidates to satisfy the design objective for the engineering of a variety of soft tissues.

  6. Ion implanted dielectric elastomer circuits

    Science.gov (United States)

    O'Brien, Benjamin M.; Rosset, Samuel; Anderson, Iain A.; Shea, Herbert R.

    2013-06-01

    Starfish and octopuses control their infinite degree-of-freedom arms with panache—capabilities typical of nature where the distribution of reflex-like intelligence throughout soft muscular networks greatly outperforms anything hard, heavy, and man-made. Dielectric elastomer actuators show great promise for soft artificial muscle networks. One way to make them smart is with piezo-resistive Dielectric Elastomer Switches (DES) that can be combined with artificial muscles to create arbitrary digital logic circuits. Unfortunately there are currently no reliable materials or fabrication process. Thus devices typically fail within a few thousand cycles. As a first step in the search for better materials we present a preliminary exploration of piezo-resistors made with filtered cathodic vacuum arc metal ion implantation. DES were formed on polydimethylsiloxane silicone membranes out of ion implanted gold nano-clusters. We propose that there are four distinct regimes (high dose, above percolation, on percolation, low dose) in which gold ion implanted piezo-resistors can operate and present experimental results on implanted piezo-resistors switching high voltages as well as a simple artificial muscle inverter. While gold ion implanted DES are limited by high hysteresis and low sensitivity, they already show promise for a range of applications including hysteretic oscillators and soft generators. With improvements to implanter process control the promise of artificial muscle circuitry for soft smart actuator networks could become a reality.

  7. Rigidity-tuning conductive elastomer

    Science.gov (United States)

    Shan, Wanliang; Diller, Stuart; Tutcuoglu, Abbas; Majidi, Carmel

    2015-06-01

    We introduce a conductive propylene-based elastomer (cPBE) that rapidly and reversibly changes its mechanical rigidity when powered with electrical current. The elastomer is rigid in its natural state, with an elastic (Young’s) modulus of 175.5 MPa, and softens when electrically activated. By embedding the cPBE in an electrically insulating sheet of polydimethylsiloxane (PDMS), we create a cPBE-PDMS composite that can reversibly change its tensile modulus between 37 and 1.5 MPa. The rigidity change takes ˜6 s and is initiated when a 100 V voltage drop is applied across the two ends of the cPBE film. This magnitude of change in elastic rigidity is similar to that observed in natural skeletal muscle and catch connective tissue. We characterize the tunable load-bearing capability of the cPBE-PDMS composite with a motorized tensile test and deadweight experiment. Lastly, we demonstrate the ability to control the routing of internal forces by embedding several cPBE-PDMS ‘active tendons’ into a soft robotic pneumatic bending actuator. Selectively activating the artificial tendons controls the neutral axis and direction of bending during inflation.

  8. Space-Qualifiable Cyanate Ester Elastomer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In Phase 1, CRG demonstrated the feasibility of a novel approach to prepare cyanate ester based elastomers. This approach polymerizes in-situ siloxane within a...

  9. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Mateiu, Ramona Valentina; Skov, Anne Ladegaard

    years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we focus on the chloro propyl functionalized silicone elastomers prepared in Madsen et al[2] and we investigate the electrical...... breakdown patterns of two similar chloro propyl functionalized silicone elastomers which break down electrically in a rather different way as well as we compare them to a silicone based reference. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) are used to evaluate the elastomers...... before and after electrical breakdown. It was shown the chemically very similar silicone elastomers broke down electrically in very different ways. These observations emphasize that the modification of the silicone backbone may open up for completely new possibilities for stabilizing the silicone...

  10. The Electrical Breakdown of Thin Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed

    2014-01-01

    Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields....... This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength....... In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field...

  11. Polymer-dispersed liquid crystal elastomers

    Science.gov (United States)

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-10-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

  12. Space-Qualifiable Cyanate Ester Elastomer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Cornerstone Research Group, Inc. (CRG) proposes to design and develop a space-qualifiable cyanate ester elastomer for application in self-deployable space structures...

  13. High-strain actuator materials based on dielectric elastomers

    DEFF Research Database (Denmark)

    Pelrine, R.; Kornbluh, R.; Kofod, G.

    2000-01-01

    Dielectric elastomers are a new class of actuator materials that exhibit excellent performance. The principle of operation, as well as methods to fabricate and test these elastomers, is summarized here. The Figure is a sketch of an elastomer film (light gray) stretched on a frame (black) and patt......Dielectric elastomers are a new class of actuator materials that exhibit excellent performance. The principle of operation, as well as methods to fabricate and test these elastomers, is summarized here. The Figure is a sketch of an elastomer film (light gray) stretched on a frame (black...

  14. Mechanochemical Reactions of Elastomers with Metals.

    Science.gov (United States)

    1984-09-01

    34i neeeeewy a"md&tf by week nmbo) Elastomers, Fracture, Free-radical reactions, Mechanochemistry , Metals , Macromolecular rupture, Organic radicals...from metallic grey to red-brown, indicating the formation of an increased amount of iron oxide . When this oxidized powder was mixed into SBR and the...Project NR 092-555In ID Technical Report No. 33 MECHANOCHEMICAL REACTIONS OF ELASTOMERS WITH METALS by A. N. Gent and W. R. Rodgers Institute of

  15. Toxicity of Pyrolysis Gases from Elastomers

    Science.gov (United States)

    Hilado, Carlos J.; Kosola, Kay L.; Solis, Alida N.; Kourtides, Demetrius A.; Parker, John A.

    1977-01-01

    The toxicity of the pyrolysis gases from six elastomers was investigated. The elastomers were polyisoprene (natural rubber), styrene-butadiene rubber (SBR), ethylene propylene diene terpolymer (EPDM), acrylonitrile rubber, chlorosulfonated polyethylene rubber, and polychloroprene. The rising temperature and fixed temperature programs produced exactly the same rank order of materials based on time to death. Acryltonitrile rubber exhibited the greatest toxicity under these test conditions; carbon monoxide was not found in sufficient concentrations to be the primary cause of death.

  16. Isolation and damping properties of magnetorheologic elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Collette, C; Kroll, G; Avraam, M; Preumont, A [University of Brussels, 50 av. F.D. Roosevelt, 1050 Brussels (Belgium); Saive, G [Techspace Aero (SAFRAN Group), 121, route de Liers, 4041 Herstal (Belgium); Guillemier, V [MATIS Benelux, 121, route de Liers, 4041 Herstal (Belgium)], E-mail: christophe.collette@ulb.ac.be

    2009-02-01

    This paper considers two systems based on a magnetorheological elastomer (MRE): a MRE isolator under a frequency varying harmonic excitation and a MRE Dynamic Vibration Absorber (DVA) mounted on a frequency-varying structure under a random excitation. It is shown that the commandability of the elastomer improves the isolation performances in the first case, and decreases the stress level in the structure in the second case.

  17. Adjustable Membrane Mirrors Incorporating G-Elastomers

    Science.gov (United States)

    Chang, Zensheu; Morgan, Rhonda M.; Xu, Tian-Bing; Su, Ji; Hishinuma, Yoshikazu; Yang, Eui-Hyeok

    2008-01-01

    Lightweight, flexible, large-aperture mirrors of a type being developed for use in outer space have unimorph structures that enable precise adjustment of their surface figures. A mirror of this type includes a reflective membrane layer bonded with an electrostrictive grafted elastomer (G-elastomer) layer, plus electrodes suitably positioned with respect to these layers. By virtue of the electrostrictive effect, an electric field applied to the G-elastomer membrane induces a strain along the membrane and thus causes a deflection of the mirror surface. Utilizing this effect, the mirror surface figure can be adjusted locally by individually addressing pairs of electrodes. G-elastomers, which were developed at NASA Langley Research Center, were chosen for this development in preference to other electroactive polymers partly because they offer superior electromechanical performance. Whereas other electroactive polymers offer, variously, large strains with low moduli of elasticity or small strains with high moduli of elasticity, G-elastomers offer both large strains (as large as 4 percent) and high moduli of elasticity (about 580 MPa). In addition, G-elastomer layers can be made by standard melt pressing or room-temperature solution casting.

  18. Fracture of elastomers by cavitation

    KAUST Repository

    Hamdi, Adel

    2014-01-01

    Cavitation phenomenon is studied in rubber-like materials by combining experimental, theoretical and numerical approaches. Specific tests are carried out on a Styrene Butadiene Rubber to point out main characteristics of cavitation phenomenon. Hydrostatic depression is numerically modelled using finite element method. Numerical results are compared to Ball\\'s and Hou & Abeyaratne\\'s models with regard to cavity nucleation in the material. Both models well fit experimental observations suggesting that the cavitation nucleation in elastomers depends on the confinement degree of the specimen. Finally, critical hydrostatic pressure and critical global deformation are proved to govern cavitation nucleation in the studied material. Critical loadings are identified by comparing experimental and numerical load-displacement curves. © 2013 Elsevier Ltd.

  19. EB radiation crosslinking of elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Bik, J.; Gluszewski, W.; Rzymski, W.M.; Zagorski, Z.P. E-mail: zagorski@ichtj.waw.pl

    2003-06-01

    Radiation-induced crosslinking is proposed as successful alternative to conventional, chemical methods of crosslinking of elastomers. Hydrogenated acrylonitrile-butadiene rubber was irradiated with 10 MeV electron beam to doses up to 300 kGy. Irradiated samples were investigated for the extent of crosslinking and for properties important for understanding of mechanisms. It follows from sol-gel analysis, that for 100 crosslinking acts there are 6-9 acts of chain scission. It is less than expected from the 20% participation of multi-ionization spurs, also in the solid state, as announced during the previous 9th Tihany Conference (Radiat. Phys. Chem. 56 (1999) 559). However, the apparent too low yield of multi-ionization spurs could be explained by partial conversion of scission products into crosslinks of specific trifunctional Y type. Our investigations confirm the usefulness of consideration of different radiation spurs in polymers, as well as in all, low LET irradiated media.

  20. Ozone decomposition

    Directory of Open Access Journals (Sweden)

    Batakliev Todor

    2014-06-01

    Full Text Available Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers. Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates

  1. The Current State of Silicone-Based Dielectric Elastomer Transducers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren

    2016-01-01

    driving voltages. In this review, the current state of sili- cone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects...

  2. Mechanical characterization of seismic base isolation elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Kulak, R.F.; Hughes, T.H.

    1991-01-01

    From the various devices proposed for seismic isolators, the laminated elastomer bearing is emerging as the preferred device for large buildings/structures, such as nuclear reactor plants. The laminated bearing is constructed from alternating thin layers of elastomer and metallic plates (shims). The elastomer is usually a carbon filled natural rubber that exhibits damping when subjected to shear. Recently, some blends of natural and synthetic rubbers have appeared. Before candidate elastomers can be used in seismic isolation bearings, their response to design-basis loads and beyond- design-basis loads must be determined. This entails the development of constitutive models and and then the determination of associated material parameters through specimen testing. This paper describes the methods used to obtain data for characterizing the mechanical response of elastomers used for seismic isolation. The data provides a data base for use in determining material parameters associated with nonlinear constitutive models. In addition, the paper presents a definition for a damping ratio that does not exhibit the usual reduction at higher strain cycles. 2 refs., 6 figs., 1 tab.

  3. Poly (ricinoleic acid) based novel thermosetting elastomer.

    Science.gov (United States)

    Ebata, Hiroki; Yasuda, Mayumi; Toshima, Kazunobu; Matsumura, Shuichi

    2008-01-01

    A novel bio-based thermosetting elastomer was prepared by the lipase-catalyzed polymerization of methyl ricinoleate with subsequent vulcanization. Some mechanical properties of the cured carbon black-filled polyricinoleate compounds were evaluated as a thermosetting elastomer. It was found that the carbon black-filled polyricinoleate compounds were readily cured by sulfur curatives to produce a thermosetting elastomer that formed a rubber-like sheet with a smooth and non-sticky surface. The curing behaviors and mechanical properties were dependent on both the molecular weight of the polyricinoleate and the amount of the sulfur curatives. Cured compounds consisting of polyricinoleate with a molecular weight of 100,800 showed good mechanical properties, such as a hardness of 48 A based on the durometer A measurements, a tensile strength at break of 6.91 MPa and an elongation at break of 350%.

  4. Dielectric elastomer actuators for facial expression

    Science.gov (United States)

    Wang, Yuzhe; Zhu, Jian

    2016-04-01

    Dielectric elastomer actuators have the advantage of mimicking the salient feature of life: movements in response to stimuli. In this paper we explore application of dielectric elastomer actuators to artificial muscles. These artificial muscles can mimic natural masseter to control jaw movements, which are key components in facial expressions especially during talking and singing activities. This paper investigates optimal design of the dielectric elastomer actuator. It is found that the actuator with embedded plastic fibers can avert electromechanical instability and can greatly improve its actuation. Two actuators are then installed in a robotic skull to drive jaw movements, mimicking the masseters in a human jaw. Experiments show that the maximum vertical displacement of the robotic jaw, driven by artificial muscles, is comparable to that of the natural human jaw during speech activities. Theoretical simulations are conducted to analyze the performance of the actuator, which is quantitatively consistent with the experimental observations.

  5. Transverse vibration of nematic elastomer Timoshenko beams

    Science.gov (United States)

    Zhao, Dong; Liu, Ying; Liu, Chuang

    2017-01-01

    Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.

  6. Protective effects in radiation modification of elastomers

    Science.gov (United States)

    Głuszewski, Wojciech; Zagórski, Zbigniew P.; Rajkiewicz, Maria

    2014-12-01

    Saturated character of ethylene/octene thermoplastic elastomers demands an application of nonconventional methods of crosslinking connections between chains of molecules. These are organic peroxides, usually in the presence of coagents or an application of ionizing radiation. Several approaches (radiation, peroxide, peroxide/plus radiation and radiation/plus peroxide) were applied in crosslinking of elastomere Engage 8200. Attention was directed to the protection effects by aromatic peroxides and by photo- and thermostabilizers on radiolysis of elastomers. Role of dose of radiation, dose rate of radiation as well as the role of composition of elastomere on the radiation yield of hydrogen and absorbtion of oxygen was investigated. DRS method was used to follow postirradiation degradation. Influence of crosslinking methods on properties of elastomers is described. Results were interpreted from the point of view of protective actions of aromatic compounds.

  7. Novel dielectric elastomer structure of soft robot

    Science.gov (United States)

    Li, Chi; Xie, Yuhan; Huang, Xiaoqiang; Liu, Junjie; Jin, Yongbin; Li, Tiefeng

    2015-04-01

    Inspired from the natural invertebrates like worms and starfish, we propose a novel elastomeric smart structure. The smart structure can function as a soft robot. The soft robot is made from a flexible elastomer as the body and driven by dielectric elastomer as the muscle. Finite element simulations based on nonlinear field theory are conducted to investigate the working condition of the structure, and guide the design of the smart structure. The effects of the prestretch, structural stiffness and voltage on the performance of the smart structure are investigated. This work can guide the design of soft robot.

  8. Thermoplastic Elastomers as LOVA Binders.

    Science.gov (United States)

    1987-01-01

    latent acid . A significant weight loss was observed around the decomposition temperature of ethyl naphthalene sulphonate . For the protonic acid as p...Equation for the Steady Shear Viscosity of Filled Polymer Melts", T.S. Stephens and H.H. Winter, in preparation, 1987. "Structure-Property Relationships...very minor weight loss was observed around 2701C with significant weight loss beginning at 4000C. In the presence of ethyl naphthalene sulphonate as

  9. Holographic Structuring of Elastomer Actuator: First True Monolithic Tunable Elastomer Optics.

    Science.gov (United States)

    Ryabchun, Alexander; Kollosche, Matthias; Wegener, Michael; Sakhno, Oksana

    2016-12-01

    Volume diffraction gratings (VDGs) are inscribed selectively by diffusive introduction of benzophenone and subsequent UV-holographic structuring into an electroactive dielectric elastomer actuator (DEA), to afford a continuous voltage-controlled grating shift of 17%. The internal stress coupling of DEA and optical domain allows for a new generation of true monolithic tunable elastomer optics with voltage controlled properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Switching Shape of Nematic Elastomers

    Science.gov (United States)

    Urayama, Kenji

    2012-02-01

    Nematic elastomers (NEs) are a novel class of materials. NEs possess both the elastic properties of rubbers and the orientational properties of liquid crystals. The combination of these two properties makes the shape of NEs very sensitive to external stimuli. We focus on the thermally induced deformation of the NE films inherently possessing the two types of inhomogeneous director alignments, i.e., hybrid and twist alignments. In the NEs with hybrid alignments (HNEs), the director continuously changes by 90 degree from planar alignment to vertical alignment between the top and bottom surfaces. In the twist NEs, the director parallel to the surfaces smoothly rotates by 90 degree around the thickness axis, and the director at the mid-plane is parallel to the long or short axis of the film. In the HNEs and TNEs, the director change along the normal of the films causes the planes at different depth to respond differently to temperature variation, and the films are thus expected to change shape. We experimentally demonstrate that (i) depending on the width/thickness ratio, the TNE ribbons form the spiral ribbons or helicoids whose spiral or helical pitch markedly depends on temperature [1], and (ii) the HNE ribbons exhibit giant bending in response to temperature variation [2]. We theoretically interpret these experimental observations on the basis of the elastic models with the data of thermally induced uniaxial deformation of the corresponding NEs with globally planar alignment.[4pt] [1] Sawa, Ye, Urayama, Takigawa, Gimenez-Pinto, Selinger, R., Selinger, J., Proc. Natl. Acad. Sci., USA, 108, 6364 (2011).[0pt] [2] Sawa, Urayama, Takigawa, DeSimone, Teresi, Macromolecules, 43, 4362 (2010).

  11. Silicone elastomers with aromatic voltage stabilizers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    and benzene rings in PDMS-PPMS copolymer was measured by UV-vis spectroscopy. The developed elastomers were inherently soft with enhanced electrical breakdown strength due to delocalized pi-electrons of aromatic rings attached to the silicone backbone. The dielectric relative permittivity of PDMS...

  12. Silicone elastomers with aromatic voltage stabilizers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    , as well as the excitation energy from the collision between electron carriers and benzene rings in PDMS-PPMS copolymer was measured by UV-vis spectroscopy. The developed elastomers were inherently soft with enhanced electrical breakdown strength due to delocalized pi-electrons of aromatic rings attached...

  13. Conductive elastomers by a new latex process

    Science.gov (United States)

    Electrically conductive polymers such as polyaniline can be used to in production of light-emitting diodes, printed circuit board components, antistatic materials, etc. Highly filled elastomers, such as those filled with metallic powders, can also conduct electricity. However, limitations due to co...

  14. Dielectric Elastomers for Fluidic and Biomedical Applications

    Science.gov (United States)

    McCoul, David James

    Dielectric elastomers have demonstrated tremendous potential as high-strain electromechanical transducers for a myriad of novel applications across all engineering disciplines. Because their soft, viscoelastic mechanical properties are similar to those of living tissues, dielectric elastomers have garnered a strong foothold in a plethora of biomedical and biomimetic applications. Dielectric elastomers consist of a sheet of stretched rubber, or elastomer, coated on both sides with compliant electrode materials; application of a voltage generates an electrostatic pressure that deforms the elastomer. They can function as soft generators, sensors, or actuators, and this last function is the focus of this dissertation. Many design configurations are possible, such as stacks, minimum energy structures, interpenetrating polymer networks, shape memory dielectric elastomers, and others; dielectric elastomers are already being applied to many fields of biomedicine. The first part of the original research presented in this dissertation details a PDMS microfluidic system paired with a dielectric elastomer stack actuator of anisotropically prestrained VHB(TM) 4910 (3M(TM)) and single-walled carbon nanotubes. These electroactive microfluidic devices demonstrated active increases in microchannel width when 3 and 4 kV were applied. Fluorescence microscopy also indicated an accompanying increase in channel depth with actuation. The cross-sectional area strains at 3 and 4 kV were approximately 2.9% and 7.4%, respectively. The device was then interfaced with a syringe pump, and the pressure was measured upstream. Linear pressure-flow plots were developed, which showed decreasing fluidic resistance with actuation, from 0.192 psi/(microL/min) at 0 kV, to 0.160 and 0.157 psi/(microL/min) at 3 and 4 kV, respectively. This corresponds to an ~18% drop in fluidic resistance at 4 kV. Active de-clogging was tested in situ with the device by introducing ~50 microm diameter PDMS microbeads and

  15. Compatibility of selected elastomers with plutonium glovebox environment

    Energy Technology Data Exchange (ETDEWEB)

    Burns, R.

    1994-06-01

    This illustrative test was undertaken as a result of on-going failure of elastomer components in plutonium gloveboxes. These failures represent one of the major sources of required maintenance to keep gloveboxes operational. In particular, it was observed that the introduction of high specific activity Pu-238 into a glovebox, otherwise contaminated with Pu-239, resulted in an inordinate failure of elastomer components. Desiring to keep replacement of elastomer components to a minimum, a decision to explore a few possible alternative elastomer candidates was undertaken and reported upon herewith. Sample specimens of Neoprene, Urethane, Viton, and Hypalon elastomeric formulations were obtained from the Bacter Rubber Company. Strips of the elastomer specimens were placed in a plutonium glovebox and outside of a glovebox, and were observed for a period of three years. Of the four types of elastomers, only Hypalon remained completely viable.

  16. Elastomers in mud motors for oil field applications

    Energy Technology Data Exchange (ETDEWEB)

    Hendrik, J. [Baker Hughes INTEQ GmbH, Celle (Germany)

    1997-08-01

    Mud motors, the most frequently used downhole drilling motors in modern drilling systems, are described in their application and function. The elastomeric liner in a mud motor acts as a huge continuous seal. Important properties of elastomers such as chemical resistance, fatigue resistance, mechanical strength, abrasion resistance, bonding to steel and processability are discussed. Advantages and disadvantages of NBR, HNBR, FKM, TFEP, and EPDM elastomers for mud motor applications are briefly described. The importance of drilling fluids and their physical and chemical impact on motor elastomers are described. Drilling fluids are categorized in: oil based-, synthetic-, and water based. Results of compatibility tests in the different drilling muds of the presented categories demonstrate the complexity of elastomer development. Elastomers with an equally good performance in all drilling muds are not available. Future developments and improvements are directed towards higher chemical resistance at higher service temperatures. This will be possible only with improved elastomer-to-metal bonding, increased mechanical and better dynamic properties.

  17. Seismic base isolation: Elastomer characterization, bearing modeling and system response

    Energy Technology Data Exchange (ETDEWEB)

    Kulak, R.F.; Wang, C.Y.; Hughes, T.H.

    1991-01-01

    This paper discusses several major aspects of seismic base isolation systems that employ laminated elastomer bearings. Elastomer constitutive models currently being used to represent the nonlinear elastic and hysteretic behavior are discussed. Some aspects of mechanical characterization testing of elastomers is presented along with representative tests results. The development of a finite element based mesh generator for laminated elastomer bearings is presented. Recent advances in the simulation of base isolated structures to earthquake motions are presented along with a sample problem. 13 refs., 19 figs., 1 tab.

  18. Controlled synthesis of SBR elastomers

    Science.gov (United States)

    Zhou, Jin-Ping

    to a great extent on the amount of block styrene. With constant styrene and vinyl contents, the copolymer with the larger and longer blocky styrene gave a lower Tg value but produced a higher loss tangent, tan delta, and thus higher hysteresis loss. The second objective of this research was to synthesize well-defmed, tin-linked, star-branched elastomers. It was found that the tetraallyltin could be used as a reversible chain transfer agent in alkyllithium-initiated diene polymerization, as a consequence of lithium/tin exchange reactions. The polymers produced had very different combinations of linear and star branched polymer, depending on the [Sn]/[Li] ratio and the polymerization procedures. Hydrolysis of these polymer mixtures by HCl in THF resulted in a single peak with a narrow molecular weight distribution, which indicates that the exchange reaction is fast and reversible. In general, the presence of alkyl-tin compounds has little, if any, effect on the polybutadiene microstructures. The linking reaction of poly(dienyl)lithium with Tin(IV) chloride proceeds as a "living" reaction because the coupled polymer chain ends can still grow when more monomer is added. Kinetic study of the interaction of poly(dienyl)lithium with tin-linked polybutadiene showed redistribution of arms and linear polymers. The mechanism of transmetallation is proposed to occur via a stable penta-coordinated alkyl-tin lithium intermediate.

  19. Graphene-silicone elastomer nanocomposite

    Science.gov (United States)

    Pan, Shuyang

    The incorporation of fillers to improve the Young's modulus, tensile strength, and elongation at failure of polymeric matrices is ubiquitous. While Young's modulus and tensile strength of the matrix increase with the filler concentration, a threshold filler concentration must be achieved for the elongation at failure to increase. Furthermore, a decrease in elongation at failure has also been observed beyond a critical filler concentration. While the increases in modulus and tensile strength have been attributed to the transfer of mechanical load to the stronger filler, the onset and reversal in elongation at failure are not understood. In this thesis, we use a functionalized graphene sheet (FGS) -- silicone elastomer (SE) nanocomposite as a model system to demonstrate the mechanisms responsible for this observed filler concentration-dependant elongation at failure as well its subsequent reversal. We will also demonstrate the mechanisms that create the continual increase in tensile strength as filler concentration increases. As the lateral size of FGS strongly influences the tensile strength of the resulting composite, in the first part of this thesis, we show that the oxidation path and the mechanical energy input influence the size of graphene oxide sheets derived from graphite oxide. The cross-planar oxidation of graphite from the (0002) plane results in periodic cracking of the uppermost graphene oxide layer, limiting its lateral dimension to less than 30 microm. We use an energy balance between the elastic strain energy associated with the undulation of graphene oxide sheets at the hydroxyl and epoxy sites, the crack formation energy, and the interaction energy between graphene layers to determine the cell size of the cracks. Under both edge-to-center and cross-planar oxidations, the size of graphene oxide sheets is determined by the aspect ratio of graphite and the mechanical energy input in processing the sheets. In the second part of this thesis, we use

  20. Isothermal aging of three polyurethane elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Guess, T.R.

    1996-05-01

    Two polyurethane systems, EN-7 and L-100, have a long history as encapsulants and coatings in Sandia programs. These materials contain significant amounts of toluene diisocyanate (TDI), a suspect human carcinogen. As part of efforts to reduce the use of hazardous materials in the workplace, PET-90A, a polyurethane with less than 0.1% free TDI, was identified as a candidate for new applications and as a replacement for the more hazardous polyurethanes in selected programs. This report documents the results of a two-year accelerated aging study of PET-90A, EN-7, and L-100 polyurethane elastomers to characterize the effect of 135{degrees}F isothermal aging on selected physical, electrical, mechanical and thermal properties. In general, there was very little change in properties over the two year period for the three elastomers. The largest changes occurred in EN-7, which is the polyurethane with the longest service history in Sandia applications.

  1. Flexible, stretchable electroadhesives based on acrylic elastomers

    Science.gov (United States)

    Duduta, Mihai; Wood, Robert J.; Clarke, David R.

    2016-04-01

    Controllable adhesion is a requirement for a wide variety of applications including robotic manipulation, as well as locomotion including walking, crawling and perching. Electroadhesives have several advantages such as reversibility, low power consumption and controllability based on applied voltage. Most demonstrations of electroadhesive devices rely on fairly rigid materials, which cannot be stretched reversibly, as needed in some applications. We have developed a fast and reliable method for building soft, stretchable electroadhesive pads based on acrylic elastomers and electrodes made of carbon nanotubes. The devices produced were tested pre-deformation and in a stretched configuration. The adhesive force was determined to be in the 0.1 - 3.0 N/cm2 range, depending on the adhering surface. The electroadhesive devices were integrated with pre-stretched dielectric elastomer actuators to create a device in which the adhesion force could be tuned by changes in either the applied voltage or total area.

  2. Bistable dielectric elastomer minimum energy structures

    Science.gov (United States)

    Zhao, Jianwen; Wang, Shu; McCoul, David; Xing, Zhiguang; Huang, Bo; Liu, Liwu; Leng, Jinsong

    2016-07-01

    Dielectric elastomer minimum energy structures (DEMES) can realize large angular deformations by small voltage-induced strains, which make them an attractive candidate for use as soft actuators. If the task only needs binary action, the bistable structure will be an efficient solution and can save energy because it requires only a very short duration of voltage to switch its state. To obtain bistable DEMES, a method to realize the two stable states of traditional DEMES is provided in this paper. Based on this, a type of symmetrical bistable DEMES is proposed, and the required actuation pulse duration is shorter than 0.1 s. When a suitable mass is attached to end of the DEMES, or two layers of dielectric elastomer are affixed to both sides of the primary frame, the DEMES can realize two stable states and can be switched by a suitable pulse duration. To calculate the required minimum pulse duration, a mathematical model is provided and validated by experiment.

  3. Dynamic Soft Elasticity in Monodomain Nematic Elastomers

    OpenAIRE

    Hotta, A; Terentjev, E. M.

    2002-01-01

    We study the linear dynamic mechanical response of monodomain nematic liquid crystalline elastomers under shear in the geometry that allows the director rotation. The aspects of time-temperature superposition are discussed at some length and Master Curves are obtained between the glassy state and the nematic transition temperature Tni. However, the time-temperature superposition did not work through the clearing point Tni, due to change from the ``soft-elasticity'' nematic regime to the ordin...

  4. Spontaneous thermal expansion of nematic elastomers

    OpenAIRE

    Tajbakhsh, A. R.; Terentjev, E.M.

    2001-01-01

    We study the monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic groups and crosslinking density, but differing in the type of crosslinking. Increasing the proportion of long di-functional segments of main-chain nematic polymer, acting as network crosslinking, results in dramatic changes in the uniaxial equilibrium thermal expansion on cooling from isotropic phase. At higher concentration of main chains their behaviour dominates th...

  5. Inorganic particle analysis of dental impression elastomers

    OpenAIRE

    Carlo,Hugo Lemes; FONSECA, Rodrigo Borges; Soares, Carlos José; Correr,Américo Bortolazzo; Correr-Sobrinho, Lourenço; Sinhoreti,Mário Alexandre Coelho

    2010-01-01

    The aim of this study was to determine quantitatively and qualitatively the inorganic particle fraction of commercially available dental elastomers. The inorganic volumetric fraction of two addition silicones (Reprosil Putty/Fluid and Flexitime Easy Putty/Fluid), three condensation silicones (Clonage Putty/Fluid, Optosil Confort/Xantopren VL and Silon APS Putty/Fluid), one polyether (Impregum Soft Light Body) and one polysulfide (Permlastic Light Body) was accessed by weighing a previously de...

  6. Characterization of graded polyurethane elastomer by FTIR

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Polyurethane elastomers with graded structure were prepared in the graded temperature field. The samples were characterized by FTIR technology. The results show that the degree of microphase separation in the samples decreases with the decrease of the curing temperature. As far as the molar ratio of NH2 and NCO is concerned, the sample exhibits better graded morphology when the ratio is 0.95. The transparence of the samples prepared also changes gradually, increasing along the direction, in which temperature decreases.

  7. Characterization of graded polyurethane elastomer by FTIR

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Polyurethane elastomers with graded structure were prepared in the graded temperature field. The samples were characterized by FTIR technology. The results show that degree of microphase separation in the samples decreases with the decrease of the curing temperature. As far as the molar ratio of NH2 and NCO is concerned, the sample exhibits better graded morphology when the ratio is 0.95. The transparence of the samples prepared also change gradually, increasing along the direction, in which temperature decrease.

  8. Polyurethane elastomers as maxillofacial prosthetic materials.

    Science.gov (United States)

    Goldberg, A J; Craig, R G; Filisko, F E

    1978-04-01

    A series of polyurethane elastomers based on an aliphatic diisocyanate and a polyether macroglycol was polymerized with various cross-link densities and OH/NCO ratios. Stoichiometries yielding between 8,600 and 12,900 gm/mole/crosslink and an OH/NCO ratio of 1.1 resulted in polymers with the low modulus, yet high strength and elongation necessary for maxillofacial applications.

  9. Stability analysis of dielectric elastomer film actuator

    Institute of Scientific and Technical Information of China (English)

    LIU YanJu; LIU LiWu; SUN ShouHua; ZHANG Zhen; LENG JinSong

    2009-01-01

    Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field, due to the electrostatic force between the two electrodes, the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value, the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases, which can be applied to design of actuators. Finally, this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.

  10. Electromechanical response of silicone dielectric elastomers

    Science.gov (United States)

    Cârlescu, V.; Prisăcaru, G.; Olaru, D.

    2016-08-01

    This paper presents an experimental technique to investigate the electromechanical properties of silicone dielectric elastomers actuated with high DC electric fields. A non-contact measurement technique is used to capture and monitor the thickness strain (contraction) of a circular film placed between two metallic disks electrodes. Two active fillers such as silica (10, 15 and 30 wt%) and barium titanate (5 and 15 wt%) were incorporated in order to increase the actuation performance. Thickness strain was measured at HV stimuli up to 4.5 kV and showed a quadratic dependence against applied electric field indicating that the induced strain is triggered by the Maxwell effect and/or electrostriction phenomenon as reported in literature. The actuation process evidences a rapid contraction upon HV activation and a slowly relaxation when the electrodes are short-circuit due to visco-elastic nature of elastomers. A maximum of 1.22 % thickness strain was obtained at low actuating field intensity (1.5 V/pm) comparable with those reported in literature for similar dielectric elastomer materials.

  11. Fiber optic pressure sensing with conforming elastomers.

    Science.gov (United States)

    Shao, Li-Yang; Jiang, Qi; Albert, Jacques

    2010-12-10

    A novel pressure sensing scheme based on the effect of a conforming elastomer material on the transmission spectrum of tilted fiber Bragg gratings is presented. Lateral pressure on the elastomer increases its contact angle around the circumference of the fiber and strongly perturbs the optical transmission of the grating. Using an elastomer with a Young's modulus of 20 MPa, a Poisson ratio of 0.48, and a refractive index of 1.42, the sensor reacts monotonically to pressures from 0 to 50 kPa (and linearly from 0 to 15 kPa), with a standard deviation of 0.25 kPa and maximum error of 0.5 kPa. The data are extracted from the optical transmission spectrum using Fourier analysis and we show that this technique makes the response of the sensor independent of temperature, with a maximum error of 2% between 25°C and 75°C. Finally, other pressure ranges can be reached by using conforming materials with different modulii or applying the pressure at different orientations.

  12. Toward a predictive model for elastomer seals

    Science.gov (United States)

    Molinari, Nicola; Khawaja, Musab; Sutton, Adrian; Mostofi, Arash

    Nitrile butadiene rubber (NBR) and hydrogenated-NBR (HNBR) are widely used elastomers, especially as seals in oil and gas applications. During exposure to well-hole conditions, ingress of gases causes degradation of performance, including mechanical failure. We use computer simulations to investigate this problem at two different length and time-scales. First, we study the solubility of gases in the elastomer using a chemically-inspired description of HNBR based on the OPLS all-atom force-field. Starting with a model of NBR, C=C double bonds are saturated with either hydrogen or intramolecular cross-links, mimicking the hydrogenation of NBR to form HNBR. We validate against trends for the mass density and glass transition temperature for HNBR as a function of cross-link density, and for NBR as a function of the fraction of acrylonitrile in the copolymer. Second, we study mechanical behaviour using a coarse-grained model that overcomes some of the length and time-scale limitations of an all-atom approach. Nanoparticle fillers added to the elastomer matrix to enhance mechanical response are also included. Our initial focus is on understanding the mechanical properties at the elevated temperatures and pressures experienced in well-hole conditions.

  13. Stability analysis of dielectric elastomer film actuator

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field,due to the electrostatic force between the two electrodes,the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value,the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases,which can be applied to design of actuators. Finally,this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.

  14. Composition decomposition

    DEFF Research Database (Denmark)

    Dyson, Mark

    2003-01-01

    This PhD is based on constructing and resolving a set of modular problems. Each problem exists as a separate entity. Each has its own characteristics, yet when combined with other, related problems, provides a dimension to a story. The relationships and order between problems has priority over....... Not only have design tools changed character, but also the processes associated with them. Today, the composition of problems and their decomposition into parcels of information, calls for a new paradigm. This paradigm builds on the networking of agents and specialisations, and the paths of communication...... that are necessary to make sense out of any design situation. The hypothesis of this project, is that Design organisation, communication and CAD-information processes must be jointly reengineered to create the dynamic structures needed for the forward projection of design knowledge into this expanding Design network....

  15. Theory Of Dewetting In A Filled Elastomer Under Stress

    Science.gov (United States)

    Peng, Steven T. J.

    1993-01-01

    Report presents theoretical study of dewetting between elastomeric binder and filler particles of highly filled elastomer under multiaxial tension and resulting dilatation of elastomer. Study directed toward understanding and predicting nonlinear stress-vs.-strain behavior of filled elastomeric rocket propellant, also applicable to rubber in highly loaded tire or in damping pad.

  16. Protection of elastomers with DLC film : deposition, characterization and performance

    NARCIS (Netherlands)

    Martinez Martinez, Diego

    2017-01-01

    Elastomers are materials which suffer from strong wear and cause high friction losses when subjected to dynamic contact, leading quite often to failure of the components in devices. In this Thesis, the protection of elastomers by the deposition of carbon-based films (DLC) is studied. To accomplish t

  17. Monitoring diver kinematics with dielectric elastomer sensors

    Science.gov (United States)

    Walker, Christopher R.; Anderson, Iain A.

    2017-04-01

    Diving, initially motivated for food purposes, is crucial to the oil and gas industry, search and rescue, and is even done recreationally by millions of people. There is a growing need however, to monitor the health and activity of divers. The Divers Alert Network has reported on average 90 fatalities per year since 1980. Furthermore an estimated 1000 divers require recompression treatment for dive-related injuries every year. One means of monitoring diver activity is to integrate strain sensors into a wetsuit. This would provide kinematic information on the diver potentially improving buoyancy control assessment, providing a platform for gesture communication, detecting panic attacks and monitoring diver fatigue. To explore diver kinematic monitoring we have coupled dielectric elastomer sensors to a wetsuit worn by the pilot of a human-powered wet submarine. This provided a unique platform to test the performance and accuracy of dielectric elastomer strain sensors in an underwater application. The aim of this study was to assess the ability of strain sensors to monitor the kinematics of a diver. This study was in collaboration with the University of Auckland's human-powered submarine team, Team Taniwha. The pilot, completely encapsulated in a hull, pedals to propel the submarine forward. Therefore this study focused on leg motion as that is the primary motion of the submarine pilot. Four carbon-filled silicone dielectric elastomer sensors were fabricated and coupled to the pilot's wetsuit. The first two sensors were attached over the knee joints, with the remaining two attached between the pelvis and thigh. The goal was to accurately measure leg joint angles thereby determining the position of each leg relative to the hip. A floating data acquisition unit monitored the sensors and transmitted data packets to a nearby computer for real-time processing. A GoPro Hero 4 silver edition was used to capture the experiments and provide a means of post-validation. The

  18. Suppression of electromechanical instability in fiber-reinforced dielectric elastomers

    Directory of Open Access Journals (Sweden)

    Rui Xiao

    2016-03-01

    Full Text Available The electromechanical instability of dielectric elastomers has been a major challenge for the application of this class of active materials. In this work, we demonstrate that dielectric elastomers filled with soft fiber can suppress the electromechanical instability and achieve large deformation. Specifically, we developed a constitutive model to describe the dielectric and mechanical behaviors of fiber-reinforced elastomers. The model was applied to study the influence of stiffness, nonlinearity properties and the distribution of fiber on the instability of dielectric membrane under an electric field. The results show that there exists an optimal fiber distribution condition to achieve the maximum deformation before failure.

  19. Active vibration isolation platform on base of magnetorheological elastomers

    Science.gov (United States)

    Mikhailov, Valery P.; Bazinenkov, Alexey M.

    2017-06-01

    The article describes the active vibration isolation platform on base of magnetorheological (MR) elastomers. An active damper based on the MR elastomers can be used as an actuator of micro- or nanopositioning for a vibroinsulated object. The MR elastomers give such advantages for active control of vibration as large range of displacements (up to 1 mm), more efficient absorption of the vibration energy, possibility of active control of amplitude-frequency characteristics and positioning with millisecond response speed and nanometer running accuracy. The article presents the results of experimental studies of the most important active damper parameters. Those are starting current, transient time for stepping, transmission coefficient of the vibration displacement amplitude.

  20. Self-Healing, High-Permittivity Silicone Dielectric Elastomer

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Skov, Anne Ladegaard

    2016-01-01

    or cuts made directly to the material due to the reassembly of the ionic bonds that are broken during damage. The dielectric elastomers presented in this paper pave the way to increased lifetimes and the ability of dielectric elastomers to survive millions of cycles in high-voltage conditions....... possesses high dielectric permittivity and consists of an interpenetrating polymer network of silicone elastomer and ionic silicone species that are cross-linked through proton exchange between amines and acids. The ionically cross-linked silicone provides self-healing properties after electrical breakdown...

  1. Soft and Ultra-soft Elastomers

    Science.gov (United States)

    Daniel, William; Burdynska, Joanna; Kirby, Sam; Zhou, Yang; Matyjaszewski, Krzysztof; Rubinstein, Michael; Sheiko, Sergei; UNC-MIRT Team

    2014-03-01

    Polymeric networks are attractive engineering materials utilized for various mechanically demanding applications. As such, much attention has been paid to reinforcement of polymer mechanical properties with little interest in how to make softer elastomers to address numerous biomedical applications including implants and cell differentiation. Without swelling in a solvent, it is challenging to obtain materials with a modulus below ca.105 Pa, which is dictated by chain entanglements. Here we present two methodologies for the creation of soft and ultra-soft dry elastomeric compounds. The first method utilizes polymer capsules as temperature responsive filler. Depending on volume fraction of microcapsules this method is capable of fine tuning modulus within an order of magnitude. The second technique uses the densely grafted molecular brush architecture to create solvent-free polymer melts and elastomers with plateau moduli in the range one hundred to ten hundred Pa. Such compounds may find uses in biomedical applications including reconstructive surgery and cell differentiation. National Science Foundation DMR-1122483.

  2. Compatibility of elastomers in palm biodiesel

    Energy Technology Data Exchange (ETDEWEB)

    Haseeb, A.S.M.A.; Masjuki, H.H.; Siang, C.T.; Fazal, M.A. [Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2010-10-15

    In recent time, environmental awareness and concern over the rapid exhaustion of fossil fuels have led to an increased popularity of biodiesel as an alternative fuel for automobiles. However, there are concerns over enhanced degradation of automotive materials in biodiesel. The present study aims to investigate the impact of palm biodiesel on the degradation behavior of elastomers such as nitrile rubber (NBR), polychloroprene, and fluoro-viton A. Static immersion tests in B0 (diesel), B10 (10% biodiesel in diesel), B100 (biodiesel) were carried out at room temperature (25 C) and at 50 C for 500 h. At the end of immersion test, degradation behavior was investigated by measuring mass, volume, hardness as well as tensile strength and elongation. The exposed elastomer surface was studied by scanning electron microscopy (SEM). Fourier Transform Infrared (FTIR) spectroscopy was carried out to identify the chemical and structural changes. Results showed that the extent of degradation was higher for both polychloroprene and NBR while fluoro-viton exhibited good resistance to degradation and was least attacked. (author)

  3. Dielectric silicone elastomers with mixed ceramic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stiubianu, George, E-mail: george.stiubianu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Ignat, Mircea [National R& D Institute for Electrical Engineering ICPE-CA Bucharest, Splaiul Unirii 313, District 3, Bucharest 030138 (Romania)

    2015-11-15

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.

  4. Dynamic analysis of structures with elastomers using substructuring with non-matched interfaces and improved modeling of elastomer properties

    Science.gov (United States)

    Lin, Hejie

    A variety of engineering structures are composed of linear structural components connected by elastomers. The components are commonly analyzed using large-scale finite element models. Examples include engine crankshafts with torsional dampers, engine structures with an elastomeric gasket between the head and the block, engine-vehicle structures using elastomeric engine mounts, etc. An analytical method is presented in this research for the dynamic analysis of large-scale structures with elastomers. The dissertation has two major parts. In the first part, a computationally efficient substructuring method is developed for substructures with non-matched interface meshes. The method is based on the conventional fixed-interface, Craig-Bampton component mode synthesis (CMS) method. However, its computational efficiency is greatly enhanced with the introduction of interface modes. Kriging interpolation at the interfaces between substructures ensures compatibility of deformation. In the second part, a series of dynamic measurements of mechanical properties of elastomers is presented. Dynamic stiffness as a function of frequency under controlled temperature and vibrational amplitude is measured. Also, the strain and stress relaxation behavior is tested to investigate the linearity and histeresis of an elastomer. The linearity of dynamic stiffness is studied and discussed in detail through the strain and stress relaxation test. The dynamic stiffness of elastomers is measured at different conditions such as temperature, frequency, and amplitude. The relationships between dynamic stiffness and temperature, and frequency and amplitude are discussed. After the dynamic properties of an elastomer are measured, a mathematical model is presented for characterizing the frequency and temperature-dependent properties of elastomers from the fundamental features of the molecular chains forming them. Experimental observations are used in the model development to greatly enhance the

  5. Toughening elastomers with sacrificial bonds and watching them break.

    Science.gov (United States)

    Ducrot, Etienne; Chen, Yulan; Bulters, Markus; Sijbesma, Rint P; Creton, Costantino

    2014-04-11

    Elastomers are widely used because of their large-strain reversible deformability. Most unfilled elastomers suffer from a poor mechanical strength, which limits their use. Using sacrificial bonds, we show how brittle, unfilled elastomers can be strongly reinforced in stiffness and toughness (up to 4 megapascals and 9 kilojoules per square meter) by introducing a variable proportion of isotropically prestretched chains that can break and dissipate energy before the material fails. Chemoluminescent cross-linking molecules, which emit light as they break, map in real time where and when many of these internal bonds break ahead of a propagating crack. The simple methodology that we use to introduce sacrificial bonds, combined with the mapping of where bonds break, has the potential to stimulate the development of new classes of unfilled tough elastomers and better molecular models of the fracture of soft materials.

  6. The Current State of Silicone-Based Dielectric Elastomer Transducers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren;

    2016-01-01

    driving voltages. In this review, the current state of sili- cone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects...... class of transducer due to their inherent lightweight and potentially large strains. For the field to progress towards industrial implementation, a leap in material devel- opment is required, specifically targeting longer lifetime and higher energy densities to provide more efficient transduction at lower...... of the elastomer are taken into account, namely dielectric losses, life- time and the very often ignored polymer network integrity and stability....

  7. Synthetic Strategies for High Dielectric Constant Silicone Elastomers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt

    Dielectric electroactive polymers (DEAPs) are a new and promising transducer technology and are often referred to as ‘artificial muscles’, due to their ability to undergo large deformations when stimulated by electric fields. DEAPs consist of a soft and thin elastomeric film (an elastomer...... synthetic strategies were developed in this Ph.D. thesis, in order to create silicone elastomers with high dielectric constants and thereby higher energy densities. The work focused on maintaining important properties such as dielectric loss, electrical breakdown strength and elastic modulus....... The methodology therefore involved chemically grafting high dielectric constant chemical groups onto the elastomer network, as this would potentially provide a stable elastomer system upon continued activation of the material. The first synthetic strategy involved the synthesis of a new type of cross...

  8. Amino alcohol-based degradable poly(ester amide) elastomers

    NARCIS (Netherlands)

    C.J. Bettinger (Christopher); J.P. Bruggeman (Joost); J.T. Borenstein (Jeffrey); R.S. Langer (Robert)

    2008-01-01

    textabstractCurrently available synthetic biodegradable elastomers are primarily composed of crosslinked aliphatic polyesters, which suffer from deficiencies including (1) high crosslink densities, which results in exceedingly high stiffness, (2) rapid degradation upon implantation, or (3) limited c

  9. EFFECTS OF GAMMA IRRADIATION ON EPDM ELASTOMERS

    Energy Technology Data Exchange (ETDEWEB)

    Clark, E.

    2011-09-22

    Two formulations of EPDM elastomer, one substituting a UV stabilizer for the normal antioxidant in this polymer, and the other the normal formulation, were synthesized and samples of each were exposed to gamma irradiation in initially pure deuterium gas to compare their radiation stability. Stainless steel containers having rupture disks were designed for this task. After 130 MRad dose of cobalt-60 radiation in the SRNL Gamma Irradiation Facility, a significant amount of gas was created by radiolysis; however the composition indicated by mass spectroscopy indicated an unexpected increase in the total amount deuterium in both formulations. The irradiated samples retained their ductility in a bend test. No change of sample weight, dimensions, or density was observed. No change of the glass transition temperature as measured by dynamic mechanical analysis was observed, and most of the other dynamic mechanical properties remained unchanged. There appeared to be an increase in the storage modulus of the irradiated samples containing the UV stabilizer above the glass transition, which may indicate hardening of the material by radiation damage. Polymeric materials become damaged by exposure over time to ionizing radiation. Despite the limited lifetime, polymers have unique engineering material properties and polymers continue to be used in tritium handling systems. In tritium handling systems, polymers are employed mainly in joining applications such as valve sealing surfaces (eg. Stem tips, valve packing, and O-rings). Because of the continued need to employ polymers in tritium systems, over the past several years, programs at the Savannah River National Laboratory have been studying the effect of tritium on various polymers of interest. In these studies, samples of materials of interest to the SRS Tritium Facilities (ultra-high molecular weight polyethylene (UHMW-PE), polytetrafluoroethylene (PTFE, Teflon{reg_sign}), Vespel{reg_sign} polyimide, and the elastomer

  10. Voltage-stabilised elastomers with increased relative permittivity and high electrical breakdown strength by means of phase separating binary copolymer blends of silicone elastomers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Yu, Liyun; Skov, Anne Ladegaard

    2017-01-01

    Increased electrical breakdown strength and increased dielectric permittivity of silicone-based dielectric elastomers are achieved by means of the addition of so-called voltage-stabilisers prepared from PDMS–PPMS copolymers as well as PDMS–PEG copolymers in order to compensate for the negative...... effect of softness on electrical stability of silicone elastomers. The voltage-stabilised elastomer, incorporating a high-permittivity PDMS–PEG copolymer, possesses increased relative permittivity, high electrical breakdown strength, excellent network integrity and low dielectric loss and paves the way...... towards specialised silicone elastomers for dielectric elastomer transducer products with inherent softness and electrical stability, and thus increased actuation at a given voltage....

  11. Modeling and control of a dielectric elastomer actuator

    Science.gov (United States)

    Gupta, Ujjaval; Gu, Guo-Ying; Zhu, Jian

    2016-04-01

    The emerging field of soft robotics offers the prospect of applying soft actuators as artificial muscles in the robots, replacing traditional actuators based on hard materials, such as electric motors, piezoceramic actuators, etc. Dielectric elastomers are one class of soft actuators, which can deform in response to voltage and can resemble biological muscles in the aspects of large deformation, high energy density and fast response. Recent research into dielectric elastomers has mainly focused on issues regarding mechanics, physics, material designs and mechanical designs, whereas less importance is given to the control of these soft actuators. Strong nonlinearities due to large deformation and electromechanical coupling make control of the dielectric elastomer actuators challenging. This paper investigates feed-forward control of a dielectric elastomer actuator by using a nonlinear dynamic model. The material and physical parameters in the model are identified by quasi-static and dynamic experiments. A feed-forward controller is developed based on this nonlinear dynamic model. Experimental evidence shows that this controller can control the soft actuator to track the desired trajectories effectively. The present study confirms that dielectric elastomer actuators are capable of being precisely controlled with the nonlinear dynamic model despite the presence of material nonlinearity and electromechanical coupling. It is expected that the reported results can promote the applications of dielectric elastomer actuators to soft robots or biomimetic robots.

  12. Treatment to Control Adhesion of Silicone-Based Elastomers

    Science.gov (United States)

    deGroh, Henry C., III; Puleo, Bernadette J.; Waters, Deborah L.

    2013-01-01

    Seals are used to facilitate the joining of two items, usually temporarily. At some point in the future, it is expected that the items will need to be separated. This innovation enables control of the adhesive properties of silicone-based elastomers. The innovation may also be effective on elastomers other than the silicone-based ones. A technique has been discovered that decreases the level of adhesion of silicone- based elastomers to negligible levels. The new technique causes less damage to the material compared to alternative adhesion mitigation techniques. Silicone-based elastomers are the only class of rubber-like materials that currently meet NASA s needs for various seal applications. However, silicone-based elastomers have natural inherent adhesive properties. This stickiness can be helpful, but it can frequently cause problems as well, such as when trying to get items apart. In the past, seal adhesion was not always adequately addressed, and has caused in-flight failures where seals were actually pulled from their grooves, preventing subsequent spacecraft docking until the seal was physically removed from the flange via an extravehicular activity (EVA). The primary method used in the past to lower elastomer seal adhesion has been the application of some type of lubricant or grease to the surface of the seal. A newer method uses ultraviolet (UV) radiation a mixture of UV wavelengths in the range of near ultraviolet (NUV) and vacuum ultraviolet (VUV) wavelengths.

  13. Polyurethane elastomers from morphology to mechanical aspects

    CERN Document Server

    Prisacariu, Cristina

    2011-01-01

    A comprehensive account of the physical / mechanical behaviour of polyurethanes (PU´s) elastomers, films and blends of variable crystallinity. Aspects covered include the elasticity and inelasticity of amorphous to crystalline PUs, in relation to their sensitivity to chemical and physical structure. A study is made of how aspects of the constitutive responses of PUs vary with composition: the polyaddition procedure, the hard segment, soft segment and chain extender (diols and diamines) are varied systematically in a large number of systems of model and novel crosslinked andthermoplastic PUs. Results will be related to: microstructural changes, on the basis of evidence from x-ray scattering (SAXS and WAXS), and also dynamic mechanical analyses (DMA), differential scanning calorimetry (DSC) and IR dichroism. Inelastic effects will be investigated also by including quantitative correlations between the magnitude of the Mullins effect and the fractional energy dissipation by hysteresis under cyclic straining, g...

  14. Highly stretchable nanoalginate based polyurethane elastomers.

    Science.gov (United States)

    Daemi, Hamed; Barikani, Mehdi; Barmar, Mohammad

    2013-06-20

    Highly stretchable elastomeric samples based on cationic polyurethane dispersions-sodium alginate nanoparticles (CPUD/SA) were prepared by the solution blending of sodium alginate and aqueous polyurethane dispersions. CPUDs were synthesized by step growth polymerization technique using N-methyldiethanolamine (MDEA) as a source of cationic emulsifier. The chemical structure and thermal-mechanical properties of these systems were characterized using FTIR and DMTA, respectively. The presence of nanoalginate particles including nanobead and nanorod particles were proved by SEM and EDX. It was observed that thermal properties of composites increased with increasing SA content. All prepared samples were known as thermoplastic-elastomers with high percentages of elongation. Excellent compatibility of prepared nanocomposites was proved by the DMTA data.

  15. EB radiation crosslinking of elastomers [rapid communication

    Science.gov (United States)

    Bik, J.; Głuszewski, W.; Rzymski, W. M.; Zagórski, Z. P.

    2003-06-01

    Radiation-induced crosslinking is proposed as successful alternative to conventional, chemical methods of crosslinking of elastomers. Hydrogenated acrylonitrile-butadiene rubber was irradiated with 10 MeV electron beam to doses up to 300 kGy. Irradiated samples were investigated for the extent of crosslinking and for properties important for understanding of mechanisms. It follows from sol-gel analysis, that for 100 crosslinking acts there are 6-9 acts of chain scission. It is less than expected from the 20% participation of multi-ionization spurs, also in the solid state, as announced during the previous 9th Tihany Conference (Radiat. Phys. Chem. 56 (1999) 559). However, the apparent too low yield of multi-ionization spurs could be explained by partial conversion of scission products into crosslinks of specific trifunctional Y type. Our investigations confirm the usefulness of consideration of different radiation spurs in polymers, as well as in all, low LET irradiated media.

  16. Dynamic damping property of magnetorheological elastomer

    Institute of Scientific and Technical Information of China (English)

    李剑锋; 龚兴龙

    2008-01-01

    Magnetorheological elastomer(MRE) is a new kind of smart materials,its dynamic mechanic performances can be controlled by an applied magnetic field.MRE is usually used as a stiffness-changeable spring in the semi-active vibration absorber.In order to get perfect vibration control effect,low dynamic damping of MRE is need.But the dynamic damping of MRE was not studied deeply in the past.The dynamic damping of MRE was studied and analyzed.The influences of different test conditions including test strain amplitude,test frequency and test magnetic field were deeply studied.MRE sample and pure silicone rubber sample were prepared and tested under different conditions.The test results show that the main source of dynamic damping is the friction between iron particles and rubber matrix.And the friction is mainly influenced by the strain amplitude and test magnetic field.

  17. Tactile display with dielectric multilayer elastomer actuatorsq

    Science.gov (United States)

    Matysek, Marc; Lotz, Peter; Schlaak, Helmut F.

    2009-03-01

    Tactile perception is the human sensation of surface textures through the vibrations generated by stroking a finger over the surface. The skin responds to several distributed physical quantities. Perhaps the most important are high-frequency vibrations, pressure distributions (static shape) and thermal properties. The integration of tactile displays in man-machine interfaces promises a more intuitive handling. For this reason many tactile displays are developed using different technologies. We present several state-of-the-art tactile displays based on different types of dielectric elastomer actuators to clarify the advantages of our matrix display based on multilayer technology. Using this technology perpendicular and hexagonal arrays of actuator elements (tactile stimulators) can be integrated into a PDMS substrate. Element diameters down to 1 mm allow stimuli at the range of the human two-point-discrimination threshold. Driving the elements by column and row addressing enables various stimulation patterns with a reduced number of feeding lines. The transient analysis determines charging times of the capacitive actuators depending on actuator geometry and material parameters. This is very important to ensure an adequate dynamic characteristic of the actuators to stimulate the human skin by vibrations. The suitability of multilayer dielectric elastomer actuators for actuation in tactile displays has been determined. Beside the realization of a static tactile display - where multilayer DEA are integrated as drives for movable contact pins - we focus on the direct use of DEA as a vibrotactile display. Finally, we present the scenario and achieved results of a recognition threshold test. Even relative low voltages in the range of 800 V generate vibrations with 100% recognition ratio within the group of participants. Furthermore, the frequency dependent characteristic of the determined recognition threshold confirms with established literature.

  18. Tissue Response to, and Degradation Rate of, Photocrosslinked Trimethylene Carbonate-Based Elastomers Following Intramuscular Implantation

    Directory of Open Access Journals (Sweden)

    Brian G. Amsden

    2010-02-01

    Full Text Available Cylindrical elastomers were prepared through the UV-initiated crosslinking of terminally acrylated, 8,000 Da star-poly(trimethylene carbonate-co-ε-caprolactone and star-poly(trimethylene carbonate-co-D,L-lactide. These elastomers were implanted intramuscularly into the hind legs of male Wistar rats to determine the influence of the comonomer on the weight loss, tissue response, and change in mechanical properties of the elastomer. The elastomers exhibited only a mild inflammatory response that subsided after the first week; the response was greater for the stiffer D,L-lactide-containing elastomers. The elastomers exhibited weight loss and sol content changes consistent with a bulk degradation mechanism. The D,L-lactide-containing elastomers displayed a nearly zeroorder change in Young’s modulus and stress at break over the 30 week degradation time, while the ε-caprolactone-containing elastomers exhibited little change in modulus or stress at break.

  19. Skin-inspired hydrogel-elastomer hybrids with robust interfaces and functional microstructures

    Science.gov (United States)

    Yuk, Hyunwoo; Zhang, Teng; Parada, German Alberto; Liu, Xinyue; Zhao, Xuanhe

    2016-06-01

    Inspired by mammalian skins, soft hybrids integrating the merits of elastomers and hydrogels have potential applications in diverse areas including stretchable and bio-integrated electronics, microfluidics, tissue engineering, soft robotics and biomedical devices. However, existing hydrogel-elastomer hybrids have limitations such as weak interfacial bonding, low robustness and difficulties in patterning microstructures. Here, we report a simple yet versatile method to assemble hydrogels and elastomers into hybrids with extremely robust interfaces (interfacial toughness over 1,000 Jm-2) and functional microstructures such as microfluidic channels and electrical circuits. The proposed method is generally applicable to various types of tough hydrogels and diverse commonly used elastomers including polydimethylsiloxane Sylgard 184, polyurethane, latex, VHB and Ecoflex. We further demonstrate applications enabled by the robust and microstructured hydrogel-elastomer hybrids including anti-dehydration hydrogel-elastomer hybrids, stretchable and reactive hydrogel-elastomer microfluidics, and stretchable hydrogel circuit boards patterned on elastomer.

  20. Skin-inspired hydrogel–elastomer hybrids with robust interfaces and functional microstructures

    Science.gov (United States)

    Yuk, Hyunwoo; Zhang, Teng; Parada, German Alberto; Liu, Xinyue; Zhao, Xuanhe

    2016-01-01

    Inspired by mammalian skins, soft hybrids integrating the merits of elastomers and hydrogels have potential applications in diverse areas including stretchable and bio-integrated electronics, microfluidics, tissue engineering, soft robotics and biomedical devices. However, existing hydrogel–elastomer hybrids have limitations such as weak interfacial bonding, low robustness and difficulties in patterning microstructures. Here, we report a simple yet versatile method to assemble hydrogels and elastomers into hybrids with extremely robust interfaces (interfacial toughness over 1,000 Jm−2) and functional microstructures such as microfluidic channels and electrical circuits. The proposed method is generally applicable to various types of tough hydrogels and diverse commonly used elastomers including polydimethylsiloxane Sylgard 184, polyurethane, latex, VHB and Ecoflex. We further demonstrate applications enabled by the robust and microstructured hydrogel–elastomer hybrids including anti-dehydration hydrogel–elastomer hybrids, stretchable and reactive hydrogel–elastomer microfluidics, and stretchable hydrogel circuit boards patterned on elastomer. PMID:27345380

  1. Bottlebrush elastomers: a promising molecular engineering route to tunable, prestrain-free dielectric elastomers (Conference Presentation)

    Science.gov (United States)

    Vatankhah-Varnosfaderani, Mohammad; Daniel, William F. M.; Zhushma, Alexandr P.; Li, Qiaoxi; Morgan, Benjamin J.; Matyjaszewski, Krzysztof; Armstrong, Daniel P.; Dobrynin, Andrey V.; Sheyko, Sergei S.; Spontak, Richard J.

    2017-04-01

    Electroactive polymers (EAPs) refer to a broad range of relatively soft materials that change size and/or shape upon application of an electrical stimulus. Of these, dielectric elastomers (DEs) generated from either chemically- or physically-crosslinked polymer networks afford the highest levels of electroactuation strain, thereby making this class of EAPs the leading technology for artificial-muscle applications. While mechanically prestraining elastic networks remarkably enhances DEs electroactuation, external prestrain protocols severely limit both actuator performance and device implementation due to gradual DE stress relaxation and the presence of a cumbersome load frame. These drawbacks have persisted with surprisingly minimal advances in the actuation of single-component elastomers since the dawn of the "pre-strain era" introduced by Pelrine et al. (Science, 2000). In this work, we present a bottom-up, molecular-based strategy for the design of prestrain-free (freestanding) DEs derived from covalently-crosslinked bottlebrush polymers. This architecture, wherein design factors such as crosslink density, graft density and graft length can all be independently controlled, yields inherently strained polymer networks that can be readily adapted to a variety of chemistries. To validate the use of these molecularly-tunable materials as DEs, we have synthesized a series of bottlebrush silicone elastomers in as-cast shapes. Examination of these materials reveals that they undergo giant electroactuation strains (>300%) at relatively low fields (design approach to controlling (electro)mechanical developed here is independent of chemistry and permits access to an unprecedented range of actuation properties from elastomeric materials with traditionally modest electroactuation performance (e.g., polydimethylsiloxane, PDMS). Experimental results obtained here compare favorably with theoretical predictions and demonstrate that the unique behavior of these materials is a

  2. Thermal tuning of a silicon photonic crystal cavity infilled with an elastomer

    NARCIS (Netherlands)

    Erdamar, A.K.; Van Leest, M.M.; Picken, S.J.; Caro. J.

    2011-01-01

    Thermal tuning of the transmission of an elastomer infilled photonic crystal cavity is studied. An elastomer has a thermal expansion-induced negative thermo-optic coefficient that leads to a strong decrease of the refractive index upon heating. This property makes elastomer highly suitable for therm

  3. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on tunable functionalized copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede;

    2015-01-01

    High driving voltages currently limit the commercial potential of dielectric elastomers (DEs). One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric permittivity was prepared through the synthesis o...

  4. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on tunable functionalized copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2015-01-01

    High driving voltages currently limit the commercial potential of dielectric elastomers (DEs). One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric permittivity was prepared through the synthesis o...

  5. Current leakage performance of dielectric elastomers under different boundary conditions

    Science.gov (United States)

    Lu, Tongqing; Shi, Zhibao; Chen, Zhiqiang; Huang, He; Wang, T. J.

    2015-10-01

    In the past decade, dielectric elastomers have become promising candidates in the applications of soft electromechanical transducers due to their outstanding properties of large deformation and high energy density. Current leakage of dielectric elastomer is one of the important dissipative mechanisms affecting the energy conversion efficiency. In this work, we experimentally investigate the current leakage performance of dielectric elastomers with different boundary conditions. We find that for displacement-type boundary conditions, the transition from Ohmic conduction to non-Ohmic conduction is abrupt near the critical electric field. By comparison, for force-type boundary conditions, the current leakage density versus electric field curve is smooth and is fit well by an exponential function. The equivalent resistivity of dielectric elastomers under force-type boundary conditions is approximately an order of magnitude smaller than that under displacement-type boundary conditions. The difference is qualitatively explained by a microscopic physical model. These results will help to design and optimize dielectric elastomer transducers to improve their energy conversion efficiency.

  6. Thermal Degradation Studies of Polyurethane/POSS Nanohybrid Elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J P; Pielichowski, K; TremblotDeLaCroix, P; Janowski, B; Todd, D; Liggat, J J

    2010-03-05

    Reported here is the synthesis of a series of Polyurethane/POSS nanohybrid elastomers, the characterization of their thermal stability and degradation behavior at elevated temperatures using a combination of Thermal Gravimetric Analysis (TGA) and Thermal Volatilization Analysis (TVA). A series of PU elastomers systems have been formulated incorporating varying levels of 1,2-propanediol-heptaisobutyl-POSS (PHIPOSS) as a chain extender unit, replacing butane diol. The bulk thermal stability of the nanohybrid systems has been characterized using TGA. Results indicate that covalent incorporation of POSS into the PU elastomer network increase the non-oxidative thermal stability of the systems. TVA analysis of the thermal degradation of the POSS/PU hybrid elastomers have demonstrated that the hybrid systems are indeed more thermally stable when compared to the unmodified PU matrix; evolving significantly reduced levels of volatile degradation products and exhibiting a {approx}30 C increase in onset degradation temperature. Furthermore, characterization of the distribution of degradation products from both unmodified and hybrid systems indicate that the inclusion of POSS in the PU network is directly influencing the degradation pathways of both the soft and hard block components of the elastomers: The POSS/PU hybrid systems show reduced levels of CO, CO2, water and increased levels of THF as products of thermal degradation.

  7. Synergistic effects in the processes of crosslinking of elastomers

    Science.gov (United States)

    Głuszewski, Wojciech; Zagórski, Zbigniew P.; Rajkiewicz, Maria

    2014-01-01

    Radiation crosslinking of elastomers is an example of the modification of polymers by ionizing radiation. In practice, often parallel both traditional crosslinking (with peroxide) and radiation treatment is applied (Bik et al., 2003, 2004). Elastomers can be irradiated both before and/or after vulcanization products. The aim of this study was to investigate the system of the mixed radiation/peroxide and peroxide/radiation crosslinking of selected elastomers (Engage 8200, HNBR). In particular, attention was directed to the influence of the protective effects of aromatic additives in elastomers (peroxides, thermal- and light stabilizers) on the phenomenon of crosslinking and postradiation oxidation. Aromatic peroxides may undergo modifications during the preirradiation, which affect the subsequent processes of vulcanization. In this way the method of gas chromatography (GC) was applied for determination of hydrogen and oxidation effects, never described before for Engage 8200. Using that approach, radiation efficiency of hydrogen evolution and oxygen absorption efficiency of the polymers has been identified. To describe the phenomena of postradiation oxidation of elastomers, the method of Diffuse Reflection Spectrophotometry (DRS) was also applied.

  8. Ageing by UV radiation of an elastomer modified bitumen

    Energy Technology Data Exchange (ETDEWEB)

    Virginie Mouillet; Fabienne Farcas; Stanislas Besson [CETE Mediterranee Pole d' activite, Aix-en-Provence (France). Laboratoire Regional des Ponts et Chaussees d' Aix-en-Provence

    2008-09-15

    Laboratory methods to simulate the short- and long-term ageing occurring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of UV radiations. If the impact of thermal ageing on the degradation of SBS elastomers in bitumens has been extensively studied, there is not study dealing with the photo-oxidation of these copolymers in a bituminous matrix. So, the aim of our study was to investigate, by FTIR spectrometry and SEC chromatography, whether the architecture of elastomers (linear or radial) might have any influence on their ageing by UV radiation in a bituminous matrix. The results show that the elastomers oxidation kinetic, unlike the disappearance kinetic of trans-butadiene double bond, does not depend on their architecture. But, when putted into the same base bitumen, the two copolymers show exactly the same oxidation kinetic and the same decreasing kinetic of trans-butadiene double bond. So, this study has revealed that inside the bituminous matrix, on the one hand, the elastomers architecture does not influence on its degradation when submitted to UV radiation and, on the other hand, there is a 'protection' of the elastomers by the studied bitumen towards UV radiation. 46 refs., 13 figs., 2 tabs.

  9. Electrical modeling of dielectric elastomer stack transducers

    Science.gov (United States)

    Haus, Henry; Matysek, Marc; Moessinger, Holger; Flittner, Klaus; Schlaak, Helmut F.

    2013-04-01

    Performance of dielectric elastomer transducers (DEST) depends on mechanical and electrical parameters. For designing DEST it is therefore necessary to know the influences of these parameters on the overall performance. We show an electrical equivalent circuit valid for a transducer consisting of multiple layers and derive the electrical parameters of the circuit depending on transducers geometry and surface resistivity of the electrodes. This allows describing the DESTs dynamic behavior as a function of fabrication (layout, sheet and interconnection resistance), material (breakdown strength, permittivity) and driving (voltage) parameters. Using this electrical model transfer function and cut-off frequency are calculated, describing the influence of transducer capacitance, resistance and driving frequency on the achievable actuation deflection. Furthermore non ideal boundary effects influencing the capacitance value of the transducer are investigated by an electrostatic simulation and limits for presuming a simple plate capacitor model for calculating the transducer capacitance are derived. Results provide the plate capacitor model is a valid assumption for typical transducer configurations but for certain aspect ratios of electrode dimensions to dielectric thickness -- arising e.g. in the application of tactile interfaces -- the influence of boundary effects is to be considered.

  10. Self-stabilizing dielectric elastomer generators

    Science.gov (United States)

    Zanini, P.; Rossiter, J.; Homer, M.

    2017-03-01

    Dielectric elastomer generators (DEGs) are an emerging technology for the conversion of mechanical into electrical energy. Despite many advantageous characteristics, there are still issues to overcome, including the need for charging at every cycle to produce an electrical output. Self-priming circuits (SPCs) are one possible solution, storing part of the electric energy output of one cycle to supply as input for the next, producing a voltage boost effect. Until now, studies regarding SPCs neglect to consider how the increasing voltage will create an electromechanical response and affect the DEG when driven by an oscillatory mechanical load. In the present work we model this force-based actuation, including coupling between the DEG and SPC, in order to predict the dynamics of the system. In such cases, the DEG has a mechanical response when charged (actuator behaviour), and as the voltage increases, this actuation-like effect increases the capacitance values that bound the cycle. We show how this inherent nonlinearity yields a reduction in the DEG’s capacitance swing and reduces the performance of the SPC, but also self-stabilizes the system. This stability is useful in the design of robust DEG energy harvesters that can operate near to, but not enter, failure mode.

  11. Mesoscopic magnetomechanical hysteresis in a magnetorheological elastomer.

    Science.gov (United States)

    Biller, A M; Stolbov, O V; Raikher, Yu L

    2015-08-01

    Field-induced magnetostatic interaction in a pair of identical particles made of a magnetically soft ferromagnet is studied. It is shown that due to saturation of the ferromagnet magnetization, this case differs significantly from the (super)paramagnetic one. A numerical solution is given, discussed, and compared with that provided by a simpler model (nonlinear mutual dipoles). We show that for multidomain ferromagnetic particles embedded in an elastomer matrix, as for paramagnetic ones in the same environment, pair clusters may form or break by a hysteresis scenario. However, the magnetization saturation brings in important features to this effect. First, the bistability state and the hysteresis take place only in a limited region of the material parameters of the system. Second, along with the hysteresis jumps occurring under the sole influence of the field, the "latent" hysteresis is possible which realizes only if the action of the field is combined with some additional (nonmagnetic) external factor. The obtained conditions, when used to assess the possibility of clustering in real magnetorheological polymers, infer an important role of mesoscopic magnetomechanical hysteresis for the macroscopic properties of these composites.

  12. Renewable Aliphatic Polyester Block Polymer Thermoplastic Elastomers

    Science.gov (United States)

    Martello, Mark Thomas

    The performance of thermoplastic elastomers is predicated on their ability to form mechanically tough physically crosslinked elastomeric networks at low temperatures and be able to flow at elevated temperatures. This dissertation focuses on renewable aliphatic polyester block polymers with amorphous polylactide (PLA) and their performance as TPEs. The goal of this work was to enhance the mechanical toughness of PLA containing TPEs; fundamental properties ranging from chemical composition and phase behavior, molecular architecture and melt processability, to melt polymerization strategies were investigated. ABA triblock polymers with PLA end-blocks and rubbery mid-blocks from substituted lactones comprised of poly(6-methyl-epsilon-caprolactone)(PMCL), poly(delta-decalactone), and poly(epsilon-decalactone)(PDL) were produced by sequential ring-opening polymerizations in the bulk. The bulk microstructure of symmetric PLA-PMCL-PLA and PLA-PDL-PLA triblock polymers formed long-range ordered morphologies and the interaction parameter of the repeat units was determined. High molar mass triblocks exhibited elastomeric behavior with good tensile strengths and high elongations. Small triblocks were coupled to produced (PLA-PDL-PLA)n multiblock polymers with high molar mass and accessible order-disorder transitions allowing for melt processing via injection molding. The mechanical toughness of the multiblocks was comparable to the high molar mass triblocks. The controlled polymerization of renewable delta-decalactone was accomplished with an organocatalyst at low temperatures in the bulk to maximize the equilibrium conversion of the monomer.

  13. Inorganic particle analysis of dental impression elastomers.

    Science.gov (United States)

    Carlo, Hugo Lemes; Fonseca, Rodrigo Borges; Soares, Carlos José; Correr, Américo Bortolazzo; Correr-Sobrinho, Lourenço; Sinhoreti, Mário Alexandre Coelho

    2010-01-01

    The aim of this study was to determine quantitatively and qualitatively the inorganic particle fraction of commercially available dental elastomers. The inorganic volumetric fraction of two addition silicones (Reprosil Putty/Fluid and Flexitime Easy Putty/Fluid), three condensation silicones (Clonage Putty/Fluid, Optosil Confort/Xantopren VL and Silon APS Putty/Fluid), one polyether (Impregum Soft Light Body) and one polysulfide (Permlastic Light Body) was accessed by weighing a previously determined mass of each material in water before and after burning samples at 600 ºC, during 3 h. Unsettled material samples were soaked in acetone and chloroform for removal of the organic portion. The remaining filler particles were sputter-coated with gold evaluation of their morphology and size, under scanning electron microscopy (SEM). Flexitime Easy Putty was the material with the highest results for volumetric particle fraction, while Impregum Soft had the lowest values. Silon 2 APS Fluid presented the lowest mean filler size values, while Clonage Putty had the highest values. SEM micrographs of the inorganic particles showed several morphologies - lathe-cut, spherical, spherical-like, sticks, and sticks mixed to lathe-cut powder. The results of this study revealed differences in particle characteristics among the elastometic materials that could lead to different results when testing mechanical properties.

  14. Energy harvesting for dielectric elastomer sensing

    Science.gov (United States)

    Anderson, Iain A.; Illenberger, Patrin; O'Brien, Ben M.

    2016-04-01

    Soft and stretchy dielectric elastomer (DE) sensors can measure large strains on robotic devices and people. DE strain measurement requires electric energy to run the sensors. Energy is also required for information processing and telemetering of data to phone or computer. Batteries are expensive and recharging is inconvenient. One solution is to harvest energy from the strains that the sensor is exposed to. For this to work the harvester must also be wearable, soft, unobtrusive and profitable from the energy perspective; with more energy harvested than used for strain measurement. A promising way forward is to use the DE sensor as its own energy harvester. Our study indicates that it is feasible for a basic DE sensor to provide its own power to drive its own sensing signal. However telemetry and computation that are additional to this will require substantially more power than the sensing circuit. A strategy would involve keeping the number of Bluetooth data chirps low during the entire period of energy harvesting and to limit transmission to a fraction of the total time spent harvesting energy. There is much still to do to balance the energy budget. This will be a challenge but when we succeed it will open the door to autonomous DE multi-sensor systems without the requirement for battery recharge.

  15. Temperature dependence of the dielectric constant of acrylic dielectric elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei [Xi' an Jiaotong University, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an (China); Xi' an Jiaotong University, School of Mechanical Engineering, Xi' an (China)

    2013-02-15

    The dielectric constant is an essential electrical parameter to the achievable voltage-induced deformation of the dielectric elastomer. This paper primarily focuses on the temperature dependence of the dielectric constant (within the range of 173 K to 373 K) for the most widely used acrylic dielectric elastomer (VHB 4910). First the dielectric constant was investigated experimentally with the broadband dielectric spectrometer (BDS). Results showed that the dielectric constant first increased with temperature up to a peak value and then dropped to a relative small value. Then by analyzing the fitted curves, the Cole-Cole dispersion equation was found better to characterize the rising process before the peak values than the Debye dispersion equation, while the decrease process afterward can be well described by the simple Debye model. Finally, a mathematical model of dielectric constant of VHB 4910 was obtained from the fitted results which can be used to further probe the electromechanical stability of the dielectric elastomers. (orig.)

  16. Silicone elastomers with superior softness and dielectric properties

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin;

    of electrical breakdown and achievable strain.[2]In this work, three liquid additives - inert silicone oil, chloropropyl-functional silicone oil, and synthesized chloropropyl-functional copolymer - were blended into commercial silicone elastomers, and their properties were investigated.The functional groups......Dielectric elastomers (DEs) change their shape and size under a high voltage or reversibly generate a high voltage when deformed. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young......’s modulus and increasing the dielectric permittivity of silicone elastomers. One such prominent method of modifying the properties is by adding suitable additives.[1] The major drawbacks for adding solid fillers are agglomeration and increasing stiffness which is often accompanied by the decrease...

  17. Silicone elastomers with superior softness and dielectric properties

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin;

    of electrical breakdown and achievable strain.[2] In this work, three liquid additives - inert silicone oil, chloropropyl-functional silicone oil, and synthesized chloropropyl-functional copolymer - were blended into commercial silicone elastomers, and their properties were investigated.The functional groups......Dielectric elastomers (DEs) change their shape and size under a high voltage or reversibly generate a high voltage when deformed. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young......’s modulus and increasing the dielectric permittivity of silicone elastomers. One such prominent method of modifying the properties is by adding suitable additives. [1] The major drawbacks for adding solid fillers are agglomeration and increasing stiffness which is often accompanied by the decrease...

  18. Castable thermoplastic urethane elastomers. II. Structure property correlations

    Energy Technology Data Exchange (ETDEWEB)

    Lagasse, R.R.; Wischmann, K.B.

    1977-01-01

    A liquid casting approach has been used to encapsulate electronic assemblies with specially-developed, soluble urethane elastomers. As a continuation of this work, the present paper correlates macromolecular morphology with both high strain ultimate and low strain dynamic mechanical properties of these thermoplastic elastomers. Although the morphology-property correlations are shown to fit within the general framework of a domain model, the possibility is raised that the liquid casting procedure might give rise to slightly different structural features than the more conventional fabrication methods (e.g., melt processing). It is anticipated that the results of this investigation will help to increase our fundamental understanding of liquid castable elastomers, which have been heretofore neglected to a significant extent.

  19. Effect of environmental stress on Sylgard 170 silicone elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Buckalew, W.H.; Wyant, F.J.

    1985-05-01

    Dow Corning Sylgard 170 Silicone Elastomer has been investigated to characterize its response to accelerated thermal aging, radiation exposure, and its behavior under applied compressive forces. Sylgard 170 response to accelerated thermal aging suggests the material properties are not particularly age dependent. Radiation exposures, however, produce significant, monotonic changes in both elongation and hardness with increasing absorbed radiation dose. Elastomer response to an applied compressive force was strongly dependent on environment temperature and degree of material confinement. Variations in temperature produced large changes in compressive forces applied to confined samples. Attempts to mitigate force fluctuations by means of pressure relief paths resulted in total loss of the applied compressive force. Thus, seal applications employing this elastomer in Class 1E equipment required to function during or following an accident should consider the potential loss of compressive force from long-term aging and potential LOCA-temperature transient conditions.

  20. Single-particle mechanism of magnetostriction in magnetoactive elastomers.

    Science.gov (United States)

    Kalita, Viktor M; Snarskii, Andrei A; Zorinets, Denis; Shamonin, Mikhail

    2016-06-01

    Magnetoactive elastomers (MAEs) are composite materials comprised of micrometer-sized ferromagnetic particles in a nonmagnetic elastomer matrix. A single-particle mechanism of magnetostriction in MAEs, assuming the rotation of a soft magnetic, mechanically rigid particle with uniaxial magnetic anisotropy in magnetic fields is identified and considered theoretically within the framework of an alternative model. In this mechanism, the total magnetic anisotropy energy of the filling particles in the matrix is the sum over single particles. Matrix displacements in the vicinity of the particle and the resulting direction of the magnetization vector are calculated. The effect of matrix deformation is pronounced well if the magnetic anisotropy coefficient K is much larger than the shear modulus µ of the elastic matrix. The feasibility of the proposed magnetostriction mechanism in soft magnetoactive elastomers and gels is elucidated. The magnetic-field-induced internal stresses in the matrix lead to effects of magnetodeformation and may increase the elastic moduli of these composite materials.

  1. Fracture Behavior of Dielectric Elastomer under Pure Shear Loading

    Science.gov (United States)

    Ahmad, D.; Patra, K.

    2017-09-01

    Dielectric elastomer has become a very important material for many emerging applications areas like optics, micro fluidics, sensors, actuators and energy harvesting. However, these elastomer components are prone to fracture or catastrophic failure because of defects likes notches, flaws, and fatigue crack, impurities which occur during production or during service. To make better use of this material, it is important to investigate fracture characteristics under different operating conditions. This study experimentally investigated the effects of notch length and strain rate on the fracture toughness, failure stretch and failure stress of acrylic elastomer under pure shear deformation mode. It is observed that failure stretch depends on notch length and independent of strain rate, but failure stress decreases with increasing notch length and increases with increasing strain rate. It is also found that fracture toughness is independent of notch lengths. However, fracture toughness is found to increase with strain rate.

  2. Single-particle mechanism of magnetostriction in magnetoactive elastomers

    Science.gov (United States)

    Kalita, Viktor M.; Snarskii, Andrei A.; Zorinets, Denis; Shamonin, Mikhail

    2016-06-01

    Magnetoactive elastomers (MAEs) are composite materials comprised of micrometer-sized ferromagnetic particles in a nonmagnetic elastomer matrix. A single-particle mechanism of magnetostriction in MAEs, assuming the rotation of a soft magnetic, mechanically rigid particle with uniaxial magnetic anisotropy in magnetic fields is identified and considered theoretically within the framework of an alternative model. In this mechanism, the total magnetic anisotropy energy of the filling particles in the matrix is the sum over single particles. Matrix displacements in the vicinity of the particle and the resulting direction of the magnetization vector are calculated. The effect of matrix deformation is pronounced well if the magnetic anisotropy coefficient K is much larger than the shear modulus µ of the elastic matrix. The feasibility of the proposed magnetostriction mechanism in soft magnetoactive elastomers and gels is elucidated. The magnetic-field-induced internal stresses in the matrix lead to effects of magnetodeformation and may increase the elastic moduli of these composite materials.

  3. Development of soft robots using dielectric elastomer actuators

    Science.gov (United States)

    Godaba, Hareesh; Wang, Yuzhe; Cao, Jiawei; Zhu, Jian

    2016-04-01

    Soft robots are gaining in popularity due to their unique attributes such as low weight, compliance, flexibility and diverse range in motion types. This paper illustrates soft robots and actuators which are developed using dielectric elastomer. These developments include a jellyfish robot, a worm like robot and artificial muscle actuators for jaw movement in a robotic skull. The jellyfish robot which employs a bulged dielectric elastomer membrane has been demonstrated too generate thrust and buoyant forces and can move effectively in water. The artificial muscle for jaw movement employs a pure shear configuration and has been shown to closely mimic the jaw motion while chewing or singing a song. Thee inchworm robot, powered by dielectric elastomer actuator can demonstrate stable movement in one-direction.

  4. Exploring dielectric elastomers as actuators for hand tremor suppression

    Science.gov (United States)

    Kelley, Christopher R.; Kauffman, Jeffrey L.

    2017-04-01

    Pathological tremor results in undesired motion of body parts, with the greatest effect typically occurring in the hands. Since common treatment methods are ineffective in some patients or have risks associated with surgery or side effects, researchers are investigating mechanical means of tremor suppression. This work explores the viability of dielectric elastomers as the actuators in a tremor suppression control system. Dielectric elastomers have many properties similar to human muscle, making them a natural fit for integration into the human biomechanical system. This investigation develops a model of the integrated wrist-actuator system to determine actuator parameters that produce the necessary control authority without significantly affecting voluntary motion. Furthermore, this paper develops a control law for the actuator voltage to increase the effective viscous damping of the system. Simulations show excellent theoretical tremor suppression, demonstrating the potential for dielectric elastomers to suppress tremor while maximizing compatibility between the actuator and the human body.

  5. Flexible and stretchable electrodes for dielectric elastomer actuators

    Science.gov (United States)

    Rosset, Samuel; Shea, Herbert R.

    2013-02-01

    Dielectric elastomer actuators (DEAs) are flexible lightweight actuators that can generate strains of over 100 %. They are used in applications ranging from haptic feedback (mm-sized devices), to cm-scale soft robots, to meter-long blimps. DEAs consist of an electrode-elastomer-electrode stack, placed on a frame. Applying a voltage between the electrodes electrostatically compresses the elastomer, which deforms in-plane or out-of plane depending on design. Since the electrodes are bonded to the elastomer, they must reliably sustain repeated very large deformations while remaining conductive, and without significantly adding to the stiffness of the soft elastomer. The electrodes are required for electrostatic actuation, but also enable resistive and capacitive sensing of the strain, leading to self-sensing actuators. This review compares the different technologies used to make compliant electrodes for DEAs in terms of: impact on DEA device performance (speed, efficiency, maximum strain), manufacturability, miniaturization, the integration of self-sensing and self-switching, and compatibility with low-voltage operation. While graphite and carbon black have been the most widely used technique in research environments, alternative methods are emerging which combine compliance, conduction at over 100 % strain with better conductivity and/or ease of patternability, including microfabrication-based approaches for compliant metal thin-films, metal-polymer nano-composites, nanoparticle implantation, and reel-to-reel production of μm-scale patterned thin films on elastomers. Such electrodes are key to miniaturization, low-voltage operation, and widespread commercialization of DEAs.

  6. Spectral Decomposition Algorithm (SDA)

    Data.gov (United States)

    National Aeronautics and Space Administration — Spectral Decomposition Algorithm (SDA) is an unsupervised feature extraction technique similar to PCA that was developed to better distinguish spectral features in...

  7. Phenomenological Theory of Isotropic-Genesis Nematic Elastomers

    Science.gov (United States)

    Lu, Bing-Sui; Ye, Fangfu; Xing, Xiangjun; Goldbart, Paul M.

    2012-06-01

    We consider the impact of the elastomer network on the nematic structure and fluctuations in isotropic-genesis nematic elastomers, via a phenomenological model that underscores the role of network compliance. The model contains a network-mediated nonlocal interaction as well as a new kind of random field that reflects the memory of the nematic order present at network formation and also encodes local anisotropy due to localized nematogenic polymers. This model enables us to predict regimes of short-ranged oscillatory spatial correlations (thermal and glassy) in the nematic alignment.

  8. Modeling shape-memory behavior of dielectric elastomers

    Science.gov (United States)

    Xiao, Rui

    2016-04-01

    In this study, we present a constitutive model to couple the shape memory and dielectric behaviors of polymers. The model adopted multiple relaxation processes and temperature-dependent relaxation time to describe the glass transition behaviors. The model was applied to simulate the thermal-mechanical-electrical behaviors of the dielectric elastomer VHB 4905. We investigated the influence of deformation temperature, voltage rate, relaxation time on the electromechanical and shape-memory behavior of dielectric elastomers. This work provides a method for combining the shape-memory properties and electroactive polymers, which can expand the applications of these soft active materials.

  9. A DECOMPOSITION METHOD OF STRUCTURAL DECOMPOSITION ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    LI Jinghua

    2005-01-01

    Over the past two decades,structural decomposition analysis(SDA)has developed into a major analytical tool in the field of input-output(IO)techniques,but the method was found to suffer from one or more of the following problems.The decomposition forms,which are used to measure the contribution of a specific determinant,are not unique due to the existence of a multitude of equivalent forms,irrational due to the weights of different determinants not matching,inexact due to the existence of large interaction terms.In this paper,a decomposition method is derived to overcome these deficiencies,and we prove that the result of this approach is equal to the Shapley value in cooperative games,and so some properties of the method are obtained.Beyond that,the two approaches that have been used predominantly in the literature have been proved to be the approximate solutions of the method.

  10. Multiresolution signal decomposition schemes

    NARCIS (Netherlands)

    J. Goutsias (John); H.J.A.M. Heijmans (Henk)

    1998-01-01

    textabstract[PNA-R9810] Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This report proposes a general axiomatic pyramid decomposition scheme for signal analysis

  11. Multiresolution signal decomposition schemes

    NARCIS (Netherlands)

    Goutsias, J.; Heijmans, H.J.A.M.

    1998-01-01

    [PNA-R9810] Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This report proposes a general axiomatic pyramid decomposition scheme for signal analysis and synthes

  12. Repeatable mechanochemical activation of dynamic covalent bonds in thermoplastic elastomers.

    Science.gov (United States)

    Imato, Keiichi; Kanehara, Takeshi; Nojima, Shiki; Ohishi, Tomoyuki; Higaki, Yuji; Takahara, Atsushi; Otsuka, Hideyuki

    2016-08-18

    Repeated mechanical scission and recombination of dynamic covalent bonds incorporated in segmented polyurethane elastomers are demonstrated by utilizing a diarylbibenzofuranone-based mechanophore and by the design of the segmented polymer structures. The repeated mechanochemical reactions can accompany clear colouration and simultaneous fading.

  13. Development of New Elastomers and Elastic Nanocomposites from Plant Oils

    Science.gov (United States)

    Zhu, Lin; Wool, Richard

    2006-03-01

    Economic and environmental concerns lead to the development of new polymers from renewable resources. In this research, new elastomers were synthesized from plant oil based resins. Acrylated oleic methyl ester (AOME), synthesized from high oleic triglycerides, can readily undergo free radical polymerization and form a linear polymer. To achieve the elastic properties, different strategies have been developed to generate an elastic network and control the crosslink density. The elastomers are reinforced by nanoclays. The intercalated state has a network structure similar to thermoplastic elastomers in which the hard segments aggregate to give ordered crystalline domains. The selected organically modified clay and AOME matrix have similar solubility parameters, therefore intercalation of the monomer/polymer into the clay layers occurs and the nano-scale multilayered structure is stable. In situ intercalation and solution intercalation were used to prepare the elastic nanocomposites. Dramatic improvement in mechanical properties was observed. Changes of tensile strength, strain, Young's modulus and fracture energy were related to the clay concentration. The fracture surface was studied to further understand clay effects on the mechanical properties. Self-Healing of the intercalated nanobeams, thermal stability, biocompatibility and biodegradability of this new elastomer were also explored.

  14. Diffraction from relief gratings on a biomimetic elastomer cast

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero, Raphael A., E-mail: rguerrero@admu.edu.ph [Department of Physics, Ateneo de Manila University, Loyola Heights, Quezon City (Philippines); Aranas, Erika B. [Department of Physics, Ateneo de Manila University, Loyola Heights, Quezon City (Philippines)

    2010-10-12

    Biomimetic optical elements combine the optimized designs of nature with the versatility of materials engineering. We employ a beetle carapace as the template for fabricating relief gratings on an elastomer substrate. Biological surface features are successfully replicated by a direct casting procedure. Far-field diffraction effects are discussed in terms of the Fraunhofer approximation in Fourier space.

  15. Conductive Elastomers for Stretchable Electronics, Sensors and Energy Harvesters

    Directory of Open Access Journals (Sweden)

    Jin-Seo Noh

    2016-04-01

    Full Text Available There have been a wide variety of efforts to develop conductive elastomers that satisfy both mechanical stretchability and electrical conductivity, as a response to growing demands on stretchable and wearable devices. This article reviews the important progress in conductive elastomers made in three application fields of stretchable technology: stretchable electronics, stretchable sensors, and stretchable energy harvesters. Diverse combinations of insulating elastomers and non-stretchable conductive materials have been studied to realize optimal conductive elastomers. It is noted that similar material combinations and similar structures have often been employed in different fields of application. In terms of stretchability, cyclic operation, and overall performance, fields such as stretchable conductors and stretchable strain/pressure sensors have achieved great advancement, whereas other fields like stretchable memories and stretchable thermoelectric energy harvesting are in their infancy. It is worth mentioning that there are still obstacles to overcome for the further progress of stretchable technology in the respective fields, which include the simplification of material combination and device structure, securement of reproducibility and reliability, and the establishment of easy fabrication techniques. Through this review article, both the progress and obstacles associated with the respective stretchable technologies will be understood more clearly.

  16. Super soft silicone elastomers with high dielectric permittivity

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Hvilsted, Søren;

    2015-01-01

    Dielectric elastomers (DEs) have many favourable properties. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young’s modulus and increasing the dielectric permittivity of silicone elasto...

  17. 21 CFR 177.2400 - Perfluorocarbon cured elastomers.

    Science.gov (United States)

    2010-04-01

    ... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use Only... generally recognized as safe (GRAS) in food or food packaging. (2) Substances used in accordance with a... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Perfluorocarbon cured elastomers. 177.2400...

  18. Physical properties of maxillofacial elastomers under conditions of accelerated aging.

    Science.gov (United States)

    Yu, R; Koran, A; Craig, R G

    1980-06-01

    The stability of the physical properties of various commercially available maxillofacial prosthetic materials was evaluated with the use of an accelerated aging chamber. The tensile strength, maximum percent elongation, shear strength, tear energy, and Shore A hardness were determined before and after accelerated aging. Results indicate that silicone 44210, a RTV rubber, is a promising elastomer for maxillofacial application.

  19. Key value propositions in applications for dielectric elastomer actuators

    DEFF Research Database (Denmark)

    Lautrop, Asger; Elena, Maria; Poole, Alan

    2015-01-01

    This work identifies and clarifies tendencies in the performance metrics of dielectric elastomer actuators with respect to different application requirements. The study is based on real proposed applications and therefore not only highlights the properties in which DEA provides value, but also...

  20. Cholesteric elastomers in external mechanical and electric fields

    Science.gov (United States)

    Menzel, Andreas M.; Brand, Helmut R.

    2007-01-01

    In our studies, we focus on the reaction of cholesteric side-chain liquid single-crystal elastomers (SCLSCEs) to static external mechanical and electric fields. By means of linearized continuum theory, different geometries are investigated: The mechanical forces are oriented in a direction either parallel or perpendicular to the axis of the cholesteric helix such that they lead to a compression or dilation of the elastomer. Whereas only a homogeneous deformation of the system is found for the parallel case, perpendicularly applied mechanical forces cause either twisting or untwisting of the cholesteric helix. This predominantly depends on the direction in which the director of the cholesteric phase is anchored at the boundaries of the elastomer, and on the sign of a material parameter that describes how deformations of the elastomer couple to the relative rotations between the elastomer and the director. It is also this material parameter that leads to an anisotropy of the mechanical reaction of the system to compression and dilation, due to the liquid crystalline order. The effect of an external electric field is studied when applied parallel to the helix axis of a perfect electric insulator. Here an instability arises at a threshold value of the field amplitude, where the latter results from a competition between the effects of the external electric field on the one hand and the influences of the boundaries of the system, the cholesteric order, and the coupling between the director and the polymer network on the other hand. The instability is either homogeneous in space in the directions perpendicular to the external electric field and includes homogeneous shearing, or, for certain values of the material parameters, there arise undulations of the elastomer and the director orientation perpendicular to the direction of the external electric field at onset. This describes a qualitatively new phenomenon not observed in cholesteric systems yet, as these undulations

  1. Dielectric elastomer actuators with zero-energy fixity

    Science.gov (United States)

    Rossiter, Jonathan; Takashima, Kazuto; Mukai, Toshiharu

    2010-04-01

    Although dielectric elastomer actuators (DEAs) are becoming more powerful and more versatile, one disadvantage of DEAs is the need to continuously supply electrical power in order to maintain an actuated state. Previous solutions to this problem have involved the construction of a bistable or multi-stable rigid mechanical structure or the addition of some external locking mechanism. Such structures and mechanisms add unwanted complexity and bulk. In this paper we present a dielectric elastomer actuator that exhibits zero-energy fixity. That is, the actuator can be switched into a rigid state where it requires no energy to maintain its actuated shape. This is achieved without any additional mechanical complexity. This actuator relies on changes to the elastic properties of the elastomer material in response to a secondary stimulus. The elastomer can be switched from a rigid glass-like state to a soft rubber-like state as required. We present a dielectric elastomer actuator that utilizes shape-memory polymer properties to achieve such state switching. We call this a dielectric shape memory polymer actuator (DSMPA). In this case control of the elastic properties is achieved through temperature control. When the material is below its glass transition temperature (Tg) it is in its rigid state and dielectric actuation has no effect. When the temperature is elevated above Tg the material becomes soft and elastic, and dielectric actuation can be exploited. We present preliminary results showing that the necessary conditions for this zero-energy fixity property have been achieved. Applications are widespread in the fields of robotics and engineering and include morphing wings that only need energy to change shape and control valves that lock rigidly into position.

  2. Decompositions of manifolds

    CERN Document Server

    Daverman, Robert J

    2007-01-01

    Decomposition theory studies decompositions, or partitions, of manifolds into simple pieces, usually cell-like sets. Since its inception in 1929, the subject has become an important tool in geometric topology. The main goal of the book is to help students interested in geometric topology to bridge the gap between entry-level graduate courses and research at the frontier as well as to demonstrate interrelations of decomposition theory with other parts of geometric topology. With numerous exercises and problems, many of them quite challenging, the book continues to be strongly recommended to eve

  3. ASSESSMENT OF THE INFLUENCE OF RADIATION AND DEFORMATION ON THE ELASTOMER DETERIORATION BY USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Jasminka Bonato

    2017-01-01

    Full Text Available Elastomers belong to the group of polymer materials and they have an important role as technical material in the shipbuilding industry. The radiation crosslinking of elastomers shows significant advantages over chemical crosslinking. It can improve mechanical strength, resistance to chemicals and insulation properties of elastomers. An undesirable side reaction, which can occur during radiation, is the degradation process. This results in cracks breaking, chemical disintegration and reduction of mechanical properties of elastomers. In this paper fuzzy logic is used to estimate the influence of radiation and deformation on the behavior of elastomer samples. A Gaussian model is created according to both the experts' experience and the measuring data. The results of the model are calculated by using the Normalized Roth Mean Square Error (NRMSE and the Roth Mean Square Error (RMSE. The so developed model gives new conceptions, which offer a possibility to improve the application of elastomer materials.

  4. Dominant modal decomposition method

    Science.gov (United States)

    Dombovari, Zoltan

    2017-03-01

    The paper deals with the automatic decomposition of experimental frequency response functions (FRF's) of mechanical structures. The decomposition of FRF's is based on the Green function representation of free vibratory systems. After the determination of the impulse dynamic subspace, the system matrix is formulated and the poles are calculated directly. By means of the corresponding eigenvectors, the contribution of each element of the impulse dynamic subspace is determined and the sufficient decomposition of the corresponding FRF is carried out. With the presented dominant modal decomposition (DMD) method, the mode shapes, the modal participation vectors and the modal scaling factors are identified using the decomposed FRF's. Analytical example is presented along with experimental case studies taken from machine tool industry.

  5. Litter Decomposition Rates, 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set contains decomposition rates for litter of Salicornia pacifica, Distichlis spicata, and Deschampsia cespitosa buried at 7 tidal marsh sites in 2015....

  6. Spectral proper orthogonal decomposition

    CERN Document Server

    Sieber, Moritz; Paschereit, Christian Oliver

    2015-01-01

    The identification of coherent structures from experimental or numerical data is an essential task when conducting research in fluid dynamics. This typically involves the construction of an empirical mode base that appropriately captures the dominant flow structures. The most prominent candidates are the energy-ranked proper orthogonal decomposition (POD) and the frequency ranked Fourier decomposition and dynamic mode decomposition (DMD). However, these methods fail when the relevant coherent structures occur at low energies or at multiple frequencies, which is often the case. To overcome the deficit of these "rigid" approaches, we propose a new method termed Spectral Proper Orthogonal Decomposition (SPOD). It is based on classical POD and it can be applied to spatially and temporally resolved data. The new method involves an additional temporal constraint that enables a clear separation of phenomena that occur at multiple frequencies and energies. SPOD allows for a continuous shifting from the energetically ...

  7. Decomposition of Polynomials

    CERN Document Server

    Blankertz, Raoul

    2011-01-01

    This diploma thesis is concerned with functional decomposition $f = g \\circ h$ of polynomials. First an algorithm is described which computes decompositions in polynomial time. This algorithm was originally proposed by Zippel (1991). A bound for the number of minimal collisions is derived. Finally a proof of a conjecture in von zur Gathen, Giesbrecht & Ziegler (2010) is given, which states a classification for a special class of decomposable polynomials.

  8. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on dipolar copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede;

    2014-01-01

    Dielectric elastomers (DES) are a promising new transducer technology, but high driving voltages limit their current commercial potential. One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric permi......-4-nitrobenzene. Here, a high increase in dielectric permittivity (similar to 70%) was obtained without compromising other favourable DE properties such as elastic modulus, gel fraction, dielectric loss and electrical breakdown strength. © 2014 Elsevier Ltd. All rights reserved....

  9. Development of a structure-property correlation for castable urethane elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Lagasse, R.R.

    1978-01-01

    A significant problem in electronic encapsulation is the poor load bearing performance of existing replacements for Adiprene-MOCA urethane elastomer. In response to this problem, this study defines the structural features that control the viscoelastic properties of the following liquid castable elastomers: Adiprene-MOCA, EN-7, and 3121-S. A review of previous investigations on a related class of materials suggests that viscoelastic properties may be more directly related to the physical structure or morphology of these elastomers, rather than their chemical structure. Accordingly, the morphology of the subject elastomers is characterized by means of electron microscopy and x-ray scattering measurements. These measurements reveal that within each elastomer incompatible chain segments cluster into separate domains, or microphases on a scale of 10 +- 1 nm. On this basis, it is concluded that the two major thermomechanical transitions present in each elastomer can be assigned to separate transitions within the two microphases. The above-ambient transition, which determines the upper use temperature of the elastomer, is specifically assigned to the glass transition of an amorphous microphase. The significance of this structure-property correltion for the liquid castable elastomers is twofold: (1) it permits generalization of mechanical property measurements on existing materials in order to predict their performance in unusual applications and (2) it leads to a rational strategy for developing improved elastomers for new, more demanding applications.

  10. Modified and Unmodified Zinc Oxide as Coagent in Elastomer Compounds

    Directory of Open Access Journals (Sweden)

    Kołodziejczak-Radzimska Agnieszka

    2014-09-01

    Full Text Available The aim of this work was to study the activity of unmodified and modified ZnO in the peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR and ethylene-propylene copolymer (EPM. In the first step, zinc oxide was obtained by emulsion precipitation. Maleic acid was introduced onto the surface of ZnO using an in situ method. The unmodified and modified zinc oxide was characterized using dispersive and morphological analysis, BET surface area analysis, and elemental, spectroscopic and thermal analysis. In the second stage of the research, the ZnO/MA systems were incorporated into the structure of elastomer compounds improving the kinetic and mechanical properties of vulcanizates. The proposed modification method had a favorable effect on the physicochemical properties of the zinc oxide and on the kinetic and mechanical properties of the vulcanizates. This study demonstrated that modification of zinc oxide by maleic acid is a promising technique.

  11. Electrical behaviour of a silicone elastomer under simulated space environment

    Science.gov (United States)

    Roggero, A.; Dantras, E.; Paulmier, T.; Tonon, C.; Balcon, N.; Rejsek-Riba, V.; Dagras, S.; Payan, D.

    2015-04-01

    The electrical behavior of a space-used silicone elastomer was characterized using surface potential decay and dynamic dielectric spectroscopy techniques. In both cases, the dielectric manifestation of the glass transition (dipole orientation) and a charge transport phenomenon were observed. An unexpected linear increase of the surface potential with temperature was observed around Tg in thermally-stimulated potential decay experiments, due to molecular mobility limiting dipolar orientation in one hand, and 3D thermal expansion reducing the materials capacitance in the other hand. At higher temperatures, the charge transport process, believed to be thermally activated electron hopping with an activation energy of about 0.4 eV, was studied with and without the silica and iron oxide fillers present in the commercial material. These fillers were found to play a preponderant role in the low-frequency electrical conductivity of this silicone elastomer, probably through a Maxwell-Wagner-Sillars relaxation phenomenon.

  12. Small, fast, and tough: Shrinking down integrated elastomer transducers

    Science.gov (United States)

    Rosset, Samuel; Shea, Herbert R.

    2016-09-01

    We review recent progress in miniaturized dielectric elastomer actuators (DEAs), sensors, and energy harvesters. We focus primarily on configurations where the large strain, high compliance, stretchability, and high level of integration offered by dielectric elastomer transducers provide significant advantages over other mm or μm-scale transduction technologies. We first present the most active application areas, including: tunable optics, soft robotics, haptics, micro fluidics, biomedical devices, and stretchable sensors. We then discuss the fabrication challenges related to miniaturization, such as thin membrane fabrication, precise patterning of compliant electrodes, and reliable batch fabrication of multilayer devices. We finally address the impact of miniaturization on strain, force, and driving voltage, as well as the important effect of boundary conditions on the performance of mm-scale DEAs.

  13. Electrical Breakdown and Mechanical Ageing in Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin

    the mechanisms behind the electrical breakdown of DEs and the second strategy is to investigate the long-term electromechanical reliability of DEs. In the first strategy, the electrothermal breakdown in polydimethylsiloxane (PDMS) elastomers was modelled in order to evaluate the thermal mechanisms behind...... the electrical failures. From the modelling based on the fitting of experimental data, it showed that the electrothermal breakdown of the PDMS elastomers was strongly influenced by the increase in both relative permittivity and conductivity. In addition to that, a methodology in determining the parameters...... that affect the breakdown strength of the pre-stretched DEs was developed. Breakdown strength was determined for samples with and without volume conservation and was found to depend strongly on the strain and the thickness of the samples. In order for DEs to be fully implementable in commercial products...

  14. Characteristics and utilization of thermoplastic elastomers (TPE)-an overview

    Energy Technology Data Exchange (ETDEWEB)

    Roestamsjah [R and D Center for Applied Chemistry, Indonesian Inst. of Sciences (Indonesia)

    1998-10-01

    The unique feature of thermoplastic elastomer, the combining of processing characteristics of thermoplastics with the physical properties of vulcanized rubber is reviewed. Highlights of TPE and its characteristics is aimed to generate interest in TPE, where SANS technique will be utilized for its characterization. The topics discussed include rubber elasticity, state of aggregation of polymers, microseparation in block copolymer system, application of TPE, and finally some notes in developing interest in TPE and SANS in Indonesia. (author)

  15. Elastomer and resin replicas for sem observation of metallic materials

    OpenAIRE

    Palin-Luc, Thierry; Sellier, E.; D?Errico, F.; Vanhaeren, M.

    2002-01-01

    International audience; The replica technique is often used to study damage evolution at the surface of specimens or industrial components and understand the physicial phenomena responsible for fatigue crack initiation before failure. Replicas are usually made from acetate cellulose film. This paper presents an alternative technique generally used by archaeologists to study lithic use-wear and bone modification. A mold is made from a dental elastomer (silicon based impression material) and a ...

  16. Fouling-release Property of Water-filled Porous Elastomers

    Institute of Scientific and Technical Information of China (English)

    Lai-yong Xie; Fei Hong; Chuan-xin He; Jian-hong Liu; Chi Wu

    2012-01-01

    Since the fouling-releasing ability of silicone elastomers increased as their modulus decreases,we designed and prepared composites with embedded tiny NaCl crytals that were soluble after their immersion in water,resulting in water-filled porous elastomers.The scanning electron microscope images confirmed such a designed water-filling porous structure.The existence of many micro-drops of water in these specially designed elastomers decreased the shear storage modulus and increased the loss factors.The decrease of shear modulus plays a leading role here and is directly related to a lower critical peeling-off stress of a pseudo-barnacle on them.Therefore,such a novel preparation with cheap salts instead of an expensive silicone provides a better way to make fouling-release paints with a lower modulus,a lower critical peeling-off stress and a better fouling-release property without a significant decrease of the cross-linking density.

  17. Energy scavenging strain absorber: application to kinetic dielectric elastomer generator

    Science.gov (United States)

    Jean-Mistral, C.; Beaune, M.; Vu-Cong, T.; Sylvestre, A.

    2014-03-01

    Dielectric elastomer generators (DEGs) are light, compliant, silent energy scavengers. They can easily be incorporated into clothing where they could scavenge energy from the human kinetic movements for biomedical applications. Nevertheless, scavengers based on dielectric elastomers are soft electrostatic generators requiring a high voltage source to polarize them and high external strain, which constitutes the two major disadvantages of these transducers. We propose here a complete structure made up of a strain absorber, a DEG and a simple electronic power circuit. This new structure looks like a patch, can be attached on human's wear and located on the chest, knee, elbow… Our original strain absorber, inspired from a sailing boat winch, is able to heighten the external available strain with a minimal factor of 2. The DEG is made of silicone Danfoss Polypower and it has a total area of 6cm per 2.5cm sustaining a maximal strain of 50% at 1Hz. A complete electromechanical analytical model was developed for the DEG associated to this strain absorber. With a poling voltage of 800V, a scavenged energy of 0.57mJ per cycle is achieved with our complete structure. The performance of the DEG can further be improved by enhancing the imposed strain, by designing a stack structure, by using a dielectric elastomer with high dielectric permittivity.

  18. Anisotropic Elastic Properties of Muscle-like Nematic Elastomers

    Science.gov (United States)

    Ratna, Banahalii; Thomseniii, Donald L.; Shenoy, Devanand; Srinivasan, Amritha; Keller, Patrick

    2001-03-01

    De Gennes suggested in 1997 that the liquid crystal elastomers are an excellent framework to mimic muscular action. We have prepared anisotropic freestanding films of nematic elastomers from laterally attached side-chain polymers that show muscle-like mechanical properties. The orientational order of the liquid crystal side groups imposes a conformational anisotropy in the polymer backbone. When the order parameter drops at the nematic-isotropic phase transition, there is a concomitant loss of order in the backbone which results in a contraction of the film in the direction of the director orientation. Dynamic mechanical data along directions parallel and perpendicular to the optic axis, show anisotropic stress-strain behavior. The film exhibits soft elasticity when strained in the perpendicular direction when the liquid crystal mesogens reorient without appreciable stress build up. Thermostrictive studies in the parallel direction show 40constriction at the nematic-isotropic phase transition. Isometric studies show that the elastic energy stored is purely entropic in origin and the elastomer acts like a spring with unusually large spring constant at the NI transition. The maximum stress measured is 300kPa. A strain rate of 5s-1 is estimated from shear relaxation studies.

  19. Statistical analysis of magnetically soft particles in magnetorheological elastomers

    Science.gov (United States)

    Gundermann, T.; Cremer, P.; Löwen, H.; Menzel, A. M.; Odenbach, S.

    2017-04-01

    The physical properties of magnetorheological elastomers (MRE) are a complex issue and can be influenced and controlled in many ways, e.g. by applying a magnetic field, by external mechanical stimuli, or by an electric potential. In general, the response of MRE materials to these stimuli is crucially dependent on the distribution of the magnetic particles inside the elastomer. Specific knowledge of the interactions between particles or particle clusters is of high relevance for understanding the macroscopic rheological properties and provides an important input for theoretical calculations. In order to gain a better insight into the correlation between the macroscopic effects and microstructure and to generate a database for theoretical analysis, x-ray micro-computed tomography (X-μCT) investigations as a base for a statistical analysis of the particle configurations were carried out. Different MREs with quantities of 2–15 wt% (0.27–2.3 vol%) of iron powder and different allocations of the particles inside the matrix were prepared. The X-μCT results were edited by an image processing software regarding the geometrical properties of the particles with and without the influence of an external magnetic field. Pair correlation functions for the positions of the particles inside the elastomer were calculated to statistically characterize the distributions of the particles in the samples.

  20. Decomposing Nekrasov Decomposition

    CERN Document Server

    Morozov, A

    2015-01-01

    AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions - this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition - into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.

  1. Decomposing Nekrasov decomposition

    Science.gov (United States)

    Morozov, A.; Zenkevich, Y.

    2016-02-01

    AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions — this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition — into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.

  2. Symmetric tensor decomposition

    CERN Document Server

    Brachat, Jerome; Mourrain, Bernard; Tsigaridas, Elias

    2009-01-01

    We present an algorithm for decomposing a symmetric tensor, of dimension n and order d as a sum of rank-1 symmetric tensors, extending the algorithm of Sylvester devised in 1886 for binary forms. We recall the correspondence between the decomposition of a homogeneous polynomial in n variables of total degree d as a sum of powers of linear forms (Waring's problem), incidence properties on secant varieties of the Veronese Variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester's approach from the dual point of view. Exploiting this duality, we propose necessary and sufficient conditions for the existence of such a decomposition of a given rank, using the properties of Hankel (and quasi-Hankel) matrices, derived from multivariate polynomials and normal form computations. This leads to the resolution of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on th...

  3. Mueller matrix differential decomposition.

    Science.gov (United States)

    Ortega-Quijano, Noé; Arce-Diego, José Luis

    2011-05-15

    We present a Mueller matrix decomposition based on the differential formulation of the Mueller calculus. The differential Mueller matrix is obtained from the macroscopic matrix through an eigenanalysis. It is subsequently resolved into the complete set of 16 differential matrices that correspond to the basic types of optical behavior for depolarizing anisotropic media. The method is successfully applied to the polarimetric analysis of several samples. The differential parameters enable one to perform an exhaustive characterization of anisotropy and depolarization. This decomposition is particularly appropriate for studying media in which several polarization effects take place simultaneously. © 2011 Optical Society of America

  4. Decomposition of residue currents

    OpenAIRE

    Andersson, Mats; Wulcan, Elizabeth

    2007-01-01

    Given a submodule $J\\subset \\mathcal O_0^{\\oplus r}$ and a free resolution of $J$ one can define a certain vector valued residue current whose annihilator is $J$. We make a decomposition of the current with respect to Ass$(J)$ that correspond to a primary decomposition of $J$. As a tool we introduce a class of currents that includes usual residue and principal value currents; in particular these currents admit a certain type of restriction to analytic varieties and more generally to construct...

  5. Iterative and variational homogenization methods for filled elastomers

    Science.gov (United States)

    Goudarzi, Taha

    Elastomeric composites have increasingly proved invaluable in commercial technological applications due to their unique mechanical properties, especially their ability to undergo large reversible deformation in response to a variety of stimuli (e.g., mechanical forces, electric and magnetic fields, changes in temperature). Modern advances in organic materials science have revealed that elastomeric composites hold also tremendous potential to enable new high-end technologies, especially as the next generation of sensors and actuators featured by their low cost together with their biocompatibility, and processability into arbitrary shapes. This potential calls for an in-depth investigation of the macroscopic mechanical/physical behavior of elastomeric composites directly in terms of their microscopic behavior with the objective of creating the knowledge base needed to guide their bottom-up design. The purpose of this thesis is to generate a mathematical framework to describe, explain, and predict the macroscopic nonlinear elastic behavior of filled elastomers, arguably the most prominent class of elastomeric composites, directly in terms of the behavior of their constituents --- i.e., the elastomeric matrix and the filler particles --- and their microstructure --- i.e., the content, size, shape, and spatial distribution of the filler particles. This will be accomplished via a combination of novel iterative and variational homogenization techniques capable of accounting for interphasial phenomena and finite deformations. Exact and approximate analytical solutions for the fundamental nonlinear elastic response of dilute suspensions of rigid spherical particles (either firmly bonded or bonded through finite size interphases) in Gaussian rubber are first generated. These results are in turn utilized to construct approximate solutions for the nonlinear elastic response of non-Gaussian elastomers filled with a random distribution of rigid particles (again, either firmly

  6. The electrical breakdown strength of pre-stretched elastomers, with and without sample volume conservation

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed;

    2015-01-01

    strength of polydimethylsiloxane (PDMS) elastomers. Breakdown strength was determined for samples with and without volume conservation and was found to depend strongly on the stretch ratio and the thickness of thesamples. PDMS elastomers are shown to increase breakdown strength by a factor of ∼3 when...

  7. Novel encapsulation technique for incorporation of high permittivity fillers into silicone elastomers

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Hvilsted, Søren; Skov, Anne Ladegaard

    2014-01-01

    as for the traditionally applied thermoplastic encapsulation. The properties of the elastomers are investigated as function of the filler content and type. The dielectric permittivity, dielectric loss, conductivity, storage modulus as well as viscous loss are compared to elastomers with the same amounts of high...

  8. Glycerol as high-permittivity liquid filler in dielectric silicone elastomers

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Yu, Liyun; Gerhard, R.

    2016-01-01

    A recently reported novel class of elastomers was tested with respect to its dielectric properties. The new elastomer materialis based on a commercially available poly(dimethylsiloxane) composition, which has been modified by embedding glycerol droplets intoits matrix. The approach has two major ......, and the applicability ofthe models is discussed. VC 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44153....

  9. Localised strain sensing of dielectric elastomers in a stretchable soft-touch musical keyboard

    Science.gov (United States)

    Xu, Daniel; Tairych, Andreas; Anderson, Iain A.

    2015-04-01

    We present a new sensing method that can measure the strain at different locations in a dielectric elastomer. The method uses multiple sensing frequencies to target different regions of the same dielectric elastomer to simultaneously detect position and pressure using only a single pair of connections. The dielectric elastomer is modelled as an RC transmission line and its internal voltage and current distribution used to determine localised capacitance changes resulting from contact and pressure. This sensing method greatly simplifies high degree of freedom systems and does not require any modifications to the dielectric elastomer or sensing hardware. It is demonstrated on a multi-touch musical keyboard made from a single low cost carbon-based dielectric elastomer with 4 distinct musical tones mapped along a length of 0.1m. Loudness was controlled by the amount of pressure applied to each of these 4 positions.

  10. Magnetic properties of hybrid elastomers with magnetically hard fillers: rotation of particles

    Science.gov (United States)

    Stepanov, G. V.; Borin, D. Yu; Bakhtiiarov, A. V.; Storozhenko, P. A.

    2017-03-01

    Hybrid magnetic elastomers belonging to the family of magnetorheological elastomers contain magnetically hard components and are of the utmost interest for the development of semiactive and active damping devices as well as actuators and sensors. The processes of magnetizing of such elastomers are accompanied by structural rearrangements inside the material. When magnetized, the elastomer gains its own magnetic moment resulting in changes of its magneto-mechanical properties, which remain permanent, even in the absence of external magnetic fields. Influenced by the magnetic field, magnetized particles move inside the matrix forming chain-like structures. In addition, the magnetically hard particles can rotate to align their magnetic moments with the new direction of the external field. Such an elastomer cannot be demagnetized by the application of a reverse field.

  11. Dielectric elastomers, with very high dielectric permittivity, based on silicone and ionic interpenetrating networks

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Hvilsted, Søren;

    2015-01-01

    Dielectric elastomers (DEs), which represent an emerging actuator and generator technology, admittedly have many favourable properties, but their high driving voltages are one of the main obstacles to commercialisation. One way to reduce driving voltage is by increasing the ratio between dielectr...... as well as relatively high breakdown strength. All IPNs have higher dielectric losses than pure silicone elastomers, but when accounting for this factor, IPNs still exhibit satisfactory performance improvements....... is demonstrated herein, and a number of many and important parameters, such as dielectric permittivity/loss, viscoelastic properties and dielectric breakdown strength, are investigated. Ionic and silicone elastomer IPNs are promising prospects for dielectric elastomer actuators, since very high permittivities......Dielectric elastomers (DEs), which represent an emerging actuator and generator technology, admittedly have many favourable properties, but their high driving voltages are one of the main obstacles to commercialisation. One way to reduce driving voltage is by increasing the ratio between dielectric...

  12. Tree decompositions with small cost

    NARCIS (Netherlands)

    Bodlaender, H.L.; Fomin, F.V.

    2002-01-01

    The f-cost of a tree decomposition ({Xi | i e I}, T = (I;F)) for a function f : N -> R+ is defined as EieI f(|Xi|). This measure associates with the running time or memory use of some algorithms that use the tree decomposition. In this paper we investigate the problem to find tree decompositions

  13. Tough Block Copolymer Organogels and Elastomers as Short Fiber Composites

    Science.gov (United States)

    Kramer, Edward J.

    2012-02-01

    The origins of the exceptional toughness and elastomeric properties of gels and elastomers from block copolymers with semicrystalline syndiotactic polypropylene blocks will be discussed. Using synchrotron X-radiation small angle (SAXS) and wide angle X-ray scattering (WAXS) experiments were simultaneously performed during step cycle tensile deformation of these elastomers and gels. From these results the toughness can be attributed to the formation, orientation and elongation of the crystalline fibrils along the tensile direction. The true stress and true strain ɛH during each cycle were recorded, including the true strain at zero load ɛH,p after each cycle that resulted from the plastic deformation of the sPP crystals in the gel or elastomer. The initial Young's modulus Einit and maximum tangent modulus Emax in each cycle undergo dramatic changes as a function of ɛH,p, with Einit decreasing for ɛH,p 100 to 1000 at the highest maximum (nominal) strain. Based on SAXS patterns from the deformed and relaxed gels, as well as on previous results on deformation of semicrystalline random copolymers by Strobl and coworkers, we propose that the initial decrease in Einit and increase in Emax with ɛH,p are due to a breakup of the network of the original sPP crystal lamellae and the conversion of the sPP lamellae into fibrils whose aspect ratio increases with further plastic deformation, respectively. The gel elastic properties can be understood quantitatively as those of a short fiber composite with a highly deformable matrix. At zero stress the random copolymer midblock chains that connect the fibrils cause these to make all angles to the tensile axis (low Einit), while at the maximum strain the stiff, crystalline sPP fibrils align with the tensile axis producing a strong, relatively stiff gel. The evolution of the crystalline structure during deformation is confirmed by WAXS and FTIR measurements.

  14. Effect of mechanical parameters on dielectric elastomer minimum energy structures

    Science.gov (United States)

    Shintake, Jun; Rosset, Samuel; Floreano, Dario; Shea, Herbert R.

    2013-04-01

    Soft robotics may provide many advantages compared to traditional robotics approaches based on rigid materials, such as intrinsically safe physical human-robot interaction, efficient/stable locomotion, adaptive morphology, etc. The objective of this study is to develop a compliant structural actuator for soft a soft robot using dielectric elastomer minimum energy structures (DEMES). DEMES consist of a pre-stretched dielectric elastomer actuator (DEA) bonded to an initially planar flexible frame, which deforms into an out-of-plane shape which allows for large actuation stroke. Our initial goal is a one-dimensional bending actuator with 90 degree stroke. Along with frame shape, the actuation performance of DEMES depends on mechanical parameters such as thickness of the materials and pre-stretch of the elastomer membrane. We report here the characterization results on the effect of mechanical parameters on the actuator performance. The tested devices use a cm-size flexible-PCB (polyimide, 50 μm thickness) as the frame-material. For the DEA, PDMS (approximately 50 μm thickness) and carbon black mixed with silicone were used as membrane and electrode, respectively. The actuators were characterized by measuring the tip angle and the blocking force as functions of applied voltage. Different pre-stretch methods (uniaxial, biaxial and their ratio), and frame geometries (rectangular with different width, triangular and circular) were used. In order to compare actuators with different geometries, the same electrode area was used in all the devices. The results showed that the initial tip angle scales inversely with the frame width, the actuation stroke and the blocking force are inversely related (leading to an interesting design trade-off), using anisotropic pre-stretch increased the actuation stroke and the initial bending angle, and the circular frame shape exhibited the highest actuation performance.

  15. Nanomechanical probing of thin-film dielectric elastomer transducers

    Science.gov (United States)

    Osmani, Bekim; Seifi, Saman; Park, Harold S.; Leung, Vanessa; Töpper, Tino; Müller, Bert

    2017-08-01

    Dielectric elastomer transducers (DETs) have attracted interest as generators, actuators, sensors, and even as self-sensing actuators for applications in medicine, soft robotics, and microfluidics. Their performance crucially depends on the elastic properties of the electrode-elastomer sandwich structure. The compressive displacement of a single-layer DET can be easily measured using atomic force microscopy (AFM) in the contact mode. While polymers used as dielectric elastomers are known to exhibit significant mechanical stiffening for large strains, their mechanical properties when subjected to voltages are not well understood. To examine this effect, we measured the depths of 400 nanoindentations as a function of the applied electric field using a spherical AFM probe with a radius of (522 ± 4) nm. Employing a field as low as 20 V/μm, the indentation depths increased by 42% at a load of 100 nN with respect to the field-free condition, implying an electromechanically driven elastic softening of the DET. This at-a-glance surprising experimental result agrees with related nonlinear, dynamic finite element model simulations. Furthermore, the pull-off forces rose from (23.0 ± 0.4) to (49.0 ± 0.7) nN implying a nanoindentation imprint after unloading. This embossing effect is explained by the remaining charges at the indentation site. The root-mean-square roughness of the Au electrode raised by 11% upon increasing the field from zero to 12 V/μm, demonstrating that the electrode's morphology change is an undervalued factor in the fabrication of DET structures.

  16. Elastomer liners for geothermal tubulars Y267 EPDM Liner Program:

    Energy Technology Data Exchange (ETDEWEB)

    Hirasuna, A.R.; Davis, D.L.; Flickinger, J.E.; Stephens, C.A.

    1987-12-01

    The elastomer, Y267 EPDM, has been identified as a hydrothermally stable material which can operate at temperatures in excess of 320/sup 0/C. The goal of the Y267 Liner Program was to demonstrate the feasibility of using this material as a liner for mild steel tubulars to prevent or mitigate corrosion. If successful, the usage of EPDM lined pipe by the geothermal community may have a significant impact on operating costs and serve as a viable alternative to the use of alloyed tubulars. Tooling procedures were developed under this program to mold a 0.64 cm (0.25'') thick Y267 EPDM liner into a tubular test section 61 cm (2') in length and 19.1 cm (7.5'') in diameter (ID). A successful effort was made to identify a potential coupling agent to be used to bond the elastomer to the steel tubular wall. This agent was found to withstand the processing conditions associated with curing the elastomer at 288/sup 0/C and to retain a significant level of adhesive strength following hydrothermal testing in a synthetic brine at 260/sup 0/C for a period of 166 hours. Bonding tests were conducted on specimens of mild carbon steel and several alloys including Hastelloy C-276. An objective of the program was to field test the lined section of pipe mentioned above at a geothermal facility in the Imperial Valley. Though a test was conducted, problems encountered during the lining operation precluded an encouraging outcome. The results of the field demonstration were inconclusive. 6 refs., 13 figs., 13 tabs

  17. Toughening wood/polypropylene composites with polyethylene octene elastomer (POE)

    Institute of Scientific and Technical Information of China (English)

    JIANG Feng; QIN Te-fu

    2006-01-01

    Polyethylene octene elastomer (POE) as impact modifier was incorporated into wood/polypropylene composites (WPC) to enhance the impact strength of the composite. Two extruding routes, i.e. direct extruding route and two-stage extruding route, were adopted to produce Wood Powder/PP/POE ternary composites. The mechanical and dynamic mechanical analysis (DMA) properties of the composites were investigated. The results showed that the addition of POE can increase the impact strength of the composites, and the composites produced via two-stage extruding route showed superior mechanical properties. The results of the DMA confirmed the mechanical tests.

  18. A mesoscopic network model for permanent set in crosslinked elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Weisgraber, T H; Gee, R H; Maiti, A; Clague, D S; Chinn, S; Maxwell, R S

    2009-01-29

    A mesoscopic computational model for polymer networks and composites is developed as a coarse-grained representation of the composite microstructure. Unlike more complex molecular dynamics simulations, the model only considers the effects of crosslinks on mechanical behavior. The elastic modulus, which depends only on the crosslink density and parameters in the bond potential, is consistent with rubber elasticity theory, and the network response satisfies the independent network hypothesis of Tobolsky. The model, when applied to a commercial filled silicone elastomer, quantitatively reproduces the experimental permanent set and stress-strain response due to changes in the crosslinked network from irradiation.

  19. A modelling approach for the heterogeneous oxidation of elastomers

    Science.gov (United States)

    Herzig, A.; Sekerakova, L.; Johlitz, M.; Lion, A.

    2017-04-01

    The influence of oxygen on elastomers, known as oxidation, is one of the most important ageing processes and becomes more and more important for nowadays applications. The interaction with thermal effects as well as antioxidants makes oxidation of polymers a complex process. Based on the polymer chosen and environmental conditions, the ageing processes may behave completely different. In a lot of cases the influence of oxygen is limited to the surface layer of the samples, commonly referred to as diffusion-limited oxidation. For the lifetime prediction of elastomer components, it is essential to have detailed knowledge about the absorption and diffusion behaviour of oxygen molecules during thermo-oxidative ageing and how they react with the elastomer. Experimental investigations on industrially used elastomeric materials are executed in order to develop and fit models, which shall be capable of predicting the permeation and consumption of oxygen as well as changes in the mechanical properties. The latter are of prime importance for technical applications of rubber components. Oxidation does not occur homogeneously over the entire elastomeric component. Hence, material models which include ageing effects have to be amplified in order to consider heterogeneous ageing, which highly depends on the ageing temperature. The influence of elevated temperatures upon accelerated ageing has to be critically analysed, and influences on the permeation and diffusion coefficient have to be taken into account. This work presents phenomenological models which describe the oxygen uptake and the diffusion into elastomers based on an improved understanding of ongoing chemical processes and diffusion limiting modifications. On the one side, oxygen uptake is modelled by means of Henry's law in which solubility is a function of the temperature as well as the ageing progress. The latter is an irreversible process and described by an inner differential evolution equation. On the other side

  20. A modelling approach for the heterogeneous oxidation of elastomers

    Science.gov (United States)

    Herzig, A.; Sekerakova, L.; Johlitz, M.; Lion, A.

    2017-09-01

    The influence of oxygen on elastomers, known as oxidation, is one of the most important ageing processes and becomes more and more important for nowadays applications. The interaction with thermal effects as well as antioxidants makes oxidation of polymers a complex process. Based on the polymer chosen and environmental conditions, the ageing processes may behave completely different. In a lot of cases the influence of oxygen is limited to the surface layer of the samples, commonly referred to as diffusion-limited oxidation. For the lifetime prediction of elastomer components, it is essential to have detailed knowledge about the absorption and diffusion behaviour of oxygen molecules during thermo-oxidative ageing and how they react with the elastomer. Experimental investigations on industrially used elastomeric materials are executed in order to develop and fit models, which shall be capable of predicting the permeation and consumption of oxygen as well as changes in the mechanical properties. The latter are of prime importance for technical applications of rubber components. Oxidation does not occur homogeneously over the entire elastomeric component. Hence, material models which include ageing effects have to be amplified in order to consider heterogeneous ageing, which highly depends on the ageing temperature. The influence of elevated temperatures upon accelerated ageing has to be critically analysed, and influences on the permeation and diffusion coefficient have to be taken into account. This work presents phenomenological models which describe the oxygen uptake and the diffusion into elastomers based on an improved understanding of ongoing chemical processes and diffusion limiting modifications. On the one side, oxygen uptake is modelled by means of Henry's law in which solubility is a function of the temperature as well as the ageing progress. The latter is an irreversible process and described by an inner differential evolution equation. On the other side

  1. Thermal Oxidation Resistance of Rare Earth-Containing Composite Elastomer

    Institute of Scientific and Technical Information of China (English)

    邱关明; 张明; 周兰香; 中北里志; 井上真一; 冈本弘

    2001-01-01

    The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.

  2. Frequency-domain trade-offs for dielectric elastomer generators

    Science.gov (United States)

    Zanini, Plinio; Rossiter, Jonathan M.; Homer, Martin

    2017-04-01

    Dielectric Elastomer Generators (DEGs) are an emerging energy harvesting technology based on a the cyclic stretching of a rubber-like membrane. However, most design processes do not take into account different excitation frequencies; thus limits the applicability studies since in real-world situations forcing frequency is not often constant. Through the use of a practical design scenario we use modeling and simulation to determine the material frequency response and, hence, carefully investigate the excitation frequencies that maximize the performance (power output, efficiency) of DEGs and the factors that influence it.

  3. Reversible large amplitude planar extension of soft elastomers

    DEFF Research Database (Denmark)

    Jensen, Mette Krog; Skov, Anne Ladegaard; Rasmussen, Henrik K.

    The newly developed planar elongation fixture, designed as an add-on to the filament stretch rheometer, is used to measure reversible large amplitude planar elongation on soft elastomers. The concept of the new fixture is to elongate an annulus by keeping the perimeter constant. The deformation....... In particular it is observed that this new approximation reproduces the order of magnitude of the deformation on the cylindrical probe. In fact it is demonstrated that the deviation from an ideal planar extension of the cylindrical probe is highly sensitive towards the choice of strain tensor. When analyzing...

  4. Band structures in the nematic elastomers phononic crystals

    Science.gov (United States)

    Yang, Shuai; Liu, Ying; Liang, Tianshu

    2017-02-01

    As one kind of new intelligent materials, nematic elastomers (NEs) represent an exciting physical system that combines the local orientational symmetry breaking and the entropic rubber elasticity, producing a number of unique physical phenomena. In this paper, the potential application of NEs in the band tuning is explored. The band structures in two kinds of NE phononic crystals (PCs) are investigated. Through changing NE intrinsic parameters, the influence of the porosity, director rotation and relaxation on the band structures in NE PCs are analyzed. This work is a meaningful try for application of NEs in acoustic field and proposes a new intelligent strategy in band turning.

  5. Formation of free radicals during mechanical degradation of elastomers.

    Science.gov (United States)

    Devries, K. L.; Williams, M. L.; Roylance, D. K.

    1971-01-01

    Solithane 113 (an amorphous polyurethane elastomer) was prepared by curing equal proportions of castor oil and trifunctional isocyanate for 6 hr 45 min at 170 F. The sample material was mechanically degraded by grinding below and above its glass transition point at liquid nitrogen and room temperatures. The EPR spectra of ground samples were recorded and the number of free radicals were determined by a computer double-integration of the recorded spectra and by a comparison of the values with those of a standard material. Curves of EPR spectra suggest that different molecular mechanisms may be active in degradation of this material below and above its glass transition temperature.

  6. Quasi-static axisymmetric eversion hemispherical domes made of elastomers

    Science.gov (United States)

    Kabrits, Sergey A.; Kolpak, Eugeny P.

    2016-06-01

    The paper considers numerical solution for the problem of quasi-static axisymmetric eversion of a spherical shell (hemisphere) under action of external pressure. Results based on the general nonlinear theory of shells made of elastomers, proposed by K. F. Chernykh. It is used two models of shells based on the hypotheses of the Kirchhoff and Timoshenko, modified K.F. Chernykh for the case of hyperelastic rubber-like material. The article presents diagrams of equilibrium states of eversion hemispheres for both models as well as the shape of the shell at different points in the diagram.

  7. Decomposition of semigroup algebras

    CERN Document Server

    Boehm, Janko; Nitsche, Max Joachim

    2011-01-01

    Let A \\subseteq B be cancellative abelian semigroups, and let R be an integral domain. We show that the semigroup ring R[B] can be decomposed, as an R[A]-module, into a direct sum of R[A]-submodules of the quotient ring of R[A]. In the case of a finite extension of positive affine semigroup rings we obtain an algorithm computing the decomposition. When R[A] is a polynomial ring over a field we explain how to compute many ring-theoretic properties of R[B] in terms of this decomposition. In particular we obtain a fast algorithm to compute the Castelnuovo-Mumford regularity of homogeneous semigroup rings. As an application we confirm the Eisenbud-Goto conjecture in a range of new cases. Our algorithms are implemented in the Macaulay2 package MonomialAlgebras.

  8. Energy harvesting by dielectric elastomer generator and self-priming circuit: verification by radio transmission

    Science.gov (United States)

    Ikegame, Toru; Takagi, Kentaro; Ito, Takamasa; Kojima, Hiroki; Yoshikawa, Hitoshi

    2017-04-01

    This paper discusses energy harvesting and its application using dielectric elastomer and self-priming circuit. With the self-priming circuit attached to the dielectric elastomer, the generated voltage increases exponentially according to the variation of the capacitance caused by applied deformation to the elastomer. Two-stage self-priming circuit is selected for optimal harvesting. The self-priming harvesting technique is able to increase the voltage of the dielectric elastomer from a few volts to kV order, however in this paper the generated voltage is limited up to 1kV in order to avoid the destruction of the dielectric elastomer. The ability of energy harvesting using dielectric elastomer and self-priming circuit is confirmed by both numerical simulation and experiments. In the experiment, the dielectric elastomer is deformed by an electric motor, and the harvested energy is stored to a charging capacitor through Zener diodes. A low-power microcomputer which has a radio transmitter is connected to the charging capacitor for the application example. The experimental results show that the temperature data can be transmitted only by the harvested energy. In addition, the efficiency of the energy harvesting is calculated by comparing the generated power with the charged power.

  9. Wrinkling of a thin film on a nematic liquid-crystal elastomer

    Science.gov (United States)

    Soni, Harsh; Pelcovits, Robert A.; Powers, Thomas R.

    2016-07-01

    Wrinkles commonly develop in a thin film deposited on a soft elastomer substrate when the film is subject to compression. Motivated by recent experiments [Agrawal et al., Soft Matter 8, 7138 (2012)], 10.1039/c2sm25734c that show how wrinkle morphology can be controlled by using a nematic elastomer substrate, we develop the theory of small-amplitude wrinkles of an isotropic film atop a nematic elastomer. The directors of the nematic elastomer are initially uniform. For uniaxial compression of the film along the direction perpendicular to the elastomer directors, the system behaves as a compressed film on an isotropic substrate. When the uniaxial compression is along the direction of nematic order, we find that the soft elasticity characteristic of liquid-crystal elastomers leads to a critical stress for wrinkling which is very small compared to the case of an isotropic substrate. We also determine the wavelength of the wrinkles at the critical stress and show how the critical stress and wavelength depend on substrate depth and the anisotropy of the polymer chains in the nematic elastomer.

  10. Wrinkling of a thin film on a nematic liquid-crystal elastomer.

    Science.gov (United States)

    Soni, Harsh; Pelcovits, Robert A; Powers, Thomas R

    2016-07-01

    Wrinkles commonly develop in a thin film deposited on a soft elastomer substrate when the film is subject to compression. Motivated by recent experiments [Agrawal et al., Soft Matter 8, 7138 (2012)]1744-683X10.1039/c2sm25734c that show how wrinkle morphology can be controlled by using a nematic elastomer substrate, we develop the theory of small-amplitude wrinkles of an isotropic film atop a nematic elastomer. The directors of the nematic elastomer are initially uniform. For uniaxial compression of the film along the direction perpendicular to the elastomer directors, the system behaves as a compressed film on an isotropic substrate. When the uniaxial compression is along the direction of nematic order, we find that the soft elasticity characteristic of liquid-crystal elastomers leads to a critical stress for wrinkling which is very small compared to the case of an isotropic substrate. We also determine the wavelength of the wrinkles at the critical stress and show how the critical stress and wavelength depend on substrate depth and the anisotropy of the polymer chains in the nematic elastomer.

  11. Interdiffusion and Spinodal Decomposition in Electrically Conducting Polymer Blends

    Directory of Open Access Journals (Sweden)

    Antti Takala

    2015-08-01

    Full Text Available The impact of phase morphology in electrically conducting polymer composites has become essential for the efficiency of the various functional applications, in which the continuity of the electroactive paths in multicomponent systems is essential. For instance in bulk heterojunction organic solar cells, where the light-induced electron transfer through photon absorption creating excitons (electron-hole pairs, the control of diffusion of the spatially localized excitons and their dissociation at the interface and the effective collection of holes and electrons, all depend on the surface area, domain sizes, and connectivity in these organic semiconductor blends. We have used a model semiconductor polymer blend with defined miscibility to investigate the phase separation kinetics and the formation of connected pathways. Temperature jump experiments were applied from a miscible region of semiconducting poly(alkylthiophene (PAT blends with ethylenevinylacetate-elastomers (EVA and the kinetics at the early stages of phase separation were evaluated in order to establish bicontinuous phase morphology via spinodal decomposition. The diffusion in the blend was followed by two methods: first during a miscible phase separating into two phases: from the measurement of the spinodal decomposition. Secondly the diffusion was measured by monitoring the interdiffusion of PAT film into the EVA film at elected temperatures and eventually compared the temperature dependent diffusion characteristics. With this first quantitative evaluation of the spinodal decomposition as well as the interdiffusion in conducting polymer blends, we show that a systematic control of the phase separation kinetics in a polymer blend with one of the components being electrically conducting polymer can be used to optimize the morphology.

  12. Design of Elastomer Structure to Facilitate Incorporation of Expanded Graphite in Silicones Without Compromising Electromechanical Integrity

    DEFF Research Database (Denmark)

    Hassouneh, Suzan Sager; Daugaard, Anders Egede; Skov, Anne Ladegaard

    2015-01-01

    The development of elastomer materials with a high dielectric permittivity has attracted increased interest over the past years due to their use in, for example, dielectric elastomers. For this particular use, both the electrically insulating properties - as well as the mechanical properties...... of the elastomer - have to be tightly controlled in order not to destroy favorable elastic properties by the addition of particles. This study focuses on improving the electromechanical properties of an enhanced PDMS matrix with expanded graphite (EG) as filler. The PDMS matrix is crosslinked by means of an 8...

  13. Voltage-induced pinnacle response in the dynamics of dielectric elastomers

    Science.gov (United States)

    Li, Bo; Zhang, Junshi; Chen, Hualing; Li, Dichen

    2016-05-01

    A dielectric elastomer is capable of large deformation under alternating electromechanical excitation. In this paper, several dynamic properties of a dielectric elastomer are investigated, in particular the effect of strain stiffening. A theoretical model is established that shows that the bias voltage affects the amplitude and the response waveform during vibration, a curve with the shape of a pinnacle. We also describe the underlying physical mechanism by considering the molecular chain length and cross-linking density of the material. A phase portrait is presented that reveals the transitional behavior of the dielectric elastomer as it switches between soft and stiffened vibration states.

  14. Self-healing of optical functions by molecular metabolism in a swollen elastomer

    Directory of Open Access Journals (Sweden)

    Mitsunori Saito

    2012-12-01

    Full Text Available Optical functions of organic dyes, e.g., fluorescence or photochromism, tend to degrade by light irradiation, which causes a short lifetime of photonic devices. Self-healing of optical functions is attainable by metabolizing bleached molecules with nonirradiated ones. A polydimethylsiloxane elastomer provides a useful matrix for dye molecules, since its flexible structure with nano-sized intermolecular spaces allows dye diffusion from a reservoir to an operation region. Swelling the elastomer with a suitable solvent promotes both dissolution and diffusion of dye molecules. This self-healing function was demonstrated by an experiment in which a photochromic elastomer exhibited improved durability against a repeated coloring-decoloring process.

  15. A simple method for reducing inevitable dielectric loss in high-permittivity dielectric elastomers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Mazurek, Piotr Stanislaw;

    2016-01-01

    Commercial viability of dielectric elastomers (DEs) is currently limited by a few obstacles, including high driving voltages (in the kV range). Driving voltage can be lowered by either decreasing the Young's modulus or increasing the dielectric permittivity of silicone elastomers, or a combinatio...... also decreased the dielectric losses of an elastomer containing dielectric permittivity-enhancing TiO2 fillers. Commercially available chloropropyl-functional silicone oil thus constitutes a facile method for improved silicone DEs, with very low dielectric losses....

  16. Finite element modelling of dielectric elastomer minimum energy structures

    Science.gov (United States)

    O'Brien, Benjamin; McKay, Thomas; Calius, Emilio; Xie, Shane; Anderson, Iain

    2009-03-01

    This paper presents an experimentally validated finite element model suitable for simulating the quasi-static behaviour of Dielectric Elastomer Minimum Energy Structure(s) (DEMES). A DEMES consists of a pre-stretched Dielectric Elastomer Actuator (DEA) adhered to a thin, flexible frame. The tension in the stretched membrane causes the frame to curl up, and when a voltage is applied, the frame returns to its initial planar state thus forming a useful bending actuator. The simulation method presented here incorporates a novel strain energy function suitable for simulating general DEA actuator elements. When compared against blocked force data from our previous work, the new model provides a good fit with an order of magnitude reduction in computational time. Furthermore, the model accurately matched experimental data on the free displacement of DEMES formed with non-equibiaxially pre-stretched VHB4905 membranes driven by 2500 V. Non-equibiaxially pre-stretching the membranes allowed control of effective frame stiffness and bending moment, this was exploited by using the model to optimise stroke at 2500 V in a hypothetical case study. Dielectric constant measurements for non-equibiaxially stretched VHB4905 are also presented.

  17. Novel Arrangements for High Performance and Durable Dielectric Elastomer Actuation

    Directory of Open Access Journals (Sweden)

    Runan Zhang

    2016-07-01

    Full Text Available This paper advances the design of Rod Pre-strained Dielectric Elastomer Actuators (RP-DEAs in their capability to generate comparatively large static actuation forces with increased lifetime via optimized electrode arrangements. RP-DEAs utilize thin stiff rods to constrain the expansion of the elastomer and maintain the in-plane pre-strain in the rod longitudinal direction. The aim is to study both the force output and the durability of the RP-DEA. Initial design of the RP-DEA had poor durability, however, it generated significantly larger force compared with the conventional DEA due to the effects of pre-strain and rod constraints. The durability study identifies the in-electro-active-region (in-AR lead contact and the non-uniform deformation of the structure as causes of pre-mature failure of the RP-DEA. An optimized AR configuration is proposed to avoid actuating undesired areas in the structure. The results show that with the optimized AR, the RP-DEA can be effectively stabilized and survive operation at least four times longer than with a conventional electrode arrangement. Finally, a Finite Element simulation was also performed to demonstrate that such AR design and optimization can be guided by analyzing the DEA structure in the state of pre-activation.

  18. Droplets sliding down inclined planes: unexpected dynamics on elastomer plates

    Science.gov (United States)

    Hourlier-Fargette, Aurelie; Antkowiak, Arnaud; Neukirch, Sebastien

    2016-11-01

    Droplet dynamics on an angled surface results from a competition between the weight of the droplet, capillary forces, and viscous dissipation inside the drop. The motion of droplets on stiff surfaces has been investigated for a long time, both experimentally and theoretically, while recent studies have shown the interesting physics underlying the sliding of droplets on soft surfaces. We focus on the dynamics of water-glycerol mixture droplets sliding down vertical plates of silicone elastomers, highlighting an unexpected behavior: the droplet dynamics on such a surface includes two regimes with different constant speeds. These results contrast with those found in the literature for droplets sliding on materials such as treated glass. We investigate the universality of this behavior on various elastomers, and study in detail the two regimes and the sharp transition observed between them. Different candidates can be responsible for the sudden speed change: bistability, chemical interaction with the substrate, softness of the material, etc. Our experiments to clarify the role of each of them reveal an unexpected link between microscopic phenomena at the scale of the polymer matrix and the macroscopic dynamics of a droplet.

  19. How does the molecular network structure influence PDMS elastomer wettability?

    Science.gov (United States)

    Melillo, Matthew; Genzer, Jan

    Poly(dimethylsiloxane) (PDMS) is one of the most common elastomers, with applications ranging from medical devices to absorbents for water treatment. Fundamental understanding of how liquids spread on the surface of and absorb into PDMS networks is of critical importance for the design and use of another application - microfluidic devices. We have systematically studied the effects of polymer molecular weight, loading of tetra-functional crosslinker, end-group chemical functionality, and the extent of dilution of the curing mixture on the mechanical and surface properties of end-linked PDMS networks. The gel and sol fractions, storage and loss moduli, liquid swelling ratios, and water contact angles have all been shown to vary greatly based on the aforementioned variables. Similar trends were observed for the commercial PDMS material, Sylgard-184. Our results have confirmed theories predicting the relationships between modulus and swelling. Furthermore, we have provided new evidence for the strong influence that substrate modulus and molecular network structure have on the wettability of PDMS elastomers. These findings will aid in the design and implementation of efficient microfluidics and other PDMS-based materials that involve the transport of liquids.

  20. Antagonistic dielectric elastomer actuator for biologically-inspired robotics

    Science.gov (United States)

    Conn, Andrew T.; Rossiter, Jonathan

    2011-04-01

    For optimal performance, actuators designed for biologically-inspired robotics applications need to be capable of mimicking the key characteristics of natural musculoskeletal systems. These characteristics include a large output stroke, high energy density, antagonistic operation and passive compliance. The actuation properties of dielectric elastomer actuators (DEAs) make them viable for use as an artificial muscle technology. However, much like the musculoskeletal system, rigid structures are needed to couple the compliant DEA layers to a load. In this paper, a cone DEA design is developed as an antagonistic, multi-DOF actuator, viable for a variety for biologically-inspired robotics applications. The design has the advantage of maintaining pre-strain through a support structure without substantially lowering the overall mass-specific power density. Prototype cone DEAs have been fabricated with VHB 4910 acrylic elastomer and have characteristic dimensions of 49mm (strut length) and 60mm (DEA diameter). Multi-DOF kinematical outputs of the cone DEAs were measured using a custom 3D motion tracking system. Experimental tests of the prototypes demonstrate antagonistic linear (+/-10mm), rotational (+/-25°) and combined multi-DOF strokes. Overall, antagonistic cone DEAs are shown to produce a complex multi-DOF output from a mass-efficient support structure and thus are well suited for being exploited in biologically-inspired robotics.

  1. Superhydrophobic/superoleophilic magnetic elastomers by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Milionis, Athanasios, E-mail: am2vy@virginia.edu [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Fragouli, Despina; Brandi, Fernando; Liakos, Ioannis; Barroso, Suset [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Athanassiou, Athanassia, E-mail: athanassia.athanassiou@iit.it [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy)

    2015-10-01

    Highlights: • We report the development of magnetic nanocomposite sheets. • Laser irradiation of the nanocomposites induces chemical and structural changes to the surface. • The laser-patterned surfaces exhibit superhydrophobicity and superoleophilicity. • The particle contribution in altering the surface and bulk properties of the material is studied. - Abstract: We report the development of magnetic nanocomposite sheets with superhydrophobic and supeoleophilic surfaces generated by laser ablation. Polydimethylsiloxane elastomer free-standing films, loaded homogeneously with 2% wt. carbon coated iron nanoparticles, were ablated by UV (248 nm), nanosecond laser pulses. The laser irradiation induces chemical and structural changes (both in micro- and nano-scale) to the surfaces of the nanocomposites rendering them superhydrophobic. The use of nanoparticles increases the UV light absorption efficiency of the nanocomposite samples, and thus facilitates the ablation process, since the number of pulses and the laser fluence required are greatly reduced compared to the bare polymer. Additionally the magnetic nanoparticles enhance significantly the superhydrophobic and oleophilic properties of the PDMS sheets, and provide to PDMS magnetic properties making possible its actuation by a weak external magnetic field. These nanocomposite elastomers can be considered for applications requiring magnetic MEMS for the controlled separation of liquids.

  2. Magnetoactive elastomer as an element of a magnetic retina fixator

    Science.gov (United States)

    Makarova, L. A.; Nadzharyan, T. A.; Alekhina, Yu A.; Stepanov, G. V.; Kazimirova, E. G.; Perov, N. S.; Kramarenko, E. Yu

    2017-09-01

    We explore the possibility of creating an effective retinal fixator on the basis of magnetoactive elastomers (MAEs) and systems of permanent magnets. MAEs consist of silicone elastomer matrix with embedded magnetic iron microparticles. We study theoretically and experimentally magnetic forces acting between MAE samples and permanent magnets in various configurations. The theoretical model is based around classical magnetostatics and Maxwell equations with different parameters accounting for peculiarities of the material and the setup. Approximation of the experimentally measured magnetization curves for MAE samples was used to find input parameters for the theoretical model. To test the model, we conducted a series of experimental measurements of magnetic forces accompanied by model predictions for the system of one cylindrical magnet and a cuboid MAE sample. Calculated dependences of the average pressure arising from magnetic interactions on the distance between the closest faces of MAE samples and a permanent magnet are in a good agreement with the experimental data. The proof on concept for smaller magnetic systems required for eye surgery includes data for 10 magnets configuration and a thin MAE band. This research demonstrates high prospects of using MAE as an element of a magnetic fixator for treatment of complicated retinal detachments.

  3. Dielectric elastomer vibrissal system for active tactile sensing

    Science.gov (United States)

    Conn, Andrew T.; Pearson, Martin J.; Pipe, Anthony G.; Welsby, Jason; Rossiter, Jonathan

    2012-04-01

    Rodents are able to dexterously navigate confined and unlit environments by extracting spatial and textural information with their whiskers (or vibrissae). Vibrissal-based active touch is suited to a variety of applications where vision is occluded, such as search-and-rescue operations in collapsed buildings. In this paper, a compact dielectric elastomer vibrissal system (DEVS) is described that mimics the vibrissal follicle-sinus complex (FSC) found in rodents. Like the vibrissal FSC, the DEVS encapsulates all sensitive mechanoreceptors at the root of a passive whisker within an antagonistic muscular system. Typically, rats actively whisk arrays of macro-vibrissae with amplitudes of up to +/-25°. It is demonstrated that these properties can be replicated by exploiting the characteristic large actuation strains and passive compliance of dielectric elastomers. A prototype DEVS is developed using VHB 4905 and embedded strain gauges bonded to the root of a tapered whisker. The DEVS is demonstrated to produce a maximum rotational output of +/-22.8°. An electro-mechanical model of the DEVS is derived, which incorporates a hyperelastic material model and Euler- Bernoulli beam equations. The model is shown to predict experimental measurements of whisking stroke amplitude and whisker deflection.

  4. Fully printed 3 microns thick dielectric elastomer actuator

    Science.gov (United States)

    Poulin, A.; Rosset, S.; Shea, H.

    2016-04-01

    In this work we present a new fabrication technique to print thin dielectric elastomer actuators (DEAs), reducing the driving voltage below 300 V while keeping good actuation performance. With operation voltages in the kV-range, standard DEAs are limited in terms of potential applications. Using thinner membranes is one of the few existing methods to achieve lower operation voltages. Typical DEAs have membranes in the 20-100 μm range, values below which membrane fabrication becomes challenging and the membrane quality and uniformity degrade. Using pad printing we produced thin silicone elastomer membranes, on which we pad-printed compliant electrodes. We then fabricated DEAs by assembling two membranes back to back. We obtain an actuation strain of 7.5% at only 245 V on a 3 μm thick DEA. In order to investigate the stiffening impact of the electrodes we developed a simple DEA model that includes their mechanical properties. We also developed a strain-mapping algorithm based on optical correlation. The simulation results and the strain-mapping measurements confirm that the stiffening impact of the electrodes increases for thinner membranes. Electrodes are an important element that cannot be neglected in the design and optimization of ultra-thin DEAs.

  5. Biodegradable and radically polymerized elastomers with enhanced processing capabilities.

    Science.gov (United States)

    Ifkovits, Jamie L; Padera, Robert F; Burdick, Jason A

    2008-09-01

    The development of biodegradable materials with elastomeric properties is beneficial for a variety of applications, including for use in the engineering of soft tissues. Although others have developed biodegradable elastomers, they are restricted by their processing at high temperatures and under vacuum, which limits their fabrication into complex scaffolds. To overcome this, we have modified precursors to a tough biodegradable elastomer, poly(glycerol sebacate) (PGS) with acrylates to impart control over the crosslinking process and allow for more processing options. The acrylated-PGS (Acr-PGS) macromers are capable of crosslinking through free radical initiation mechanisms (e.g., redox and photo-initiated polymerizations). Alterations in the molecular weight and % acrylation of the Acr-PGS led to changes in formed network mechanical properties. In general, Young's modulus increased with % acrylation and the % strain at break increased with molecular weight when the % acrylation was held constant. Based on the mechanical properties, one macromer was further investigated for in vitro and in vivo degradation and biocompatibility. A mild to moderate inflammatory response typical of implantable biodegradable polymers was observed, even when formed as an injectable system with redox initiation. Moreover, fibrous scaffolds of Acr-PGS and a carrier polymer, poly(ethylene oxide), were prepared via an electrospinning and photopolymerization technique and the fiber morphology was dependent on the ratio of these components. This system provides biodegradable polymers with tunable properties and enhanced processing capabilities towards the advancement of approaches in engineering soft tissues.

  6. A novel variable stiffness mechanism for dielectric elastomer actuators

    Science.gov (United States)

    Li, Wen-Bo; Zhang, Wen-Ming; Zou, Hong-Xiang; Peng, Zhi-Ke; Meng, Guang

    2017-08-01

    In this paper, a novel variable stiffness mechanism is proposed for the design of a variable stiffness dielectric elastomer actuator (VSDEA) which combines a flexible strip with a DEA in a dielectric elastomer minimum energy structure. The DEA induces an analog tuning of the transverse curvature of the strip, thus conveniently providing a voltage-controllable flexural rigidity. The VSDEA tends to be a fully flexible and compact structure with the advantages of simplicity and fast response. Both experimental and theoretical investigations are carried out to reveal the variable stiffness performances of the VSDEA. The effect of the clamped location on the bending stiffness of the VSDEA is analyzed, and then effects of the lengths, the loading points and the applied voltages on the bending stiffness are experimentally investigated. An analytical model is developed to verify the availability of this variable stiffness mechanism, and the theoretical results demonstrate that the bending stiffness of the VSDEA decreases as the applied voltage increases, which agree well with the experimental data. Moreover, the experimental results show that the maximum change of the relative stiffness can reach about 88.80%. It can be useful for the design and optimization of active variable stiffness structures and DEAs for soft robots, vibration control, and morphing applications.

  7. A novel duct silencer using dielectric elastomer absorbers

    Science.gov (United States)

    Lu, Zhenbo; Cui, Yongdong; Zhu, Jian; Debiasi, Marco

    2014-03-01

    A novel duct silencer was developed using dielectric elastomer absorbers (DEAs). Dielectric elastomer, a lightweight, high elastic energy density and large deformation under high DC/AC voltages smart material, was used to fabricate this new generation actuator. The acoustic performances of this duct silencer were experimentally investigated in a transmission loss (TL) measurement system using two-load method. It was found that the resonance peaks of this new duct silencer could be controlled by applying various DC voltages, a maximum resonance shift of 59.5Hz for the resonance peaks was achieved which indicated that this duct silencer could be adjusted to absorb broadband range noise without any addition mechanical part. Furthermore, the resonance shift and multiple resonances mechanisms using DEAs were proposed and discussed in the present paper which was aiming to achieve broadband noise reduction. The present results also provide insight into the appropriateness of the absorber for possible use as new acoustic treatment to replace the traditional acoustic treatment.

  8. Synthesis and characterization of energetic thermoplastic elastomers for propellant formulations

    Directory of Open Access Journals (Sweden)

    Aparecida M. Kawamoto

    2009-01-01

    Full Text Available Synthesis and characterization of energetic ABA-type thermoplastic elastomers for propellant formulations has been carried out. Following the working plan elaborated, the synthesis and characterization of Poly 3- bromomethyl-3-methyl oxetane (PolyBrMMO, Poly 3- azidomethyl-3-methyl oxetane (PolyAMMO, Poly 3,3-bis-azidomethyl oxetane (PolyBAMO and Copolymer PolyBAMO/AMMO (by TDI end capping has been successfully performed. The thermoplastic elastomers (TPEs were synthesized using the chain elongation process PolyAMMO, GAP and PolyBAMO by diisocyanates. In this method 2.4-toluene diisocyanate (TDI is used to link block A (hard and mono- functional to B (soft and di-functional. For the hard A-block we used PolyBAMO and for the soft B-block we used PolyAMMO or GAP.This is a joint project set up, some years ago, between the Chemistry Division of the Institute of Aeronautics and Space (IAE - subordinated to the Brazilian Ministry of Defense - and the Fraunhofer Institut Chemische Technologie (ICT, in Germany. The products were characterized by different techniques as IR- and (1H,13CNMR spectroscopies, elemental and thermal analyses. New methodologies based on FT-IR analysis have been developed as an alternative for the determination of the molecular weight and CHNO content of the energetic polymers.

  9. Strong, Resilient, and Sustainable Aliphatic Polyester Thermoplastic Elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Watts, Annabelle; Kurokawa, Naruki; Hillmyer, Marc A. (UMM)

    2017-05-03

    Thermoplastic elastomers (TPEs) composed of ABA block polymers exhibit a wide variety of properties and are easily processable as they contain physical, rather than chemical, cross-links. Poly(γ-methyl-ε-caprolactone) (PγMCL) is an amorphous polymer with a low entanglement molar mass (Me = 2.9 kg mol–1), making it a suitable choice for tough elastomers. Incorporating PγMCL as the midblock with polylactide (PLA) end blocks (fLA = 0.17) results in TPEs with high stresses and elongations at break (σB = 24 ± 2 MPa and εB = 1029 ± 20%, respectively) and low levels of hysteresis. The use of isotactic PLA as the end blocks (fLLA = 0.17) increases the strength and toughness of the material (σB = 30 ± 4 MPa, εB = 988 ± 30%) due to its semicrystalline nature. This study aims to demonstrate how the outstanding properties in these sustainable materials are a result of the entanglements, glass transition temperature, segment–segment interaction parameter, and crystallinity, resulting in comparable properties to the commercially relevant styrene-based TPEs.

  10. Asymmetry bistability for a coupled dielectric elastomer minimum energy structure

    Science.gov (United States)

    Li, Wen-Bo; Zhang, Wen-Ming; Zou, Hong-Xiang; Peng, Zhi-Ke; Meng, Guang

    2016-11-01

    In this paper, a novel design of asymmetry bistability for a coupled dielectric elastomer minimum energy structure (DEMES) is presented. The structure can be stable both in the stretched and curved configurations, which are induced by the geometry coupling effect of two DEMESs with perpendicular bending axes. The unique asymmetry bistability and fully flexible compact design of the coupled DEMES can enrich the active morphing modes of the dielectric elastomer actuators. A theoretical model of the system’s strain energy is established to explain the bistability. Furthermore, a prototype is fabricated to verify the conceptual design. The experimental results show that when the applied voltage is below a critical transition one, the structure behaves as a conventional DEMES, once the applied voltage exceeds the critical voltage, the structure could change from the stretched (curved) configuration to the curved (stretched) configuration abruptly and maintain in a new stable configuration when the voltage is removed. A multi-segment structure with the coupled DEMES is also presented and fabricated, and it displays various voltage-actuated morphings. It indicates that the coupled DEMES and the multi-segment structures can be useful for the soft and shape-shifting robots.

  11. Adaptive Integrand Decomposition

    CERN Document Server

    Mastrolia, Pierpaolo; Primo, Amedeo; Bobadilla, William J Torres

    2016-01-01

    We present a simplified variant of the integrand reduction algorithm for multiloop scattering amplitudes in $d = 4 - 2\\epsilon$ dimensions, which exploits the decomposition of the integration momenta in parallel and orthogonal subspaces, $d=d_\\parallel+d_\\perp$, where $d_\\parallel$ is the dimension of the space spanned by the legs of the diagrams. We discuss the advantages of a lighter polynomial division algorithm and how the orthogonality relations for Gegenbauer polynomilas can be suitably used for carrying out the integration of the irreducible monomials, which eliminates spurious integrals. Applications to one- and two-loop integrals, for arbitrary kinematics, are discussed.

  12. Clustering via Kernel Decomposition

    DEFF Research Database (Denmark)

    Have, Anna Szynkowiak; Girolami, Mark A.; Larsen, Jan

    2006-01-01

    Methods for spectral clustering have been proposed recently which rely on the eigenvalue decomposition of an affinity matrix. In this work it is proposed that the affinity matrix is created based on the elements of a non-parametric density estimator. This matrix is then decomposed to obtain...... posterior probabilities of class membership using an appropriate form of nonnegative matrix factorization. The troublesome selection of hyperparameters such as kernel width and number of clusters can be obtained using standard cross-validation methods as is demonstrated on a number of diverse data sets....

  13. Symmetric Tensor Decomposition

    DEFF Research Database (Denmark)

    Brachat, Jerome; Comon, Pierre; Mourrain, Bernard

    2010-01-01

    of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on this characterization and on linear algebra computations with Hankel matrices. The impact of this contribution is two-fold. First it permits an efficient computation...... of total degree d as a sum of powers of linear forms (Waring’s problem), incidence properties on secant varieties of the Veronese variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester’s approach from the dual point of view...

  14. Mode decomposition evolution equations.

    Science.gov (United States)

    Wang, Yang; Wei, Guo-Wei; Yang, Siyang

    2012-03-01

    Partial differential equation (PDE) based methods have become some of the most powerful tools for exploring the fundamental problems in signal processing, image processing, computer vision, machine vision and artificial intelligence in the past two decades. The advantages of PDE based approaches are that they can be made fully automatic, robust for the analysis of images, videos and high dimensional data. A fundamental question is whether one can use PDEs to perform all the basic tasks in the image processing. If one can devise PDEs to perform full-scale mode decomposition for signals and images, the modes thus generated would be very useful for secondary processing to meet the needs in various types of signal and image processing. Despite of great progress in PDE based image analysis in the past two decades, the basic roles of PDEs in image/signal analysis are only limited to PDE based low-pass filters, and their applications to noise removal, edge detection, segmentation, etc. At present, it is not clear how to construct PDE based methods for full-scale mode decomposition. The above-mentioned limitation of most current PDE based image/signal processing methods is addressed in the proposed work, in which we introduce a family of mode decomposition evolution equations (MoDEEs) for a vast variety of applications. The MoDEEs are constructed as an extension of a PDE based high-pass filter (Europhys. Lett., 59(6): 814, 2002) by using arbitrarily high order PDE based low-pass filters introduced by Wei (IEEE Signal Process. Lett., 6(7): 165, 1999). The use of arbitrarily high order PDEs is essential to the frequency localization in the mode decomposition. Similar to the wavelet transform, the present MoDEEs have a controllable time-frequency localization and allow a perfect reconstruction of the original function. Therefore, the MoDEE operation is also called a PDE transform. However, modes generated from the present approach are in the spatial or time domain and can be

  15. Hydrogen peroxide catalytic decomposition

    Science.gov (United States)

    Parrish, Clyde F. (Inventor)

    2010-01-01

    Nitric oxide in a gaseous stream is converted to nitrogen dioxide using oxidizing species generated through the use of concentrated hydrogen peroxide fed as a monopropellant into a catalyzed thruster assembly. The hydrogen peroxide is preferably stored at stable concentration levels, i.e., approximately 50%-70% by volume, and may be increased in concentration in a continuous process preceding decomposition in the thruster assembly. The exhaust of the thruster assembly, rich in hydroxyl and/or hydroperoxy radicals, may be fed into a stream containing oxidizable components, such as nitric oxide, to facilitate their oxidation.

  16. Elastomer Change Out - Justification for minimizing the removal of elastomers in order to prevent cross contamination in a multiproduct facility.

    Science.gov (United States)

    Parks, Michael; O'Dwyer, Niamh; Bollinger, Jeremy; Johnson, Alan; Goss, Brian; Wyman, Ned; Arroyo, Adeyma; Wood, Joseph; Willison-Parry, Derek

    2017-09-19

    The primary objective of any Biopharmaceutical Product Changeover (PCO) program is to employ control strategies before, during, and after the manufacturing process, as well as from the beginning of the lifecycle approach for the equipment and validation, which will minimize the opportunity for cross- contamination when switching between products. Evaluation of the need for an Elastomer Change Out (ECO) should be considered as a segment of an overall changeover assessment. Lifecycle systems (e.g. Preventive Maintenance (PM), Cleanability Coupon Testing, Good Engineering Practices, etc.) and procedures should be in place and data should be generated demonstrating the soft parts do not harbor residues from the previous product campaign(s). The determination of whether or not to replace elastomers/soft parts should be made in the context of all of these systems along with the proper assessment of Risk. By understanding the actual value of ECO in terms of the overall PCO program, and the other systems and procedures that are in place that protect against cross contamination, the need for ECO for every product changeover is not necessary. The purpose of this paper is to review the practice of ECO at product changeover, evaluate the need for an ECO using a risk based approach, and provide rationale for justifying the reduction or elimination of ECO at product changeover. Copyright © 2017, Parenteral Drug Association.

  17. Spectral Tensor-Train Decomposition

    DEFF Research Database (Denmark)

    Bigoni, Daniele; Engsig-Karup, Allan Peter; Marzouk, Youssef M.

    2016-01-01

    The accurate approximation of high-dimensional functions is an essential task in uncertainty quantification and many other fields. We propose a new function approximation scheme based on a spectral extension of the tensor-train (TT) decomposition. We first define a functional version of the TT.......e., the “cores”) comprising the functional TT decomposition. This result motivates an approximation scheme employing polynomial approximations of the cores. For functions with appropriate regularity, the resulting spectral tensor-train decomposition combines the favorable dimension-scaling of the TT...... decomposition with the spectral convergence rate of polynomial approximations, yielding efficient and accurate surrogates for high-dimensional functions. To construct these decompositions, we use the sampling algorithm \\tt TT-DMRG-cross to obtain the TT decomposition of tensors resulting from suitable...

  18. MACH: Fast Randomized Tensor Decompositions

    CERN Document Server

    Tsourakakis, Charalampos E

    2009-01-01

    Tensors naturally model many real world processes which generate multi-aspect data. Such processes appear in many different research disciplines, e.g, chemometrics, computer vision, psychometrics and neuroimaging analysis. Tensor decompositions such as the Tucker decomposition are used to analyze multi-aspect data and extract latent factors, which capture the multilinear data structure. Such decompositions are powerful mining tools, for extracting patterns from large data volumes. However, most frequently used algorithms for such decompositions involve the computationally expensive Singular Value Decomposition. In this paper we propose MACH, a new sampling algorithm to compute such decompositions. Our method is of significant practical value for tensor streams, such as environmental monitoring systems, IP traffic matrices over time, where large amounts of data are accumulated and the analysis is computationally intensive but also in "post-mortem" data analysis cases where the tensor does not fit in the availa...

  19. Electromechanical phase transition in dielectric elastomers under uniaxial tension and electrical voltage

    Science.gov (United States)

    Huang, Rui; Suo, Zhigang

    2012-02-01

    Subject to forces and voltage, a dielectric elastomer may undergo electromechanical phase transition. A phase diagram is constructed for an ideal dielectric elastomer membrane under uniaxial force and voltage, reminiscent of the phase diagram for liquid-vapor transition of a pure substance. We identify a critical point for the electromechanical phase transition. Two states of deformation (thick and thin) may coexist during the phase transition, with the mismatch in lateral stretch accommodated by wrinkling of the membrane in the thin state. The processes of electromechanical phase transition under various conditions are discussed. A reversible cycle is suggested for electromechanical energy conversion using the dielectric elastomer membrane, analogous to the classical Carnot cycle for a heat engine. The amount of energy conversion, however, is limited by failure of the dielectric elastomer due to electrical breakdown. With a particular combination of material properties, the electromechanical energy conversion can be significantly extended by taking advantage of the phase transition without electrical breakdown.

  20. Stress-induced birefringence in elastomers doped with ferrofluid magnetic particles: Mechanical and optical investigation

    Energy Technology Data Exchange (ETDEWEB)

    Sena, C. [Instituto de Fisica, Universidade de Sao Paulo, Caixa postal 66318, Sao Paulo, SP 05315-970 (Brazil); Bailey, C. [Liquid Crystal Institute, Kent State University, P.O. Box 5190, Kent, OH 44242-0001 (United States); Godinho, M.H. [Faculdade de Ciencias e Tecnologia e CENIMAT, Universidade Nova de Lisboa, Quinta da Torre, P-2829-516 Caparica (Portugal); Figueirinhas, J.L. [CFMC, Universidade de Lisboa, Avenida Prof. Gama Pinto 2, 1649 003 Lisbon (Portugal); Palffy-Muhoray, P. [Liquid Crystal Institute, Kent State University, P.O. Box 5190, Kent, OH 44242-0001 (United States); Figueiredo Neto, A.M. [Instituto de Fisica, Universidade de Sao Paulo, Caixa postal 66318, Sao Paulo, SP 05315-970 (Brazil)]. E-mail: afigueiredo@if.usp.br

    2006-05-15

    Magnetic nanoparticles from magnetic colloidal suspensions were incorporated in the urethane/urea elastomer (PU/PBDO) by adding to the prepolymers solution in toluene diverse amounts of magnetite grains. It is shown that ferrofluid grains can be efficiently incorporated into the elastomer according to this procedure. Mechanical and optical experiments performed show that the elastomer preparation procedure (casting) introduces a structural anisotropy on the optically isotropic sample. This fact is put in evidence by the measurements of the Young's moduli and orientation of the sample's optical axis under stress. The dependence of the phase shift of both the pure and ferrofluid-doped elastomer samples under strain is linear, and the strain-optic coefficient is show to be linear with the ferrofluid concentration.

  1. SYNTHESIS OF POLYURETHANE MODIFIED BISMALEIMIDE(UBMI)AND POLYURETHANE-IMIDE ELASTOMER

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Urethane modified bismaleimide(UBMI)was synthesized by the reaction of maleic anhydride(MA)with NCO group terminated polyurethane prepolymer(PUP)in presence of acetone.The product was determined by infrared analysis.Then ultrasonic assistant process was introduced into the solvent removal of the prepolymer mixture of UBMI and PUP.Polyurethane-imide(PUI)elastomer was synthesized from the above PUP-UBMI prepolymer mixture by the infusion technology with 2,5-dimethyl-2,5-bis(tert-butylperoxy)-hexane(B25)as liquid initiator at 120℃.The thermal properties and stress-strain behavior of PUI elastomer was characterised by thermogravimetric(TG)analysis and tensile testing apparatus,respectively.Compared with pure polyurethane elastomer,the PUI elastomer composite showed the better thermal stability.

  2. CLINICAL TRIALS FOR VAS DEFERENS OCCLUSION BY PERCUTANEOUS INJECTION OF POLYURETHANE ELASTOMER TO FORM PLUGS

    Institute of Scientific and Technical Information of China (English)

    ZHAOSheng-Cai; etal.

    1989-01-01

    A non-incision method of vss occlusion based on the percutaneous injection of polyurethane elastomer solution to form a plug is described. The procedure was conducted under aseptic procedure and local fidocaine anaesthesia. Two different kinds of

  3. Research on the damping properties of Fe12O19Sr/the polyurethane elastomer composite

    Science.gov (United States)

    Li, Y.; Qin, Yan; Sun, P. C.; Huang, Z. X.

    2016-07-01

    Magnetic elastomer composite is a promising damping material. In this paper, both strontium ferrite (Fe12O19Sr) powders and polyurethane elastomer which were mixed by mechanical blending method were used as the magnetic filler and as the matrix respectively, the properties of the magnetic damping composite materials were studied. The results show that the magnetic properties of the magnetic elastomers composite are enhanced with the ferrite loading. The mechanical properties and Shore hardness are highly influenced by mass fraction of ferrite particles. The damping properties of magnetic elastomer composite reach best when the strontium ferrite loading is 15phr, and the damping properties deteriorate when the loading continue increasing. The damping properties of the composites with the X direction of magnetization are better than that with Y direction of magnetization.

  4. Soft conductive elastomer materials for stretchable electronics and voltage controlled artificial muscles.

    Science.gov (United States)

    Stoyanov, Hristiyan; Kollosche, Matthias; Risse, Sebastian; Waché, Rémi; Kofod, Guggi

    2013-01-25

    Block copolymer elastomer conductors (BEC) are mixtures of block copolymers grafted with conducting polymers, which are found to support very large strains, while retaining a high level of conductivity. These novel materials may find use in stretchable electronics. The use of BEC is demonstrated in a capacitive strain sensor and in an artificial muscle of the dielectric elastomer actuator type, supporting more than 100% actuation strain and capacity strain sensitivity up to 300%.

  5. Experimental investigation on vibration characteristics of sandwich beams with magnetorheological elastomers cores

    Institute of Scientific and Technical Information of China (English)

    魏克湘; 孟光; 张文明; 朱石沙

    2008-01-01

    A sandwich beam specimen was fabricated by treating with MR elastomers between two thin aluminum face-plates.Experiment was carried out to investigate the vibration responses of the sandwich beam with respect to the intensity of the magnetic field and excitation frequencies.The results show that the sandwich beams with MR elastomers cores have the capabilities of shifting natural frequencies and the vibration amplitudes decrease with the variation of the intensity of external magnetic field.

  6. Dry Rolling Friction and Wear of Elastomer Systems and Their Finite Element Modelling

    OpenAIRE

    Xu, Dan

    2009-01-01

    Elastomers and their various composites, and blends are frequently used as engineering working parts subjected to rolling friction movements. This fact already substantiates the importance of a study addressing the rolling tribological properties of elastomers and their compounds. It is worth noting that until now the research and development works on the friction and wear of rubber materials were mostly focused on abrasion and to lesser extent on sliding type of loading. As the tribological ...

  7. Friction and wear characteristics of elastomers in lubricated contact with EALs

    OpenAIRE

    Mofidi, Mohammad; Simmons, Gregory; Prakash, Braham

    2008-01-01

    The friction and wear characteristics of several elastomers have been studied during reciprocating sliding conditions when lubricated with uncontaminated environmentally adapted lubricants and the same lubricants contaminated with moisture. The elastomers studied are Nitrile Butadiene Rubber (NBR), Hydrogenated Nitrile Butadiene Rubber (HNBR), and Fluorocarbon Rubber (FKM). The lubricants used are complex ester and polyol ester as well as both aged and non-aged polyol esters with 5% water con...

  8. Nonlinear viscoelastic response of highly filled elastomers under multiaxial finite deformation

    Science.gov (United States)

    Peng, Steven T. J.; Landel, Robert F.

    1990-01-01

    A biaxial tester was used to obtain precise biaxial stress responses of highly filled, high strain capability elastomers. Stress-relaxation experiments show that the time-dependent part of the relaxation response can be reasonably approximated by a function which is strain and biaxiality independent. Thus, isochronal data from the stress-relaxation curves can be used to determine the stored energy density function. The complex behavior of the elastomers under biaxial deformation may be caused by dewetting.

  9. The in-situ generation of silica reinforcement in modified polydimethylsiloxane elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Prabakar, S [New Mexico Univ., Albuquerque, NM (United States). Advanced Materials Lab.; Bates, S.E.; Black, E.P.; Ulibarri, T.A. [Sandia National Labs., Albuquerque, NM (United States)

    1996-06-01

    Structure and properties of a series of modified polydimethylsiloxane (PDMS) elastomers reinforced by {ital in situ} generated silic particles were investigated. The PDMS elastomer was modified by systematically varying the molecular weight between reactive groups incorporated into the backbone. Tetraethoxysilane (TEOS) and partial hydrolyzate of TEOS were used to generate silic particles. Chemistry and phase structure of the materials were investigated by {sup 29}Si magic angle spinning nuclear magnetic resonance spectroscopy and swelling experiments.

  10. The electro-mechanical phase transition of Gent model dielectric elastomer tube with two material constants

    Science.gov (United States)

    Liu, Liwu; Luo, Xiaojian; Fei, Fan; Wang, Yixing; Leng, Jinsong; Liu, Yanju

    2013-04-01

    Applied to voltage, a dielectric elastomer membrane may deform into a mixture of two states under certain conditions. One of which is the flat state and the other is the wrinkled state. In the flat state, the membrane is relatively thick with a small area, while on the contrary, in the wrinkled state, the membrane is relatively thin with a large area. The coexistence of these two states may cause the electromechanical phase transition of dielectric elastomer. The phase diagram of idea dielectric elastomer membrane under unidirectional stress and voltage inspired us to think about the liquid-to-vapor phase transition of pure substance. The practical working cycle of a steam engine includes the thermodynamical process of liquid-to-vapor phase transition, the fact is that the steam engine will do the maximum work if undergoing the phase transition process. In this paper, in order to consider the influence of coexistent state of dielectric elastomer, we investigate the homogeneous deformation of the dielectric elastomer tube. The theoretical model is built and the relationship between external loads and stretch are got, we can see that the elastomer tube experiences the coexistent state before reaching the stretching limit from the diagram. We think these results can guide the design and manufacture of energy harvesting equipments.

  11. PLA-based biodegradable and tunable soft elastomers for biomedical applications.

    Science.gov (United States)

    Harrane, Amine; Leroy, Adrien; Nouailhas, Hélène; Garric, Xavier; Coudane, Jean; Nottelet, Benjamin

    2011-12-01

    Although desirable for biomedical applications, soft degradable elastomers having balanced amphiphilic behaviour are rarely described in the literature. Indeed, mainly highly hydrophobic elastomers or very hydrophilic elastomers with hydrogel behaviours are found. In this work, we developed thermoset degradable elastomers based on the photo-cross-linking of poly(lactide)-poly(ethylene glycol)-poly(lactide) (PLA-PEG-PLA) triblock prepolymers. The originality of the proposed elastomers comes from the careful choice of the prepolymer amphiphilicity and from the possible modulation of their mechanical properties and degradation rates provided by cross-linkers of different nature. This is illustrated with the hydrophobic and rigid 2,4,6-triallyloxy-1,3,5-triazine compared to the hydrophilic and soft pentaerythritol triallyl ether. Thermal properties, mechanical properties, swelling behaviours, degradation rates and cytocompatibility have been evaluated. Results show that it is possible to generate a family of degradable elastomers covering a broad range of properties from a single biocompatible and biodegradable prepolymer.

  12. Fabrication and characterization of thermoplastic elastomer dry adhesives with high strength and low contamination.

    Science.gov (United States)

    Bin Khaled, Walid; Sameoto, Dan

    2014-05-14

    Polydimethylsiloxane (PDMS) and polyurethane elastomers have commonly been used to manufacture mushroom shaped gecko-inspired dry adhesives with high normal adhesion strength. However, the thermosetting nature of these two materials severely limits the commercial viability of their manufacturing due to long curing times and high material costs. In this work, we introduce poly(styrene-ethylene/butylene-styrene) (SEBS) thermoplastic elastomers as an alternative for the manufacture of mushroom shaped dry adhesives with both directional and nondirectional performance. These materials are attractive for their potential to be less contaminating via oligomer transfer than thermoset elastomers, as well as being more suited to mass manufacturing. Low material transfer properties are attractive for adhesives that could potentially be used in cleanroom environments for microscale assembly and handling in which device contamination is a serious concern. We characterized a thermoplastic elastomer in terms of oligomer transfer using X-ray photoelectron spectroscopy and found that the SEBS transfers negligible amounts of its own oligomers, during contact with a gold-coated silicon surface, which may be representative of the metallic bond pads found in micro-electro-mechanical systems devices. We also demonstrate the fabrication of mushroom shaped isotropic and anisotropic adhesive fibers with two different SEBS elastomer grades using thermocompression molding and characterize the adhesives in terms of their shear-enhanced normal adhesion strength. The overall adhesion of one of the thermoplastic elastomer adhesives was found to be stronger or comparable to their polyurethane counterparts with identical dimensions.

  13. Electromechanical performance analysis of inflated dielectric elastomer membrane for micro pump applications

    Science.gov (United States)

    Saini, Abhishek; Ahmad, Dilshad; Patra, Karali

    2016-04-01

    Dielectric elastomers have received a great deal of attention recently as potential materials for many new types of sensors, actuators and future energy generators. When subjected to high electric field, dielectric elastomer membrane sandwiched between compliant electrodes undergoes large deformation with a fast response speed. Moreover, dielectric elastomers have high specific energy density, toughness, flexibility and shape processability. Therefore, dielectric elastomer membranes have gained importance to be applied as micro pumps for microfluidics and biomedical applications. This work intends to extend the electromechanical performance analysis of inflated dielectric elastomer membranes to be applied as micro pumps. Mechanical burst test and cyclic tests were performed to investigate the mechanical breakdown and hysteresis loss of the dielectric membrane, respectively. Varying high electric field was applied on the inflated membrane under different static pressure to determine the electromechanical behavior and nonplanar actuation of the membrane. These tests were repeated for membranes with different pre-stretch values. Results show that pre-stretching improves the electromechanical performance of the inflated membrane. The present work will help to select suitable parameters for designing micro pumps using dielectric elastomer membrane. However this material lacks durability in operation.This issue also needs to be investigated further for realizing practical micro pumps.

  14. Starch-based bio-elastomers functionalized with red beetroot natural antioxidant.

    Science.gov (United States)

    Tran, Thi Nga; Athanassiou, Athanassia; Basit, Abdul; Bayer, Ilker S

    2017-02-01

    Red beetroot (RB) powder was incorporated into starch-based bio-elastomers to obtain flexible biocomposites with tunable antioxidant properties. Starch granules within the bio-elastomers affected the release of the antioxidant molecule betanin in the RB powder. The bio-elastomers were hydrophobic and resisted dissolution in water, hence the release of betanin was due to diffusion rather than polymer matrix disintegration. Hydrophobicity was maintained even after water immersion. Released betanin demonstrated highly efficient antioxidant scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(+)). RB powder was also found to increase the Young's modulus of the bio-elastomers without compromising their elongation ability. Infrared spectral analysis indicated weak interactions through hydrogen bonding among starch granules, RB powder and PDMS polymer within the bio-elastomers. Hence, as a simple but intelligent biomaterial consisting of mainly edible starch and RB powder the present bio-elastomers can be used in active packaging for a variety of pharmaceutical, medical, and food applications.

  15. Conductive magnetorheological elastomer: fatigue dependent impedance-mechanic coupling properties

    Science.gov (United States)

    Wang, Yu; Xuan, Shouhu; Ge, Lin; Wen, Qianqian; Gong, Xinglong

    2017-01-01

    This work investigated the relationship between the impedance properties and dynamic mechanical properties of magnetorheological elastomers (MREs) under fatigue loading. The storage modulus and the impedance properties of MREs were highly influenced by the pressure and magnetic field. Under the same experimental condition, the two characteristics exhibited similar fatigue dependent change trends. When pressure was smaller than 10 N, the capacitance of MRE could be divided into four sections with the increase of the cyclic numbers. The relative equivalent circuit model was established to fit the experimental results of the impedance spectra. Each parameter of circuit element reflected the change of fatigue loading, relative microstructure of MRE, MRE-electrode interface layer, respectively. Based on the above analysis, the real-time and nondestructive impedance method was demonstrated to be high potential on detecting the fatigue of the MRE device.

  16. Stretchable biocompatible electronics by embedding electrical circuitry in biocompatible elastomers.

    Science.gov (United States)

    Jahanshahi, Amir; Salvo, Pietro; Vanfleteren, Jan

    2012-01-01

    Stretchable and curvilinear electronics has been used recently for the fabrication of micro systems interacting with the human body. The applications range from different kinds of implantable sensors inside the body to conformable electrodes and artificial skins. One of the key parameters in biocompatible stretchable electronics is the fabrication of reliable electrical interconnects. Although very recent literature has reported on the reliability of stretchable interconnects by cyclic loading, work still needs to be done on the integration of electrical circuitry composed of rigid components and stretchable interconnects in a biological environment. In this work, the feasibility of a developed technology to fabricate simple electrical circuits with meander shaped stretchable interconnects is presented. Stretchable interconnects are 200 nm thin Au layer supported with polyimide (PI). A stretchable array of light emitting diodes (LEDs) is embedded in biocompatible elastomer using this technology platform and it features a 50% total elongation.

  17. Numerical investigation of smart base isolation system employing MR elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Usman, M; Sung, S H; Jang, D D; Jung, H J [Department of Civil and Environmental Engineering, KAIST, 305-701, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Koo, J H [Department of Mechanical and Manufacturing Engineering, Miami University, Oxford, Ohio 45056 (United States)], E-mail: hjung@kaist.ac.kr

    2009-02-01

    This paper evaluates the dynamic performance of a newly proposed smart base isolation system employing Magneto-Rheological Elastomers (MREs). MREs belong to a class of smart materials whose elastic modulus or stiffness can be adjusted by varying the magnitude of the magnetic field. The base isolation systems are considered as one of the most effective devices for vibration reduction of civil engineering structures in the event of earthquakes. The proposed base isolation system strives to enhance the performance of the conventional base-isolation system by using controllable MREs. To validate the effectiveness of the MRE-based isolation system, an extensive simulation study has been performed using a five degree-of-freedom structure under several historical earthquake excitations. The results show that the proposed system outperformed the conventional system in reducing the responses of the structure in all the seismic excitations considered in the study.

  18. A solid-state dielectric elastomer switch for soft logic

    Science.gov (United States)

    Chau, Nixon; Slipher, Geoffrey A.; O'Brien, Benjamin M.; Mrozek, Randy A.; Anderson, Iain A.

    2016-03-01

    In this paper, we describe a stretchable solid-state electronic switching material that operates at high voltage potentials, as well as a switch material benchmarking technique that utilizes a modular dielectric elastomer (artificial muscle) ring oscillator. The solid-state switching material was integrated into our oscillator, which self-started after 16 s and performed 5 oscillations at a frequency of 1.05 Hz with 3.25 kV DC input. Our materials-by-design approach for the nickel filled polydimethylsiloxane based switch has resulted in significant improvements over previous carbon grease-based switches in four key areas, namely, sharpness of switching behavior upon applied stretch, magnitude of electrical resistance change, ease of manufacture, and production rate. Switch lifetime was demonstrated to be in the range of tens to hundreds of cycles with the current process. An interesting and potentially useful strain-based switching hysteresis behavior is also presented.

  19. Auto-origami with liquid crystal elastomers: a simulation study

    Science.gov (United States)

    Konya, Andrew; Selinger, Robin

    2013-03-01

    Liquid crystal elastomers (LCE) undergo shape transformations induced by stimuli such as heating/cooling or illumination. When a non-uniform director field is imposed on a sample during crosslinking, it encodes a complex actuation trajectory which may include a combination of bends, twists, and folds along with changes in Gaussian curvature. Taking a materials-by-design approach, we perform finite element simulations to explore director geometries which produce such auto-origami behavior. By cataloging and assembling a variety of basic motifs including those identified by Modes and Warner, we design director geometries that yield a variety of target structures. Assembling a sample with domains of two LCE materials with different isotropic-nematic transition temperatures provides a means for sequencing steps in the resulting actuation choreography on heating/cooling. Supported by NSF-DMR-1106014.

  20. Derivation of stiffness matrix in constitutive modeling of magnetorheological elastomer

    Science.gov (United States)

    Leng, D.; Sun, L.; Sun, J.; Lin, Y.

    2013-02-01

    Magnetorheological elastomers (MREs) are a class of smart materials whose mechanical properties change instantly by the application of a magnetic field. Based on the specially orthotropic, transversely isotropic stress-strain relationships and effective permeability model, the stiffness matrix of constitutive equations for deformable chain-like MRE is considered. To valid the components of shear modulus in this stiffness matrix, the magnetic-structural simulations with finite element method (FEM) are presented. An acceptable agreement is illustrated between analytical equations and numerical simulations. For the specified magnetic field, sphere particle radius, distance between adjacent particles in chains and volume fractions of ferrous particles, this constitutive equation is effective to engineering application to estimate the elastic behaviour of chain-like MRE in an external magnetic field.

  1. Programming complex shapes in thin nematic elastomer and glass sheets

    Science.gov (United States)

    Plucinsky, Paul; Lemm, Marius; Bhattacharya, Kaushik

    2016-07-01

    Nematic elastomers and glasses are solids that display spontaneous distortion under external stimuli. Recent advances in the synthesis of sheets with controlled heterogeneities have enabled their actuation into nontrivial shapes with unprecedented energy density. Thus, these have emerged as powerful candidates for soft actuators. To further this potential, we introduce the key metric constraint which governs shape-changing actuation in these sheets. We then highlight the richness of shapes amenable to this constraint through two broad classes of examples which we term nonisometric origami and lifted surfaces. Finally, we comment on the derivation of the metric constraint, which arises from energy minimization in the interplay of stretching, bending, and heterogeneity in these sheets.

  2. Muscular MEMS—the engineering of liquid crystal elastomer actuators

    Science.gov (United States)

    Petsch, S.; Khatri, B.; Schuhladen, S.; Köbele, L.; Rix, R.; Zentel, R.; Zappe, H.

    2016-08-01

    A new class of soft-matter actuator, the liquid crystal elastomer (LCE), shows promise for application in a wide variety of mechanical microsystems. Frequently referred to as an ‘artificial muscle’, this family of materials exhibits large actuation stroke and generates considerable force, in a compact form which may easily be combined with the structures and devices commonly used in microsystems and MEMS. We show here how standard microfabrication techniques may be used to integrate LCEs into mechanical microsystems and present an in-depth analysis of their mechanical and actuation properties. Using an example from micro-optics and optical MEMS, we demonstrate that their performance and flexibility allows realization of entirely new types of tunable optical functionality.

  3. Rheological properties of carbon nanotubes-reinforced magnetorheological elastomer

    Science.gov (United States)

    Aziz, S. A. A.; Mazlan, SA; Nik Ismail, N. I.; Ubaidillah; Khairi, MHA; Yunus, NA

    2017-01-01

    Magnetorheological elastomer (MRE) based on the natural rubber with different types of multiwall carbon nanotubes (MWCNT) as additives were synthesized. MRE with pristine MWCNTs was prepared as a control and the carboxylated (MWCNT-COOH), as well as hydroxylated (MWCNT-OH) were introduced as new additives in MRE. Their rheological properties under different magnetic field were evaluated by using the rheometer (MCR 302, AntonPaar, Austria) equipped with the electromagnetic device. The dependency of MREs towards excitation frequencies under different magnetic field was investigated. It is shown that the storage modulus and loss factor of MRE with functionalized MWCNTs exhibited noticeable increment in MR performance compared to control parallel with the frequencies increment.

  4. Thermal stability of segmented polyurethane elastomers reinforced by clay particles

    Directory of Open Access Journals (Sweden)

    Pavličević Jelena

    2009-01-01

    Full Text Available The aim of this work was to determine the influence of clay nanoparticles on thermal properties of segmented polyurethanes based on hexamethylene- diisocyanate, aliphatic polycarbonate diol and 1,4-butanediol as chain extender. The organically modified particles of montmorillonite and bentonite were used as reinforcing fillers. The structure of elastomeric materials was varied either by diol type or chain extender content. The ratio of OH groups from diol and chain extender (R was either 1 or 10. Thermal properties of prepared materials were determined using modulated differential scanning calorimetry (MDSC. Thermal stability of obtained elastomers has been studied by simultaneously thermogravimetry coupled with DSC. The glass transition temperature, Tg, of soft segments for all investigated samples was about -33°C. On the basis of DTG results, it was concluded that obtained materials were very stable up to 300°C.

  5. Measurement of Equation of State of Silicone Elastomer

    Science.gov (United States)

    Winter, R. E.; Whiteman, G.; Haining, G. S.; Salisbury, D. A.; Tsembelis, K.

    2004-07-01

    Silicone Elastomer, ("Sylgard 184 ®"), samples were mounted between copper plates. Manganin stress gauges were placed within the front copper plate, halfway through the Sylgard and at the interface between the Sylgard and the rear copper plate. A series of experiments was performed in which the front plate was impacted by copper plates projected at a range of velocities. It was assumed that a Grüneisen Gamma form with a constant Γ could fit the Equation of State of the sample. A trial set of EoS parameters, including Gamma, was entered into a spreadsheet, then the state variables for the different stress jumps were calculated with the aid of a "Goalseek" function. This enabled the stresses and times for each jump to be calculated. Comparing these predictions with the experimentally determined parameters enabled optimum values of the EoS parameters to be identified.

  6. Collapse of Non-Rectangular Channels in a Soft Elastomer

    Science.gov (United States)

    Tepayotl-Ramirez, Daniel; Park, Yong-Lae; Lu, Tong; Majidi, Carmel

    2013-03-01

    We examine the collapse of microchannels in a soft elastomer by treating the sidewalls as in- denters that penetrate the channel base. This approach leads to a closed-form algebraic mapping between applied pressure and cross-sectional deformation that are in strong agreement with ex- perimental measurements and Finite Element Analysis (FEA) simulation. Applications of this new approach to modeling soft microchannel collapse range from lab-on-a-chip microfluidics for pressure-controlled protein filtration to soft-matter pressures sensing. We demonstrate the latter by comparing theoretical predictions with experimental measurements of the pressure-controlled electrical resistance of liquid-phase Gallium alloy microchannels embedded in a soft silicone elas- tomer.

  7. Active vibration isolation with a dielectric elastomer stack actuator

    Science.gov (United States)

    Kaal, William; Bartel, Torsten; Herold, Sven

    2017-05-01

    This work presents the development, simulation and experimental investigation of a demonstrator for active vibration isolation with dielectric elastomers (DEs). The electromechanical behavior of the developed DE stack actuator is first characterized experimentally and a suitable simulation model is parametrized accordingly. The potential of the actuator for active vibration isolation is shown in a specially designed single axis test rig. The influence of different control strategies on the transmission behavior from the excited base to the mass is studied. A special aspect of the control strategy is the compensation of the specific nonlinearities. The analysis proves the potential of DE actuators for active vibration isolation purposes. The presented broadband active isolation could enable the use of DEs in various technical fields of application.

  8. Development of an isolator working with magnetorheological elastomers and fluids

    Science.gov (United States)

    Sun, S. S.; Yang, J.; Li, W. H.; Du, H.; Alici, G.; Yan, T. H.; Nakano, Masami

    2017-01-01

    This paper reports an isolator whose damping and stiffness can be simultaneously controlled by magnetorheological (MR) fluids and MR elastomers. A hydraulically actuated MTS machine was used to test this variable stiffness and damping isolator after its prototype. The field-dependent responses including stiffness variability and damping variability, together with the amplitude-dependent response and frequency-dependent responses were separately tested and analyzed successively. The experimental results prove the successful implementation of the as-designed MRE-F isolator with obvious variable damping and stiffness. A new phenomenological model incorporating Bingham model and four-parameter model was developed to describe the dynamic properties of the isolator. The successful development, experimental testing, and modelling of this innovative variable stiffness and damping isolator make the concept of variable stiffness and damping become feasible.

  9. Thermoplastic Polyurethane Elastomer Nanocomposites: Morphology, Thermophysical, and Flammability Properties

    Directory of Open Access Journals (Sweden)

    Wai K. Ho

    2010-01-01

    Full Text Available Novel materials based on nanotechnology creating nontraditional ablators are rapidly changing the technology base for thermal protection systems. Formulations with the addition of nanoclays and carbon nanofibers in a neat thermoplastic polyurethane elastomer (TPU were melt-compounded using twin-screw extrusion. The TPU nanocomposites (TPUNs are proposed to replace Kevlar-filled ethylene-propylene-diene-monomer rubber, the current state-of-the-art solid rocket motor internal insulation. Scanning electron microscopy analysis was conducted to study the char characteristics of the TPUNs at elevated temperatures. Specimens were examined to analyze the morphological microstructure during the pyrolysis reaction and in fully charred states. Thermophysical properties of density, specific heat capacity, thermal diffusivity, and thermal conductivity of the different TPUN compositions were determined. To identify dual usage of these novel materials, cone calorimetry was employed to study the flammability properties of these TPUNs.

  10. Influence of melt mixer on injection molding of thermoset elastomers

    Science.gov (United States)

    Rochman, Arif; Zahra, Keith

    2016-10-01

    One of the drawbacks in injection molding is that the plasticizing screw is short such that polymers having high concentrations of additives, such as thermoset elastomers, might not mix homogeneously within the short period of time during the plasticizing stage. In this study, various melt mixers inside the nozzle chamber, together forming a mixing nozzle, were developed. Three different materials were investigated, namely nitrile butadiene rubber (NBR), ethylene propylene-diene monomer (EPDM) and fluorocarbon (FKM). The use of these melt mixers resulted in better homogeneity and properties of the molded parts despite a curing time reduction of 10 s. This was due to the increase in mixing and shearing introduced a higher rate of crosslinking formation in the molded parts.

  11. Mechanical and Thermal Properties of Polysiloxanes and NBR Blend Elastomer

    Institute of Scientific and Technical Information of China (English)

    WANG Yanbing; HUANG Zhixiong; ZHANG Lianmeng; MEI Qilin

    2006-01-01

    A series of elastomers, based on NBR, polysiloxanes (PS) were prepared and characterized by tensile tests, thermogravimetry (TG) and differential scanning calorimetry ( DSC ). Two kinds of vulcanizing agent, DMDBH ( 2 , 5- dimethyl- 2 , 5- di ( t- batyl perory ) hexane ) and DCP ( dicumylperoxide ) were used to investigate the irfluence of different vulcanizing agents on properties of PS/NBR. The addition of PS to NBR was found to improve the thermal stability and decrease the tensile strength of NBR. The tensile strength decreased considerably while the elongation at break increased obviously with the increase of PS content. The series using DMDBH as vulcanizing agent showed a higher tensile strength and elongation at break than the series using DCP as vulcanizing agent. Simultaneity the thermal stability increased with the increase of PS content.

  12. Study on Dynamic Vulcanized EPDM/PP Thermoplastic Elastomer

    Institute of Scientific and Technical Information of China (English)

    YANG ShiYuan

    2001-01-01

    @@ Based upon the THE,HAAK RHEOCORD 90 and Wx-ray observation,a study was made on the structure and property of ethylene-propylene-ethlidene norborene (EPDM)/polyprolene (PP) blending systems ,and the experimental results were fully explained. (1) The effect of Mooney viscosity (ML)of EPDM、 melt flow rate(MFR) of peroxide(DCP) and mixing steps on mechanical properties of EPDM/PP blends was studied. The results showed that the mechanical and process properties of EPDM?PP thermoplastic elastomers were better using EPDM with the ML of 60 and PP with MFR of 7.5g/10min as matrix,DCP with the content of 1.2 per cent with the help of twostep curing process at the temperature of 170-175 ℃.

  13. Study on Dynamic Vulcanized EPDM/PP Thermoplastic Elastomer

    Institute of Scientific and Technical Information of China (English)

    YANG; ShiYuan

    2001-01-01

    Based upon the THE,HAAK RHEOCORD 90 and Wx-ray observation,a study was made on the structure and property of ethylene-propylene-ethlidene norborene (EPDM)/polyprolene (PP) blending systems ,and the experimental results were fully explained.  (1) The effect of Mooney viscosity (ML)of EPDM、 melt flow rate(MFR) of peroxide(DCP) and mixing steps on mechanical properties of EPDM/PP blends was studied. The results showed that the mechanical and process properties of EPDM?PP thermoplastic elastomers were better using EPDM with the ML of 60 and PP with MFR of 7.5g/10min as matrix,DCP with the content of 1.2 per cent with the help of twostep curing process at the temperature of 170-175 ℃.……

  14. Tunable Properties of Magnetoactive Elastomers for Biomedical Applications

    Science.gov (United States)

    Makarova, Liudmila A.; Alekhina, Yuliya A.; Rusakova, Tatiana S.; Perov, Nikolai S.

    The remote controllable magneto-mechanical devices based on MAEs (magnetoactive elastomers) can be obtained through variation of magnetic parameters of MAEs. Such devices can be used as the elements of peristaltic systems, artificial muscles, hyperthermia or drug delivery. MAEs with different matrix rigidity and filler particles type were investigated with VSM Lakeshore 7400 series and immittance meter Aktakom AM-3016 model. The dependencies of magnetostatic and magnetodynamic properties of MAEs with different types of magnetic particles on concentration of the magnetic filler and DC magnetic field strength were studied. There is a possibility to control the "magnetic hardness", energy absorption and heating, relaxation properties of MAEs which allow to use MAEs as the main element of the tunable devices for biomedical applications.

  15. A flexible micro fluid transport system featuring magnetorheological elastomer

    Science.gov (United States)

    Behrooz, Majid; Gordaninejad, Faramarz

    2016-02-01

    This study presents a flexible magnetically-actuated micro fluid transport system utilizing an isotropic magnetorheological elastomer (MRE). Theoretical modeling and analysis of this system is presented for a two-dimensional model. This fluid transport system can propel the fluid by applying a fluctuating magnetic field on the MRE. The magneto-fluid-structure interaction analysis is employed to determine movement of the solid domain and the velocity of the fluid under a controllable magnetic field. The effects of key material, geometric, and magnetic parameters on the behavior of this system are examined. It is demonstrated that the proposed system can propel the fluid unidirectionally, and the volume of the transported fluid is significantly affected by some of the design parameters.

  16. Stronger multilayer acrylic dielectric elastomer actuators with silicone gel coatings

    Science.gov (United States)

    Lau, Gih-Keong; La, Thanh-Giang; Sheng-Wei Foong, Ervin; Shrestha, Milan

    2016-12-01

    Multilayer dielectric elastomer actuators (DEA) perform worst off than single-layer DEAs due to higher susceptibility to electro-thermal breakdown. This paper presents a hot-spot model to predict the electro-thermal breakdown field of DEAs and its dependence on thermal insulation. To inhibit the electrothermal breakdown, silicone gel coating was applied as barrier coating to multilayer acrylic DEA. The gel coating helps suppress the electro-thermally induced puncturing of DEA membrane at the hot spot. As a result, the gel-coated DEAs, in either a single layer or a multilayer stack, can produce 30% more isometric stress change as compared to those none-coated. These gel-coated acrylic DEAs show great potential to make stronger artificial muscles.

  17. Numerical investigation of smart base isolation system employing MR elastomer

    Science.gov (United States)

    Usman, M.; Sung, S. H.; Jang, D. D.; Jung, H. J.; Koo, J. H.

    2009-02-01

    This paper evaluates the dynamic performance of a newly proposed smart base isolation system employing Magneto-Rheological Elastomers (MREs). MREs belong to a class of smart materials whose elastic modulus or stiffness can be adjusted by varying the magnitude of the magnetic field. The base isolation systems are considered as one of the most effective devices for vibration reduction of civil engineering structures in the event of earthquakes. The proposed base isolation system strives to enhance the performance of the conventional base-isolation system by using controllable MREs. To validate the effectiveness of the MRE-based isolation system, an extensive simulation study has been performed using a five degree-of-freedom structure under several historical earthquake excitations. The results show that the proposed system outperformed the conventional system in reducing the responses of the structure in all the seismic excitations considered in the study.

  18. Organically Modified Aero-Sol Gel Silica for Elastomer Reinforcement

    Science.gov (United States)

    Pratsinis, S. E.; Kohls, D. J.; Beaucage, G.

    2000-03-01

    We have developed facilities to produce organically functionalized silicas using a novel, room-temperature, aerosol, chemical reactor (ASG reactor). This reactor can produce exceedingly high surface area nano-structured materials (up to 800 m2/g) with tuned interfacial chemistries. This poster will present our results on dynamic mechanical properties of elastomer compounds with ASG-organically modified silicas and comparison with conventional carbon black, conventional precipated and fumed silica as well as blends of the conventional materials. The mass-fractal structure as determined by SAXS and SALS, as well as conventional gas and DBP absorption measurements and microscopy will be presented. Hyeon-Lee, J.; Beaucage, G.; Pratsinis, S. E. (1997) Chem. of Mat. 9, 2400. Hyeon-Lee, J.; Beaucage, G.; Pratsinis, S. E.; Vemury, S. (1998) Langmuir 5751.

  19. Experimental study on the dielectric properties of polyacrylate dielectric elastomer

    Science.gov (United States)

    Qiang, Junhua; Chen, Hualing; Li, Bo

    2012-02-01

    The dielectric constant of elastomeric dielectric material is an essential physical parameter, whose value may affect the electromechanical deformation of a dielectric elastomer actuator. Since the dielectric constant is influenced by several external factors as reported before, and no certain value has been confirmed to our knowledge, in the present paper, on the basis of systematical comparison of recent past literature, we conducted extensive works on the measurement of dielectric properties of VHB films, involving five influencing factors: prestretch (both equal and unequal biaxial), electrical frequency, electrode material, stress relaxation time and temperature. Experimental results directly show that the dielectric response changes according to these factors, based on which we investigate the significance of each factor, especially the interaction of two external conditions on the dielectric constant of deformable dielectric, by presenting a physical picture of the mechanism of polarization.

  20. A solid-state dielectric elastomer switch for soft logic

    Energy Technology Data Exchange (ETDEWEB)

    Chau, Nixon [Biomimetics Laboratory, Auckland Bioengineering Institute, The University of Auckland, Level 6, 70 Symonds Street, Auckland 1010 (New Zealand); Slipher, Geoffrey A., E-mail: geoffrey.a.slipher.civ@mail.mil; Mrozek, Randy A. [U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States); O' Brien, Benjamin M. [StretchSense, Ltd., 27 Walls Rd., Penrose, Auckland 1061 (New Zealand); Anderson, Iain A. [Biomimetics Laboratory, Auckland Bioengineering Institute, The University of Auckland, Level 6, 70 Symonds Street, Auckland 1010 (New Zealand); StretchSense, Ltd., 27 Walls Rd., Penrose, Auckland 1061 (New Zealand); Department of Engineering Science, School of Engineering, The University of Auckland, Level 3, 70 Symonds Street, Auckland 1010 (New Zealand)

    2016-03-07

    In this paper, we describe a stretchable solid-state electronic switching material that operates at high voltage potentials, as well as a switch material benchmarking technique that utilizes a modular dielectric elastomer (artificial muscle) ring oscillator. The solid-state switching material was integrated into our oscillator, which self-started after 16 s and performed 5 oscillations at a frequency of 1.05 Hz with 3.25 kV DC input. Our materials-by-design approach for the nickel filled polydimethylsiloxane based switch has resulted in significant improvements over previous carbon grease-based switches in four key areas, namely, sharpness of switching behavior upon applied stretch, magnitude of electrical resistance change, ease of manufacture, and production rate. Switch lifetime was demonstrated to be in the range of tens to hundreds of cycles with the current process. An interesting and potentially useful strain-based switching hysteresis behavior is also presented.

  1. Dynamic analyses of viscoelastic dielectric elastomers incorporating viscous damping effect

    Science.gov (United States)

    Zhang, Junshi; Zhao, Jianwen; Chen, Hualing; Li, Dichen

    2017-01-01

    In this paper, based on the standard linear solid rheological model, a dynamics model of viscoelastic dielectric elastomers (DEs) is developed with incorporation of viscous damping effect. Numerical calculations are employed to predict the damping effect on the dynamic performance of DEs. With increase of damping force, the DEs show weak nonlinearity and vibration strength. Phase diagrams and Poincaré maps are utilized to detect the dynamic stability of DEs, and the results indicate that a transition from aperiodic vibration to quasi-periodic vibration occurs with enlargement of damping force. The resonance properties of DEs including damping effect are subsequently analyzed, demonstrating a reduction of resonant frequency and resonance peak with increase of damping force.

  2. Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers.

    Science.gov (United States)

    Lehmann, W; Skupin, H; Tolksdorf, C; Gebhard, E; Zentel, R; Krüger, P; Lösche, M; Kremer, F

    2001-03-22

    Mechanisms for converting electrical energy into mechanical energy are essential for the design of nanoscale transducers, sensors, actuators, motors, pumps, artificial muscles, and medical microrobots. Nanometre-scale actuation has to date been mainly achieved by using the (linear) piezoelectric effect in certain classes of crystals (for example, quartz), and 'smart' ceramics such as lead zirconate titanate. But the strains achievable in these materials are small--less than 0.1 per cent--so several alternative materials and approaches have been considered. These include grafted polyglutamates (which have a performance comparable to quartz), silicone elastomers (passive material--the constriction results from the Coulomb attraction of the capacitor electrodes between which the material is sandwiched) and carbon nanotubes (which are slow). High and fast strains of up to 4 per cent within an electric field of 150 MV x m(-1) have been achieved by electrostriction (this means that the strain is proportional to the square of the applied electric field) in an electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Here we report a material that shows a further increase in electrostriction by two orders of magnitude: ultrathin (less than 100 nanometres) ferroelectric liquid-crystalline elastomer films that exhibit 4 per cent strain at only 1.5 MV x m(-1). This giant electrostriction was obtained by combining the properties of ferroelectric liquid crystals with those of a polymer network. We expect that these results, which can be completely understood on a molecular level, will open new perspectives for applications.

  3. Synthesis of thermoplastic poly(ester-olefin elastomers

    Directory of Open Access Journals (Sweden)

    Tanasijević Branka

    2004-01-01

    Full Text Available A series of thermoplastic poly(ester-olefin elastomers, based on poly(ethylene-stat-butylene, HO-PEB-OH, as the soft segment and poly (butylene terephthalate, PBT, as the hard segment, were synthesized by a catalyzed transesterification reaction in solution. The incorporation of soft hydrogenated poly(butadiene segments into the copolyester backbone was accomplished by the polycondensation of α, ω-dihydroxyl telechelic HO-PEB-OH, (PEB Mn = 3092 g/mol with 1,4-butanediol (BD and dimethyl terephthalate (DMT in the presence of a 50 wt-% high boiling solvent i.e., 1,2,4-trichlorobenzene. The molar ratio of the starting comonomers was selected to result in a constant hard to soft weight ratio of 60:40. The synthesis was optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate (Ti(OBu4, and stabilizer, N,N'-diphenyl-p-phenylenediamine (DPPD, as well as the reaction time. It was found that the optimal catalyst concentration (Ti(OBu4 for the synthesis of these thermoplastic elastomers was 1.0 mmol/mol ester and the optimal DPPD concentration was 1.0 wt-%. The extent of the reaction was followed by measuring the inherent viscosity of the reaction mixture. The effectiveness of the incorporation of the soft segments into the copolymer chains was proved by Soxhlet extraction with chloroform. The molecular structures, composition and the size of the synthesized poly(ester-butylenes were verified by 1H NMR spectroscopy, viscometry of dilute solutions and the complex dynamic melt viscosity. The thermal properties of poly(ester-olefins were investigated by differential scanning calorimetry (DSC. The degree of crystallinity was also determined by DSC. The thermal and thermo-oxidative stability were investigated by thermogravimetric analysis (TGA. The rheological properties of poly(ester-olefins were investigated by dynamic mechanical spectroscopy in the melt and solid state.

  4. Toughening mechanism in elastomer-modified epoxy resins, part 2

    Science.gov (United States)

    Yee, A. F.; Pearson, R. A.

    1984-01-01

    The role of matrix ductility on the toughenability and toughening mechanism of elastomer-modified DGEBRA epoxies was investigated. Matrix ductility was varied by using epoxide resins of varying epoxide monomer molecular weights. These epoxide resins were cured using 4,4' diaminodiphenyl sulfone (DDS) and, in some cases, modified with 10% HYCAR(r)CTBN 1300X8. Fracture roughness values for the neat epoxies were found to be almost independent on the monomer molecular weight of the epoxide resin used. However, it was found that the fracture toughness of the elastomer-modified epoxies was very dependent upon the epoxide monomer molecular weight. Tensile dilatometry indicated that the toughening mechanism, when present, is similar to the mechanisms found for the piperidine cured epoxies in Part 1. SEM and OM corroborate this finding. Dynamic mechanical studies were conducted to shed light on the toughenability of the epoxies. The time-dependent small strain behavior of these epoxies were separated into their bulk and shear components. The bulk component is related to brittle fracture, whereas the shear component is related to yielding. It can be shown that the rates of shear and bulk strain energy buildup for a given stress are uniquely determined by the values of Poisson's ratio, nu. It was found that nu increases as the monomer molecular weight of the epoxide resin used increases. This increase in nu can be associated with the low temperature beta relaxation. The effect of increasing cross-link density is to shift the beta relaxation to higher temperatures and to decrease the magnitude of the beta relaxation. Thus, increasing cross-link density decreases nu and increases the tendency towards brittle fracture.

  5. Large Lightweight Mirrors Controlled by Dielectric Elastomer Artifical Muscle

    Science.gov (United States)

    Kornbluh, R. D.; Flamm, D. S.; Vujkovic-Civijin, P.; Pelrine, R. E.; Huestis, D. L.

    2002-05-01

    We will describe a new concept for control of the lightweight large-aperture mirrors that will be required for future space-based astronomy and remote sensing applications. To be cost effective and practical, such optical systems must be lightweight and capable of deployment from highly compacted stowed configurations. Optical systems based on membrane mirrors or other lightweight structures can address some of these needs, but such flexible gossamer structures present challenges in achieving and maintaining the required shape or figure. For the past 9 years SRI has been exploring dielectric elastomer artifical muscle technology for active control of objects and structures [1-2]. The basic functional element is a thin polymer film coated on both sides by a compliant electrode material. When voltage is applied between the top and bottom electrodes, an electrostrictive compressive force squeezes the film, causing it to expand in area. The induced forces are related to the square of the voltage. If we assemble a large mirror from numerous independently addressable elements, sophisticated control is possible, even including adaptive optics. Dielectric elastomers have many advantages over other electroactive polymers and other smart-materials actuation technologies that have been considered in the past. For example, from many candidate materials we can choose ones with high planar strains, low power dissipation, tolerance of the space environment, and ease of commercial fabrication into large sheets. [1] R. Pelrine, R. Kornbluh, Q. Pei, and J. Joseph, Science 287, 386 (2000). [2] R. Pelrine, P. Sommer-Larson, R. Kornbluh, R. Heydt, G. Kofod, Q. Pei, and P. Gravesen, in Smart Structures and Materials 2001: Electroactive Polymer Actuators and Devices, ed. Y. Bar-Cohen, Proc. SPIE 4329, 335 (2001).

  6. Modelling and control of double-cone dielectric elastomer actuator

    Science.gov (United States)

    Branz, F.; Francesconi, A.

    2016-09-01

    Among various dielectric elastomer devices, cone actuators are of large interest for their multi-degree-of-freedom design. These objects combine the common advantages of dielectric elastomers (i.e. solid-state actuation, self-sensing capability, high conversion efficiency, light weight and low cost) with the possibility to actuate more than one degree of freedom in a single device. The potential applications of this feature in robotics are huge, making cone actuators very attractive. This work focuses on rotational degrees of freedom to complete existing literature and improve the understanding of such aspect. Simple tools are presented for the performance prediction of the device: finite element method simulations and interpolating relations have been used to assess the actuator steady-state behaviour in terms of torque and rotation as a function of geometric parameters. Results are interpolated by fit relations accounting for all the relevant parameters. The obtained data are validated through comparison with experimental results: steady-state torque and rotation are determined at a given high voltage actuation. In addition, the transient response to step input has been measured and, as a result, the voltage-to-torque and the voltage-to-rotation transfer functions are obtained. Experimental data are collected and used to validate the prediction capability of the transfer function in terms of time response to step input and frequency response. The developed static and dynamic models have been employed to implement a feedback compensator that controls the device motion; the simulated behaviour is compared to experimental data, resulting in a maximum prediction error of 7.5%.

  7. Synthesis and properties of butadiene-alpha-methylstyrene thermoplastic elastomer

    Directory of Open Access Journals (Sweden)

    A. V. Firsova

    2016-01-01

    Full Text Available Butadiene-α-methylstyrene block – copolymer – a thermoplastic elastomer (TPE-R DMST occupies a special place among the ethylene – vinyl aromatic block copolymers. TPE-R DMST comprising as plastic – poly-α-methylstyrene unit and elastic – polybutadiene block. TPE-R DMST has high heat resistance, flexibility, abrasion resistance compared to butadiene-styrene thermoplastic elastomer (TPE DST. The synthesis of block copolymers of butadiene and α-methylstyrene was carried out. The process of polymerization the α-methylstyrene characterized the high speed of polymerization in polar medium and low reaction speed in hydrocarbon solvents. Anionic catalyst nbutyllithium (n-BuLi and high concentration – 60–80% α-methylstyrene in the mixture influenced by synthesis of the 1st block of TPE-R DMST, it’s technologically difficult. Found that the low temperature of polymerization α-methylstyrene (+61 o C, the reversibility of these reactions and the high concentration of residual monomer are very importance. It was revealed that a high polymerization rate α-methylstyrene can be achieved by conducting the reaction in a hydrocarbon solvent with polar additives compounds such as tetrahydrofuran (THF and methyl tert-butyl ether (MTBE. The conditions for the synthesis of P-DMST were developed. The kinetics of polymerization for the first DMST-P unit was obtained. Analysis of physical and mechanical properties DMST-P samples was conducted. The optimum content of bound α-methylstyrene block copolymer provides a good combination of properties in a relatively wide temperature range. The tensile strength at normal and elevated temperatures, the hardness and the stiffness of the polymer increased by increasing the content of bound α-methylstyrene. The elongation and the elasticity reduced by increasing the content of bound α-methylstyrene.

  8. Molecular beam deposition of high-permittivity polydimethylsiloxane for nanometer-thin elastomer films in dielectric actuators

    DEFF Research Database (Denmark)

    M. Weiss, Florian; Madsen, Frederikke Bahrt; Töpper, Tino

    2016-01-01

    monitoring. Using atomic force microscopy, the film surface morphology and mechanics were characterized after growth termination and subsequent curing. The Young's modulus of the elastomer corresponded to (1.8 ± 0.2) MPa and is thus a factor of two lower than that of DMS-V05. Consequently, the properties......To realize low-voltage dielectric elastomer actuators (DEAs) for artificial muscles, a high-permittivity elastomer and a related thin-film deposition technique must be selected. For polydimethylsiloxane, fillers or functionalized crosslinkers have been incorporated into the elastomer to improve...

  9. Autonomous Gaussian Decomposition

    CERN Document Server

    Lindner, Robert R; Murray, Claire E; Stanimirović, Snežana; Babler, Brian L; Heiles, Carl; Hennebelle, Patrick; Goss, W M; Dickey, John

    2014-01-01

    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21cm absorption spectra from the 21cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the HI line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the up...

  10. Erbium hydride decomposition kinetics.

    Energy Technology Data Exchange (ETDEWEB)

    Ferrizz, Robert Matthew

    2006-11-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.

  11. Differentially Private Spatial Decompositions

    CERN Document Server

    Cormode, Graham; Shen, Entong; Srivastava, Divesh; Yu, Ting

    2011-01-01

    Differential privacy has recently emerged as the de facto standard for private data release. This makes it possible to provide strong theoretical guarantees on the privacy and utility of released data. While it is well-known how to release data based on counts and simple functions under this guarantee, it remains to provide general purpose techniques to release different kinds of data. In this paper, we focus on spatial data such as locations and more generally any data that can be indexed by a tree structure. Directly applying existing differential privacy methods to this type of data simply generates noise. Instead, we introduce a new class of "private spatial decompositions": these adapt standard spatial indexing methods such as quadtrees and kd-trees to provide a private description of the data distribution. Equipping such structures with differential privacy requires several steps to ensure that they provide meaningful privacy guarantees. Various primitives, such as choosing splitting points and describi...

  12. Decomposition methods for unsupervised learning

    DEFF Research Database (Denmark)

    Mørup, Morten

    2008-01-01

    This thesis presents the application and development of decomposition methods for Unsupervised Learning. It covers topics from classical factor analysis based decomposition and its variants such as Independent Component Analysis, Non-negative Matrix Factorization and Sparse Coding to their genera......This thesis presents the application and development of decomposition methods for Unsupervised Learning. It covers topics from classical factor analysis based decomposition and its variants such as Independent Component Analysis, Non-negative Matrix Factorization and Sparse Coding...... methods and clustering problems is derived both in terms of classical point clustering but also in terms of community detection in complex networks. A guiding principle throughout this thesis is the principle of parsimony. Hence, the goal of Unsupervised Learning is here posed as striving for simplicity...... in the decompositions. Thus, it is demonstrated how a wide range of decomposition methods explicitly or implicitly strive to attain this goal. Applications of the derived decompositions are given ranging from multi-media analysis of image and sound data, analysis of biomedical data such as electroencephalography...

  13. Thermal decomposition of lutetium propionate

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2010-01-01

    The thermal decomposition of lutetium(III) propionate monohydrate (Lu(C2H5CO2)3·H2O) in argon was studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy and X-ray diffraction. Dehydration takes place around 90 °C. It is followed by the decomposition of the anhydrous ...... of the oxycarbonate to the rare-earth oxide proceeds in a different way, which is here reminiscent of the thermal decomposition path of Lu(C3H5O2)·2CO(NH2)2·2H2O...

  14. AUTONOMOUS GAUSSIAN DECOMPOSITION

    Energy Technology Data Exchange (ETDEWEB)

    Lindner, Robert R.; Vera-Ciro, Carlos; Murray, Claire E.; Stanimirović, Snežana; Babler, Brian [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Heiles, Carl [Radio Astronomy Lab, UC Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Hennebelle, Patrick [Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp-CNRS-Université Paris Diderot, F-91191 Gif-sur Yvette Cedex (France); Goss, W. M. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville, Socorro, NM 87801 (United States); Dickey, John, E-mail: rlindner@astro.wisc.edu [University of Tasmania, School of Maths and Physics, Private Bag 37, Hobart, TAS 7001 (Australia)

    2015-04-15

    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21 cm absorption spectra from the 21 cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the H i line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the upcoming Square Kilometer Array and pathfinder telescopes.

  15. Some nonlinear space decomposition algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Tai, Xue-Cheng; Espedal, M. [Univ. of Bergen (Norway)

    1996-12-31

    Convergence of a space decomposition method is proved for a general convex programming problem. The space decomposition refers to methods that decompose a space into sums of subspaces, which could be a domain decomposition or a multigrid method for partial differential equations. Two algorithms are proposed. Both can be used for linear as well as nonlinear elliptic problems and they reduce to the standard additive and multiplicative Schwarz methods for linear elliptic problems. Two {open_quotes}hybrid{close_quotes} algorithms are also presented. They converge faster than the additive one and have better parallelism than the multiplicative method. Numerical tests with a two level domain decomposition for linear, nonlinear and interface elliptic problems are presented for the proposed algorithms.

  16. Aging Behavior and Performance Projections for a Polysulfide Elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Celina, Mathias C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Giron, Nicholas Henry [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Quintana, Adam [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-05-01

    The accelerated aging behavior and aging state of a 30 year old field retrieved polysulfide elastomer was examined. The material is used as an environmental thread sealant for a stainless steel bolt in a steel threaded insert in an aluminum assembly. It is a two component curable polysulfide elastomer that is commercially available in a similar formulation as was applied 30 years ago. The primary goal of this study was to establish if aging over 30 years under moderate aging conditions (mostly ambient temperature and humidity) resulted in significant property changes, or if accelerated aging could identify developing aging pathways which would prevent the extended use of this material. The aging behavior of this material was examined in three ways: A traditional accelerated thermo-oxidative aging study between 95 to 140°C which focused on physical and chemical properties changes, an evaluation of the underlying oxidation rates between RT and 125°C, and an assessment of the aging state of a small 30 year old sample. All three data sets were used to establish aging characteristics, their time evolution, and to extrapolate the observed behavior to predict performance limits at RT. The accelerated aging study revealed a relatively high average activation energy of ~130 kJ/mol which gives overconfident performance predictions. Oxidation rates showed a decreasing behavior with aging time and a lower E a of ~84 kJ/mol from time - temperature superposition , but also predicted sufficient additional performance at RT. Consistent with these projections for extended RT performance, only small changes were observed for the 30 year old material. Extrapolations using this partially aged material also predict ongoing use as a viable option. Unexpected RT degradation could only develop into a concern should the oxidation rate not trend lower over time as was observed at elevated temperature. Considering all data acquired in this limited aging study , there are no immediately

  17. Aging Behavior and Performance Projections for a Polysulfide Elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Celina, Mathias C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Giron, Nicholas Henry [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Quintana, Adam [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-05-01

    The accelerated aging behavior and aging state of a 30 year old field retrieved polysulfide elastomer was examined. The material is used as an environmental thread sealant for a stainless steel bolt in a steel threaded insert in an aluminum assembly. It is a two component curable polysulfide elastomer that is commercially available in a similar formulation as was applied 30 years ago. The primary goal of this study was to establish if aging over 30 years under moderate aging conditions (mostly ambient temperature and humidity) resulted in significant property changes, or if accelerated aging could identify developing aging pathways which would prevent the extended use of this material. The aging behavior of this material was examined in three ways: A traditional accelerated thermo-oxidative aging study between 95 to 140°C which focused on physical and chemical properties changes, an evaluation of the underlying oxidation rates between RT and 125°C, and an assessment of the aging state of a small 30 year old sample. All three data sets were used to establish aging characteristics, their time evolution, and to extrapolate the observed behavior to predict performance limits at RT. The accelerated aging study revealed a relatively high average activation energy of ~130 kJ/mol which gives overconfident performance predictions. Oxidation rates showed a decreasing behavior with aging time and a lower E a of ~84 kJ/mol from time - temperature superposition , but also predicted sufficient additional performance at RT. Consistent with these projections for extended RT performance, only small changes were observed for the 30 year old material. Extrapolations using this partially aged material also predict ongoing use as a viable option. Unexpected RT degradation could only develop into a concern should the oxidation rate not trend lower over time as was observed at elevated temperature. Considering all data acquired in this limited aging study , there are no immediately

  18. A self-healing poly(dimethyl siloxane) elastomer

    Science.gov (United States)

    Keller, Michael Wade

    2007-12-01

    In this work, self-healing functionality is imparted to a poly(dimethyl siloxane) (PDMS) elastomer with low modulus and high strain-to-failure behavior. This material utilizes a two-microcapsule system to provide a mechanism for autonomic repair of damage. One microcapsule type contains a functionalized high-molecular-weight resin and organometallic catalyst compounds. The second microcapsule type contains a functional copolymer (initiator) that facilitates the crosslinking of the resin via the action of the catalyst. The healing response is triggered when damage, in the form of a tear, puncture, or crack, propagates through the material and ruptures a resin and initiator capsule. Ruptured capsules release their contents onto the crack plane, initiating polymerization. The polymerized material bonds the two crack faces together regaining much of the original strength, of the matrix material. The mechanical behavior of the microcapsules is studied using a combination of individual microcapsule compression tests and in-situ microscopic analysis. Single-capsule compression tests are performed to extract the modulus of the capsule shell wall and to investigate the behavior of microcapsules under large deformations. The capsules are shown to survive matrix deformation in excess of 45%. Although the microcapsules are robust and endure large matrix deformations, an approaching tear does successfully rupture the capsules. A tear test protocol is adopted to assess the healing efficiency of this new material. Self-healing PDMS specimens with 5 wt% initiator and 5 wt% resin microcapsules recover 97% of the original tear strength. Complete recovery of tear strength is possible under certain conditions. Addition of microcapsules to the PDMS matrix increases the tear strength of the material by 25%. Embedded microcapsules also increase the elastic stiffness by as much as 57%. The self-healing performance of the elastomer is also investigated under torsional fatigue loading. The

  19. Synthesis of antibacterial amphiphilic elastomer based on polystyrene-block-polyisoprene-block-polystyrene via thiol-ene addition

    Energy Technology Data Exchange (ETDEWEB)

    Keleş, Elif, E-mail: elifkelesh@hotmail.com [Department of Chemistry, Bülent Ecevit University, Zonguldak 67100 (Turkey); Hazer, Baki, E-mail: bhazer2@yahoo.com [Department of Chemistry, Bülent Ecevit University, Zonguldak 67100 (Turkey); Cömert, Füsun B. [Department of Microbiology, Faculty of Medicine, Bülent Ecevit University, 67600 Zonguldak (Turkey)

    2013-04-01

    A new type of amphiphilic antibacterial elastomer has been described. Thermoplastic elastomer, polystyrene–block-polyisoprene–block-polystyrene (PS–b-PI–b-PS) triblock copolymer was functionalized in toluene solution by free radical mercaptan addition in order to obtain an amphiphilic antibacterial elastomer. Thiol terminated PEG was grafted through the double bonds of PS–b-PI–b-PS via free radical thiol-ene coupling reaction. The antibacterial properties of the amphiphilic graft copolymers were observed. The original and the modified polymers were used to create microfibers in an electro-spinning process. Topology of the electrospun micro/nanofibers were studied by using scanning electron microscopy (SEM). The chemical structures of the amphiphilic comb type graft copolymers were elucidated by the combination of elemental analysis, {sup 1}H NMR, {sup 13}C NMR, GPC and FTIR. - Graphical abstract: Double bonds of polyisoprene units in polystyrene–block-polyisoprene–block-polystyrene triblock copolymer were partially capped with PEG containing mercapto end group via thiol-ene addition in order to obtain antibacterial amphiphilic elastomer. Nano fibers from amphiphilic graft polymers solution were produced by electrospinning. The PEG grafted copolymer inhibits very effectively bacterial growth. Highlights: ► A commercial synthetic elastomer was grafted with PEG to obtain amphiphilic elastomer. ► Amphiphilic elastomer shows antibacterial properties. ► Electrospun micro fibers of the amphiphilic elastomer tend to globular formation.

  20. Microbial degradation of linseed oil-based elastomer and subsequent accumulation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer.

    Science.gov (United States)

    Pramanik, Nilkamal; Das, Rakesh; Rath, Tanmoy; Kundu, P P

    2014-10-01

    The microbial synthesis of environment-friendly poly(3-hydroxybutyrate--co-3-hydroxyvalerate), PHBV, has been performed by using an alkaliphilic microorganism, Alkaliphilus oremlandii OhILAs strain (GenBank Accession number NR_043674.1), at pH 8 and at a temperature of 30-32 °C through the biodegradation of linseed oil-based elastomer. The yield of the copolymer on dry cell weight basis is 90 %. The elastomers used for the biodegradation have been synthesized by cationic polymerization technique. The yield of the PHBV copolymer also varies with the variation of linseed oil content (30-60 %) in the elastomer. Spectroscopic characterization ((1)H NMR and FTIR) of the accumulated product through biodegradation of linseed oil-based elastomers indicates that the accumulated product is a PHBV copolymer consisting of 13.85 mol% of 3-hydroxyvalerate unit. The differential scanning calorimetry (DSC) results indicate a decrease in the melting (T m) and glass transition temperature (T g) of PHBV copolymer with an increase in the content of linseed oil in the elastomer, which is used for the biodegradation. The gel permeation chromatography (GPC) results indicate that the weight average molecular weight (M w) of PHBV copolymer decreases with an increasing concentration of linseed oil in the elastomer. The surface morphology of the elastomer before and after biodegradation is observed under scanning electron microscope (SEM) and atomic force microscope (AFM); these results indicate about porous morphology of the biodegraded elastomer.

  1. Mechanical and Electrical Ageing Effects on the Long-Term Stretching of Silicone Dielectric Elastomers with Soft Fillers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin; Yu, Liyun

    2016-01-01

    Dielectric elastomer materials for actuators need to be soft and stretchable while possessing high dielectric permittivity. Soft silicone elastomers can be obtained through the use of silicone oils, while enhanced permittivity can be obtained through the use of dipolar groups on the polymer backb...

  2. Mechanical and Electrical Ageing Effects on the Long-Term Stretching of Silicone Dielectric Elastomers with Soft Fillers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin; Yu, Liyun

    2016-01-01

    Dielectric elastomer materials for actuators need to be soft and stretchable while possessing high dielectric permittivity. Soft silicone elastomers can be obtained through the use of silicone oils, while enhanced permittivity can be obtained through the use of dipolar groups on the polymer backb...

  3. Finite element analysis and validation of dielectric elastomer actuators used for active origami

    Science.gov (United States)

    McGough, Kevin; Ahmed, Saad; Frecker, Mary; Ounaies, Zoubeida

    2014-09-01

    The field of active origami explores the incorporation of active materials into origami-inspired structures in order to serve as a means of actuation. Active origami-inspired structures capable of folding into complex three-dimensional (3D) shapes have the potential to be lightweight and versatile compared to traditional methods of actuation. This paper details the finite element analysis and experimental validation of unimorph actuators. Actuators are fabricated by adhering layers of electroded dielectric elastomer (3M VHB F9473PC) onto a passive substrate layer (3M Magic Scotch Tape). Finite element analysis of the actuators simulates the electromechanical coupling of the dielectric elastomer under an applied voltage by applying pressures to the surfaces of the dielectric elastomer where the compliant electrode (conductive carbon grease) is present. 3D finite element analysis of the bending actuators shows that applying contact boundary conditions to the electroded region of the active and passive layers provides better agreement to experimental data compared to modeling the entire actuator as continuous. To improve the applicability of dielectric elastomer-based actuators for active origami-inspired structures, folding actuators are developed by taking advantage of localized deformation caused by a passive layer with non-uniform thickness. Two-dimensional analysis of the folding actuators shows that agreement to experimental data diminishes as localized deformation increases. Limitations of using pressures to approximate the electromechanical coupling of the dielectric elastomer under an applied electric field and additional modeling considerations are also discussed.

  4. Study on the control of the compositions and properties of a biodegradable polyester elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Liu Quanyong; Weng Jingyi; Zhang Liqun [Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029 (China); Tan Tianwei, E-mail: liu_quanyong@126.co, E-mail: zhanglq@mail.buct.edu.c [Key Laboratory of Bioprocess of Beijing, Beijing University of Chemical Technology, Beijing 100029 (China)

    2009-04-15

    Biodegradable polyester elastomers are widely reported to be applied in varied biomedical fields. In this paper, we attempt to investigate how both the thermal-curing time and molar ratio of the monomers affect the final compositions and properties of the novel poly(glycerol-sebacate-citrate) (PGSC) elastomers. First, PGSC elastomers are obtained after the thermal curing of the moldable mixtures consisting of citric acid and poly(glycerol-sebacate) (PGS) prepolymers synthesized in the lab. Then further studies show that, on the one hand, the control of longer thermal-curing time results in elastomers with less sol, lower swelling degree, slower degradation, greater mechanical strength and higher glass transition temperature and, on the other hand, the crosslink with more citric acid is advantageous to greatly improving their mechanical strength and glass transition temperatures, simultaneously decreasing their sol contents, swelling degrees and degradation rates. The PGSC elastomers show thermosetting properties, certain strength, mass losses lower than 20% after 4-week degradation and durative water absorption during degradation. Thus they might be potentially used as degradable bio-coatings, varied soft biomedical membranes and drug delivery matrices.

  5. Study on the control of the compositions and properties of a biodegradable polyester elastomer.

    Science.gov (United States)

    Liu, Quanyong; Tan, Tianwei; Weng, Jingyi; Zhang, Liqun

    2009-04-01

    Biodegradable polyester elastomers are widely reported to be applied in varied biomedical fields. In this paper, we attempt to investigate how both the thermal-curing time and molar ratio of the monomers affect the final compositions and properties of the novel poly(glycerol-sebacate-citrate) (PGSC) elastomers. First, PGSC elastomers are obtained after the thermal curing of the moldable mixtures consisting of citric acid and poly(glycerol-sebacate) (PGS) prepolymers synthesized in the lab. Then further studies show that, on the one hand, the control of longer thermal-curing time results in elastomers with less sol, lower swelling degree, slower degradation, greater mechanical strength and higher glass transition temperature and, on the other hand, the crosslink with more citric acid is advantageous to greatly improving their mechanical strength and glass transition temperatures, simultaneously decreasing their sol contents, swelling degrees and degradation rates. The PGSC elastomers show thermosetting properties, certain strength, mass losses lower than 20% after 4-week degradation and durative water absorption during degradation. Thus they might be potentially used as degradable bio-coatings, varied soft biomedical membranes and drug delivery matrices.

  6. Enhanced electromechanical performance of bio-based gelatin/glycerin dielectric elastomer by cellulose nanocrystals.

    Science.gov (United States)

    Ning, Nanying; Wang, Zhifei; Yao, Yang; Zhang, Liqun; Tian, Ming

    2015-10-05

    To meet the growing demand of environmental protection and resource saving, it is imperative to explore bio-based elastomers as next-generation dielectric elastomers (DEs). In this study, we used a bio-based gelatin/glycerin (GG) elastomer as the DE matrix because GG exhibits high dielectric constant (ɛr). Cellulose nanocrystals (CNCs), extracted from natural cellulose fibers, were used to improve the mechanical strength of GG elastomer. The results showed that CNCs with a large number of hydroxyl groups disrupted the hydrogen bonds between gelatin molecules and formed new stronger hydrogen bonds with gelatin molecules. A good interfacial adhesion between CNCs and GG was formed, and thus a good dispersion of CNCs in GG matrix was obtained, leading to the improved mechanical strength of GG. More interestingly, the ɛr of GG elastomer was obviously increased by adding 5 wt% of CNCs, ascribed to the increase in the polarizability of gelatin chains caused by the disruption of hydrogen bonds of gelatin. As a result, a 230% increase in the actuated strain at low electric field of GG was obtained by adding 5 wt% of CNCs. Since CNCs, gelatin and glycerol are all bio-based, this study offers a new method to prepare high performance DE for its application in biological and medical fields.

  7. Domain structure and time-dependent properties of a crosslinked urethane elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Lagasse, R.R.

    1977-09-01

    The morphology of a chemically crosslinked urethane elastomer is correlated with its time-dependent mechanical properties. Evaluation of this amorphous elastomer by electron microscopy and small-angle x-ray scattering reveals that incompatible chain segments cluster into separate microphases having a periodicity in electron density of about 90 A. This observed domain structure is similar to that seen previously in uncrosslinked, thermoplastic urethane elastomers. As in earlier studies on such linear systems, thermal pretreatment of the crosslinked elastomer causes a time-dependent change in its room temperature modulus. However, the magnitude of this modulus change (about 20%) is generally less than observed previously with the linear systems. Another contrast with previous findings is that this time-dependent phenomenon is apparently not caused by thermally activated changes in microphase segregation. Rather, the observed time dependence in modulus is believed to be caused by molecular relaxation resulting in densification of amorphous packing within the hard-segment domains. The validity of this proposed mechanism is supported by differential scanning calorimetry experiments showing evidence of enthalpy relaxation during room-temperature aging of the elastomer. This relaxation is qualitatively similar to that observed previously during sub-T/sub g/ annealing of single-phase glassy polymers.

  8. Strain-responsive structural colored elastomers by fixing colloidal crystal assembly.

    Science.gov (United States)

    Ito, Tatsunori; Katsura, Chihiro; Sugimoto, Hideki; Nakanishi, Eiji; Inomata, Katsuhiro

    2013-11-12

    Colloidal crystal assembly film was prepared by using monodispersed colloidal particles of cross-linked random copolymer of methyl methacrylate and ethyl acrylate prepared by soap-free emulsion polymerization. The colloidal crystal film exhibited structural color when swollen with ethyl acrylate monomer. The structural color was maintained even after polymerization of the swelling monomer and cross-linker, suggesting the colloidal crystalline order was successfully fixed and embedded in the matrix of poly(ethyl acrylate) elastomer. Stretching deformation of the structural colored elastomer induced a sensitive change to shorter wavelength color. Peak wavelength of the UV-vis absorption spectrum of the stretched elastomer revealed an excellent proportional relationship with film thickness. In the swollen colloidal crystal film, ethyl acrylate was absorbed in the colloidal particle; therefore, poly(ethyl acrylate) chain should be penetrating into the colloidal particle after the polymerization of the matrix elastomer. This interpenetrated polymer network structure was considered to be effective for the rubber-like elasticity and sensitive strain-responsive color-changing phenomena of the structural colored elastomer.

  9. Thin-film dielectric elastomer sensors to measure the contraction force of smooth muscle cells

    Science.gov (United States)

    Araromi, O.; Poulin, A.; Rosset, S.; Favre, M.; Giazzon, M.; Martin-Olmos, C.; Liley, M.; Shea, H.

    2015-04-01

    The development of thin-film dielectric elastomer strain sensors for the characterization of smooth muscle cell (SMC) contraction is presented here. Smooth muscle disorders are an integral part of diseases such as asthma and emphysema. Analytical tools enabling the characterization of SMC function i.e. contractile force and strain, in a low-cost and highly parallelized manner are necessary for toxicology screening and for the development of new and more effective drugs. The main challenge with the design of such tools is the accurate measurement of the extremely low contractile cell forces expected as a result of SMC monolayer contraction (as low as ~ 100 μN). Our approach utilizes ultrathin (~5 μm) and soft elastomer membranes patterned with elastomer-carbon composite electrodes, onto which the SMCs are cultured. The cell contraction induces an in-plane strain in the elastomer membrane, predicted to be in the order 1 %, which can be measured via the change in the membrane capacitance. The cell force can subsequently be deduced knowing the mechanical properties of the elastomer membrane. We discuss the materials and fabrication methods selected for our system and present preliminary results indicating their biocompatibility. We fabricate functional capacitive senor prototypes with good signal stability over the several hours (~ 0.5% variation). We succeed in measuring in-plane strains of 1 % with our fabricated devices with good repeatability and signal to noise ratio.

  10. Response analysis of dielectric elastomer spherical membrane to harmonic voltage and random pressure

    Science.gov (United States)

    Jin, Xiaoling; Wang, Yong; Chen, Michael Z. Q.; Huang, Zhilong

    2017-03-01

    Spherical membranes consisting of dielectric elastomer play important roles in flexible and stretchable devices, such as flexible actuators, sensors and loudspeakers. Executing various functions of devices depends on the dynamical behaviors of dielectric elastomer spherical membranes to external electrical and/or mechanical excitations. This manuscript concentrates on the random aspect of dielectric elastomer spherical membranes, i.e., the random response to combined excitations of harmonic voltage and random pressure. To analytically evaluate the response statistics of the stretch ratio, a specific transformation and stochastic averaging technique are successively adopted to solve the strongly nonlinear equation with respect to the stretch ratio. The stochastic differential equations for the system first integral and the phase difference between harmonic excitation and response are first derived through this transformation. The Fokker-Planck-Kolmogorov equation with respect to the stationary probability density of the system first integral and the phase difference is obtained. The stationary probability densities and the response statistics of the stretch ratio and its rate of change are then subsequently calculated. The phenomenon of stochastic jumps is found and the stochastic jump bifurcates with the variations of the frequency and the amplitude of the harmonic voltage and the intensity of the random pressure. The efficacy and accuracy of the analytical results are verified by comparing with the results from Monte Carlo simulation. Besides, the reliability of the dielectric elastomer spherical membrane is discussed briefly. The obtained results could provide options in implementing and designing dielectric elastomer structures for dynamic applications.

  11. Decomposition of indwelling EMG signals

    OpenAIRE

    2008-01-01

    Decomposition of indwelling electromyographic (EMG) signals is challenging in view of the complex and often unpredictable behaviors and interactions of the action potential trains of different motor units that constitute the indwelling EMG signal. These phenomena create a myriad of problem situations that a decomposition technique needs to address to attain completeness and accuracy levels required for various scientific and clinical applications. Starting with the maximum a posteriori probab...

  12. TREE DECOMPOSITIONS OF MULTIGRAPHS

    Institute of Scientific and Technical Information of China (English)

    SHI Minyong

    1999-01-01

    For a graph G, ifE(G) can be partitioned into several pairwise disjointsets as { E1, E2,……,El} such thatthe subgraph induced by Ei is a tree of orderki, (i=1,2, ……, l), then G is said to have a {k1,k2,……, kl}-tree-decomposition, denoted by {k1,k2,……, kl}∈G.For k≥1 and l≥0, a collection(G)(k,l) is the setof multigraphs such that G∈(G)(k,l) if and only if ε(G) = k(|G|-1)-l and ε(H)≤max{(k-1)(|H|-1), k(|H|-1)-l} for any subgraph H of G.We prove that (1) If k≥2, 0≤l≤3 and G∈(G)(k,l) of order n≥l+1, then {n,n,……, n-l}∈ G. (2) If k≥2 and G∈(G)(k,2) oforder n≥3, then {n,n,……, n,n-2}∈G and {n,n,……, n,n-1,n-1}∈G. (3) If k3 and G∈(G)(k,3) oforder n≥4, then {n,n,……, n,n-3}∈G ,{ n,n,……, n,n-1,n-2}∈ G and {n,n, ……, n,n-1,n-1,n-1}∈G.

  13. Decomposition of indwelling EMG signals.

    Science.gov (United States)

    Nawab, S Hamid; Wotiz, Robert P; De Luca, Carlo J

    2008-08-01

    Decomposition of indwelling electromyographic (EMG) signals is challenging in view of the complex and often unpredictable behaviors and interactions of the action potential trains of different motor units that constitute the indwelling EMG signal. These phenomena create a myriad of problem situations that a decomposition technique needs to address to attain completeness and accuracy levels required for various scientific and clinical applications. Starting with the maximum a posteriori probability classifier adapted from the original precision decomposition system (PD I) of LeFever and De Luca (25, 26), an artificial intelligence approach has been used to develop a multiclassifier system (PD II) for addressing some of the experimentally identified problem situations. On a database of indwelling EMG signals reflecting such conditions, the fully automatic PD II system is found to achieve a decomposition accuracy of 86.0% despite the fact that its results include low-amplitude action potential trains that are not decomposable at all via systems such as PD I. Accuracy was established by comparing the decompositions of indwelling EMG signals obtained from two sensors. At the end of the automatic PD II decomposition procedure, the accuracy may be enhanced to nearly 100% via an interactive editor, a particularly significant fact for the previously indecomposable trains.

  14. Coalescence control of elastomer clusters by fixed surface charges.

    Science.gov (United States)

    Gauer, Cornelius; Wu, Hua; Morbidelli, Massimo

    2010-02-04

    We studied the coalescence behavior of a fluorinated elastomer colloid, stabilized by fixed surface charges, with a glass transition temperature of about -20 degrees C, as a function of temperature under diffusion-limited cluster-cluster aggregation (DLCA) conditions. We first measured the aggregation kinetics by in situ dynamic light scattering and then simulated it through the Smoluchowski approach (i.e., population balance equations) using the only unknown parameter, the fractal dimension D(f) of the clusters, as the fit parameter. It was found that the estimated D(f) value increased as the temperature increased, starting from 1.7 at 25 degrees C and reaching the upper limit of 3.0 for T > or = 55 degrees C. These results indicate that the coalescence extent increases as the temperature increases. Such temperature-dependent coalescence behavior cannot be explained by thermodynamic considerations, and it must be related to a certain kinetic resistance. We explain this effect by considering the resistance of the fixed charges to relocation on the particle surface, which decreases as the temperature increases.

  15. Reduction of surface charges during coalescence of elastomer particles.

    Science.gov (United States)

    Gauer, Cornelius; Wu, Hua; Morbidelli, Massimo

    2010-07-15

    Reaction-limited aggregation of soft elastomer particles has been studied with specific attention to the fate of surface charges during coalescence. The employed system is an aqueous dispersion of fluoroelastomer particles, which are known to coalesce completely at 70 degrees C. In contrast to diffusion-limited conditions, under reaction-limited conditions the stability of the system is expected to change during aggregation because of surface reduction and charge accumulation resulting from coalescence. This allows investigating the mechanism of charge relocation during cluster coalescence. For particles stabilized by ionic surfactants, it has been found that the charges are mobile (i.e., they redistribute between aqueous solution and particle surface according to their adsorption equilibrium) (Gauer, C.; Jia, Z.; Wu, H.; Morbidelli, M. Langmuir 2009, 25, 9703). In this work, we consider the case of fixed charges, as those given by charged polymer end groups covalently bound to the particle surface. We demonstrate that a loss of fixed surface charges occurs during the coalescence and strongly affects the time evolution and the shape of the resulting cluster mass distribution.

  16. Performance of bolted closure joint elastomers under cask aging conditions

    Energy Technology Data Exchange (ETDEWEB)

    Verst, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Sindelar, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Skidmore, E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Daugherty, W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-07-23

    The bolted closure joint of a bare spent fuel cask is susceptible to age-related degradation and potential loss of confinement function under long-term storage conditions. Elastomeric seals, a component of the joint typically used to facilitate leak testing of the primary seal that includes the metallic seal and bolting, is susceptible to degradation over time by several mechanisms, principally via thermo-oxidation, stress-relaxation, and radiolytic degradation under time and temperature condition. Irradiation and thermal exposure testing and evaluation of an ethylene-propylene diene monomer (EPDM) elastomeric seal material similar to that used in the CASTOR® V/21 cask for a matrix of temperature and radiation exposure conditions relevant to the cask extended storage conditions, and development of semiempirical predictive models for loss of sealing force is in progress. A special insert was developed to allow Compressive Stress Relaxation (CSR) measurements before and after the irradiation and/or thermal exposure without unloading the elastomer. A condition of the loss of sealing force for the onset of leakage was suggested. The experimentation and modeling being performed could enable acquisition of extensive coupled aging data as well as an estimation of the timeframe when loss of sealing function under aging (temperature/radiation) conditions may occur.

  17. Dielectric elastomer actuators for octopus inspired suction cups.

    Science.gov (United States)

    Follador, M; Tramacere, F; Mazzolai, B

    2014-09-25

    Suction cups are often found in nature as attachment strategy in water. Nevertheless, the application of the artificial counterpart is limited by the dimension of the actuators and their usability in wet conditions. A novel design for the development of a suction cup inspired by octopus suckers is presented. The main focus of this research was on the modelling and characterization of the actuation unit, and a first prototype of the suction cup was realized as a proof of concept. The actuation of the suction cup is based on dielectric elastomer actuators. The presented device works in a wet environment, has an integrated actuation system, and is soft. The dimensions of the artificial suction cups are comparable to proximal octopus suckers, and the attachment mechanism is similar to the biological counterpart. The design approach proposed for the actuator allows the definition of the parameters for its development and for obtaining a desired pressure in water. The fabricated actuator is able to produce up to 6 kPa of pressure in water, reaching the maximum pressure in less than 300 ms.

  18. Stretchable, adhesive and ultra-conformable elastomer thin films.

    Science.gov (United States)

    Sato, Nobutaka; Murata, Atsushi; Fujie, Toshinori; Takeoka, Shinji

    2016-11-16

    Thermoplastic elastomers are attractive materials because of the drastic changes in their physical properties above and below the glass transition temperature (Tg). In this paper, we report that free-standing polystyrene (PS, Tg: 100 °C) and polystyrene-polybutadiene-polystyrene triblock copolymer (SBS, Tg: -70 °C) thin films with a thickness of hundreds of nanometers were prepared by a gravure coating method. Among the mechanical properties of these thin films determined by bulge testing and tensile testing, the SBS thin films exhibited a much lower elastic modulus (ca. 0.045 GPa, 212 nm thickness) in comparison with the PS thin films (ca. 1.19 GPa, 217 nm thickness). The lower elastic modulus and lower thickness of the SBS thin films resulted in higher conformability and thus higher strength of adhesion to an uneven surface such as an artificial skin model with roughness (Ra = 10.6 μm), even though they both have similar surface energies. By analyzing the mechanical properties of the SBS thin films, the elastic modulus and thickness of the thin films were strongly correlated with their conformability to a rough surface, which thus led to a high adhesive strength. Therefore, the SBS thin films will be useful as coating layers for a variety of materials.

  19. Characterization of Ferrofluid-based Stimuli-responsive Elastomers

    Directory of Open Access Journals (Sweden)

    Sandra dePedro

    2016-12-01

    Full Text Available Stimuli-responsive materials undergo physicochemical, and/or structural changes when a specific actuation is applied. They are heterogeneous composites, consisting of a non-responsive matrix where functionality is provided by the filler. Surprisingly, the synthesis of Polydimethylsiloxane (PDMS-based stimuli-responsive elastomers (SRE has seldomly been presented. Here we present the structural, biological, optical, magnetic and mechanical properties of several magnetic SRE (M-SRE obtained by combining PDMS and isoparafin-based ferrofluid (FF. Independently of the FF concentration, results shown a similar aggregation level, with the nanoparticles (NP mostly isolated (>60%. In addition to the superparamagnetic behaviour, the samples show no cytotoxicity except the sample with the highest FF concentration. Spectral response shows FF concentrations where both optical readout and magnetic actuation can simultaneously be used. The Young’s modulus increases with the FF concentration until the elastomeric network is distorted. Our results demonstrate that PDMS can host up to 24.6% FF. When applied to soft microsystems, a large displacement for relatively low magnetic fields (< 0.3 T is achieved. The herein presented M-SRE characterization can be used for a large number of disciplines where magnetic actuation can be combined with optical detection, mechanical elements and biological samples.

  20. Modeling a dielectric elastomer as driven by triboelectric nanogenerator

    Science.gov (United States)

    Chen, Xiangyu; Jiang, Tao; Wang, Zhong Lin

    2017-01-01

    By integrating a triboelectric nanogenerator (TENG) and a thin film dielectric elastomer actuator (DEA), the DEA can be directly powered and controlled by the output of the TENG, which demonstrates a self-powered actuation system toward various practical applications in the fields of electronic skin and soft robotics. This paper describes a method to construct a physical model for this integrated TENG-DEA system on the basis of nonequilibrium thermodynamics and electrostatics induction theory. The model can precisely simulate the influences from both the viscoelasticity and current leakage to the output performance of the TENG, which can help us to better understand the interaction between TENG and DEA devices. Accordingly, the established electric field, the deformation strain of the DEA, and the output current from the TENG are systemically analyzed by using this model. A comparison between real measurements and simulation results confirms that the proposed model can predict the dynamic response of the DEA driven by contact-electrification and can also quantitatively analyze the relaxation of the tribo-induced strain due to the leakage behavior. Hence, the proposed model in this work could serve as a guidance for optimizing the devices in the future studies.

  1. Soft mobile robots driven by foldable dielectric elastomer actuators

    Science.gov (United States)

    Sun, Wenjie; Liu, Fan; Ma, Ziqi; Li, Chenghai; Zhou, Jinxiong

    2016-08-01

    A cantilever beam with elastic hinge pulled antagonistically by two dielectric elastomer (DE) membranes in tension forms a foldable actuator if one DE membrane is subject to a voltage and releases part of tension. Simply placing parallel rigid bars on the prestressed DE membranes results in enhanced actuators working in a pure shear state. We report design, analysis, fabrication, and experiment of soft mobile robots that are moved by such foldable DE actuators. We describe systematic measurement of the foldable actuators and perform theoretical analysis of such actuators based on minimization of total energy, and a good agreement is achieved between model prediction and measurement. We develop two versions of prototypes of soft mobile robots driven either by two sets of DE membranes or one DE membrane and elastic springs. We demonstrate locomotion of these soft mobile robots and highlight several key design parameters that influence locomotion of the robots. A 45 g soft robot driven by a cyclic triangle voltage with amplitude 7.4 kV demonstrates maximal stroke 160 mm or maximal rolling velocity 42 mm/s. The underlying mechanics and physics of foldable DE actuators can be leveraged to develop other soft machines for various applications.

  2. Inkjet printed multiwall carbon nanotube electrodes for dielectric elastomer actuators

    Science.gov (United States)

    Baechler, Curdin; Gardin, Samuele; Abuhimd, Hatem; Kovacs, Gabor

    2016-05-01

    Dielectric elastomers (DE’s) offer promising applications as soft and light-weight electromechanical actuators. It is known that beside the dielectric material, the electrode properties are of particular importance regarding the DE performance. Therefore, in recent years various studies have focused on the optimization of the electrode in terms of conductivity, stretchability and reliability. However, less attention was given to efficient electrode processing and deposition methods. In the present study, digital inkjet printing was used to deposit highly conductive and stretchable electrodes on silicone. Inkjet printing is a versatile and cost effective deposition method, which allows depositing complex-shaped electrode patterns with high precision. The electrodes were printed using an ink based on industrial low-cost MWCNT. Experiments have shown that the strain-conductivity properties of the printed electrode are strongly depended on the deposition parameters like drop-spacing and substrate temperature. After the optimization of the printing parameters, thin film electrodes could be deposited showing conductivities of up to 30 S cm-1 without the need of any post-treatment. In addition, electromechanical tests with fabricated DE actuators have revealed that the inkjet printed MWCNT electrodes are capable to self-clear in case of a dielectric breakdown.

  3. Compatibility Studies on Elastomers and Polymers with Ethanol Blended Gasoline

    Directory of Open Access Journals (Sweden)

    J. S. Dhaliwal

    2014-01-01

    Full Text Available This paper reports the compatibility studies of 10% ethanol blended gasoline (E10 with four types of elastomer materials, namely, Neoprene rubber, Nitrile rubber, hydrogenated Nitrile butadiene rubber (HNBR, and Polyvinyl chloride/Nitrile butadiene rubber blend (PVC/NBR, and two types of plastic materials, namely, Nylon-66 and Polyoxymethylene (Delrin. These materials have applications in automotives as engine seals, gaskets, fuel system seals and hoses, and so forth. Two types of the ethanol blended gasoline mixtures were used: (a gasoline containing 5% ethanol (E5, which is commercial form of gasoline available in India, and (b gasoline containing 10% ethanol (E10. The above materials were immersed in E5 and E10 for 500 hrs at 55°C. A set of eight different properties in E5 and E10 (visual inspection, weight change, volume change, tensile strength, percent elongation, flexural strength, impact strength, and hardness were measured after completion of 500 hrs and compared with reference specimens (specimens at 55°C without fuel and specimens at ambient conditions. Variation observed in different materials with respect to the above eight properties has been used to draw inference about the compatibility of these elastomeric/polymer materials with E10 fuel vis-à-vis E5 fuels. The data presented in this study is comparative in nature between the results of E10 and E5.

  4. Colour gamuts in polychromatic dielectric elastomer artificial chromatophores

    Science.gov (United States)

    Rossiter, Jonathan; Conn, Andrew; Cerruto, Antonio; Winters, Amy; Roke, Calum

    2014-03-01

    Chromatophores are the colour changing organelles in the skins of animals including fish and cephalopods. The ability of cephalopods in particular to rapidly change their colouration in response to environmental changes, for example to camouflage against a new background, and in social situations, for example to attract a mate or repel a rival, is extremely attractive for engineering, medical, active clothing and biomimetic robotic applications. The rapid response of these chromatophores is possible by the direct coupling of fast acting muscle and pigmented saccules. In artificial chromatophores we are able to mimic this structure using electroactive polymer artificial muscles. In contrast to prior research which has demonstrated monochromatic artificial chromatophores, here we consider a novel multi-colour, multi-layer, artificial chromatophore structure inspired by the complex dermal chromatophore unit in nature and which exploits dielectric elastomer artificial muscles as the electroactive actuation mechanism. We investigate the optical properties of this chromatophore unit and explore the range of colours and effects that a single unit and a matrix of chromatophores can produce. The colour gamut of the multi-colour chromatophore is analysed and shows its suitability for practical display and camouflage applications. It is demonstrated how, by varying actuator strain and chromatophore base colour, the gamut can be shifted through colour space, thereby tuning the artificial chromatophore to a specific environment or application.

  5. Simulation of the transient electromechanical behaviour of dielectric elastomer transducers

    Science.gov (United States)

    Mößinger, Holger; Förster-Zügel, Florentine; Schlaak, Helmut F.

    2016-04-01

    To design systems utilizing dielectric elastomer transducers (DET) models are necessary to describe the behaviour of the DET and assess the system performance in advance. For basic set-ups simple analytical models or lumped parameter models are available and provide reasonable results. For more complex set-ups these models only allow a rough estimation of the system performance, not accurate enough to achieve an optimal system design. Therefore system designers typically resort to numerical simulation tools. Commercially available tools and models specialize on either electrical or mechanical domain thus simplifying or even neglecting effects in the other domain respectively. In this work we present a simulation tool taking into account the transient electrical and mechanical behaviour of DET under different mechanical load conditions and electrical driving frequencies. Our model can describe transient electrical and mechanical behaviour, such as electrical resistance, mechanical hyperelastic and viscosity of the electrodes and dielectric material. Model parameters are derived from measurements of the dielectric and the electrode resistance as well as e.g. the materials Young's modulus. The results from the simulation are compared to simple lumped parameter based models.

  6. Opportunities of hydrostatically coupled dielectric elastomer actuators for haptic interfaces

    Science.gov (United States)

    Carpi, Federico; Frediani, Gabriele; De Rossi, Danilo

    2011-04-01

    As a means to improve versatility and safety of dielectric elastomer actuators (DEAs) for several fields of application, so-called 'hydrostatically coupled' DEAs (HC-DEAs) have recently been described. HC-DEAs are based on an incompressible fluid that mechanically couples a DE-based active part to a passive part interfaced to the load, so as to enable hydrostatic transmission. This paper presents ongoing developments of HC-DEAs and potential applications in the field of haptics. Three specific examples are considered. The first deals with a wearable tactile display used to provide users with tactile feedback during electronic navigation in virtual environments. The display consists of HCDEAs arranged in contact with finger tips. As a second example, an up-scaled prototype version of an 8-dots refreshable cell for dynamic Braille displays is shown. Each Braille dot consists of a miniature HC-DEA, with a diameter lower than 2 mm. The third example refers to a device for finger rehabilitation, conceived to work as a sort of active version of a rehabilitation squeezing ball. The device is designed to dynamically change its compliance according to an electric control. The three examples of applications intend to show the potential of the new technology and the prospective opportunities for haptic interfaces.

  7. Reduced Order Models for Dynamic Behavior of Elastomer Damping Devices

    Science.gov (United States)

    Morin, B.; Legay, A.; Deü, J.-F.

    2016-09-01

    In the context of passive damping, various mechanical systems from the space industry use elastomer components (shock absorbers, silent blocks, flexible joints...). The material of these devices has frequency, temperature and amplitude dependent characteristics. The associated numerical models, using viscoelastic and hyperelastic constitutive behaviour, may become computationally too expensive during a design process. The aim of this work is to propose efficient reduced viscoelastic models of rubber devices. The first step is to choose an accurate material model that represent the viscoelasticity. The second step is to reduce the rubber device finite element model to a super-element that keeps the frequency dependence. This reduced model is first built by taking into account the fact that the device's interfaces are much more rigid than the rubber core. To make use of this difference, kinematical constraints enforce the rigid body motion of these interfaces reducing the rubber device model to twelve dofs only on the interfaces (three rotations and three translations per face). Then, the superelement is built by using a component mode synthesis method. As an application, the dynamic behavior of a structure supported by four hourglass shaped rubber devices under harmonic loads is analysed to show the efficiency of the proposed approach.

  8. Soft mobile robots driven by foldable dielectric elastomer actuators

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Wenjie; Liu, Fan; Ma, Ziqi; Li, Chenghai; Zhou, Jinxiong, E-mail: jxzhouxx@mail.xjtu.edu.cn [State Key Laboratory for Strength and Vibration of Mechanical Structures and School of Aerospace, Xi' an Jiaotong University, Xi' an 710049 (China)

    2016-08-28

    A cantilever beam with elastic hinge pulled antagonistically by two dielectric elastomer (DE) membranes in tension forms a foldable actuator if one DE membrane is subject to a voltage and releases part of tension. Simply placing parallel rigid bars on the prestressed DE membranes results in enhanced actuators working in a pure shear state. We report design, analysis, fabrication, and experiment of soft mobile robots that are moved by such foldable DE actuators. We describe systematic measurement of the foldable actuators and perform theoretical analysis of such actuators based on minimization of total energy, and a good agreement is achieved between model prediction and measurement. We develop two versions of prototypes of soft mobile robots driven either by two sets of DE membranes or one DE membrane and elastic springs. We demonstrate locomotion of these soft mobile robots and highlight several key design parameters that influence locomotion of the robots. A 45 g soft robot driven by a cyclic triangle voltage with amplitude 7.4 kV demonstrates maximal stroke 160 mm or maximal rolling velocity 42 mm/s. The underlying mechanics and physics of foldable DE actuators can be leveraged to develop other soft machines for various applications.

  9. Fluid electrodes for submersible robotics based on dielectric elastomer actuators

    Science.gov (United States)

    Christianson, Caleb; Goldberg, Nathaniel; Cai, Shengqiang; Tolley, Michael T.

    2017-04-01

    Recently, dielectric elastomer actuators (DEAs) have gathered interest for soft robotics due to their low cost, light weight, large strain, low power consumption, and high energy density. However, developing reliable, compliant electrodes for DEAs remains an ongoing challenge due to issues with fabrication, uniformity of the conductive layer, and mechanical stiffening of the actuators caused by conductive materials with large Young's moduli. In this work, we present a method for preparing, patterning, and utilizing conductive fluid electrodes. Further, when we submerse the DEAs in a bath containing a conductive fluid connected to ground, the bath serves as a second electrode, obviating the need for depositing a conductive layer to serve as either of the electrodes required of most DEAs. When we apply a positive electrical potential to the conductive fluid in the actuator with respect to ground, the electric field across the dielectric membrane causes charge carriers in the solution to apply an electrostatic force on the membrane, which compresses the membrane and causes the actuator to deform. We have used this process to develop a tethered submersible robot that can swim in a tank of saltwater at a maximum measured speed of 9.2 mm/s. Since saltwater serves as the electrode, we overcome buoyancy issues that may be a challenge for pneumatically actuated soft robots and traditional, rigid robotics. This research opens the door to low-power underwater robots for search and rescue and environmental monitoring applications.

  10. Amorphous carbon interlayers for gold on elastomer stretchable conductors

    Science.gov (United States)

    Manzoor, M. U.; Tuinea-Bobe, C. L.; McKavanagh, F.; Byrne, C. P.; Dixon, D.; Maguire, P. D.; Lemoine, P.

    2011-06-01

    Gold on polydimethylsiloxane (PDMS) stretchable conductors were prepared using a novel approach by interlacing an hydrogenated amorphous carbon (a-C : H) layer between the deposited metal layer and the elastomer. AFM analysis of the a-C : H film surface before gold deposition shows nanoscale buckling, the corresponding increase in specific surface area corresponds to a strain compensation for the first 4-6% of bi-axial tensile loading. Without this interlayer, the deposited gold films show much smaller and uni-directional ripples as well as more cracks and delaminations. With a-C : H interlayer, the initial electrical resistivity of the metal film decreases markedly (280-fold decrease to 8 × 10-6 Ω cm). This is not due to conduction within the carbon interlayer; both a-C : H/PDMS and PDMS substrates are electrically insulating. Upon cyclic tensile loading, both films become more resistive, but return to their initial state after 20 tensile cycles up to 60% strain. Profiling experiments using secondary ion mass spectroscopy and x-ray photoelectron spectroscopy indicate that the a-C : H layer intermixes with the PDMS, resulting in a graded layer of decreasing stiffness. We believe that both this graded layer and the surface buckling contribute to the observed improvement in the electrical performance of these stretchable conductors.

  11. Flexible dielectric elastomer actuators for wearable human-machine interfaces

    Science.gov (United States)

    Bolzmacher, Christian; Biggs, James; Srinivasan, Mandayam

    2006-03-01

    Wearable dielectric elastomer actuators have the potential to enable new technologies, such as tactile feedback gloves for virtual reality, and to improve existing devices, such as automatic blood pressure cuffs. They are potentially lighter, quieter, thinner, simpler, and cheaper than pneumatic and hydraulic systems now used to make compliant, actuated interfaces with the human body. Achieving good performance without using a rigid frame to prestrain the actuator is a fundamental challenge in using these actuators on body. To answer this challenge, a new type of fiber-prestrained composite actuator was developed. Equations that facilitate design of the actuator are presented, along with FE analysis, material tests, and experimental results from prototypes. Bending stiffness of the actuator material was found to be comparable to textiles used in clothing, confirming wearability. Two roll-to-roll machines are also presented that permit manufacture of this material in bulk as a modular, compact, prestressed composite that can be cut, stacked, and staggered, in order to build up actuators for a range of desired forces and displacements. The electromechanical properties of single- layered actuators manufactured by this method were measured (N=5). At non-damaging voltages, blocking force ranged from 3,7-5,0 gram per centimeter of actuator width, with linear strains of 20,0-30%. Driving the actuators to breakdown produced maximum force of 8,3-10 gram/cm, and actuation strain in excess 30%. Using this actuator, a prototype tactile display was constructed and demonstrated.

  12. Work of adhesion and separation between soft elastomers

    Science.gov (United States)

    Lu, Nanshu

    2015-03-01

    The JKR (Johnson-Kendall-Roberts) method is widely used to measure the work of adhesion between soft materials. In this paper, the JKR theory is summarized and three dimensionless parameters are proposed to design a proper JKR experiment. The work of adhesion and the work of separation between two commonly used soft elastomers PDMS (Sylgard 184) and Ecoflex 0300 are obtained with the measured pull-in and pull-off forces using a dynamical mechanical analyzer (DMA). The effect of crosslinking density and solvent extraction are examined. It is found that the pull-in adhesion stays more or less constant for all contact pairs we measured. While the effect of crosslinking density is not significant for pristine PDMS, it is very obvious that the higher self-adhesion can be found in less crosslinked PDMS after solvent extraction. Such an effect is even more drastic for PDMS-to-Ecoflex adhesion. A unified adhesion mechanism is proposed to explain these complex adhesion behaviors. It is concluded that the chain-matrix interaction is the most effective adhesion mechanism compared to chain-chain or matrix-matrix interactions and the three interactions are exclusive to each other. This work is supported by the NSF CMMI award under Grant No. 1301335.

  13. Electromechanical behavior of fiber-reinforced dielectric elastomer membrane

    Directory of Open Access Journals (Sweden)

    Chi Li

    2015-04-01

    Full Text Available Based on its large deformation, light weight, and high energy density, dielectric elastomer (DE has been used as driven muscle in many areas. We design the fiber-reinforced DE membrane by adding fibers in the membrane. The deformation and driven force direction of the membrane can be tuned by changing the fiber arrangements. The actuation in the perpendicular direction of the DE membrane with long fibers first increases and then decreases by the increasing of the fiber spacing in the perpendicular direction. The horizontal actuation of the membrane decreases by decreasing the spacing of short fibers. In the membrane-inflating structure, the radially arranged fibers will break the axisymmetric behavior of the structure. The top area of the inflated balloon without fiber will buckle up when the voltage reaches a certain level. Finite element simulations based on nonlinear field theory are conducted to investigate the effects of fiber arrangement and verify the experimental results. This work can guide the design of fiber-reinforced DE.

  14. Effect of surface properties of elastomer colloids on their coalescence and aggregation kinetics.

    Science.gov (United States)

    Gauer, Cornelius; Wu, Hua; Morbidelli, Massimo

    2009-10-20

    We study the aggregation kinetics of two elastomer colloids with similar bulk polymer properties but with different surface charge groups in order to understand the role of the surface properties in particle coalescence during aggregation. It is confirmed that clusters of the elastomer particles stabilized purely by ionic surfactants coalesce in both reaction-limited and diffusion-limited aggregation (RLCA and DLCA) regimes and that the coalescence is independent of the coagulant type. On the other hand, clusters formed by elastomer particles stabilized by charged polymer end groups, which are fixed on the particle surface, are fractal objects with a fractal dimension of 1.7 in the DLCA and 2.1 in the RLCA regime. This indicates insignificant cluster coalescence during aggregation, most likely due to a hindrance effect of the fixed charges.

  15. Mechanical behavior of a suite of elastomers used for seismic base isolation

    Energy Technology Data Exchange (ETDEWEB)

    Kulak, R.F.; Hughes, T.H.

    1995-07-01

    Several practical systems have been developed to protect structures and their contents from the potential devastating consequences of earthquakes. The use of seismic isolation has recently proven to be an effective means to mitigate earthquake damage. With seismic isolation, the structures are decoupled from the strong horizontal ground accelerations. The use of high damping elastomer, steel lamiriated seismic isolation bearings has been proven to be an effective method for seismic base isolation. This paper describes recent research conducted at Argonne National Laboratory to find the mechanical response characteristics of a suite of elastomers compounded for use in elastomeric seismic isolation bearings. The response characteristics were obtained by testing small coupons of each elastomer in a high precision dynamic testing machine. Specifically, the paper reports on tests performed to find the variations in stiffness and energy dissipation with strain level, loading rate, and cycle number. The paper also reports on the effects that strain level has on stiffness recovery.

  16. Effects of vapor grown carbon nanofibers on electrical and mechanical properties of a thermoplastic elastomer

    Science.gov (United States)

    Basaldua, Daniel Thomas

    Carbon nanofiber (CNF) reinforced composites are exceptional materials that exhibit superior properties compared to conventional composites. This paper presents the development of a vapor grown carbon nanofiber (VGCNF) thermoplastic polyurethane (TPU) composite by a melt mixing process. Dispersion and distribution of CNFs inside the TPU matrix were examined through scanning electron microscopy to determine homogeneity. The composite material underwent durometer, thermal gravimetric analysis, differential scanning calorimetry, heat transfer, hysteresis, dynamic modulus, creep, tensile, abrasion, and electrical conductivity testing to characterize its properties and predict behavior. The motivation for this research is to develop an elastomer pad that is an electrically conductive alternative to the elastomer pads currently used in railroad service. The material had to be a completely homogenous electrically conductive CNF composite that could withstand a harsh dynamically loaded environment. The new material meets mechanical and conductive requirements for use as an elastomer pad in a rail suspension.

  17. Failure life determination of oilfield elastomer seals in sour gas/dimethyl disulfide environments

    Energy Technology Data Exchange (ETDEWEB)

    Kennelley, K.J.; Abrams, P.I. (Exxon Production Research Co., Houston, TX (US)); Vicic, J.C. (FMC Corp., Central Engineering Labs., Santa Clara, CA (US)); Cain, D. (FMC Corp., Wellhead Equipment, Houston, TX (US))

    1989-01-01

    Previous screening tests of various oilfield elastomers in sour gas/dimethyl disulfide environments indicated that hydrogenated nitrile (HNBR), tetrafluoroethylene-propylene (TFE/P), ethylene-propylene-diene (EPDM), and perfluorinated rubber (FFKM) elastomers may perform satisfactorily in these environments. This paper describes subsequent failure life tests conducted with the subject elastomers in the sour gas/dimethyl disulfide test environment at several elevated temperatures (> 135{degrees}C). The materials were tested in the form of O-rings (size 214), which were used to seal an autoclave containing the test environment at 14 MPa gas pressure. The results were used to extrapolate time to failure at a common reference temperature of 135{degrees}C. The performance of EPDM and HNBR in the sour gas/dimethyl disulfide mixture substantially exceeded a projected 20-year service life at 135{degrees}C, while FFKM and TFE/P did not.

  18. [Application of thermoplastic elastomer in hot-melt pressure sensitive adhesives for transtermal drug delivery].

    Science.gov (United States)

    Yan, Xiaoping; Zheng, Rui; Guan, Shijie; Yi, Bowen

    2009-06-01

    Development of drug dosage forms to a great extent depends on the development of drug auxiliary materials. The development of a new type of polymeric drug auxiliary materials will bring on the developing of a novel dosage forms technology and a flood of new drug dosage forms. Thermoplastic elastomer is a new type of drug polymeric auxiliary materials, at present, which has a broad application in the field of hot-melt pressure sensitive adhesives. This review mainly discussed a new transtermal Chinese drug delivery system, including matrix composition of the formula, modified thermoplastic elastomer for hot-melt pressure sensitive adhesives and their development prospects in the traditional Chinese drug delivery system. It suggested that thermoplastic elastomer of hot-melt pressure sensitive adhesives has broad development prospects in the field of the transtermal drug delivery system for traditional Chinese medicine.

  19. Real interest parity decomposition

    Directory of Open Access Journals (Sweden)

    Alex Luiz Ferreira

    2009-09-01

    Full Text Available The aim of this paper is to investigate the general causes of real interest rate differentials (rids for a sample of emerging markets for the period of January 1996 to August 2007. To this end, two methods are applied. The first consists of breaking the variance of rids down into relative purchasing power pariety and uncovered interest rate parity and shows that inflation differentials are the main source of rids variation; while the second method breaks down the rids and nominal interest rate differentials (nids into nominal and real shocks. Bivariate autoregressive models are estimated under particular identification conditions, having been adequately treated for the identified structural breaks. Impulse response functions and error variance decomposition result in real shocks as being the likely cause of rids.O objetivo deste artigo é investigar as causas gerais dos diferenciais da taxa de juros real (rids para um conjunto de países emergentes, para o período de janeiro de 1996 a agosto de 2007. Para tanto, duas metodologias são aplicadas. A primeira consiste em decompor a variância dos rids entre a paridade do poder de compra relativa e a paridade de juros a descoberto e mostra que os diferenciais de inflação são a fonte predominante da variabilidade dos rids; a segunda decompõe os rids e os diferenciais de juros nominais (nids em choques nominais e reais. Sob certas condições de identificação, modelos autorregressivos bivariados são estimados com tratamento adequado para as quebras estruturais identificadas e as funções de resposta ao impulso e a decomposição da variância dos erros de previsão são obtidas, resultando em evidências favoráveis a que os choques reais são a causa mais provável dos rids.

  20. Long-term effects of intragastric instillations of silastic 386 foam elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Smith, D.M.; Drake, G.A.; London, J.E.

    1981-12-01

    Young male Sprague-Dawley rats (87 days old) were given a single dose (5 g/kg body weight (BW)) of Silastic 386 foam elastomer intragastrically (IG), and young female Swiss-Webster mice (83 days old) were given a single dose (5 g/kg BW) IG, or a dose (1 g/kg BW) IG on each of 5 consecutive days, of Silastic 386 foam elastomer. All animals were then maintained for the rest of their lives and autopsied at death. No significant effects resulting from the oral administration of this of this material were seen in any of the rats or mice.

  1. Effect of heating rate on toxicity of pyrolysis gases from some elastomers

    Science.gov (United States)

    Hilado, C. J.; Kosola, K. L.; Solis, A. N.

    1977-01-01

    The effect of heating rate on the toxicity of the pyrolysis gases from six elastomers was investigated, using a screening test method. The elastomers were polyisoprene (natural rubber), styrene-butadiene rubber (SBR), ethylene propylene diene terpolymer (EPDM), acrylonitrile rubber, chlorosulfonated polyethylene rubber, and polychloroprene. The rising temperature and fixed temperature programs produced exactly the same rank order of materials based on time to death. Acrylonitrile rubber exhibited the greatest toxicity under these test conditions, and carbon monoxide was not found in sufficient concentrations to be the primary cause of death.

  2. Role of uncrosslinked chains in the sliding dynamics of droplets on elastomers

    CERN Document Server

    Hourlier-Fargette, Aurélie; Neukirch, Sébastien

    2016-01-01

    We observe and investigate an unexpected behavior in the dynamics of aqueous droplets sliding down on vertical plates of soft silicone elastomers, where two successive velocity regimes are present. This macroscopic observation is found to be closely related to microscopic phenomena at the scale of the polymer network: we demonstrate that uncrosslinked chains found in most widely used commercial elastomers are responsible for this surprising sliding behavior, and a direct visualization of these uncrosslinked oligomers is performed. The speed change is shown to be correlated to a sudden change of surface tension of the droplets.

  3. Degradation patterns of silicone-based dielectric elastomers in electrical fields

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    2017-01-01

    . This shortcoming has been attempted optimized through different approaches during recent years. Material optimization with the sole purpose of increasing the dielectric permittivity may lead to the introduction of problematic phenomena such as premature electrical breakdown due to high leakage currents of the thin...... elastomer film. Within this work, electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers are investigated. Results showed that different types of polymer backbone chemistries lead to differences in electrical breakdown patterns, which were revealed through SEM imaging...

  4. Cross-Linked Liquid Crystalline Systems From Rigid Polymer Networks to Elastomers

    CERN Document Server

    Broer, Dirk

    2011-01-01

    With rapidly expanding interest in liquid crystalline polymers and elastomers among the liquid crystal community, researchers are currently exploring the wide range of possible application areas for these unique materials, including optical elements on displays, tunable lasers, strain gauges, micro-structures, and artificial muscles. Written by respected scientists from academia and industry around the world, who are not only active in the field but also well-known in more traditional areas of research, "Cross-Linked Liquid Crystalline Systems: From Rigid Polymer Networks to Elastomers&qu

  5. Piecewise-adaptive decomposition methods

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, J.I. [Room I-320-D, E.T.S. Ingenieros Industriales, Universidad de Malaga, Plaza El Ejido, s/n, 29013 Malaga (Spain)], E-mail: jirs@lcc.uma.es

    2009-05-30

    Piecewise-adaptive decomposition methods are developed for the solution of nonlinear ordinary differential equations. These methods are based on some theorems that show that Adomian's decomposition method is a homotopy perturbation technique and coincides with Taylor's series expansions for autonomous ordinary differential equations. Piecewise-decomposition methods provide series solutions in intervals which are subject to continuity conditions at the end points of each interval, and their adaption is based on the use of either a fixed number of approximants and a variable step size, a variable number of approximants and a fixed step size or a variable number of approximants and a variable step size. It is shown that the appearance of noise terms in the decomposition method is related to both the differential equation and the manner in which the homotopy parameter is introduced, especially for the Lane-Emden equation. It is also shown that, in order to avoid the use of numerical quadrature, there is a simple way of introducing the homotopy parameter in the two first-order ordinary differential equations that correspond to the second-order Thomas-Fermi equation. It is also shown that the piecewise homotopy perturbation methods presented here provide more accurate results than a modified Adomian decomposition technique which makes use of Pade approximants and the homotopy analysis method, for the Thomas-Fermi equation.

  6. Distributed k-Core Decomposition

    CERN Document Server

    Montresor, Alberto; Miorandi, Daniele

    2011-01-01

    Among the novel metrics used to study the relative importance of nodes in complex networks, k-core decomposition has found a number of applications in areas as diverse as sociology, proteinomics, graph visualization, and distributed system analysis and design. This paper proposes new distributed algorithms for the computation of the k-core decomposition of a network, with the purpose of (i) enabling the run-time computation of k-cores in "live" distributed systems and (ii) allowing the decomposition, over a set of connected machines, of very large graphs, that cannot be hosted in a single machine. Lower bounds on the algorithms complexity are given, and an exhaustive experimental analysis on real-world graphs is provided.

  7. Thermal decomposition of ammonium hexachloroosmate

    DEFF Research Database (Denmark)

    Asanova, T I; Kantor, Innokenty; Asanov, I. P.

    2016-01-01

    Structural changes of (NH4)2[OsCl6] occurring during thermal decomposition in a reduction atmosphere have been studied in situ using combined energy-dispersive X-ray absorption spectroscopy (ED-XAFS) and powder X-ray diffraction (PXRD). According to PXRD, (NH4)2[OsCl6] transforms directly...... to metallic Os without the formation of any crystalline intermediates but through a plateau where no reactions occur. XANES and EXAFS data by means of Multivariate Curve Resolution (MCR) analysis show that thermal decomposition occurs with the formation of an amorphous intermediate {OsCl4}x with a possible...... polymeric structure. Being revealed for the first time the intermediate was subjected to determine the local atomic structure around osmium. The thermal decomposition of hexachloroosmate is much more complex and occurs within a minimum two-step process, which has never been observed before....

  8. The role of oxidation and enzymatic hydrolysis on the in vivo degradation of trimethylene carbonate based photocrosslinkable elastomers.

    Science.gov (United States)

    Chapanian, Rafi; Tse, M Yat; Pang, Stephen C; Amsden, Brian G

    2009-01-01

    The in vivo degradation of trimethylene carbonate (TMC) containing elastomers was investigated, and the mechanism of degradation explored through in vitro degradation under enzymatic and oxidative conditions. The elastomers were prepared via UV initiated crosslinking of prepolymers of TMC and equimolar amounts of TMC and epsilon-caprolactone (CL). The degradation process was followed by investigating the changes in the mechanical properties, mass loss, water uptake, sol content, differential scanning calorimetry, and surface chemistry through attenuated total reflectance infrared (ATR-FTIR) spectroscopy. During in vivo degradation, TMC and TMCCL elastomers exhibited surface erosion. The tissue response was of greater intensity in the case of the TMC elastomer. Both elastomers exhibited degradation in cholesterol esterase containing solutions in vitro, but no parallels were found between the rate of in vivo degradation and the rate of in vitro degradation. Only the TMCCL elastomer degraded in lipase. Degradation in a stable superoxide anion in vitro medium was consistent with the observed in vivo degradation results, indicating a dominant role of oxidation through the secretion of this reactive oxygen species by adherent phagocytic cells in the degradation of these elastomers.

  9. The characterization of silicone type dielectric elastomer filled with nano sized BaTiO3 particles

    Science.gov (United States)

    Liu, Liwu; Zhang, Wei; Bo, Tao; Zhao, Wei; Lv, Xiongfei; Li, Jinrong; Zhang, Zhen

    2015-04-01

    In this paper, the characterization and electromechanical stability behavior of nano sized BaTiO3 particle filled dielectric elastomer has been analyzed experimentally and theoretically. The free energy function involving a new dielectric energy density function and Mooney-Rivlin elastic strain energy function has been used to carry out the analysis. To give a comprehensive dielectric energy function, the influence of the BaTiO3 weight fraction on the dielectric property of the dielectric elastomer has been considered. The analytical results show that with the increasing weight fraction of BaTiO3 or the electrostrictive factor, the critical electric field of silicone elastomer decreases, i.e. the elastomer's stability is reduced. Meanwhile, with the increasing material constant ratio k which is the ratio of the two material constants appeared in the Mooney-Rivilin elastic strain energy function, the critical nominal electric field will increase. These results are useful in not only helping us to understand the influence of the filled nano-BaTiO3 particles on the electromechanical stability of silicone dielectric elastomer, but also giving great guidance to obtain specific dielectric elastomer actuators to meet the demand of users by changing the dielectric property of the elastomer.

  10. Design of an innovative dielectric elastomer actuator for space applications

    Science.gov (United States)

    Branz, Francesco; Sansone, Francesco; Francesconi, Alessandro

    2014-03-01

    The capability of Dielectric Elastomers to show large deformations under high voltage loads has been deeply investigated to develop a number of actuators concepts. From a space systems point of view, the advantages introduced by this class of smart materials are considerable and include high conversion efficiency, distributed actuation, self-sensing capability, light weight and low cost. This paper focuses on the design of a solid-state actuator capable of high positioning resolution. The use of Electroactive Polymers makes this device interesting for space mechanisms applications, such as antenna and sensor pointing, solar array orientation, attitude control, adaptive structures and robotic manipulators. In particular, such actuation suffers neither wear, nor fatigue issues and shows highly damped vibrations, thus requiring no maintenance and transferring low disturbance to the surrounding structures. The main weakness of this actuator is the relatively low force/torque values available. The proposed geometry allows two rotational degrees of freedom, and simulations are performed to measure the expected instant angular deflection at zero load and the stall torque of the actuator under a given high voltage load. Several geometric parameters are varied and their influence on the device behaviour is studied. Simplified relations are extrapolated from the numerical results and represent useful predicting tools for design purposes. Beside the expected static performances, the dynamic behaviour of the device is also assessed and the input/output transfer function is estimated. Finally, a prototype design for laboratory tests is presented; the experimental activity aims to validate the preliminary results obtained by numerical analysis.

  11. Robust hybrid elastomer/metal-oxide superhydrophobic surfaces.

    Science.gov (United States)

    Hoshian, S; Jokinen, V; Franssila, S

    2016-08-21

    We introduce a new type of hybrid material: a nanostructured elastomer covered by a hard photoactive metal-oxide thin film resembling the exoskeleton of insects. It has extreme water repellency and fast self-recovery after damage. A new fabrication method for replicating high aspect ratio, hierarchical re-entrant aluminum structures into polydimethylsiloxane (PDMS) is presented. The method is based on a protective titania layer deposited by atomic layer deposition (ALD) on the aluminum template. The ALD titania transfers to the elastomeric scaffold via sacrificial release etching. The sacrificial release method allows for high aspect ratio, even 100 μm deep and successful release of overhanging structures, unlike conventional peeling. The ALD titania conformally covers the 3D multihierarchical structures of the template and protects the polymer during the release etch. Afterwards it prevents the high aspect ratio nanostructures from elasticity based collapse. The resulting nanostructured hybrid PDMS/titania replicas display robust superhydrophobicity without any further fluoro-coating or modification. Their mechanical and thermal robustness results from a thick nanostructured elastomeric layer which is conformally covered by ceramic titania instead of a monolayer hydrophobic coating. We have demonstrated the durability of these replicas against mechanical abrasion, knife scratches, rubbing, bending, peel tape test, high temperature annealing, UV exposure, water jet impingement and long term underwater storage. Though the material loses its superhydrophobicity in oxygen plasma exposure, a fast recovery from superhydrophilic to superhydrophobic can be achieved after 20 min UV irradiation. UV-assisted recovery is correlated with the high photoactivity of ALD titania film. This novel hybrid material will be applicable to the large area superhydrophobic surfaces in practical outdoor applications.

  12. Electrical breakdown detection system for dielectric elastomer actuators

    Science.gov (United States)

    Ghilardi, Michele; Busfield, James J. C.; Carpi, Federico

    2017-04-01

    Electrical breakdown of dielectric elastomer actuators (DEAs) is an issue that has to be carefully addressed when designing systems based on this novel technology. Indeed, in some systems electrical breakdown might have serious consequences, not only in terms of interruption of the desired function but also in terms of safety of the overall system (e.g. overheating and even burning). The risk for electrical breakdown often cannot be completely avoided by simply reducing the driving voltages, either because completely safe voltages might not generate sufficient actuation or because internal or external factors might change some properties of the actuator whilst in operation (for example the aging or fatigue of the material, or an externally imposed deformation decreasing the distance between the compliant electrodes). So, there is the clear need for reliable, simple and cost-effective detection systems that are able to acknowledge the occurrence of a breakdown event, making DEA-based devices able to monitor their status and become safer and "selfaware". Here a simple solution for a portable detection system is reported that is based on a voltage-divider configuration that detects the voltage drop at the DEA terminals and assesses the occurrence of breakdown via a microcontroller (Beaglebone Black single-board computer) combined with a real-time, ultra-low-latency processing unit (Bela cape an open-source embedded platform developed at Queen Mary University of London). The system was used to both generate the control signal that drives the actuator and constantly monitor the functionality of the actuator, detecting any breakdown event and discontinuing the supplied voltage accordingly, so as to obtain a safer controlled actuation. This paper presents preliminary tests of the detection system in different scenarios in order to assess its reliability.

  13. Optimization of electrode placement in electromyographic control of dielectric elastomers

    Science.gov (United States)

    Walbran, Scott H.; Calius, Emilio P.; Dunlop, G. Reg; Anderson, Iain A.

    2009-03-01

    Human intention recognition is becoming a key part of powered prosthetics research. With the advent of smart materials, the usefulness of powered prosthetics has increased. Correspondingly, there is a greater need for control technology. Electromyography (EMG) has previously been used to control myoelectric hands; however the approach to electrode placement has been speculative at best. Carpi, Raspopovic and De Rossi have shown that dielectric elastomer actuators (DEAs) can be controlled by a variety of human electrophysiological signals, including EMG. To control a DEA device with multiple degrees of freedom using EMG, multiple electrode sites are required. This paper presents an approach to control an array of DEAs using a series of electrodes and an optimized electrode data filtering scheme to maximize classification accuracy when differentiating between hand grasps. A silicon mould of a human forearm was created with an array of electrodes embedded within it. Data from each electrode site was recorded using the Universal Electrophysiological Mapping (UnEmap) system developed at the University of Auckland Bioengineering Institute for the amplification and filtering of multiple biopotential signals. The recorded data was then processed off-line, in order to calculate spatial gradients; this would determine which electrode sites would give the best bipolar readings. The spatial gradients were then compared to each other in order to find the optimal electrode sites. Several points in the extensor compartment of the forearm were found to be useful in recognizing grasping, while several points in the flexor compartment of the forearm were found to be useful in differentiating between grasps.

  14. Inkjet printing of carbon black electrodes for dielectric elastomer actuators

    Science.gov (United States)

    Schlatter, Samuel; Rosset, Samuel; Shea, Herbert

    2017-04-01

    Inkjet printing is an appealing technique to print electrodes for Dielectric Elastomer Actuators (DEAs). Here we present the preparation and ink-jet printing of a carbon black electrode mixture and characterise its properties. Carbon black has been used extensively in the past because it is very compliant; however, it has a high resistance and can be very dirty to work with. In this paper we show that carbon black remains an appropriate electrode material, and when inkjet printed can be used to fabricate devices meeting today's demanding requirements. DEAs are becoming thinner to decrease actuation voltages and are shrinking in size to match the scale of the devices in the biomedical field, tuneable optics, and microfluidics. Inkjet printing addresses both of these problems. Firstly, Inkjet printing is a non-contact technique and can print on very thin freestanding membranes. Secondly, the high precision of inkjet printers makes it possible to print complex electrode geometries in the millimetre scale. We demonstrate the advantages of inkjet printing and carbon black electrodes by conducting a full characterisation of the printed electrodes. The printed carbon black electrodes have resistances as low as 13kΩ/□, an elastic modulus of approximately 1MPa, and a cyclic resistance swing which increases by 7% over 1500 cycles at 50% stretch. We also demonstrate a DEA with printed carbon black electrodes with a diametral stretch of 8.8% at an electric field of approximately 94V/μm. Finally a qualitative test is conducted to show that the printed carbon black electrode is extremely hardwearing.

  15. Adhesion of Silicone Elastomer Seals for NASA's Crew Exploration Vehicle

    Science.gov (United States)

    deGroh, Henry C., III; Miller, Sharon K. R.; Smith, Ian M.; Daniels, Christopher C.; Steinetz, Bruce M

    2008-01-01

    Silicone rubber seals are being considered for a number of interfaces on NASA's Crew Exploration Vehicle (CEV). Some of these joints include the docking system, hatches, and heat shield-to-back shell interface. A large diameter molded silicone seal is being developed for the Low Impact Docking System (LIDS) that forms an effective seal between the CEV and International Space Station (ISS) and other future Constellation Program spacecraft. Seals between the heat shield and back shell prevent high temperature reentry gases from leaking into the interface. Silicone rubber seals being considered for these locations have inherent adhesive tendencies that would result in excessive forces required to separate the joints if left unchecked. This paper summarizes adhesion assessments for both as-received and adhesion-mitigated seals for the docking system and the heat shield interface location. Three silicone elastomers were examined: Parker Hannifin S0899-50 and S0383-70 compounds, and Esterline ELA-SA-401 compound. For the docking system application various levels of exposure to atomic oxygen (AO) were evaluated. Moderate AO treatments did not lower the adhesive properties of S0899-50 sufficiently. However, AO pretreatments of approximately 10(exp 20) atoms/sq cm did lower the adhesion of S0383-70 and ELA-SA-401 to acceptable levels. For the heat shield-to-back shell interface application, a fabric covering was also considered. Molding Nomex fabric into the heat shield pressure seal appreciably reduced seal adhesion for the heat shield-to-back shell interface application.

  16. EFFECTS OF GAMMA IRRADIATION ON EPDM ELASTOMERS (REVISION 1)

    Energy Technology Data Exchange (ETDEWEB)

    Clark, E.

    2013-09-13

    Two formulations of EPDM elastomer, one substituting a UV stabilizer for the normal antioxidant in this polymer, and the other the normal formulation, were synthesized and samples of each were exposed to gamma irradiation in initially pure deuterium gas to compare their radiation stability. Stainless steel containers having rupture disks were designed for this task. After 130 MRad dose of cobalt-60 radiation in the SRNL Gamma Irradiation Facility, a significant amount of gas was created by radiolysis; however the composition indicated by mass spectroscopy indicated an unexpected increase in the total amount deuterium in both formulations. The irradiated samples retained their ductility in a bend test. No change of sample weight, dimensions, or density was observed. No change of the glass transition temperature as measured by dynamic mechanical analysis was observed, and most of the other dynamic mechanical properties remained unchanged. There appeared to be an increase in the storage modulus of the irradiated samples containing the UV stabilizer above the glass transition, which may indicate hardening of the material by radiation damage. Revision 1 adds a comparison with results of a study of tritium exposed EPDM. The amount of gas produced by the gamma irradiation was found to be equivalent to about 280 days exposure to initially pure tritium gas at one atmosphere. The glass transition temperature of the tritium exposed EPDM rose about 10°C. over 280 days, while no glass transition temperature change was observed for gamma irradiated EPDM. This means that gamma irradiation in deuterium cannot be used as a surrogate for tritium exposure.

  17. Functionalized Materials From Elastomers to High Performance Thermoplastics

    Energy Technology Data Exchange (ETDEWEB)

    Salazar, Laura Ann [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    Synthesis and incorporation of functionalized materials continues to generate significant research interest in academia and in industry. If chosen correctly, a functional group when incorporated into a polymer can deliver enhanced properties, such as adhesion, water solubility, thermal stability, etc. The utility of these new materials has been demonstrated in drug-delivery systems, coatings, membranes and compatibilizers. Two approaches exist to functionalize a material. The desired moiety can be added to the monomer either before or after polymerization. The polymers used range from low glass transition temperature elastomers to high glass transition temperature, high performance materials. One industrial example of the first approach is the synthesis of Teflon(reg. sign). Poly(tetrafluoroethylene) (PTFE or Teflon(reg. sign)) is synthesized from tetrafluoroethylene, a functionalized monomer. The resulting material has significant property differences from the parent, poly(ethylene). Due to the fluorine in the polymer, PTFE has excellent solvent and heat resistance, a low surface energy and a low coefficient of friction. This allows the material to be used in high temperature applications where the surface needs to be nonabrasive and nonstick. This material has a wide spread use in the cooking industry because it allows for ease of cooking and cleaning as a nonstick coating on cookware. One of the best examples of the second approach, functionalization after polymerization, is the vulcanization process used to make tires. Natural rubber (from the Hevea brasiliensis) has a very low glass transition temperature, is very tacky and would not be useful to make tires without synthetic alteration. Goodyear's invention was the vulcanization of polyisoprene by crosslinking the material with sulfur to create a rubber that was tough enough to withstand the elements of weather and road conditions. Due to the development of polymerization techniques to make cis

  18. Structural dynamics and interfacial properties of filler-reinforced elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Fritzsche, J; Klueppel, M, E-mail: Manfred.Klueppel@DIKautschuk.de [Deutsches Institut fuer Kautschuktechnologie e V, Eupener Strasse 33, D-30519 Hannover (Germany)

    2011-01-26

    The combined effect of filler networking and reduced chain mobility close to the filler interface is analyzed based on investigations of the relaxation dynamics of a solution of styrene butadiene rubber filled with different loadings and types of nanostructured carbon blacks. Dynamic-mechanical and dielectric spectra are studied in a wide frequency and temperature range. By referring to a tunneling process of charge carriers over nanoscopic gaps between adjacent carbon black particles the gap distance is evaluated from the dielectric spectra. This distance corresponds to the length of glassy-like polymer bridges forming flexible bonds between adjacent filler particles of the filler network. It is found that the gap distance decreases with increasing filler loading and specific surface area which correlates with an increase of the apparent activation energy of the filler network evaluated from dynamic-mechanical data. Due to the thermal activation of glassy-like polymer bridges the time-temperature superposition principle is not fulfilled for filled elastomers and the introduction of vertical shift factors is necessary to obtain viscoelastic master curves. The change in the low frequency viscoelastic properties by the incorporation of fillers is shown to be related to the superimposed dynamics of the filler network governed by the viscoelastic response of the glassy-like polymer bridges. This effect is distinguished from the reduced chain mobility close to the filler surface which results in a broadening of the glass transition on the high temperature or low frequency side. The microstructure-based interpretation of viscoelastic data is supported by an analysis of the relaxation time spectra.

  19. Structural dynamics and interfacial properties of filler-reinforced elastomers

    Science.gov (United States)

    Fritzsche, J.; Klüppel, M.

    2011-01-01

    The combined effect of filler networking and reduced chain mobility close to the filler interface is analyzed based on investigations of the relaxation dynamics of a solution of styrene butadiene rubber filled with different loadings and types of nanostructured carbon blacks. Dynamic-mechanical and dielectric spectra are studied in a wide frequency and temperature range. By referring to a tunneling process of charge carriers over nanoscopic gaps between adjacent carbon black particles the gap distance is evaluated from the dielectric spectra. This distance corresponds to the length of glassy-like polymer bridges forming flexible bonds between adjacent filler particles of the filler network. It is found that the gap distance decreases with increasing filler loading and specific surface area which correlates with an increase of the apparent activation energy of the filler network evaluated from dynamic-mechanical data. Due to the thermal activation of glassy-like polymer bridges the time-temperature superposition principle is not fulfilled for filled elastomers and the introduction of vertical shift factors is necessary to obtain viscoelastic master curves. The change in the low frequency viscoelastic properties by the incorporation of fillers is shown to be related to the superimposed dynamics of the filler network governed by the viscoelastic response of the glassy-like polymer bridges. This effect is distinguished from the reduced chain mobility close to the filler surface which results in a broadening of the glass transition on the high temperature or low frequency side. The microstructure-based interpretation of viscoelastic data is supported by an analysis of the relaxation time spectra.

  20. Functionalized Materials From Elastomers to High Performance Thermoplastics

    Energy Technology Data Exchange (ETDEWEB)

    Laura Ann Salazar

    2003-05-31

    Synthesis and incorporation of functionalized materials continues to generate significant research interest in academia and in industry. If chosen correctly, a functional group when incorporated into a polymer can deliver enhanced properties, such as adhesion, water solubility, thermal stability, etc. The utility of these new materials has been demonstrated in drug-delivery systems, coatings, membranes and compatibilizers. Two approaches exist to functionalize a material. The desired moiety can be added to the monomer either before or after polymerization. The polymers used range from low glass transition temperature elastomers to high glass transition temperature, high performance materials. One industrial example of the first approach is the synthesis of Teflon(reg. sign). Poly(tetrafluoroethylene) (PTFE or Teflon(reg. sign)) is synthesized from tetrafluoroethylene, a functionalized monomer. The resulting material has significant property differences from the parent, poly(ethylene). Due to the fluorine in the polymer, PTFE has excellent solvent and heat resistance, a low surface energy and a low coefficient of friction. This allows the material to be used in high temperature applications where the surface needs to be nonabrasive and nonstick. This material has a wide spread use in the cooking industry because it allows for ease of cooking and cleaning as a nonstick coating on cookware. One of the best examples of the second approach, functionalization after polymerization, is the vulcanization process used to make tires. Natural rubber (from the Hevea brasiliensis) has a very low glass transition temperature, is very tacky and would not be useful to make tires without synthetic alteration. Goodyear's invention was the vulcanization of polyisoprene by crosslinking the material with sulfur to create a rubber that was tough enough to withstand the elements of weather and road conditions. Due to the development of polymerization techniques to make cis

  1. Chemical modification of PDMS surface without impacting the viscoelasticity: Model systems for a better understanding of elastomer/elastomer adhesion and friction

    OpenAIRE

    DIRANY, Mohammed; DIES, Laëtitia; Restagno, Frédéric; Léger, Liliane; Poulard, Christophe; MIQUELARD-GARNIER, Guillaume

    2015-01-01

    The influence of both viscoelastic and interfacial parameters on the surface properties of elastomers is difficult to study. Here, we describe a simple route to achieve surface modification of PDMS without impacting the viscoelastic properties of the bulk. PEG modified PDMS surfaces were synthesized by two step surface modification based on hydrosilylation. The covalent grafting of PEG on the surface has been evidenced by AFM and ATR-FTIR, and its effect on the hydrophilicity characterized by...

  2. Rank-based decompositions of morphological templates.

    Science.gov (United States)

    Sussner, P; Ritter, G X

    2000-01-01

    Methods for matrix decomposition have found numerous applications in image processing, in particular for the problem of template decomposition. Since existing matrix decomposition techniques are mainly concerned with the linear domain, we consider it timely to investigate matrix decomposition techniques in the nonlinear domain with applications in image processing. The mathematical basis for these investigations is the new theory of rank within minimax algebra. Thus far, only minimax decompositions of rank 1 and rank 2 matrices into outer product expansions are known to the image processing community. We derive a heuristic algorithm for the decomposition of matrices having arbitrary rank.

  3. Plasma Polymerization Surface Modification of Carbon Black and its Effect in Elastomers

    NARCIS (Netherlands)

    Mathew, T.; Datta, R.N.; Dierkes, W.K.; Talma, A.G.; Ooij, van W.J.; Noordermeer, J.W.M.

    2011-01-01

    Surface modification of carbon black by plasma polymerization was aimed to reduce its surface energy in order to compatibilize the filler with various elastomers. A fullerenic carbon black was used for the modification process. Thermogravimetric analysis, wetting behavior with liquids of known surfa

  4. Spontaneous formation of photochromic coatings made of reversible microfibrils and nanofibrils on an elastomer substrate.

    Science.gov (United States)

    Oropesa-Nuñez, Reinier; Fragouli, Despina; Pignatelli, Francesca; Scarpellini, Alice; Gigliotti, Efisio; Samoylova, Elena; Athanassiou, Athanassia

    2014-11-04

    We report the spontaneous formation of photochromic microcrystalline and nanocrystalline fibrils forming dense coatings of cactuslike supramolecular structures on the surface of a soft poly(dimethylsiloxane) (PDMS) elastomer. The initial deposition of the photochromic molecules of diarylethenes on the elastomer is done by dip adsorption, a process that permits the homogeneous distribution of the molecules not only on the surface but also in the inner part of the polymer. Detailed thermal and microscopy studies reveal that the growth process of the fibrils is initiated by the formation of crystal seeds of the diarylethene in the proximity of the elastomer's surface empty voids and progresses toward the elastomer-air interface as a result of the high mobility of the molecules at room temperature. Fibril formation is possible only when the molecules are in the open form because the UV irradiation responsible for their transformation to the close isomeric form immediately after deposition totally prohibits the crystals' formation. Furthermore, the UV irradiation of the grown supramolecular assemblies provokes their destruction, but when the irradiated samples are left to recover under ambient conditions, they form new assemblies of fibrils in a faster and more efficient way. The resulting systems exhibit superhydrophobic to slightly hydrophobic properties with differences of almost 80° in water contact angles upon dark storage-UV irradiation cycles. The proposed systems can be an alternative to the facile formation of reversible photochromic fibrils on soft polymer surfaces for utilization on diverse soft devices, where controlled surface morphology and wettability are desired.

  5. Experimentally verified model of viscoelastic behavior of multilayer unimorph dielectric elastomer actuators

    Science.gov (United States)

    Kadooka, Kevin; Imamura, Hiroya; Taya, Minoru

    2016-10-01

    This work presents a linear viscoelastic model to describe the time-dependent actuation behavior of multilayer unimorph dielectric elastomer actuators (MUDEA), with experimental validation by actuators produced by a robotic dispenser system. MUDEA are a type of soft actuator which can produce large bending deformation without prestretch typically required by dielectric elastomer actuators. Current analytical and finite element models of MUDEA do not consider material viscoelasticity and cannot predict the change over time of performance metrics such as tip displacement and blocking force. The linear viscoelastic model presented in this work is based on a linear elastic model for the MUDEA extended to account for viscous effects by the elastic-viscoelastic correspondence principle. The model is easily implemented because it is based on explicit expressions which can be evaluated numerically by any computer algebra system. The model was used to predict the tip displacement and blocking force of MUDEAs consisting of two, four, six, eight, and ten layers of dielectric elastomer material. The model predictions agreed well with experimental data obtained from MUDEA produced by a robotic dispenser system, which was capable of producing multilayered structures of thin layers of dielectric elastomer and carbon nanotube based electrode material.

  6. Novel co-agents for improved properties in peroxide cure of saturated elastomers

    NARCIS (Netherlands)

    Alvarez Grima, Maria Montserrat

    2007-01-01

    Peroxide vulcanisation is a widely used cure system for elastomers and offers many possibilities for use, mainly because of the availability of co-agents and scorch retarders. The range of applications of peroxide cure could significantly be widened, if certain mechanical properties could be improve

  7. Anisotropic optical response of optically opaque elastomers with conductive fillers as revealed by terahertz polarization spectroscopy

    Science.gov (United States)

    Okano, Makoto; Watanabe, Shinichi

    2016-12-01

    Elastomers are one of the most important materials in modern society because of the inherent viscoelastic properties due to their cross-linked polymer chains. Their vibration-absorbing and adhesive properties are especially useful and thus utilized in various applications, for example, tires in automobiles and bicycles, seismic dampers in buildings, and seals in a space shuttle. Thus, the nondestructive inspection of their internal states such as the internal deformation is essential in safety. Generally, industrial elastomers include various kinds of additives, such as carbon blacks for reinforcing them. The additives make most of them opaque in a wide spectral range from visible to mid-infrared, resulting in that the nondestructive inspection of the internal deformation is quite difficult. Here, we demonstrate transmission terahertz polarization spectroscopy as a powerful technique for investigating the internal optical anisotropy in optically opaque elastomers with conductive additives, which are transparent only in the terahertz frequency region. The internal deformation can be probed through the polarization changes inside the material due to the anisotropic dielectric response of the conductive additives. Our study about the polarization-dependent terahertz response of elastomers with conductive additives provides novel knowledge for in situ, nondestructive evaluation of their internal deformation.

  8. Theoretical study of the electromechanical efficiency of a loaded tubular dielectric elastomer actuator

    DEFF Research Database (Denmark)

    Rechenbach, Björn; Willatzen, Morten; Lassen, Benny

    2016-01-01

    The electromechanical efficiency of a loaded tubular dielectric elastomer actuator (DEA) is investigated theoretically. In previous studies, the external system, on which the DEA performs mechanical work, is implemented implicitly by prescribing the stroke of the DEA in a closed operation cycle...

  9. Inflated dielectric elastomer actuator for eyeball's movements: fabrication, analysis and experiments

    Science.gov (United States)

    Liu, Yanju; Shi, Liang; Liu, Liwu; Zhang, Zhen; Leng, Jinsong

    2008-03-01

    Bio-mimetic actuators are inspired to the human or animal organ and they are aimed at replicating actions exerted by the main organic muscles. We present here an inflated dielectric Electroactive Polymer actuator based on acrylic elastomer aiming at mimicing the ocular muscular of the human eye. Two sheets of polyacrylic elastomer coated with conductive carbon grease are sticked to a rotatable backbone, which function like an agonist-antagonist configuration. When stimulating the two elastomer sheets separately, the rotatable mid-arc of the actuator is capable of rotating from -50° to 50°. Experiments shows that the inflated actuator, compared with uninflated one, performs much bigger rotating angle and more strengthened. Connected with the actuator via an elastic tensive line, the eyeball rotates around the symmetrical axes. The realization of more accurate movements and emotional expressions of our native eye system is the next step of our research and still under studied. This inflated dielectric elastomer actuator shows as well great potential application in robofish and adaptive stucture.

  10. Interpenetrating polymer networks based on a thermoplastic elastomer, using radiation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Shirodkar, Bhavna D. E-mail: bhavna@student.unsw.edu.au; Burford, Robert

    2001-07-01

    Styrene-butadiene-styrene thermoplastic elastomers can be transformed into Interpenetrating polymer networks using {gamma}-radiation crosslinking. Trimethylol propanetriacrylate was used as the radiation crosslinker for styrene. The study shows that the hardness of the sample increased with radiation dose while the tensile strength remained constant.

  11. Interpenetrating polymer networks based on a thermoplastic elastomer, using radiation techniques

    Science.gov (United States)

    Shirodkar, Bhavna D.; Burford, Robert P.

    2001-07-01

    Styrene-butadiene-styrene thermoplastic elastomers can be transformed into Interpenetrating polymer networks using γ-radiation crosslinking. Trimethylol propanetriacrylate was used as the radiation crosslinker for styrene. The study shows that the hardness of the sample increased with radiation dose while the tensile strength remained constant.

  12. Inverse grey-box model-based control of a dielectric elastomer actuator

    DEFF Research Database (Denmark)

    Jones, Richard William; Sarban, Rahimullah

    2012-01-01

    An accurate physical-based electromechanical model of a commercially available tubular dielectric elastomer (DE) actuator has been developed and validated. In this contribution, the use of the physical-based electromechanical model to formulate a model-based controller is examined. The choice...

  13. A new soft dielectric silicone elastomer matrix with high mechanical integrity and low losses

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2015-01-01

    in Young's modulus, however, is often accompanied by the loss of mechanical stability and thereby the lifetime of the DE. A new soft elastomer matrix, with no loss of mechanical stability and high dielectric permittivity, was prepared through the use of alkyl chloride-functional siloxane copolymers...

  14. Geometry optimization of tubular dielectric elastomer actuators with anisotropic metallic electrodes

    DEFF Research Database (Denmark)

    Rechenbach, Björn; Willatzen, Morten; Sarban, R.;

    2014-01-01

    This paper presents an experimentally verified static three-dimensional model for core free tubular dielectric elastomer actuators with anisotropic compliant metal electrodes. Due to the anisotropy of the electrodes, the performance (force versus voltage, force versus stroke, and stroke versus vo...

  15. Manufacture of Bulk Magnetorheological Elastomers Using Vacuum Assisted Resin Transfer Molding

    Science.gov (United States)

    Woods, B. K. S.; Wereley, N.; Hoffmaster, R.; Nersessian, N.

    Magnetorheological elastomers (MREs) consist of ferromagnetic particles embedded in a compliant matrix (i.e. elastomer). Due to the magnetic interaction of the ferromagnetic particles, MREs exhibit field dependent physical properties. Very significant changes in the modulus and loss factor of the elastomer can be realized. This makes MREs a promising candidate for active vibration control mechanisms. One factor currently limiting the implementation of this technology is the lack of an efficient manufacturing method that is practical for mass production. Most of the specimens created for previous MRE research were made using simple casting or mechanical mixing methods that are not ideal. In this research a new methodology for producing MREs using Vacuum Assisted Resin Transfer Molding (VARTM) was investigated. The method was used with a range of iron particles sizes and silicon elastomer systems and found to be effective within certain limits of applicability. The specimens produced were tested in compression under a range of magnetic fields to validate the presence of the MR effect. Relative changes in compressive modulus ranging from 35% to 150% (depending on volume fraction), under fields of around 0.3T were observed.

  16. Investigation of air entrapment and weld line defects in micro injection moulded thermoplastic elastomer micro rings

    DEFF Research Database (Denmark)

    Hasnaes, F.B.; Tosello, Guido; Calaon, Matteo;

    2015-01-01

    The micro injection moulding (μIM) process for the production of micro rings in thermoplastic elastomers (TPE) was investigated and optimized. The objective was to minimize the formation of air entrapments and the depth of micro weld line created on the surface of the TPE micro moulded rings...

  17. Reconfigurable biodegradable shape-memory elastomers via Diels-Alder coupling.

    Science.gov (United States)

    Ninh, Chi; Bettinger, Christopher J

    2013-07-08

    Synthetic biodegradable elastomers are a class of polymers that have demonstrated far-reaching utility as biomaterials for use in many medical applications. Biodegradable elastomers can be broadly classified into networks prepared by either step-growth or chain-growth polymerization. Each processing strategy affords distinct advantages in terms of capabilities and resulting properties of the network. This work describes the synthesis, processing, and characterization of cross-linked polyester networks based on Diels-Alder coupling reactions. Hyperbranched furan-modified polyester precursors based on poly(glycerol-co-sebacate) are coupled with bifunctional maleimide cross-linking agents. The chemical and thermomechanical properties of the elastomers are characterized at various stages of network formation. Experimental observations of gel formation are compared to theoretical predictions derived from Flory-Stockmayer relationships. This cross-linking strategy confers unique advantages in processing and properties including the ability to fabricate biodegradable reconfigurable covalent networks without additional catalysts or reaction byproducts. Reconfigurable biodegradable networks using Diels-Alder cycloaddition reactions permit the fabrication of shape-memory polymers with complex permanent geometries. Biodegradable elastomers based on polyester networks with molecular reconfigurability achieve vastly expanded properties and processing capabilities for potential applications in medicine and beyond.

  18. Anisotropic conductance of the multiwall carbon nanotube array/silicone elastomer composite film

    Energy Technology Data Exchange (ETDEWEB)

    Yao Yuan; Liu Changhong; Fan Shoushan [Tsinghua-Foxconn Nanotechnology Research Center and Department of Physics, Tsinghua University, Beijing 100084 (China)

    2006-09-14

    Multiwall carbon nanotube array/silicone elastomer composite films have been fabricated with an in situ injection modelling method. The transverse conductivity of the composite films is larger than the lateral conductivity because the aligned carbon nanotube array is embedded into the polymer matrix. The nonlinear I-V curve has been analysed and the temperature-dependent transport behaviour has been investigated.

  19. Numerical study of liquid crystal elastomers by a mixed finite element method

    KAUST Repository

    LUO, C.

    2011-08-22

    Liquid crystal elastomers present features not found in ordinary elastic materials, such as semi-soft elasticity and the related stripe domain phenomenon. In this paper, the two-dimensional Bladon-Terentjev-Warner model and the one-constant Oseen-Frank energy expression are combined to study the liquid crystal elastomer. We also impose two material constraints, the incompressibility of the elastomer and the unit director norm of the liquid crystal. We prove existence of minimiser of the energy for the proposed model. Next we formulate the discrete model, and also prove that it possesses a minimiser of the energy. The inf-sup values of the discrete linearised system are then related to the smallest singular values of certain matrices. Next the existence and uniqueness of the Lagrange multipliers associated with the two material constraints are proved under the assumption that the inf-sup conditions hold. Finally numerical simulations of the clamped-pulling experiment are presented for elastomer samples with aspect ratio 1 or 3. The semi-soft elasticity is successfully recovered in both cases. The stripe domain phenomenon, however, is not observed, which might be due to the relative coarse mesh employed in the numerical experiment. Possible improvements are discussed that might lead to the recovery of the stripe domain phenomenon. © Copyright Cambridge University Press 2011.

  20. Tactile sensor integrated dielectric elastomer actuator for simultaneous actuation and sensing

    Science.gov (United States)

    Kadooka, Kevin; Imamura, Hiroya; Taya, Minoru

    2016-04-01

    Dielectric elastomers (DE) are a subgroup of electroactive polymers which may be used as soft transducers. Such soft transducers exhibit high energy density and silent operation, which makes them desirable for life-like robotic systems such as a robotic hand. A robotic hand must be able to sense the object being manipulated, in terms of normal and shear force being applied, and note when contact has been achieved or lost. To this end, a dielectric elastomer actuator (DEA) with integrated tactile sensing has been developed to provide simultaneous actuation and sensing. The tactile sensing dielectric elastomer actuator consists of a unimorph-type structure, where the active portion is a laminate of alternating DE and electrode material which expands under applied voltage, and the sensing portion is a stiffer sensing dielectric elastomer which has no electrical connection to the active portion. Under applied voltage, the deformation of the active portion expands but is constrained on one side by the sensing portion, resulting in bending actuation. The sensing portion is a DE with electrodes patterned to form 2x2 capacitive sensing arrays. Dome-shaped bumps positioned over the sensing arrays redistribute tactile forces onto the sensor segments, so that measurement of the capacitance change across the array allows for reconstruction of magnitude and direction of the incoming force.

  1. Tensile and impact properties of three-component PP/wood/elastomer composites

    Directory of Open Access Journals (Sweden)

    B. Pukanszky

    2012-03-01

    Full Text Available Polypropylene (PP was reinforced with wood flour and impact modified with elastomers to increase stiffness and impact resistance simultaneously. Elastomer content changed in four (0, 5, 10 and 20 wt%, while that of wood content in seven steps, the latter from 0 to 60 wt% in 10 wt% steps. Structure and adhesion were controlled by the addition of functionalized (maleated polymers. Composites were homogenized in a twin-screw extruder and then injection molded to tensile bars. Fracture resistance was characterized by standard and instrumented impact tests. The results showed that the components are dispersed independently of each other even when a functionalized elastomer is used for impact modification, at least under the conditions of this study. Impact resistance does not change much as a function of wood content in PP/wood composites, but decreases drastically from the very high level of the PP/elastomer blend to almost the same value obtained without impact modifier in the three-component materials. Increasing stiffness and fiber related local deformation processes led to small fracture toughness at large wood content. Micromechanical deformation processes depend mainly on the strength of PP/wood interaction; debonding and pull-out take place at poor adhesion, while fiber fracture dominates when adhesion is strong. Composites with sufficiently large impact resistance cannot be prepared in the usual range of wood contents (50–60 wt%.

  2. Effect of Surface Treated Silicon Dioxide Nanoparticles on Some Mechanical Properties of Maxillofacial Silicone Elastomer

    Directory of Open Access Journals (Sweden)

    Sara M. Zayed

    2014-01-01

    Full Text Available Current materials used for maxillofacial prostheses are far from ideal and there is a need for novel improved materials which mimic as close as possible the natural behavior of facial soft tissues. This study aimed to evaluate the effect of adding different concentrations of surface treated silicon dioxide nanoparticles (SiO2 on clinically important mechanical properties of a maxillofacial silicone elastomer. 147 specimens of the silicone elastomer were prepared and divided into seven groups (n=21. One control group was prepared without nanoparticles and six study groups with different concentrations of nanoparticles, from 0.5% to 3% by weight. Specimens were tested for tear strength (ASTM D624, tensile strength (ASTM D412, percent elongation, and shore A hardness. SEM was used to assess the dispersion of nano-SiO2 within the elastomer matrix. Data were analyzed by one-way ANOVA and Scheffe test (α=0.05. Results revealed significant improvement in all mechanical properties tested, as the concentration of the nanoparticles increased. This was supported by the results of the SEM. Hence, it can be concluded that the incorporation of surface treated SiO2 nanoparticles at concentration of 3% enhanced the overall mechanical properties of A-2186 silicone elastomer.

  3. Blended Polyurethane and Tropoelastin as a Novel Class of Biologically Interactive Elastomer.

    Science.gov (United States)

    Wise, Steven G; Liu, Hongjuan; Yeo, Giselle C; Michael, Praveesuda L; Chan, Alex H P; Ngo, Alan K Y; Bilek, Marcela M M; Bao, Shisan; Weiss, Anthony S

    2016-03-01

    Polyurethanes are versatile elastomers but suffer from biological limitations such as poor control over cell attachment and the associated disadvantages of increased fibrosis. We address this problem by presenting a novel strategy that retains elasticity while modulating biological performance. We describe a new biomaterial that comprises a blend of synthetic and natural elastomers: the biostable polyurethane Elast-Eon and the recombinant human tropoelastin protein. We demonstrate that the hybrid constructs yield a class of coblended elastomers with unique physical properties. Hybrid constructs displayed higher elasticity and linear stress-strain responses over more than threefold strain. The hybrid materials showed increased overall porosity and swelling in comparison to polyurethane alone, facilitating enhanced cellular interactions. In vitro, human dermal fibroblasts showed enhanced proliferation, while in vivo, following subcutaneous implantation in mice, hybrid scaffolds displayed a reduced fibrotic response and tunable degradation rate. To our knowledge, this is the first example of a blend of synthetic and natural elastomers and is a promising approach for generating tailored bioactive scaffolds for tissue repair.

  4. The ecology of carrion decomposition

    Science.gov (United States)

    Carrion, or the remains of dead animals, is something that most people would like to avoid. It is visually unpleasant, emits foul odors, and may be the source of numerous pathogens. Decomposition of carrion, however, provides a unique opportunity for scientists to investigate how nutrients cycle t...

  5. Microbial interactions during carrion decomposition

    Science.gov (United States)

    This addresses the microbial ecology of carrion decomposition in the age of metagenomics. It describes what is known about the microbial communities on carrion, including a brief synopsis about the communities on other organic matter sources. It provides a description of studies using state-of-the...

  6. Wavefront reconstruction by modal decomposition

    CSIR Research Space (South Africa)

    Schulze, C

    2012-08-01

    Full Text Available We propose a new method to determine the wavefront of a laser beam based on modal decomposition by computer-generated holograms. The hologram is encoded with a transmission function suitable for measuring the amplitudes and phases of the modes...

  7. Stepwise decomposition in controlpath synthesis

    NARCIS (Netherlands)

    Berg, ten A.J.W.M.

    1990-01-01

    A method is presented for the synthesis of the microarchitecture of controlpaths. This method is called stepwise decomposition. It focuses primarily on controlpaths of instruction set processors, however it is also applicable for more general Finite State Machine synthesis. Many of the current contr

  8. Stepwise decomposition in controlpath synthesis

    NARCIS (Netherlands)

    ten Berg, A.J.W.M.; ten Berg, A.J.W.M.

    1990-01-01

    A method is presented for the synthesis of the microarchitecture of controlpaths. This method is called stepwise decomposition. It focuses primarily on controlpaths of instruction set processors, however it is also applicable for more general Finite State Machine synthesis. Many of the current contr

  9. Modular Decomposition of Boolean Functions

    NARCIS (Netherlands)

    J.C. Bioch (Cor)

    2002-01-01

    textabstractModular decomposition is a thoroughly investigated topic in many areas such as switching theory, reliability theory, game theory and graph theory. Most appli- cations can be formulated in the framework of Boolean functions. In this paper we give a uni_ed treatment of modular decompositio

  10. Modular Decomposition of Boolean Functions

    NARCIS (Netherlands)

    J.C. Bioch (Cor)

    2002-01-01

    textabstractModular decomposition is a thoroughly investigated topic in many areas such as switching theory, reliability theory, game theory and graph theory. Most appli- cations can be formulated in the framework of Boolean functions. In this paper we give a uni_ed treatment of modular

  11. Thermal Decomposition of Dicyclopentadienylarylvanadium Compounds

    NARCIS (Netherlands)

    Boekel, C.P.; Jelsma, A.; Teuben, J.H.; Liefde Meijer, H.J. de

    1977-01-01

    The thermolysis of compounds of the type Cp2VR (R = aryl) in the solid state has been studied. A distinct increase in thermal stability is observed upon substitution of the ortho-position of the aryl group. Thermal decomposition occurs with formation of RH, Cp2V, a vanadocene homologue with the

  12. Multiple Descriptions Using Sparse Decompositions

    DEFF Research Database (Denmark)

    Jensen, Tobias Lindstrøm; Østergaard, Jan; Dahl, Joachim

    2010-01-01

    In this paper, we consider the design of multiple descriptions (MDs) using sparse decompositions. In a description erasure channel only a subset of the transmitted descriptions is received. The MD problem concerns the design of the descriptions such that they individually approximate the source...

  13. Gauss decomposition for quantum groups and duality

    CERN Document Server

    Damaskinsky, E V; Lyakhovsky, V D; Sokolov, M A

    1995-01-01

    The Gauss decomposition of quantum groups and supergroups are considered. The main attention is paid to the R-matrix formulation of the Gauss decomposition and its properties as well as its relation to the contraction procedure. Duality aspects of the Gauss decomposition are also touched. For clarity of exposition a few simple examples are considered in some details.

  14. Functionality Decomposition by Compositional Correctness Preserving Transformation

    NARCIS (Netherlands)

    Brinksma, Hendrik; Langerak, Romanus

    1995-01-01

    We present an algorithm for the decomposition of processes in a process algebraic framework. Decomposition, or the refinement of process substructure, is an important design principle in the top-down development of concurrent systems. In the approach that we follow the decomposition is based on a

  15. Morphing Metal and Elastomer Bicontinuous Foams for Reversible Stiffness, Shape Memory, and Self-Healing Soft Machines.

    Science.gov (United States)

    Van Meerbeek, Ilse M; Mac Murray, Benjamin C; Kim, Jae Woo; Robinson, Sanlin S; Zou, Perry X; Silberstein, Meredith N; Shepherd, Robert F

    2016-04-13

    A metal-elastomer-foam composite that varies in stiffness, that can change shape and store shape memory, that self-heals, and that welds into monolithic structures from smaller components is presented.

  16. Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

    DEFF Research Database (Denmark)

    Yu, Liyun; Skov, Anne Ladegaard

    2016-01-01

    One prominent method of modifying the properties of dielectric elastomers (DEs) is by adding suitable metal oxide fillers. However, almost all commercially available silicone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting...... metal oxide filled elastomer may contain too much filler. We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler. Liquid silicone rubber (LSR) has relatively low viscosity, which is favorable for loading inorganic fillers. In the present...... study, four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber (RTV) were investigated. The resulting elastomers were evaluated with respect to their dielectric permittivity, tear and tensile strengths, electrical breakdown, thermal stability...

  17. The preparation and physical properties of polysulfide-based elastomers through one-pot thiol-ene click reaction

    Directory of Open Access Journals (Sweden)

    Y. W. Quan

    2013-07-01

    Full Text Available In this paper, polysulfide-based elastomers were successfully prepared through a simple one-pot thiol-ene click reaction of the liquid polysulfide oligomer with bisphenol-A diacrylate resin. Real-time Fourier transform infrared spectroscopy (FTIR analysis showed that the molecular weight of the liquid polysulfide oligomer had no effect on mercaptan functional group conversion. The obtained elastomers continued to keep low temperature flexibility of polysulfide except Elastomer-LP3, which was due to higher content of bisphenol-A structure. All the samples had a tensile strength of over 0.7 MPa, which was comparable to that of polysulfide polymer cured by metal oxide. Moreover, the samples exhibited higher thermal stability than metal oxide cured polysulfide. This vulcanization methodology will provide a fast, efficient, and environmentally friendly approach (without metal oxides and plasticizers for preparing polysulfide elastomers.

  18. Nonlinear mode decomposition: A noise-robust, adaptive decomposition method

    Science.gov (United States)

    Iatsenko, Dmytro; McClintock, Peter V. E.; Stefanovska, Aneta

    2015-09-01

    The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool—nonlinear mode decomposition (NMD)—which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques—which, together with the adaptive choice of their parameters, make it extremely noise robust—and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.

  19. Nonlinear mode decomposition: a noise-robust, adaptive decomposition method.

    Science.gov (United States)

    Iatsenko, Dmytro; McClintock, Peter V E; Stefanovska, Aneta

    2015-09-01

    The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool-nonlinear mode decomposition (NMD)-which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques-which, together with the adaptive choice of their parameters, make it extremely noise robust-and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.

  20. Seismic performance evaluation of an MR elastomer-based smart base isolation system using real-time hybrid simulation

    Science.gov (United States)

    Eem, S. H.; Jung, H. J.; Koo, J. H.

    2013-05-01

    Recently, magneto-rheological (MR) elastomer-based base isolation systems have been actively studied as alternative smart base isolation systems because MR elastomers are capable of adjusting their modulus or stiffness depending on the magnitude of the applied magnetic field. By taking advantage of the MR elastomers’ stiffness-tuning ability, MR elastomer-based smart base isolation systems strive to alleviate limitations of existing smart base isolation systems as well as passive-type base isolators. Until now, research on MR elastomer-based base isolation systems primarily focused on characterization, design, and numerical evaluations of MR elastomer-based isolators, as well as experimental tests with simple structure models. However, their applicability to large civil structures has not been properly studied yet because it is quite challenging to numerically emulate the complex behavior of MR elastomer-based isolators and to conduct experiments with large-size structures. To address these difficulties, this study employs the real-time hybrid simulation technique, which combines physical testing and computational modeling. The primary goal of the current hybrid simulation study is to evaluate seismic performances of an MR elastomer-based smart base isolation system, particularly its adaptability to distinctly different seismic excitations. In the hybrid simulation, a single-story building structure (non-physical, computational model) is coupled with a physical testing setup for a smart base isolation system with associated components (such as laminated MR elastomers and electromagnets) installed on a shaking table. A series of hybrid simulations is carried out under two seismic excitations having different dominant frequencies. The results show that the proposed smart base isolation system outperforms the passive base isolation system in reducing the responses of the structure for the excitations considered in this study.

  1. Variance decomposition in stochastic simulators

    KAUST Repository

    Le Maître, O. P.

    2015-06-28

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  2. Variance decomposition in stochastic simulators.

    Science.gov (United States)

    Le Maître, O P; Knio, O M; Moraes, A

    2015-06-28

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  3. Variance decomposition in stochastic simulators

    Science.gov (United States)

    Le Maître, O. P.; Knio, O. M.; Moraes, A.

    2015-06-01

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  4. Preparation and electro-response of chitosan-g-poly (acrylic acid) hydrogel elastomers with interpenetrating network

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jianli [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi' an, 710062 (China); School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi' an, 710062 (China); Gao, Ling-xiang, E-mail: gaolx@snnu.edu.cn [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi' an, 710062 (China); School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi' an, 710062 (China); Han, Xuewu; Chen, Tao; Luo, Jue; Liu, Kaiqiang; Gao, Ziwei; Zhang, Weiqiang [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi' an, 710062 (China); School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi' an, 710062 (China)

    2016-02-01

    In this article, novel chitosan-g-poly (acrylic acid) hydrogel elastomers were successfully sythesised by grafting chitosan (CTS) onto poly acrylic acid (PAA) through radical polymerization in the presence/absence of direct current electric field. Their structure and electro-response were evaluated through scanning electron microscopy (SEM), infrared spectroscopy (IR), and dynamic mechanical analyser (DMA), respectively. Stress-strain test showed that the toughness of the chitosan-g-PAA elastomer is higher than the PAA gel. The result demonstrates the elastomers obtained in the presence/absence of electric field with similar chemical composition possess different microstructure. The positive electro responsive effect appeared on the elastomers, and both of storage modulus increment and increment sensitivity yielded maximum value at the AA concentration of 14.09 wt% under the applied electric field of 1.5 kV/mm. Thermo gravimetry and differential scanning calorimetry (TG-DSC) showed the elastomers cured under an applied electric field have stronger intramolecular bonding and higher cross-linking density. - Highlights: • The chitosan-g-poly (acrylic acid) hydrogel elastomers have been prepared. • They have ordered structure and positive electro-response under an electric field. • The maximum electro-response occurs near or at the AA wt% of 14.09 under 1.5 kV/mm.

  5. Electrochemical decomposition of chlorinated hydrocarbons

    OpenAIRE

    McGee, Gerard Anthony

    1993-01-01

    This work involves the characterisation of the electrochemical decomposition of chlorinated hydrocarbons. A variety of methods were employed involving the use of catalytic reagents to enhance the rate at which chlorinated organic compounds are reduced. The first reagent used was oxygen which was electrochemically reduced to superoxide in nonaqueous solvents. Superoxide is a reactive intermediate and decomposes chlorinated hydrocarbons. However it was found that since the rate of reaction betw...

  6. Thermal decomposition of natural dolomite

    Indian Academy of Sciences (India)

    S Gunasekaran; G Anbalagan

    2007-08-01

    Thermal decomposition behaviour of dolomite sample has been studied by thermogravimetric (TG) measurements. Differential thermal analysis (DTA) curve of dolomite shows two peaks at 777.8°C and 834°C. The two endothermic peaks observed in dolomite are essentially due to decarbonation of dolomite and calcite, respectively. The TG data of the decomposition steps have also been analysed using various differential, difference-differential and integral methods, viz. Freeman–Carroll, Horowitz–Metzger, Coats–Redfern methods. Values of activation entropy, Arrhenius factor, and order of reaction have been approximated and compared. Measured activation energies vary between 97 and 147 kJ mol-1. The large fluctuation in activation energy is attributed to the presence of impurities such as SiO2, Al2O3, Fe2O3, Cl- etc in the samples. FTIR and XRD analyses confirm the decomposition reaction. SEM observation of the heat-treated samples at 950°C shows cluster of grains, indicating the structural transformation.

  7. A Lagrangian Dynamic Mode Decomposition

    CERN Document Server

    Sesterhenn, Jörn

    2016-01-01

    Temporal or spatial structures are readily extracted from complex data by modal decompositions like POD or DMD. Subspaces of that decompositions serve as reduced order models and define spatial structures in time or temporal structures in space. Convecting phenomena pose a major problem to those decompositions. A structure travelling with a certain group velocity will be perceived as a plethora of modes in time or space respectively. This manifests itself for example in poorly decaying Singular Values when using a POD. The poor decay is very counter-intuitive, since we expect a single structure to be represented by a few modes. The intuition proves to be correct and we show that in a properly chosen reference frame along the characteristic defined by the group velocity, a POD or DMD reduces moving structures to a few modes, as expected. Beyond serving as a reduced model, the re- sulting entity can be used to define a constant or minimally changing structure in turbulent flows. This can be interpreted as an em...

  8. The thermal decomposition of nitrocellulose

    Energy Technology Data Exchange (ETDEWEB)

    Jones, D. E. G.; Turcotte, R.; Acheson, B.; Kwok, Q. S. M.; Vachon, M. [Natural Resources Canada, CANMET Canadian Explosives Research Laboratory, Ottawa, ON (Canada)

    2003-03-01

    In the past, the thermal decomposition of nitrocellulose, the main high-energy component of explosives and solid rocket propellant compositions, was studied using DSC, thermogravimetry and accelerating rate calorimetry. This paper discusses new results obtained by accelerating rate calorimetry (ARC), heat flux calorimetry (HFC), simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) coupled to FTIR and mass spectrometry (MS). Experiments with ARC showed that both the onset temperature and the activation energy for the thermal decomposition depend on sample mass. Evaluating the thermal decomposition of nitrocellulose using HFC at various pressures of argon between ambient and 27 MPa showed that the true onset temperature and the width of the corresponding exotherms are a strong function of the initial pressure. Also presented are the results of investigations conducted using TG-DTA-FTIR-MS in air and in helium. Corresponding to the sharp exotherm observed in helium, many gaseous product species were detected in a narrow band in FTIR and MS spectra. The main species observed by FTIR were carbon dioxide, formic acid, carbon monoxide and trace amounts of formaldehyde, nitrous oxide and water. In comparison, the products detected in air were found to occur in a much wider temperature range. Absorbances of carbon dioxide, nitrogen dioxide and water were observed to have been strongly enhanced in air, while organic species such as formic acid and formaldehyde were significantly depressed. 13 refs., 1 tab., 8 figs.

  9. Poly(vinylidene fluoride) polymer based nanocomposites with enhanced energy density by filling with polyacrylate elastomers and BaTiO3 nanoparticles

    Science.gov (United States)

    Yu, Ke; Bai, Yuanyuan; Zhou, Yongcun; Niu, Yujuan; Wang, Hong

    2014-02-01

    Polyacrylate elastomers were introduced into poly(vinylidene fluoride) polymer-based nanocomposites filled with BaTiO3 nanoparticles and the three-phase nanocomposite films were prepared. The energy discharged of the nanocomposite with 3 vol. % polyacrylate elastomers is 8.8 J/cm3, approximately 11% higher compared to that of the nanocomposite without adding polyacrylate elastomers. Large elastic deformation of the polyacrylate elastomers increases Maxwell-Wagner-Sillars interfacial polarization and space charge polarization of the nanocomposites with the electric field increasing, which results in increased maximum polarization and energy discharged of the nanocomposites.

  10. Green silicone elastomer obtained from a counterintuitively stable mixture of glycerol and PDMS

    DEFF Research Database (Denmark)

    Mazurek, P.; Hvilsted, S.; Skov, A. L.

    2016-01-01

    for obtaining elastomeric composites with uniformly distributed glycerol droplets. Various compositions, containing from 0 to 140 parts of glycerol per 100 parts of PDMS by weight, were prepared and investigated in terms of ATR-FTIR, broadband dielectric spectroscopy, mechanical properties as well as optical......A green and cheap silicone-based elastomer has been developed. Through the simple mixing-in of biodiesel-originating glycerol into commercially available polydimethylsiloxane (PDMS) pre-polymer, a glycerol-in-PDMS emulsion was produced. This counterintuitively stable mixture became a basis...... and scanning electron microscopy. The materials were proven additionally to exhibit a strong affinity to water, which was investigated by simple water absorption tests. Incorporating glycerol into PDMS decreased the Young's modulus of the composites yet the ultimate strain of the elastomer was not compromised...

  11. The Mechanical Properties of Polyurethane Elastomer Reinforced and Toughened By CaSO4-Whisker

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    CaSO4 whisker reinforcing and toughening mechanisms for polyurethane elastomer were studied. The effects of dispersity of CaSO4 whisker and interfacial bonding state on reinforcement and toughness were discussed.The microanalyses showed that CaSO4 whisker reinforcing mechanism for polyurethane elastomer mainly was load transferring and its toughening mechanism involved crack deflection and whisker pullout.The results indicated that composites with 5%-10% CaSO4 whisker exhibited the best mechanical properties. Good bonding interface was formed between whisker and matrix after the surface of CaSO4 whisker was treated by silane coupling agent.The fairly improved strength and toughness are attributed to the better interfacial bonding state.

  12. Enhanced microactuation with magnetic field curing of magnetorheological elastomers based on iron–natural rubber nanocomposites

    Indian Academy of Sciences (India)

    M P Vasudevan; P M Sudeep; I A Al-Omari; Philip Kurian; P M Ajayan; T N Narayanan; M R Anantharaman

    2015-06-01

    The incorporation of nanoparticles of iron in a natural rubber matrix leads to flexible magnetorheological (MR) materials. Rod-shaped MR elastomers based on natural rubber and nanosized iron have been moulded both with and without the application of an external magnetic field during curing. These MR elastomer rods and filler material were characterized by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Magnetic properties were investigated by using vibrating sample magnetometry. Microactuation studies were carried ou t by employing a laser Doppler vibrometer. It is seen that microactuation of field cured samples have been enhanced by two times when compared with that of zero field cured samples. The effect of alignment of magnetic particles during field-assisted curing was also studied by using a dynamic mechanical analyzer. A plausible model is put forwarded to explain the observed enhancement of actuation for field cured samples.

  13. Dynamics of supersonic microparticle impact on elastomers revealed by real-time multi-frame imaging.

    Science.gov (United States)

    Veysset, David; Hsieh, Alex J; Kooi, Steven; Maznev, Alexei A; Masser, Kevin A; Nelson, Keith A

    2016-05-09

    Understanding high-velocity microparticle impact is essential for many fields, from space exploration to medicine and biology. Investigations of microscale impact have hitherto been limited to post-mortem analysis of impacted specimens, which does not provide direct information on the impact dynamics. Here we report real-time multi-frame imaging studies of the impact of 7 μm diameter glass spheres traveling at 700-900 m/s on elastomer polymers. With a poly(urethane urea) (PUU) sample, we observe a hyperelastic impact phenomenon not seen on the macroscale: a microsphere undergoes a full conformal penetration into the specimen followed by a rebound which leaves the specimen unscathed. The results challenge the established interpretation of the behaviour of elastomers under high-velocity impact.

  14. Shape-memory effect of nanocomposites based on liquid-crystalline elastomers

    Science.gov (United States)

    Marotta, A.; Lama, G. C.; Gentile, G.; Cerruti, P.; Carfagna, C.; Ambrogi, V.

    2016-05-01

    In this work, nanocomposites based on liquid crystalline (LC) elastomers were prepared and characterized in their shape memory properties. For the synthesis of materials, p-bis(2,3-epoxypropoxy)-α-methylstilbene (DOMS) was used as mesogenic epoxy monomer, sebacic acid (SA) as curing agent and multi-walled carbon nanotubes (MWCNT) and graphene oxide (GO) as fillers. First, an effective compatibilization methodology was set up to improve the interfacial adhesion between the matrix and the carbonaceous nanofillers, thus obtaining homogeneous distribution and dispersion of the nanofillers within the polymer phase. Then, the obtained nanocomposite films were characterized in their morphological and thermal properties. In particular, the effect of the addition of the nanofillers on liquid crystalline behavior, as well as on shape-memory properties of the realized materials was investigated. It was found that both fillers were able to enhance the thermomechanical response of the LC elastomers, making them good candidates as shape memory materials.

  15. Influence of carbonyl iron particle coating with silica on the properties of magnetorheological elastomers

    Science.gov (United States)

    Małecki, P.; Królewicz, M.; Hiptmair, F.; Krzak, J.; Kaleta, J.; Major, Z.; Pigłowski, J.

    2016-10-01

    In this paper, the influence of encapsulating carbonyl iron particles with various silica coatings on the properties of magnetorheological elastomers (MREs) was investigated. A soft styrene-ethylene-butylene-styrene thermoplastic elastomer was used as the composite’s polymer matrix. Spherical carbonyl iron powder (CIP) acted as the ferromagnetic filler. In order to improve the metal-polymer interaction, carbonyl iron particles were coated with two types of single and six types of double silica layers. The first layer was created through a TMOS or TEOS hydrolysis whereas the second one was composed of organosilanes. The mechanical properties of MREs containing 38.5 vol% of CIP were analysed under dynamic loading conditions. To investigate the magnetorheological effect in these composites, a 430 mT magnetic field, generated by an array of permanent magnets, was applied during testing. The results revealed that the magnetomechanical response of the MREs differs substantially, depending on the kind of particle coating.

  16. Temperature effect on the performance of a dissipative dielectric elastomer generator with failure modes

    Science.gov (United States)

    Chen, S. E.; Deng, L.; He, Z. C.; Li, Eric; Li, G. Y.

    2016-05-01

    Research on dielectric elastomer generators (DEGs) which can be utilized to convert mechanical energy to electrical energy has gained wide attention lately. However, very few works account for the operating temperature, viscoelasticity and current leakage in the analysis of DEGs simultaneously. In this study, under several compound four-stroke conversion cycles, the electromechanical performance and energy conversion of a dissipative DEG made of a very-high-bond (VHB) elastomer are investigated at different operating temperatures. The performance parameters such as energy density and conversion efficiency are calculated under different temperatures. Moreover, the common failure modes of the generator are considered: material rupture, loss of tension, electrical breakdown and electromechanical instability. The numerical results have distinctly shown that the operating temperature plays an important role in the performance of DEGs, which could possibly make a larger conversion efficiency for the DEG.

  17. Large amplitude oscillatory measurements as mechanical characterization methods for soft elastomers

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard

    2012-01-01

    oscillating elongation (LAOE)1 and planar elongation2, 3 make the ideal set of experiments to evaluate the mechanical performance of DEAPs. We evaluate the mechanical performance of several soft elastomers applicable for DEAP purposes such as poly(propyleneoxide) (PPO) networks3, 4 and traditional unfilled......Mechanical characterization of soft elastomers is usually done either by traditional shear rheometry in the linear viscoelastic (LVE) regime (i.e. low strains) or by extensional rheology in the nonlinear regime. However, in many commercially available rheometers for nonlinear extensions......) but provides no information on the strain hardening or softening effects at larger strains, and the mechanical breakdown strength. Therefore it is obvious that LVE can not be used as the single mechanical characterization tool in large strain applications. We show how the data set of LVE, and large amplitude...

  18. Effects of RTC-silicone maxillofacial prosthetic elastomers on cell cultures.

    Science.gov (United States)

    Polyzois, G L; Hensten-Pettersen, A; Kullman, A

    1994-05-01

    The use of a wide variety of materials in the construction of maxillofacial prostheses makes biocompatibility testing a necessity. However, the dental literature contains few reports of biocompatibility testing of maxillofacial prosthetic materials. The cytotoxic profiles of five room-temperature cross-linking (RTC)-silicone elastomers were investigated by means of two in vitro cell culture techniques. Mouse fibroblast cells (L929) were used, and the results indicated that RTC-silicone elastomers adversely affected cells in culture and that storage of samples for 1 week in saline solution did not alter this effect. Clinical follow-up of patients wearing prostheses made of these silicone materials is warranted to evaluate host reactions in long-term contact with human mucous membrane and skin tissue.

  19. High-performance electromechanical transduction using laterally-constrained dielectric elastomers part I: Actuation processes

    Science.gov (United States)

    Koh, Soo Jin Adrian; Keplinger, Christoph; Kaltseis, Rainer; Foo, Choon-Chiang; Baumgartner, Richard; Bauer, Siegfried; Suo, Zhigang

    2017-08-01

    A dielectric elastomer transducer is a deformable capacitor, and is under development as a sensor, actuator, or generator. Among various geometric configurations, laterally-constrained transducer, also known as pure-shear transducer, is easy to implement and effective to couple mechanical force and electrical voltage. This analytical study reveals that lateral pre-stretch enhances actuation, far exceeding previously reported actuation strokes. Laterally-constrained transducers exhibit complex electromechanical behavior. As voltage increases, an actuator may undergo electromechanical instability, or form wrinkles, or suffer electrical breakdown. We survey the behavior of actuators under all possible states of pre-stretches, and identify five modes of actuation. Our analysis predicts that laterally-constrained actuators can achieve actuation stroke of 1000% for an acrylic elastomer, and 230% for natural rubber. This analysis opens the door to design actuators of simple geometry capable of a very large range of electromechanical actuation.

  20. Improvement of the service properties of elastomer compositions by introduction of carbon nanomaterials

    Science.gov (United States)

    Vishnevskii, K. V.; Shashok, Zh. S.; Prokopchuk, N. R.; Krauklis, A. V.; Zhdanok, S. A.

    2012-09-01

    The influence of a carbon nanomaterial obtained in a high-voltage discharge plasma on the endurance of elastomer compositions has been investigated for the first time. The results of these investigations agree with those obtained in determining the parameters of the vulcanization kinetics, conventional tensile strength, relative breaking elongation, and resistance to thermal aging and swelling in liquid hydrocarbon media of highly filled rubbers based on butadiene-nitrile caoutchoucs. To verify the assumed mechanism underlying the action of a carbon nanomaterial on elastomer compositions, the parameters of their vulcanizing network have been determined using the method of equilibrium swelling. It is shown that the introduction of a carbon nanomaterial into polar caoutchouc-based rubber allows one to substantially improve its service characteristics and endurance.

  1. EXPERIMENTAL INVESTIGATION OF THE ADHESIVE CONTACT WITH ELASTOMERS: EFFECT OF SURFACE ROUGHNESS

    Directory of Open Access Journals (Sweden)

    Lars Voll

    2015-04-01

    Full Text Available Adhesion between an elastomer and a steel indenter was studied experimentally and described with an analytical model. Cylindrical indenters having different roughness were brought into contact with an elastomer with various normal forces. After a “holding time”, the indenter was pulled with a constant velocity, which was the same in all experiments. We have studied the regime of relatively small initial normal loadings, large holding times and relatively large pulling velocities, so that the adhesive force did not depend on the holding time but did depend on the initially applied normal force and was approximately proportional to the pulling velocity. Under these conditions, we found that the adhesive force is inversely proportional to the roughness and proportional to the normal force. For the theoretical analysis, we used a previously published MDR-based model.

  2. A characterisation of the magnetically induced movement of NdFeB-particles in magnetorheological elastomers

    Science.gov (United States)

    Schümann, M.; Borin, D. Y.; Huang, S.; Auernhammer, G. K.; Müller, R.; Odenbach, S.

    2017-09-01

    Magnetorheological elastomers are a type of smart hybrid material where elastic properties of a soft elastomer matrix are combined with magnetic properties of magnetic micro particles. This combination leads to a complex interplay of magnetic and elastic phenomena, of which the magnetorheological effect is the best described. In this paper, magnetically hard NdFeB-particles were used to obtain remanent magnetic properties. X-ray microtomography has been utilised to analyse the particle movement induced by magnetic fields. A particle tracking was performed; thus, it was possible to characterise the movement of individual particles. Beyond that, a comprehensive analysis of the orientation of all particles was performed at different states of magnetisation and global particle arrangements. For the first time, this method was successfully applied to a magnetorheological material with a technically relevant amount of magnetic NdFeB-particles. A significant impact of the magnetic field on the rotation and translation of the particles was shown.

  3. The level of cross-linking and the structure of anisotropic magnetorheological elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Borin, Dmitry, E-mail: dmitry.borin@tu-dresden.de [Institute of Fluid Mechanics, Technische Universitaet Dresden, Dresden 01062 (Germany); Guenther, David [Institute of Fluid Mechanics, Technische Universitaet Dresden, Dresden 01062 (Germany); Hintze, Christian; Heinrich, Gert [Leibniz Institute of Polymer Research, Dresden 01069 (Germany); Odenbach, Stefan [Institute of Fluid Mechanics, Technische Universitaet Dresden, Dresden 01062 (Germany)

    2012-10-15

    The influence of the concentration of the magnetic powder on the level of cross-linking of magnetorheological elastomers (MREs) has been studied. Afterwards the structural characterisation of manufactured MREs has been performed by using non-destructive method, specifically the computed tomography. The correlation between internal structures of MREs and the developing of its cross-linking level during the curing was found. It was shown that changes in the concentration of the powder significantly affect morphologies of the sample.

  4. Nonlinear electroelastic deformations of dielectric elastomer composites: II - Non-Gaussian elastic dielectrics

    Science.gov (United States)

    Lefèvre, Victor; Lopez-Pamies, Oscar

    2017-02-01

    This paper presents an analytical framework to construct approximate homogenization solutions for the macroscopic elastic dielectric response - under finite deformations and finite electric fields - of dielectric elastomer composites with two-phase isotropic particulate microstructures. The central idea consists in employing the homogenization solution derived in Part I of this work for ideal elastic dielectric composites within the context of a nonlinear comparison medium method - this is derived as an extension of the comparison medium method of Lopez-Pamies et al. (2013) in nonlinear elastostatics to the coupled realm of nonlinear electroelastostatics - to generate in turn a corresponding solution for composite materials with non-ideal elastic dielectric constituents. Complementary to this analytical framework, a hybrid finite-element formulation to construct homogenization solutions numerically (in three dimensions) is also presented. The proposed analytical framework is utilized to work out a general approximate homogenization solution for non-Gaussian dielectric elastomers filled with nonlinear elastic dielectric particles that may exhibit polarization saturation. The solution applies to arbitrary (non-percolative) isotropic distributions of filler particles. By construction, it is exact in the limit of small deformations and moderate electric fields. For finite deformations and finite electric fields, its accuracy is demonstrated by means of direct comparisons with finite-element solutions. Aimed at gaining physical insight into the extreme enhancement in electrostriction properties displayed by emerging dielectric elastomer composites, various cases wherein the filler particles are of poly- and mono-disperse sizes and exhibit different types of elastic dielectric behavior are discussed in detail. Contrary to an initial conjecture in the literature, it is found (inter alia) that the isotropic addition of a small volume fraction of stiff (semi

  5. Development of Photocrosslinkable Urethane-Doped Polyester Elastomers for Soft Tissue Engineering

    OpenAIRE

    Zhang, Yi; Tran, Richard T.; Gyawali, Dipendra; Yang, Jian

    2011-01-01

    Finding an ideal biomaterial with the proper mechanical properties and biocompatibility has been of intense focus in the field of soft tissue engineering. This paper reports on the synthesis and characterization of a novel crosslinked urethane-doped polyester elastomer (CUPOMC), which was synthesized by reacting a previously developed photocrosslinkable poly (octamethylene maleate citrate) (POMC) prepolymers (pre-POMC) with 1,6-hexamethylene diisocyanate (HDI) followed by thermo- or photo-cro...

  6. Preparation and Mechanical Performance of Rare Earth-Containing Composite Elastomer

    Institute of Scientific and Technical Information of China (English)

    邱关明; 周兰香; 张明; 中北里志; 井上真一; 冈本弘

    2001-01-01

    Rare earth-containing PSBR sheet was prepared by reaction of rare earth alkoxide with quaternary ammonium salt of pyridine modified SBR (PSBR) latex, and then it was blended with natural rubber (NR) to produce rare earth-containing composite elastomer. It is found that mechanical performance can be improved remarkably. Analyzed by infrared spectrometry (IR), differential scanning calorimetry (DSC) and cross-linking densitometry, the relationship between structure and performance was discussed.

  7. High dielectric permittivity elastomers from well-dispersed expanded graphite in low concentrations

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Hassouneh, Suzan Sager; Kostrzewska, Malgorzata;

    2013-01-01

    The development of elastomer materials with a high dielectric permittivity has attracted increased interest over the last years due to their use in for example dielectric electroactive polymers. For this particular use, both the electrically insulating properties - as well as the mechanical...... by the addition of traditional fillers in the necessary amounts would either lose their stability or their softness. Furthermore the influence of several mixing procedures on the electrical and mechanical properties is investigated. © 2013 SPIE....

  8. Switchable adhesion for wafer-handling based on dielectric elastomer stack transducers

    Science.gov (United States)

    Grotepaß, T.; Butz, J.; Förster-Zügel, F.; Schlaak, H. F.

    2016-04-01

    Vacuum grippers are often used for the handling of wafers and small devices. In order to evacuate the gripper, a gas flow is created that can harm the micro structures on the wafer. A promising alternative to vacuum grippers could be adhesive grippers with switchable adhesion. There have been some publications of gecko-inspired adhesive devices. Most of these former works consist of a structured surface which adheres to the object manipulated and an actuator for switching the adhesion. Until now different actuator principles have been investigated, like smart memory alloys and pneumatics. In this work for the first time dielectric elastomer stack transducers (DEST) are combined with a structured surface. DESTs are a promising new transducer technology with many applications in different industry sectors like medical devices, human-machine-interaction and soft robotics. Stacked dielectric elastomer transducers show thickness contraction originating from the electromechanical pressure of two compliant electrodes compressing an elastomeric dielectric when a voltage is applied. Since DESTs and the adhesive surfaces previously described are made of elastomers, it is self-evident to combine both systems in one device. The DESTs are fabricated by a spin coating process. If the flat surface of the spinning carrier is substituted for example by a perforated one, the structured elastomer surface and the DEST can be fabricated in one process. By electrical actuation the DEST contracts and laterally expands which causes the gecko-like cilia to adhere on the object to manipulate. This work describes the assembly and the experimental results of such a device using switchable adhesion. It is intended to be used for the handling of glass wafers.

  9. Ionic Liquids Applied to Improve the Dispersion of Coagent Particles in an Elastomer

    OpenAIRE

    Magdalena Maciejewska; Marian Zaborski

    2013-01-01

    The aim of this work was to study the activity of several ionic liquids (alkylimidazolium salts) that are used to improve the dispersion of coagent particles in peroxide-cross-linked hydrogenated acrylonitrile butadiene elastomer (HNBR). Hydrotalcite grafted with monoallyl maleate was applied as a coagent for the HNBR vulcanization. In this paper, we discuss the effect of the ionic liquids (alkylimidazolium salts) with respect to their anion (bromide, chloride, tetrafluoroborate, and hexafluo...

  10. Effect of single-particle magnetostriction on the shear modulus of compliant magnetoactive elastomers

    OpenAIRE

    Kalita, Viktor; Snarskii, Andrew; Shamonin, Mikhail; Zorinets, Denys

    2017-01-01

    The influence of an external magnetic field on the static shear strain and the effective shear modulus of a magnetoactive elastomer (MAE) is studied theoretically in the framework of a recently introduced approach to the single-particle magnetostriction mechanism [V. M. Kalita et al, Phys. Rev. E 93, 062503 (2016)]. The planar problem of magnetostriction in an MAE with soft magnetic inclusions in the form of a thin disk (platelet) having the magnetic anisotropy in the plane of this disk is so...

  11. Fluorogel Elastomers with Tunable Transparency, Elasticity, ShapeMemory, and Antifouling Properties**

    Energy Technology Data Exchange (ETDEWEB)

    Yao, X; Dunn, SS; Kim, P; Duffy, M; Alvarenga, J; Aizenberg, J

    2014-03-18

    Omniphobic fluorogel elastomers were prepared by photocuring perfluorinated acrylates and a perfluoropolyether crosslinker. By tuning either the chemical composition or the temperature that control the crystallinity of the resulting polymer chains, a broad range of optical and mechanical properties of the fluorogel can be achieved. After infusing with fluorinated lubricants, the fluorogels showed excellent resistance to wetting by various liquids and anti-biofouling behavior, while maintaining cytocompatiblity.

  12. Fluorogel Elastomers with Tunable Transparency, Elasticity, Shape-Memory, and Antifouling Properties**

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Xi; Dunn, Stuart; Kim, Philseok; Duffy, Meredith; Alvarenga, Jack; Aizenberg, Joanna

    2014-04-22

    Omniphobic fluorogel elastomers were prepared by photocuring perfluorinated acrylates and a perfluoropolyether crosslinker. By tuning either the chemical composition or the temperature that control the crystallinity of the resulting polymer chains, a broad range of optical and mechanical properties of the fluorogel can be achieved. After infusing with fluorinated lubricants, the fluorogels showed excellent resistance to wetting by various liquids and anti-biofouling behavior, while maintaining cytocompatiblity.

  13. Filler reinforcement in cross-linked elastomer nanocomposites: insights from fully atomistic molecular dynamics simulation.

    Science.gov (United States)

    Pavlov, Alexander S; Khalatur, Pavel G

    2016-06-28

    Using a fully atomistic model, we perform large-scale molecular dynamics simulations of sulfur-cured polybutadiene (PB) and nanosilica-filled PB composites. A well-integrated network without sol fraction is built dynamically by cross-linking the coarse-grained precursor chains in the presence of embedded silica nanoparticles. Initial configurations for subsequent atomistic simulations are obtained by reverse mapping of the well-equilibrated coarse-grained systems. Based on the concept of "maximally inflated knot" introduced by Grosberg et al., we show that the networks simulated in this study behave as mechanically isotropic systems. Analysis of the network topology in terms of graph theory reveals that mechanically inactive tree-like structures are the dominant structural components of the weakly cross-linked elastomer, while cycles are mainly responsible for the transmission of mechanical forces through the network. We demonstrate that quantities such as the system density, thermal expansion coefficient, glass transition temperature and initial Young's modulus can be predicted in qualitative and sometimes even in quantitative agreement with experiments. The nano-filled system demonstrates a notable increase in the glass transition temperature and an approximately two-fold increase in the nearly equilibrium value of elastic modulus relative to the unfilled elastomer even at relatively small amounts of filler particles. We also examine the structural rearrangement of the nanocomposite subjected to tensile deformation. Under high strain-rate loading, the formation of structural defects (microcavities) within the polymer bulk is observed. The nucleation and growth of cavities in the post-yielding strain hardening regime mainly take place at the elastomer/nanoparticle interfaces. As a result, the cavities are concentrated just near the embedded nanoparticles. Therefore, while the silica nanofiller increases the elastic modulus of the elastomer, it also creates a more

  14. Modified Silicone Elastomer Vaginal Gels for Sustained Release of Antiretroviral HIV Microbicides

    OpenAIRE

    Forbes, Claire J.; Mccoy, Clare F.; Murphy, Diarmaid J.; David Woolfson, A.; Moore, John P.; Evans, Abbey; Robin J Shattock; Karl Malcolm, R.

    2014-01-01

    We previously reported non-aqueous silicone elastomer gels (SEGs) for sustained vaginal administration of the CCR5-targeted entry inhibitor maraviroc. Here, we describe chemically modified SEGs (h-SEGs) in which the hydrophobic cyclomethicone component was partially replaced with relatively hydrophilic silanol-terminated polydimethylsiloxanes (st-PDMS). Maraviroc and emtricitabine (a nucleoside reverse transcriptase inhibitor), both currently under evaluation as topical microbicides to counte...

  15. Elastomer-Carbon Nanostructure Composites as Prospective Materials for Flexible Robotic Tactile Sensors

    OpenAIRE

    Knite, M; Podiņš, G; Zīke, S; Zavickis, J

    2008-01-01

    Our recent achievements in the design, processing and studies of physical properties of elastomer – nano-structured carbon composites as prospective compressive strain sensor materials for robotic tactile elements are presented. Composites made of polyisoprene matrix and high-structured carbon black or multi-wall carbon nano-tube filler have been designed and manufactured to develop completely flexible conductive polymer nano-composites for tactile sensing elements. Electrical resistance of t...

  16. Stretchable living materials and devices with hydrogel-elastomer hybrids hosting programmed cells.

    Science.gov (United States)

    Liu, Xinyue; Tang, Tzu-Chieh; Tham, Eléonore; Yuk, Hyunwoo; Lin, Shaoting; Lu, Timothy K; Zhao, Xuanhe

    2017-02-28

    Living systems, such as bacteria, yeasts, and mammalian cells, can be genetically programmed with synthetic circuits that execute sensing, computing, memory, and response functions. Integrating these functional living components into materials and devices will provide powerful tools for scientific research and enable new technological applications. However, it has been a grand challenge to maintain the viability, functionality, and safety of living components in freestanding materials and devices, which frequently undergo deformations during applications. Here, we report the design of a set of living materials and devices based on stretchable, robust, and biocompatible hydrogel-elastomer hybrids that host various types of genetically engineered bacterial cells. The hydrogel provides sustainable supplies of water and nutrients, and the elastomer is air-permeable, maintaining long-term viability and functionality of the encapsulated cells. Communication between different bacterial strains and with the environment is achieved via diffusion of molecules in the hydrogel. The high stretchability and robustness of the hydrogel-elastomer hybrids prevent leakage of cells from the living materials and devices, even under large deformations. We show functions and applications of stretchable living sensors that are responsive to multiple chemicals in a variety of form factors, including skin patches and gloves-based sensors. We further develop a quantitative model that couples transportation of signaling molecules and cellular response to aid the design of future living materials and devices.

  17. More power to the people: getting the most from a dielectric elastomer generator

    CERN Document Server

    Illenberger, Patrin; Kojima, Hiroki; Madawala, Udaya; Anderson, Iain

    2016-01-01

    A dielectric elastomer generator (DEG) can be used for converting mechanical energy from natural motion sources such as walking, waves, trees etc, into electrical energy. A DEG is comprised of a soft and flexible Dielectric Elastomer capacitor (DE), a Priming Circuit (PC), which transfers high potential charge onto/off the DE electrodes, and a power extraction circuit which harvests the generated power. To generate power, the PC must charge and discharge the DE in synchronization with the DE's capacitance change. A simple circuit to do this exists: the self-priming circuit (SPC). The SPC consists of diodes and capacitors which passively switch between charge delivery and charge receiving states in synchronization with the DE's capacitance change. Until now there has been no understanding of how to design a SPC in order to maximize harvested energy from the dielectric elastomer (DE). A new mathematical model for a SPC is presented, leading to design and optimization. An accuracy of 0.1% between model, simulati...

  18. Sample Size Effect of Magnetomechanical Response for Magnetic Elastomers by Using Permanent Magnets

    Directory of Open Access Journals (Sweden)

    Tsubasa Oguro

    2017-01-01

    Full Text Available The size effect of magnetomechanical response of chemically cross-linked disk shaped magnetic elastomers placed on a permanent magnet has been investigated by unidirectional compression tests. A cylindrical permanent magnet with a size of 35 mm in diameter and 15 mm in height was used to create the magnetic field. The magnetic field strength was approximately 420 mT at the center of the upper surface of the magnet. The diameter of the magnetoelastic polymer disks was varied from 14 mm to 35 mm, whereas the height was kept constant (5 mm in the undeformed state. We have studied the influence of the disk diameter on the stress-strain behavior of the magnetoelastic in the presence and in the lack of magnetic field. It was found that the smallest magnetic elastomer with 14 mm diameter did not exhibit measurable magnetomechanical response due to magnetic field. On the opposite, the magnetic elastomers with diameters larger than 30 mm contracted in the direction parallel to the mechanical stress and largely elongated in the perpendicular direction. An explanation is put forward to interpret this size-dependent behavior by taking into account the nonuniform field distribution of magnetic field produced by the permanent magnet.

  19. Development of Photocrosslinkable Urethane-Doped Polyester Elastomers for Soft Tissue Engineering.

    Science.gov (United States)

    Zhang, Yi; Tran, Richard T; Gyawali, Dipendra; Yang, Jian

    2011-01-01

    Finding an ideal biomaterial with the proper mechanical properties and biocompatibility has been of intense focus in the field of soft tissue engineering. This paper reports on the synthesis and characterization of a novel crosslinked urethane-doped polyester elastomer (CUPOMC), which was synthesized by reacting a previously developed photocrosslinkable poly (octamethylene maleate citrate) (POMC) prepolymers (pre-POMC) with 1,6-hexamethylene diisocyanate (HDI) followed by thermo- or photo-crosslinking polymerization. The mechanical properties of the CUPOMCs can be tuned by controlling the molar ratios of pre-POMC monomers, and the ratio between the prepolymer and HDI. CUPOMCs can be crosslinked into a 3D network through polycondensation or free radical polymerization reactions. The tensile strength and elongation at break of CUPOMC synthesized under the known conditions range from 0.73±0.12MPa to 10.91±0.64MPa and from 72.91±9.09% to 300.41±21.99% respectively. Preliminary biocompatibility tests demonstrated that CUPOMCs support cell adhesion and proliferation. Unlike the pre-polymers of other crosslinked elastomers, CUPOMC pre-polymers possess great processability demonstrated by scaffold fabrication via a thermally induced phase separation method. The dual crosslinking methods for CUPOMC pre-polymers should enhance the versatile processability of the CUPOMC used in various conditions. Development of CUPOMC should expand the choices of available biodegradable elastomers for various biomedical applications such as soft tissue engineering.

  20. Methods to improve harvested energy and conversion efficiency of viscoelastic dielectric elastomer generators

    Science.gov (United States)

    Zhou, Jianyou; Jiang, Liying; Khayat, Roger E.

    2017-05-01

    As a new transduction technology, dielectric elastomer generators (DEGs) are capable of converting mechanical energy from diverse sources into electrical energy. However, their energy harvesting performance is strongly affected by the material viscoelasticity. Based on the finite-deformation viscoelasticity theory and the nonlinear coupled field theory for dielectric elastomers, this work presents a theoretical framework to model the performance of DEGs. Motivated by the recent experiments of DEGs with a triangular harvesting scheme, we propose a method to optimize the harvesting cycle, which could significantly improve the conversion efficiency of viscoelastic DEGs. From our simulation results, choosing a higher voltage power source appears to be an effective way to improve the performance of DEGs. In addition, optimizing the period of the discharging process of DEG can markedly increase its efficiency. Also, we have uncovered that the triangular harvesting scheme for DEGs, which is expected to harvest energy close to the maximum achievable energy, could be actually realized by choosing dielectric elastomers with a higher fraction of time-independent polymer networks. The theoretical framework and simulation results presented in this work are expected to benefit the optimal design of DEGs for different applications.

  1. Enhancement in Magnetorheological Effect of Magnetorheological Elastomers by Surface Modification of Iron Particles

    Institute of Scientific and Technical Information of China (English)

    Wan-quan Jiang; Jing-jing Yao; Xing-long Gong; Lin Chen

    2008-01-01

    In order to obtain magnetorheological(MR) elastomers with high magnetorheological effect,a family of anisotropic rubber-based MR elastomers was developed using a new form of chemical modification.Three different kinds of surfactants,i.e.anionic,nonionic and compound surfactants,were employed separately to modify iron particles.The MR effect was evaluated by measuring the dynamic shear modulus of MR elastomer with a magneto-combined dynamic mechanical analyzer.Results show that the relative MR effect can be up to 188% when the iron particles are modified with 15% Span 80.Besides the surface activity of Span 80,however,such high modifying effect is partly due to the plasticizing effect of Span 80.Compared with the single surfactant,the superior surface activity of compound surfactant makes the relative MR effect reach 77% at a low content of 0.4%.Scanning electron microscope observation shows that the modification of compound surfactant results in perfect compatibility between particles and rubber matrix and special self-assembled structure of particles.Such special structure has been proved beneficial to the improvement of the relative MR effect.

  2. Dielectric elastomer for stretchable sensors: influence of the design and material properties

    Science.gov (United States)

    Jean-Mistral, C.; Iglesias, S.; Pruvost, S.; Duchet-Rumeau, J.; Chesné, S.

    2016-04-01

    Dielectric elastomers exhibit extended capabilities as flexible sensors for the detection of load distributions, pressure or huge deformations. Tracking the human movements of the fingers or the arms could be useful for the reconstruction of sporting gesture, or to control a human-like robot. Proposing new measurements methods are addressed in a number of publications leading to improving the sensitivity and accuracy of the sensing method. Generally, the associated modelling remains simple (RC or RC transmission line). The material parameters are considered constant or having a negligible effect which can lead to serious reduction of accuracy. Comparisons between measurements and modelling require care and skill, and could be tricky. Thus, we propose here a comprehensive modelling, taking into account the influence of the material properties on the performances of the dielectric elastomer sensor (DES). Various parameters influencing the characteristics of the sensors have been identified: dielectric constant, hyper-elasticity. The variations of these parameters as a function of the strain impact the linearity and sensitivity of the sensor of few percent. The sensitivity of the DES is also evaluated changing geometrical parameters (initial thickness) and its design (rectangular and dog-bone shapes). We discuss the impact of the shape regarding stress. Finally, DES including a silicone elastomer sandwiched between two high conductive stretchable electrodes, were manufactured and investigated. Classic and reliable LCR measurements are detailed. Experimental results validate our numerical model of large strain sensor (>50%).

  3. Stretchable living materials and devices with hydrogel–elastomer hybrids hosting programmed cells

    Science.gov (United States)

    Liu, Xinyue; Tang, Tzu-Chieh; Tham, Eléonore; Yuk, Hyunwoo; Lin, Shaoting; Lu, Timothy K.; Zhao, Xuanhe

    2017-01-01

    Living systems, such as bacteria, yeasts, and mammalian cells, can be genetically programmed with synthetic circuits that execute sensing, computing, memory, and response functions. Integrating these functional living components into materials and devices will provide powerful tools for scientific research and enable new technological applications. However, it has been a grand challenge to maintain the viability, functionality, and safety of living components in freestanding materials and devices, which frequently undergo deformations during applications. Here, we report the design of a set of living materials and devices based on stretchable, robust, and biocompatible hydrogel–elastomer hybrids that host various types of genetically engineered bacterial cells. The hydrogel provides sustainable supplies of water and nutrients, and the elastomer is air-permeable, maintaining long-term viability and functionality of the encapsulated cells. Communication between different bacterial strains and with the environment is achieved via diffusion of molecules in the hydrogel. The high stretchability and robustness of the hydrogel–elastomer hybrids prevent leakage of cells from the living materials and devices, even under large deformations. We show functions and applications of stretchable living sensors that are responsive to multiple chemicals in a variety of form factors, including skin patches and gloves-based sensors. We further develop a quantitative model that couples transportation of signaling molecules and cellular response to aid the design of future living materials and devices. PMID:28202725

  4. Compatibility Assessment of Fuel System Elastomers with Bio-oil and Diesel Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kass, Michael D.; Janke, Christopher J.; Connatser, Raynella M.; Lewis, Samuel A.; Keiser, James R.; Gaston, Katherine

    2016-08-18

    Bio-oil derived via fast pyrolysis is being developed as a renewable fuel option for petroleum distillates. The compatibility of neat bio-oil with six elastomer types was evaluated against the elastomer performance in neat diesel fuel, which served as the baseline. The elastomers included two fluorocarbons, six acrylonitrile butadiene rubbers (NBRs), and one type each of fluorosilicone, silicone, styrene butadiene rubber (SBR), polyurethane, and neoprene. Specimens of each material were exposed to the liquid and gaseous phases of the test fuels for 4 weeks at 60 degrees C, and properties in the wetted and dried states were measured. Exposure to bio-oil produced significant volume expansion in the fluorocarbons, NBRs, and fluorosilicone; however, excessive swelling (over 80%) was only observed for the two fluorocarbons and two NBR grades. The polyurethane specimens were completely degraded by the bio-oil. In contrast, both silicone and SBR exhibited lower swelling levels in bio-oil compared to neat diesel fuel. The implication is that, while polyurethane and fluorocarbon may not be acceptable seal materials for bio-oils, silicone may offer a lower cost alternative.

  5. Polysiloxane-based luminescent elastomers prepared by thiol-ene "click" chemistry.

    Science.gov (United States)

    Zuo, Yujing; Lu, Haifeng; Xue, Lei; Wang, Xianming; Wu, Lianfeng; Feng, Shengyu

    2014-09-26

    Side-chain vinyl poly(dimethylsiloxane) has been modified with mercaptopropionic acid, methyl 3-mercaptopropionate, and mercaptosuccinic acid. Coordinative bonding of Eu(III) to the functionalized polysiloxanes was then carried out and crosslinked silicone elastomers were prepared by thiol-ene curing reactions of these composites. All these europium complexes could be cast to form transparent, uniform, thin elastomers with good flexibility and thermal stability. The networks were characterized by FTIR, NMR, UV/Vis, and luminescence spectroscopy as well as by scanning electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The europium elastomer luminophores exhibited intense red light at 617 nm under UV excitation at room temperature due to the (5)D0 →(7)F2 transition in Eu(III) ions. The newly synthesized luminescent materials offer many advantages, including the desired mechanical flexibility. They cannot be dissolved or fused, and so they have potential for use in optical and electronic applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Melt compounding with graphene to develop functional, high-performance elastomers

    Science.gov (United States)

    Araby, Sherif; Zaman, Izzuddin; Meng, Qingshi; Kawashima, Nobuyuki; Michelmore, Andrew; Kuan, Hsu-Chiang; Majewski, Peter; Ma, Jun; Zhang, Liqun

    2013-04-01

    Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer—ethylene-propylene-diene monomer rubber (EPDM)—using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment.

  7. Graphene-Elastomer Composites with Segregated Nanostructured Network for Liquid and Strain Sensing Application.

    Science.gov (United States)

    Lin, Yong; Dong, Xuchu; Liu, Shuqi; Chen, Song; Wei, Yong; Liu, Lan

    2016-09-14

    One of the critical issues for the fabrication of desirable sensing materials has focused on the construction of an effective continuous network with a low percolation threshold. Herein, graphene-based elastomer composites with a segregated nanostructured graphene network were prepared by a novel and effective ice-templating strategy. The segregated graphene network bestowed on the natural rubber (NR) composites an ultralow electrical percolation threshold (0.4 vol %), 8-fold lower than that of the NR/graphene composites with homogeneous dispersion morphology (3.6 vol %). The resulting composites containing 0.63 vol % graphene exhibited high liquid sensing responsivity (6700), low response time (114 s), and good reproducibility. The unique segregated structure also provides this graphene-based elastomer (containing 0.42 vol % graphene) with exceptionally high stretchability, sensitivity (gauge factor ≈ 139), and good reproducibility (∼400 cycles) of up to 60% strain under cyclic tests. The fascinating performances highlight the potential applications of graphene-elastomer composites with an effective segregated network as multifunctional sensing materials.

  8. Pseudo-Casimir stresses and elasticity of a confined elastomer film

    Science.gov (United States)

    Lu, Bing-Sui; Naji, Ali; Podgornik, Rudolf

    Investigations of the elastic behavior of bulk elastomers have traditionally proceeded on the basis of classical rubber elasticity, which regards chains as thermally fluctuating but disregards the thermal fluctuations of the cross-links. Here, we consider an incompressible and flat elastomer film of an axisymmetric shape confined between two large hard co-planar substrates, with the axis of the film perpendicular to the substrates. We address the impact that thermal fluctuations of the cross-links have on the free energy of elastic deformation of the system, subject to the requirement that the fluctuating elastomer cannot detach from the substrates. We examine the behavior of the deformation free energy for one case where a rigid pinning boundary condition is applied to a class of elastic fluctuations at the confining surfaces, and another case where the same elastic fluctuations are subjected to soft "gluing" potentials. We find that there can be significant departures (both quantitative and qualitative) from the prediction of classical rubber elasticity theory when elastic fluctuations are included. Finally, we compare the character of the attractive part of the elastic fluctuation-induced, or pseudo-Casimir, stress with the standard thermal Casimir stress in confined but non-elastomeric systems, finding the same power law decay behavior when a rigid pinning boundary condition is applied, for the case of the gluing potential, we find that the leading order correction to the attractive part of the fluctuation stress decays inversely with the inter-substrate separation.

  9. Modeling of a corrugated dielectric elastomer actuator for artificial muscle applications

    Science.gov (United States)

    Kadooka, Kevin; Taya, Minoru; Naito, Keishi; Saito, Makoto

    2015-04-01

    Dielectric elastomer actuators have many advantages, including light weight, simplicity, high energy density, and silent operation. These features make them suitable to replace conventional actuators and transducers, especially in artificial muscle applications where large contractile strains are necessary for lifelike motions. This paper will introduce the concept of a corrugated dielectric elastomer actuator (DEA), which consists of dielectric elastomer (DE) laminated to a thin elastic layer to induce bending motion at each of the corrugations, resulting in large axial deformation. The location of the DE and elastic layers can be configured to provide tensile or compressive axial strain. Such corrugated DE actuators are also highly scalable: linking multiple actuators in series results in greater deformation, whereas multiple actuators in parallel results in larger force output. Analytical closed-form solutions based on linear elasticity were derived for the displacement and force output of curved unimorph and corrugated DEA, both consisting of an arbitrary number of lamina. A total strain energy analysis and Castigiliano's theorem were used to predict the nonlinear force-displacement behavior of the corrugated actuator. Curved unimorph and corrugated DEA were fabricated using VHB F9469PC as the DE material. Displacement of the actuators observed during testing agreed well with the modeling results. Large contractile strain (25.5%) was achieved by the corrugated DEA. Future work includes investigating higher performance DE materials such as plasticized PVDF terpolymers, processed by thin film deposition methods.

  10. Condition Monitoring of a Thermally Aged HTPB/IPDI Elastomer by NMR CP Recovery Times

    Energy Technology Data Exchange (ETDEWEB)

    ASSINK,ROGER A.; LANG,DAVID; CELINA,MATHIAS C.

    2000-07-24

    A hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer is commonly used as propellant binder material. The thermal degradation of the binder is believed to be an important parameter governing the performance of the propellant. The aging of these binders can be monitored by mechanical property measurements such as modulus or tensile elongation. These techniques, however, are not easily adapted to binder agents that are dispersed throughout a propellant. In this paper the authors investigated solid state NMR relaxation times as a means to predict the mechanical properties of the binder as a function of aging time. {sup 1}H spin-lattice and spin-spin relaxation times were found to be insensitive to the degree of thermal degradation of the elastomer. Apparently these relaxation times depend on localized motions that are only weakly correlated with mechanical properties. A strong correlation was found between the {sup 13}C cross-polarization (CP) NMR time constant, T{sub cp}, and the tensile elongation at break of the elastomer as a function of aging time. A ramped-amplitude CP experiment was shown to be less sensitive to imperfections in setting critical instrumental parameters for this mobile material.

  11. Evaluation of sliding friction and contact mechanics of elastomers based on dynamic-mechanical analysis

    Science.gov (United States)

    Le Gal, André; Yang, Xin; Klüppel, Manfred

    2005-07-01

    The paper presents a combined experimental and theoretical approach to the understanding of hysteresis and adhesion contributions to rubber friction on dry and lubricated rough surfaces. Based on a proper analysis of the temperature- and frequency-dependent behaviors of nonlinear viscoelastic materials such as filler reinforced elastomer materials, master curves for the viscoelastic moduli are constructed. It is shown that the classical williams-Landel-Ferry equation cannot be applied in its simple form, but needs the introduction of an energy term describing the temperature dependency of glassy polymer bridges, which transmit the forces within flocculated filler clusters. The activation energy for carbon black and silica-filled elastomers is compared based on two different evaluation methods. The obtained dynamic data are shown to be related to a different friction behavior of elastomers regarding the two filler systems. Theoretical predictions of the stationary frictional behavior of the systems are in fair agreement with the experimental friction data at low sliding velocities. It is found that the formulated adhesion plays a dominant role on rough dry surfaces within this range of velocities.

  12. NARX neural network modeling and robustness analysis of magnetorheological elastomer isolator

    Science.gov (United States)

    Fu, Jie; Liao, Guanyao; Yu, Miao; Li, Peidong; Lai, Junjie

    2016-12-01

    Due to the controllability of the stiffness and damping under the applied magnetic field, magnetorheological elastomer isolator has been proved effective in the field of vibration control. For the realization of vibration control application, an accurate MRE isolator model is a non-trivial task. However, the existing parametric modeling methods are required to identify too many parameters, which are difficult to implement. Moreover, the corresponding inverse dynamic model of the isolator cannot even be obtained by the identified model inversion. Therefore, this paper proposes a nonparametric neural network approach to approximate the dynamic behaviors of magnetorheological elastomer isolator with the characteristics of nonlinearity and hysteresis. Firstly, the dynamic characteristics of the isolator in shear-compression mixed mode are experimentally tested under different loading conditions. Secondly, based on the experimental data, a NARX neural network with three-layer structure is developed to approximate the functional relationship between inputs (displacement, velocity and current) and output (force) of magnetorheological elastomer isolator. Thirdly, the effectiveness of the network model is validated by comparing the predicted force and experimental force. Finally, considering the common occurrence of inputs with noise disturbance in real application, the robustness of the network is also verified for displacement and current inputs with noise disturbance, respectively. The results of the network generalization for experimental data show that the proposed NARX network is more robust and optimal than BP network.

  13. Application of Sulphur-Free Lignins as a Filler for Elastomers: Effect of Hexamethylenetetramine Treatment

    Directory of Open Access Journals (Sweden)

    Paola Frigerio

    2014-01-01

    Full Text Available Lignins from a steam explosion process in crude and purified forms and modified sulphur-free commercial lignin (Protobind 3000® were characterised to establish their chemical compositions. Then, the lignins were tested again after treatment with hexamethylenetetramine (HMT. The resulting products were used to make rubber composites, and their mechanical properties were compared to rubber composites made with carbon black to test the possibility of using HMT-treated lignins as a partial replacement for carbon black in the production of rubber composites. In the crude lignin, a significant amount of impurities were detected, such as ash and residual polysaccharides, and these substances interfered in filler-elastomer interactions. The purified lignin maintained a high content of strongly polarised hydroxyl groups that interfered with the interaction of the filler and elastomer, resulting in low performance. Improvements in the mechanical properties were observed using Protobind 3000® lignin or purified lignin with HMT added during mixing with the rubber. Finally, the mixing of HMT-treated lignin with elastomers resulted in composites with higher reinforcement abilities compared to previously described rubber composites. However, in all samples, a poor and unsatisfactory dispersion of lignin in the polymeric matrix was observed. This is likely due to the incompatibility of lignin with the hydrophobic rubber, resulting in lower performances compared to the carbon black.

  14. Dielectric Elastomer Generator with Improved Energy Density and Conversion Efficiency Based on Polyurethane Composites.

    Science.gov (United States)

    Yin, Guoling; Yang, Yu; Song, Feilong; Renard, Christophe; Dang, Zhi-Min; Shi, Chang-Yong; Wang, Dongrui

    2017-02-15

    Dielectric elastomer generators (DEGs), which follow the physics of variable capacitors and harvest electric energy from mechanical work, have attracted intensive attention over the past decade. The lack of ideal dielectric elastomers, after nearly two decades of research, has become the bottleneck for DEGs' practical applications. Here, we fabricated a series of polyurethane-based ternary composites and estimated their potential as DEGs to harvest electric energy for the first time. Thermoplastic polyurethane (PU) with high relative permittivity (∼8) was chosen as the elastic matrix. Barium titanate (BT) nanoparticles and dibutyl phthalate (DBP) plasticizers, which were selected to improve the permittivity and mechanical properties, respectively, were blended into the PU matrix. As compared to pristine PU, the resultant ternary composite films fabricated through a solution casting approach showed enhanced permittivity, remarkably reduced elastic modulus, and relatively good electrical breakdown strength, dielectric loss, and strain at break. Most importantly, the harvested energy density of PU was significantly enhanced when blended with BT and DBP. A composite film containing 25 phr of BT and 60 phr of DBP with the harvested energy density of 1.71 mJ/cm(3) was achieved, which is about 4 times greater than that of pure PU and 8 times greater than that of VHB adhesives. Remarkably improved conversion efficiency of mechano-electric energy was also obtained via cofilling BT and DBP into PU. The results shown in this work strongly suggest compositing is a very promising way to provide better dielectric elastomer candidates for forthcoming practical DEGs.

  15. Modelling volatility by variance decomposition

    DEFF Research Database (Denmark)

    Amado, Cristina; Teräsvirta, Timo

    on the multiplicative decomposition of the variance is developed. It is heavily dependent on Lagrange multiplier type misspecification tests. Finite-sample properties of the strategy and tests are examined by simulation. An empirical application to daily stock returns and another one to daily exchange rate returns...... illustrate the functioning and properties of our modelling strategy in practice. The results show that the long memory type behaviour of the sample autocorrelation functions of the absolute returns can also be explained by deterministic changes in the unconditional variance....

  16. Azimuthal decomposition of optical modes

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2012-07-01

    Full Text Available of Optical Modes Angela Dudley1, Igor Litvin1, Filippus S. Roux1 and Andrew Forbes1,2,3 1 CSIR National Laser Centre, Pretoria, South Africa 2 School of Physics, University of KwaZulu-Natal, Durban, South Africa 3 Laser Research Institute, University... of Stellenbosch, Stellenbosch, South Africa Presented at the 2012 South African Institute of Physics Conference University of Pretoria Pretoria, South Africa 12 July 2012 To decompose the azimuthal modes we need two steps: generation and decomposition...

  17. Non-isothermal decomposition kinetics of magnesite

    OpenAIRE

    Maitra, S; Mukherjee, S.; Saha, N; Pramanik, J

    2007-01-01

    Kinetics of thermal decomposition of Indian magnesite was studied by thermo-gravimetric analysis under non-isothermal condition. Coats and Redfern Integral approximation method was used to determine the kinetic parameters. Using the kinetic parameters different kinetic functions were analyzed with the experimental data to ascertain the decomposition mechanism of magnesium carbonate and it was observed that the decomposition reaction followed a contracting sphere kinetic mechanism.

  18. The preparation of an elastomer/silicate layer nanocompound with an exfoliated structure and a strong ionic interfacial interaction by utilizing an elastomer latex containing pyridine groups.

    Science.gov (United States)

    He, Shao-jian; Wang, Yi-qing; Feng, Yi-ping; Liu, Qing-sheng; Zhang, Li-qun

    2010-03-19

    A great variety of polymer/layered silicate (PLS) nanocomposites have been reported, however, there are few exfoliated PLS nanocomposites and their inorganic-organic interfaces are still a great problem, especially for the elastomers. In this research, a kind of exfoliated elastomer/silicate layer nanocompound was prepared and proved by XRD and TEM, in which 10 phr Na(+)-montmorillonite was dispersed in butadiene-styrene-vinyl pyridine rubber by latex compounding method with acidic flocculants. Moreover, a dynamic mechanical thermal analyzer (DMTA) suggested a strong interfacial interaction (interaction parameter B(H) = 4.91) between the silicate layers and macromolecules in addition to the weak inorganic-organic interfacial interaction, and solid state (15)N NMR indicated the formation of a strong ionic interface through the acidifying pyridine. Subsequently, a remarkable improvement of the dispersing morphology, mechanical performance and gas barrier property appeared, compared to that using calcium ion flocculants. This supports the formation of an exfoliated structure and an improved interfacial interaction.

  19. Highly Scalable Matching Pursuit Signal Decomposition Algorithm

    Data.gov (United States)

    National Aeronautics and Space Administration — In this research, we propose a variant of the classical Matching Pursuit Decomposition (MPD) algorithm with significantly improved scalability and computational...

  20. On Schubert decompositions of quiver Grassmannians

    Science.gov (United States)

    Lorscheid, Oliver

    2014-02-01

    In this paper, we introduce Schubert decompositions for quiver Grassmannians and investigate certain classes of quiver Grassmannians with a Schubert decomposition into affine spaces. The main theorem puts the cells of a Schubert decomposition into relation to the cells of a certain simpler quiver Grassmannian. This allows us to extend known examples of Schubert decompositions into affine spaces to a larger class of quiver Grassmannians. This includes exceptional representations of the Kronecker quiver as well as representations of forests with block matrices of the form (0100). Finally, we draw conclusions on the Euler characteristics and the cohomology of quiver Grassmannians.

  1. Direct observation of nanowire growth and decomposition

    DEFF Research Database (Denmark)

    Rackauskas, Simas; Shandakov, Sergey D; Jiang, Hua

    2017-01-01

    knowledge, so far this has been only postulated, but never observed at the atomic level. By means of in situ environmental transmission electron microscopy we monitored and examined the atomic layer transformation at the conditions of the crystal growth and its decomposition using CuO nanowires selected...... as a model object. The atomic layer growth/decomposition was studied by varying an O2 partial pressure. Three distinct regimes of the atomic layer evolution were experimentally observed: growth, transition and decomposition. The transition regime, at which atomic layer growth/decomposition switch takes place...

  2. Decomposition methods in turbulence research

    Directory of Open Access Journals (Sweden)

    Uruba Václav

    2012-04-01

    Full Text Available Nowadays we have the dynamical velocity vector field of turbulent flow at our disposal coming thanks advances of either mathematical simulation (DNS or of experiment (time-resolved PIV. Unfortunately there is no standard method for analysis of such data describing complicated extended dynamical systems, which is characterized by excessive number of degrees of freedom. An overview of candidate methods convenient to spatiotemporal analysis for such systems is to be presented. Special attention will be paid to energetic methods including Proper Orthogonal Decomposition (POD in regular and snapshot variants as well as the Bi-Orthogonal Decomposition (BOD for joint space-time analysis. Then, stability analysis using Principal Oscillation Patterns (POPs will be introduced. Finally, the Independent Component Analysis (ICA method will be proposed for detection of coherent structures in turbulent flow-field defined by time-dependent velocity vector field. Principle and some practical aspects of the methods are to be shown. Special attention is to be paid to physical interpretation of outputs of the methods listed above.

  3. Thermal decomposition of mercuric sulfide

    Energy Technology Data Exchange (ETDEWEB)

    Leckey, J.H.; Nulf, L.E.

    1994-10-28

    The rate of thermal decomposition of mercuric sulfide (HgS) has been measured at temperatures from 265 to 345 C. These data have been analyzed using a first-order chemical reaction model for the time dependence of the reaction and the Arrhenius equation for the temperature dependence of the rate constant. Using this information, the activation energy for the reaction was found to be 55 kcal/mol. Significant reaction vessel surface effects obscured the functional form of the time dependence of the initial portion of the reaction. The data and the resulting time-temperature reaction-rate model were used to predict the decomposition rate of HgS as a function of time and temperature in thermal treatment systems. Data from large-scale thermal treatment studies already completed were interpreted in terms of the results of this study. While the data from the large-scale thermal treatment studies were consistent with the data from this report, mass transport effects may have contributed to the residual amount of mercury which remained in the soil after most of the large-scale runs.

  4. Decomposition of Diethylstilboestrol in Soil

    DEFF Research Database (Denmark)

    Gregers-Hansen, Birte

    1964-01-01

    The rate of decomposition of DES-monoethyl-1-C14 in soil was followed by measurement of C14O2 released. From 1.6 to 16% of the added C14 was recovered as C14O2 during 3 months. After six months as much as 12 to 28 per cent was released as C14O2.Determination of C14 in the soil samples after the e...... not inhibit the CO2 production from the soil.Experiments with γ-sterilized soil indicated that enzymes present in the soil are able to attack DES.......The rate of decomposition of DES-monoethyl-1-C14 in soil was followed by measurement of C14O2 released. From 1.6 to 16% of the added C14 was recovered as C14O2 during 3 months. After six months as much as 12 to 28 per cent was released as C14O2.Determination of C14 in the soil samples after...

  5. In vitro mutagenicity testing. II. Silastic 386 Foam Elastomer, Irganox 1010, mixture of Sylgard 184 with Encapsulating Resin and Curing Agent, and dimethylbenzanthracene. [Ames test

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.Y.; Smith, D.M.

    1980-02-01

    Four materials, Silastic 386 Foam Elastomer, Irganox 1010, Sylgard 184 with Encapsulating Resin and Curing Agent, and 7,12-dimethylbenzanthracene (DMBA), were tested for in vitro mutagenicity by the Ames Salmonella assay method. Silastic 386 Foam Elastomer, Irganox 1010, and Sylgard 184 Encapsulating Resin with Curing Agent were not mutagenic; the mutagenicity of DMBA was corroborated.

  6. Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

    Directory of Open Access Journals (Sweden)

    Liyun Yu

    2015-10-01

    Full Text Available One prominent method of modifying the properties of dielectric elastomers (DEs is by adding suitable metal oxide fillers. However, almost all commercially available silicone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting metal oxide filled elastomer may contain too much filler. We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler. Liquid silicone rubber (LSR has relatively low viscosity, which is favorable for loading inorganic fillers. In the present study, four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber (RTV were investigated. The resulting elastomers were evaluated with respect to their dielectric permittivity, tear and tensile strengths, electrical breakdown, thermal stability and dynamic viscosity. Filled silicone elastomers with high loadings of nano-sized titanium dioxide (TiO2 particles were also studied. The best overall performing formulation had 35 wt.% TiO2 nanoparticles in the POWERSIL® XLR LSR, where the excellent ensemble of relative dielectric permittivity of 4.9 at 0.1 Hz, breakdown strength of 160 V µm−1, tear strength of 5.3 MPa, elongation at break of 190%, a Young’s modulus of 0.85 MPa and a 10% strain response (simple tension in a 50 V μm−1 electric field was obtained.

  7. Electrical breakdown of an acrylic dielectric elastomer: effects of hemispherical probing electrode’s size and force

    Directory of Open Access Journals (Sweden)

    Bin Chen

    2015-10-01

    Full Text Available Dielectric elastomers are widely investigated as soft electromechanically active polymers (EAPs for actuators, stretch/force sensors, and mechanical energy harvesters to generate electricity. Although the performance of such devices is limited by the dielectric strength of the constitutive material, the electrical breakdown of soft elastomers for electromechanical transduction is still scarcely studied. Here, we describe a custom-made setup to measure electrical breakdown of soft EAPs, and we present data for a widely studied acrylic elastomer (VHB 4905 from 3M. The elastomer was electrically stimulated via a planar and a hemispherical metal electrode. The breakdown was characterized under different conditions to investigate the effects of the radius of curvature and applied force of the hemispherical electrode. With a given radius of curvature, the breakdown field increased by about 50% for a nearly 10-fold increase of the applied mechanical stress, while with a given mechanical stress the breakdown field increased by about 20% for an approximately twofold increase of the radius of curvature. These results indicate that the breakdown field is highly dependent on the boundary conditions, suggesting the need for reporting breakdown data always in close association with the measurement conditions. These findings might help future investigations in elucidating the ultimate breakdown mechanism/s of soft elastomers.

  8. Tree decompositions and social graphs

    CERN Document Server

    Adcock, Aaron B; Mahoney, Michael W

    2014-01-01

    Recent work has established that large informatics graphs such as social and information networks have non-trivial tree-like structure when viewed at moderate size scales. Here, we present results from the first detailed empirical evaluation of the use of tree decomposition (TD) heuristics for structure identification and extraction in social graphs. Although TDs have historically been used in structural graph theory and scientific computing, we show that---even with existing TD heuristics developed for those very different areas---TD methods can identify interesting structure in a wide range of realistic informatics graphs. Among other things, we show that TD methods can identify structures that correlate strongly with the core-periphery structure of realistic networks, even when using simple greedy heuristics; we show that the peripheral bags of these TDs correlate well with low-conductance communities (when they exist) found using local spectral computations; and we show that several types of large-scale "...

  9. Nonnegative Decomposition of Multivariate Information

    CERN Document Server

    Williams, Paul L

    2010-01-01

    Of the various attempts to generalize information theory to multiple variables, the most widely utilized, interaction information, suffers from the problem that it is sometimes negative. Here we reconsider from first principles the general structure of the information that a set of sources provides about a given variable. We begin with a new definition of redundancy as the minimum information that any source provides about each possible outcome of the variable, averaged over all possible outcomes. We then show how this measure of redundancy induces a lattice over sets of sources that clarifies the general structure of multivariate information. Finally, we use this redundancy lattice to propose a definition of partial information atoms that exhaustively decompose the Shannon information in a multivariate system in terms of the redundancy between synergies of subsets of the sources. Unlike interaction information, the atoms of our partial information decomposition are never negative and always support a clear i...

  10. Regular Decompositions for H(div) Spaces

    Energy Technology Data Exchange (ETDEWEB)

    Kolev, Tzanio [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing; Vassilevski, Panayot [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing

    2012-01-01

    We study regular decompositions for H(div) spaces. In particular, we show that such regular decompositions are closely related to a previously studied “inf-sup” condition for parameter-dependent Stokes problems, for which we provide an alternative, more direct, proof.

  11. Complete azimuthal decomposition of optical fields

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2013-02-01

    Full Text Available By using digital holograms, we present a simple technique for performing a complete azimuthal decomposition of an arbitrary laser mode. The match-filter, used to perform the azimuthal decomposition, is bounded by an annular ring, allowing us...

  12. Some Aspects of Thermochemical Decomposition of Peat

    Directory of Open Access Journals (Sweden)

    Y. A. Losiuk

    2008-01-01

    Full Text Available The paper considers peculiar features of thermochemical decomposition of peat as a result of quick pyrolysis. Evaluation of energy and economic expediency of the preliminary peat decomposition process for obtaining liquid and gaseous products has been made in the paper. The paper reveals prospects pertaining to application of the given technology while generating electric power and heat.

  13. Some Aspects of Thermochemical Decomposition of Peat

    OpenAIRE

    Y. A. Losiuk; S. V. Gibric; S. V. Korchinenko

    2008-01-01

    The paper considers peculiar features of thermochemical decomposition of peat as a result of quick pyrolysis. Evaluation of energy and economic expediency of the preliminary peat decomposition process for obtaining liquid and gaseous products has been made in the paper. The paper reveals prospects pertaining to application of the given technology while generating electric power and heat.

  14. Climate history shapes contemporary leaf litter decomposition

    Science.gov (United States)

    Michael S. Strickland; Ashley D. Keiser; Mark A. Bradford

    2015-01-01

    Litter decomposition is mediated by multiple variables, of which climate is expected to be a dominant factor at global scales. However, like other organisms, traits of decomposers and their communities are shaped not just by the contemporary climate but also their climate history. Whether or not this affects decomposition rates is underexplored. Here we source...

  15. Decompositions of Revised Monotone Signed Fuzzy Measures

    Institute of Scientific and Technical Information of China (English)

    张强; 刘克

    2003-01-01

    The concept of fuzzy measure was introduced by Sugeno in 1974. A notion of signed fuzzy measure is introduced in this paper, and its elementary properties are briefly discussed. An analogue of Hahn decomposition theorem is established under the null-null-additive condition. A version of the Jordan decomposition theorem is proved under the null-additive condition.

  16. Helmholtz Hodge decomposition of scalar optical fields.

    Science.gov (United States)

    Bahl, Monika; Senthilkumaran, P

    2012-11-01

    It is shown that the vector field decomposition method, namely, the Helmholtz Hodge decomposition, can also be applied to analyze scalar optical fields that are ubiquitously present in interference and diffraction optics. A phase gradient field that depicts the propagation and Poynting vector directions can hence be separated into solenoidal and irrotational components.

  17. A global HMX decomposition model

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, M.L.

    1996-12-01

    HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) decomposes by competing reaction pathways to form various condensed and gas-phase intermediate and final products. Gas formation is related to the development of nonuniform porosity and high specific surface areas prior to ignition in cookoff events. Such thermal damage enhances shock sensitivity and favors self-supported accelerated burning. The extent of HMX decomposition in highly confined cookoff experiments remains a major unsolved experimental and modeling problem. The present work is directed at determination of global HMX kinetics useful for predicting the elapsed time to thermal runaway (ignition) and the extent of decomposition at ignition. Kinetic rate constants for a six step engineering based global mechanism were obtained using gas formation rates measured by Behrens at Sandia National Laboratories with his Simultaneous Modulated Beam Mass Spectrometer (STMBMS) experimental apparatus. The six step global mechanism includes competition between light gas (H[sub 2]Awe, HCN, CO, H[sub 2]CO, NO, N[sub 2]Awe) and heavy gas (C[sub 2]H[sub 6]N[sub 2]Awe and C[sub 4]H[sub 10]N0[sub 2]) formation with zero order sublimation of HMX and the mononitroso analog of HMX (mn-HMX), C[sub 4]H[sub 8]N[sub 8]Awe[sub 7]. The global mechanism was applied to the highly confined, One Dimensional Time to eXplosion (ODTX) experiment and hot cell experiments by suppressing the sublimation of HMX and mn-HMX. An additional gas-phase reaction was also included to account for the gas-phase reaction of N[sub 2]Awe with H[sub 2]CO. Predictions compare adequately to the STMBMS data, ODTX data, and hot cell data. Deficiencies in the model and future directions are discussed.

  18. Directed Graphs, Decompositions, and Spatial Linkages

    CERN Document Server

    Shai, Offer; Whiteley, Walter

    2010-01-01

    The decomposition of a system of constraints into small basic components is an important tool of design and analysis. Specifically, the decomposition of a linkage into minimal components is a central tool of analysis and synthesis of linkages. In this paper we prove that every pinned 3-isostatic (minimally rigid) graph (grounded linkage) has a unique decomposition into minimal strongly connected components (in the sense of directed graphs) which we call 3-Assur graphs. This analysis extends the Assur decompositions of plane linkages previously studied in the mathematical and the mechanical engineering literature. These 3-Assur graphs are the central building blocks for all kinematic linkages in 3-space. They share a number of key combinatorial and geometric properties with the 2-Assur graphs, including an associated lower block-triangular decomposition of the pinned rigidity matrix which provides a format for extending the motion induced by inserting one driver in a bottom Assur linkage to the joints of the e...

  19. Multilinear operators for higher-order decompositions.

    Energy Technology Data Exchange (ETDEWEB)

    Kolda, Tamara Gibson

    2006-04-01

    We propose two new multilinear operators for expressing the matrix compositions that are needed in the Tucker and PARAFAC (CANDECOMP) decompositions. The first operator, which we call the Tucker operator, is shorthand for performing an n-mode matrix multiplication for every mode of a given tensor and can be employed to concisely express the Tucker decomposition. The second operator, which we call the Kruskal operator, is shorthand for the sum of the outer-products of the columns of N matrices and allows a divorce from a matricized representation and a very concise expression of the PARAFAC decomposition. We explore the properties of the Tucker and Kruskal operators independently of the related decompositions. Additionally, we provide a review of the matrix and tensor operations that are frequently used in the context of tensor decompositions.

  20. Interpenetrated polymer networks based on commercial silicone elastomers and ionic networks with high dielectric permittivity and self-healing properties

    DEFF Research Database (Denmark)

    Ogliani, Elisa; Yu, Liyun; Skov, Anne Ladegaard

    ,1 Hz), and the commercial elastomers RT625 and LR3043/30 provide thebest viscoelastic properties to the systems, since they maintain low viscous losses upon addition of ionic network. The values ofthe breakdown strength in all cases remain higher than that of the reference pure PDMS network (ranging......The dielectric elastomers (DEs) technology can be used in many advanced applications, such as actuators, generators and sensors, showing advantageous and promising properties[1]. However, the main disadvantage is the high driving voltage required for the actuation process which limits...... the applicability. One method used to avoid this limitation is to increase the dielectric permittivity of the material in order to improve the actuation response at a given field. Recently, interpenetrating polymer networks (IPNs) based on covalently cross-linked commercial silicone elastomers and ionic networks...

  1. Research progress of thermoplastic nylon elastomers%热塑性尼龙弹性体研究进展

    Institute of Scientific and Technical Information of China (English)

    许雯靓; 宋文川

    2011-01-01

    This paper described the synthesis mechanism of thermoplastic nylon elastomers and the basic properties of raw materials for the synthesis.The basic properties of thermoplastic nylon elastomers were in detail presented,including high tensile strength,thermal stability,and many other excellent performances.Meanwhile,the production status and the current situation of domestic and foreign research of thermoplastic nylon elastomers were summarized.%介绍了热塑性尼龙弹性体(TPAE)的合成机理和合成原料的基本性质.对热塑性尼龙弹性体的性能做出了详细阐述.综述了热塑性尼龙弹性体的生产现状和国内外研究状况.

  2. 热塑性弹性体最新发展现状%Present Situation and Development of Thermoplastic Elastomers

    Institute of Scientific and Technical Information of China (English)

    雷小平; 樊宏斌; 周青; 陈春儿; 宋海胜

    2011-01-01

    In this paper, we introduce thermoplastic elastomers of the major researched categories about styrene type, olefin, polyurethane and polyester thermoplastic elastomers and list parts latest study of domestic and foreign about these several categories , and summarize the previous practice and experience to point out that the production and R & D trends of the future thermoplastic elastomers .%介绍了苯乙烯类、烯烃类、聚氨酯类、聚酯类等主要的热塑性弹性体研究大类,列举了国内外关于这几大类的部分最新研究发现,并总结前人的实践与经验,指出未来热塑性弹性体的生产及研发趋势。

  3. Modification of Silicone Elastomer Surfaces with Zwitterionic Polymers: Short-Term Fouling Resistance and Triggered Biofouling Release.

    Science.gov (United States)

    Shivapooja, Phanindhar; Yu, Qian; Orihuela, Beatriz; Mays, Robin; Rittschof, Daniel; Genzer, Jan; López, Gabriel P

    2015-11-25

    We present a method for dual-mode-management of biofouling by modifying surface of silicone elastomers with zwitterionic polymeric grafts. Poly(sulfobetaine methacrylate) was grafted from poly(vinylmethylsiloxane) elastomer substrates using thiol-ene click chemistry and surface-initiated, controlled radical polymerization. These surfaces exhibited both fouling resistance and triggered fouling-release functionality. The zwitterionic polymers exhibited fouling resistance over short-term (∼hours) exposure to bacteria and barnacle cyprids. The biofilms that eventually accumulated over prolonged-exposure (∼days) were easily detached by applying mechanical strain to the elastomer substrate. Such dual-functional surfaces may be useful in developing environmentally and biologically friendly coatings for biofouling management on marine, industrial, and biomedical equipment because they can obviate the use of toxic compounds.

  4. Synthesis of antibacterial amphiphilic elastomer based on polystyrene-block-polyisoprene-block-polystyrene via thiol-ene addition.

    Science.gov (United States)

    Keleş, Elif; Hazer, Baki; Cömert, Füsun B

    2013-04-01

    A new type of amphiphilic antibacterial elastomer has been described. Thermoplastic elastomer, polystyrene-block-polyisoprene-block-polystyrene (PS-b-PI-b-PS) triblock copolymer was functionalized in toluene solution by free radical mercaptan addition in order to obtain an amphiphilic antibacterial elastomer. Thiol terminated PEG was grafted through the double bonds of PS-b-PI-b-PS via free radical thiol-ene coupling reaction. The antibacterial properties of the amphiphilic graft copolymers were observed. The original and the modified polymers were used to create microfibers in an electro-spinning process. Topology of the electrospun micro/nanofibers were studied by using scanning electron microscopy (SEM). The chemical structures of the amphiphilic comb type graft copolymers were elucidated by the combination of elemental analysis, (1)H NMR, (13)C NMR, GPC and FTIR.

  5. Novel scalable silicone elastomer and poly(2-hydroxyethyl methacrylate) (PHEMA) composite materials for tissue engineering and drug delivery applications

    DEFF Research Database (Denmark)

    Mohanty, Soumyaranjan; Hemmingsen, Mette; Wojcik, Magdalena

    2013-01-01

    In recent years hydrogels have received increasing attention as potential materials for applications in regenerative medicine. They can be used for scaffold materials providing structural integrity to tissue constructs, for controlled delivery of drugs and proteins to cell and tissues......, and for support materials in tissue growth. However, the real challenge is to obtain sufficiently good mechanical properties of the hydrogel. The present study shows the combination of two normally non-compatible materials, silicone elastomer and poly(2-hydroxyethyl methacrylate) (PHEMA), into a novel composite...... material with increased hydrophilicity in regard to virgin silicone elastomer, making it suitable as a scaffold for tissue engineering and with the concomitant possibility for delivering drug from the scaffold to the tissue. Interpenetrating polymer networks (IPNs) of silicone elastomer and PHEMA...

  6. Factors controlling bark decomposition and its role in wood decomposition in five tropical tree species

    Science.gov (United States)

    Dossa, Gbadamassi G. O.; Paudel, Ekananda; Cao, Kunfang; Schaefer, Douglas; Harrison, Rhett D.

    2016-01-01

    Organic matter decomposition represents a vital ecosystem process by which nutrients are made available for plant uptake and is a major flux in the global carbon cycle. Previous studies have investigated decomposition of different plant parts, but few considered bark decomposition or its role in decomposition of wood. However, bark can comprise a large fraction of tree biomass. We used a common litter-bed approach to investigate factors affecting bark decomposition and its role in wood decomposition for five tree species in a secondary seasonal tropical rain forest in SW China. For bark, we implemented a litter bag experiment over 12 mo, using different mesh sizes to investigate effects of litter meso- and macro-fauna. For wood, we compared the decomposition of branches with and without bark over 24 mo. Bark in coarse mesh bags decomposed 1.11–1.76 times faster than bark in fine mesh bags. For wood decomposition, responses to bark removal were species dependent. Three species with slow wood decomposition rates showed significant negative effects of bark-removal, but there was no significant effect in the other two species. Future research should also separately examine bark and wood decomposition, and consider bark-removal experiments to better understand roles of bark in wood decomposition. PMID:27698461

  7. Low temperature behaviour of elastomers in seals; Tieftemperaturverhalten von Elastomeren im Dichtungseinsatz

    Energy Technology Data Exchange (ETDEWEB)

    Jaunich, Matthias

    2012-04-25

    Elastomeric seals are of high importance as machine parts and construction elements, but in spite of this the low temperature limit for the use of a seal was not fully understood. Hence, the required safety relevant evaluation of the lowest acceptable operating seal temperature is difficult. Therefore the presented work was aimed to understand the temperature dependent material behaviour of representative elastomers and to conclude from this knowledge the low temperature limit down to which such seals could safely fulfil the desired requirements. Starting with the published statement that a seal can safely work below its glass transition temperature the influence of the glass-rubber-transition was investigated. At first the glass-rubber-transition temperatures of the selected elastomers were determined applying several techniques to allow a comparison with the behaviour of the seals during component tests. Furthermore a new method to characterise the low temperature behaviour of elastomers was developed that emulates the key features of the standardised compression set test used for seal materials. In comparison to the standardized test this new method allows a much faster measurement that can be automatically performed. Using a model based data analysis an extrapolation of the results to different temperatures can be performed and therefore the necessary measuring expenditure can be additionally reduced. For the temperature dependent characterisation of the failure process of real seals a measurement setup was designed and the materials behaviour was investigated. By use of the results of all applied characterisation techniques the observed dependence of the failure temperature on the degree of compression could be explained for the investigated seals under static load. Additionally information about the behaviour of such seals under dynamic load could be gained from the time dependent material behaviour by use of the time temperature superposition relationship

  8. Modelling liquid crystal elastomers and potential application as a reversibly switchable adhesive

    Science.gov (United States)

    Adams, James

    2013-03-01

    Liquid crystal elastomers (LCEs) are rubbery materials that composed of liquid crystalline polymers (LCPs) crosslinked into a network. The rod-like mesogens incorporated into the LCPs are have random orientations in the high temperature isotropic phase, but can adopt the canonical liquid crystalline phases as the temperature is lowered. Smectic liquid crystal elastomers have highly anisotropic mechanical behaviour. This arises in side chain smectic-A systems because the smectic layers behave as if they are embedded in the rubber matrix. The macroscopic mechanical behaviour of these solids is sensitive to the buckling of the layers, so is a multiscale problem. A coarse grained free energy that includes the fine-scale buckling of the layers has been developed, which enables continuum modelling of these systems. In the first part of this talk I present a model of the mechanical behaviour of side chain smectic elastomers. The properties of nematic LCEs, such as their high loss tangent, and mechanical strain hardening, might enable them to be used as reversibly switchable pressure sensitive adhesive (PSA). PSAs are typically made from viscoelastic polymers. The quality of their adhesion can be measured by the tack energy, which is the work required to separate two bodies. To obtain a high tack energy a PSA should be capable of a large strain. It should strain soften at low strain to produce crack blunting, and then strain harden at high strain to stiffen the fibrils formed late in the debonding process. I will present a model of the tack energy of weakly crosslinked nematic polymers. To describe the constitutive properties of this system the nematic dumbbell model of Maffettone et al. was used. This constutitive model was then combined with the block model of Yamaguchi et al. describing PSAs. It was found that the parallel orientation of the nematic has a higher tack energy than both the isotropic and the perpendicular director orientation. This work is supported by

  9. Effect of temperature on the electromechanical actuation of viscoelastic dielectric elastomers

    Science.gov (United States)

    Liu, Lei; Sun, Wenjie; Sheng, Junjie; Chang, Longfei; Li, Dichen; Chen, Hualing

    2015-10-01

    The electromechanical deformation of viscoelastic dielectric elastomers (DEs) is primarily governed by three material parameters: permittivity, Young's modulus, and relaxation time. All three parameters are functions of temperature, so a complete description of the electromechanical behaviour of a DE must take thermal effects into account. In this paper, we have established a physical model for viscoelastic DEs that takes temperature effects into consideration. The actuation of a DE was measured under different temperatures to verify the model. A peak actuation stretch was obtained at around 363 K both experimentally and theoretically. Moreover, we also demonstrate the contribution of strain-stiffening induced by greater pre-stretching to the improvement of thermostability.

  10. Light-induced nonhomogeneity and gradient bending in photochromic liquid crystal elastomers

    Institute of Scientific and Technical Information of China (English)

    JIN; Lihua; JIANG; Xin; HUO; Yongzhong

    2006-01-01

    The recently reported opto-mechanical effect of some photochromic liquid crystal elastomers (LCEs) is studied. It is found that in such LCEs, material parameters such as the Young's modulus and the stress-free strains will become nonhomogeneous Analytical expressions for the dependence of the material parameters on the space variable and possibly on the time variable are obtained. Exponential dependence can be derived under certain approximations. As an example, the light-induced bending of a beam is studied. Two neutral planes are found in the beam. Thus, along the thickness of the beam,there are extensions in the upper and lower parts and contractions in the middle.

  11. Progress in radiation processing vol 1; food/environment/elastomers and polymers

    Energy Technology Data Exchange (ETDEWEB)

    Nablo, S.V. (ed.)

    1984-10-01

    This paper reports on the planning process for the conference on Radiation Processing. The final program was made up of six sessions on food applications, four on elastomers and polymers, two on environmental applications with eighteen additional sessions over the five day conference period. The emerging industrial applications of electron processing were highlighted in those sessions on graphics, magnetic media and semiconductors and there was some difficulty presenting a materials handling session due to the continuing reluctance of the equipment manufacturers to discuss proprietary details of web, sheet, formed product and wire handling machinery.

  12. fs- and ns-laser processing of polydimethylsiloxane (PDMS) elastomer: Comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Stankova, N.E., E-mail: nestankova@yahoo.com [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, Sofia 1784 (Bulgaria); Atanasov, P.A.; Nedyalkov, N.N.; Stoyanchov, T.R. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, Sofia 1784 (Bulgaria); Kolev, K.N.; Valova, E.I.; Georgieva, J.S.; Armyanov, St.A. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, Sofia 1113 (Bulgaria); Amoruso, S.; Wang, X.; Bruzzese, R. [CNR-SPIN, Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); Grochowska, K.; Śliwiński, G. [Photophysics Department, The Szewalski Institute, Polish Academy of Sciences, 14 Fiszera St., 80-231 Gdańsk (Poland); Baert, K.; Hubin, A. [Vrije Universiteit Brussels, Faculty of Engineering, Research group, SURF “Electrochemical and Surface Engineering” (Belgium); Delplancke, M.P.; Dille, J. [Université Libre de Bruxelles, Materials Engineering, Characterization, Synthesis and Recycling (Service 4MAT), Faculté des Sciences Appliquées, 1050 Brussels (Belgium)

    2015-05-01

    Highlights: • fs- and ns-laser (266 and 532 nm) processing of PDMS-elastomer, in air, is studied. • High definition tracks (on the PDMS-elastomer surface) for electrodes are produced. • Selective Pt or Ni metallization of the tracks is produced via electroless plating. • Irradiated and metallized tracks are characterized by μ-Raman spectrometry and SEM. • DC resistance of Pt and Ni tracks is always between 0.5 and 15 Ω/mm. - Abstract: Medical grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial as encapsulation and/or as substrate insulator carrier for long term neural implants because of its remarkable properties. Femtosecond (λ = 263 and 527 nm) and nanosecond (266 and 532 nm) laser processing of PDMS-elastomer surface, in air, is investigated. The influence of different processing parameters, including laser wavelength, pulse duration, fluence, scanning speed and overlapping of the subsequent pulses, on the surface activation and the surface morphology are studied. High definition tracks and electrodes are produced. Remarkable alterations of the chemical composition and structural morphology of the ablated traces are observed in comparison with the native material. Raman spectra illustrate well-defined dependence of the chemical composition on the laser fluence, pulse duration, number of pulses and wavelength. An extra peak about ∼512–518 cm{sup −1}, assigned to crystalline silicon, is observed after ns- or visible fs-laser processing of the surface. In all cases, the intensities of Si−O−Si symmetric stretching at 488 cm{sup −1}, Si−CH{sub 3} symmetric rocking at 685 cm{sup −1}, Si−C symmetric stretching at 709 cm{sup −1}, CH{sub 3} asymmetric rocking + Si−C asymmetric stretching at 787 cm{sup −1}, and CH{sub 3} symmetric rocking at 859 cm{sup −1}, modes strongly decrease. The laser processed areas are also analyzed by SEM and optical microscopy. Selective Pt or Ni metallization of the laser processed

  13. Application of silicone based elastomers for manufacturing of Green Fiber Bottle

    DEFF Research Database (Denmark)

    Saxena, Prateek; Bissacco, Giuliano

    Due to ever-increasing demand of sustainable products, eco-friendly packaging solutions are finding their importance in the paper packaging industry. Green Fiber Bottle (GFB) is an alternative to plastic, glass and metal based packaging for beverages. The tool concept for manufacturing of paper...... bottle uses a silicone based elastomer as the core. The expansion of core in the tool resists shrinkage of paper during drying as well as helps in obtaining good fiber compaction. The feasibility of the tool concept in the production of GFB is discussed in this work....

  14. Molecular Dynamics and Morphology of High Performance Elastomers and Fibers by Solid State NMR

    Science.gov (United States)

    2016-06-30

    Fibers by Solid-State NMR The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued as an...ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 PBO fiber; environmental degradation; solid-state NMR ...non peer-reviewed journals: Final Report: Molecular Dynamics and Morphology of High-Performance Elastomers and Fibers by Solid-State NMR Report Title

  15. Space radiation effects on an elastomer-toughened epoxy-graphite composite

    Science.gov (United States)

    Sykes, G. F.; Slemp, W. S.

    1985-01-01

    An elastomer-toughened epoxy-graphite composite system (CE339/T300) was evaluated for its potential durability in the space radiation environment. The physical and chemical response of this system was characterized following exposure to radiation doses equivalent to 20 to 30 years in geosynchronous orbit using 1 MeV electrons. The results show that electrons generate extensive crosslinking and embrittlement of the matrix. This embrittlement results in chemical and mechanical property changes that would limit the service life of this epoxy system in some space structure applications.

  16. The Friction Wear Properties and Application of Thermoplastic Polyester Elastomer and Polyoxymethylene

    Institute of Scientific and Technical Information of China (English)

    HU Ping; HUANG Chou; ZHENG Hua; TAN Zhan-ao; HUANG Zhang-chan

    2004-01-01

    The experiment of injection molding, Dais-simulating test, morphological structure investigation(Scanning Electron Microscopy, SEM),X-ray photoelectron spectroscopy(XPS)were performed on mini-automobile spherical seat which was made of thermoplastic polyester elastomer(TPEE)and oiled polyoxymethylene(POM),respectively. The friction-wear properties between the frictionl pair of polymer spherical seat and metallic(iron)spherical pin were studied. The test results indicate that the antifriction property of TPEE is superior to that of POM, while its surface chemical effect is inferior to that of POM.

  17. Change in color of a maxillofacial prosthetic silicone elastomer, following investment in molds of different materials

    Science.gov (United States)

    Sethi, Tania; Kheur, Mohit; Coward, Trevor; Patel, Naimesha

    2015-01-01

    Purpose: In the authors’ experience, the color of silicone elastomer following polymerization in molds made of gypsum products is slightly different from the color that was matched in the presence of the patient, before the silicone is packed. It is hypothesized that the investing materials and separating media have an effect on the color during the polymerization process of the silicone. Materials and Methods: This study compares and evaluates the change in color of silicone elastomer packed in three commonly used investing materials - Dental stone (white color), dental stone (green color), and die stone (orange color); coated with three different separating media – Alginate-based medium, soap solution and a resin-based die hardening material. Pigmented silicone samples of dimensions 1.5 cm × 2 cm × 0.5 cm were made from the elastomer in the above-mentioned mold materials using combinations of the mentioned separating media. These served as test group samples. Control group samples were made by packing a mix of the same pigmented elastomer in stainless steel molds. The L*, a*, b* values of the test and control group samples were determined using a spectrophotometer. The change in color (Delta E) was calculated between the control and test groups. Results: The mean L, a, b values for the control group were, 31.8, 26.2, and 36.3, respectively. Average values of change in color (Delta E) for samples packed utilizing alginate-based medium, die hardener, and soap solution, respectively in white dental stone (2.70, 2.74, and 2.88), green dental stone (2.19, 2.23, 2.42), and orange die stone (3.19, 2.72, 2.80) were tabulated. Conclusion: Among the investing materials studied, die stone showed the most color change (3.19), which was statistically significant. Among the separating media, die hardener showed the least color change (2.23). The best combination of an investing material and separating media as per this investigation is a dental stone (green) and alginate

  18. Micro injection moulding process validation for high precision manufacture of thermoplastic elastomer micro suspension rings

    DEFF Research Database (Denmark)

    Calaon, M.; Tosello, G.; Elsborg Hansen, R.

    Micro injection moulding (μIM) is one of the most suitable micro manufacturing processes for flexible mass-production of multi-material functional micro components. The technology was employed in this research used to produce thermoplastic elastomer (TPE) micro suspension rings identified...... as critical component in micro acoustic applications (e.g. phono cartridges, see Figure 1a). The suspension ring holds in place the preassembled aluminium cantilever, magnet and diamond tip seen (see Figure 1b and 1c). The specific damping properties of the TPE material reduces vibrations differently depended...

  19. PROPERTIES OF POLYURETHANE ELASTOMERS BASED ON POLY (OXYETHYLENE-co-OXYTETRAMETHYLENE) DIOL

    Institute of Scientific and Technical Information of China (English)

    Chen-yu Su; Guang-li Zhang; Hong-zhi Zhang

    2001-01-01

    Polyurethane elastomers derived from 4,4′-methylene bis(phenyl isocyanate), butylene glycol and the low oxyethylene moiety content copolyether of tetrahydrofuran and ethylene oxide, obtained by copolymerization using heteropolyacid-ethylene oxide initiator system, were prepared. The polyurethanes exhibited an increased water absorption and much better low temperature resilience, which remained high even at a temperature of-3℃, while that of polyurethane based upon poly(tetramethylene ether) glycol of the same molecular weight, I.e. Being 2000, and molecular weight distribution, I.e. In the range of 1.4-1.5, starts to decrease dramatically at 5℃.``

  20. A High-Voltage Class D Audio Amplifier for Dielectric Elastomer Transducers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    Dielectric Elastomer (DE) transducers have emerged as a very interesting alternative to the traditional electrodynamic transducer. Lightweight, small size and high maneuverability are some of the key features of the DE transducer. An amplifier for the DE transducer suitable for audio applications...... is proposed and analyzed. The amplifier addresses the issue of a high impedance load, ensuring a linear response over the midrange region of the audio bandwidth (100 Hz – 3.5 kHz). THD+N below 0.1% are reported for the ± 300 V prototype amplifier producing a maximum of 125 Var at a peak efficiency of 95 %....

  1. Effect of Filler Concentration on Thermal Stability of Vinyl Copolymer Elastomer (VCE) Composites

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Dali [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hubbard, Kevin Mark [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Devlin, David James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Henderson, Kevin C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Pacheco, Robin Montoya [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-06

    To study the thermal stability of vinyl copolymer elastomer (VCE) in its composite form, systematic TGA characterizations were conducted in both nonisothermal and isothermal modes. The effects of filler concentration on the aging behaviors of the VCE/filler composites were investigated under nitroplasticizer (NP) environment. FTIR characterization was used to probe the structural changes in the VCE polymer before and after the thermal treatments. This study suggests that the filler concentration significantly deteriorates the thermal stability of NP at a moderate temperature (< 70 °C). The degradation of NP, in turn, accelerates the aging process of the VCE polymer in its composite form.

  2. Rate dependent constitutive behavior of dielectric elastomers and applications in legged robotics

    Science.gov (United States)

    Oates, William; Miles, Paul; Gao, Wei; Clark, Jonathan; Mashayekhi, Somayeh; Hussaini, M. Yousuff

    2017-04-01

    Dielectric elastomers exhibit novel electromechanical coupling that has been exploited in many adaptive structure applications. Whereas the quasi-static, one-dimensional constitutive behavior can often be accurately quantified by hyperelastic functions and linear dielectric relations, accurate predictions of electromechanical, rate-dependent deformation during multiaxial loading is non-trivial. In this paper, an overview of multiaxial electromechanical membrane finite element modeling is formulated. Viscoelastic constitutive relations are extended to include fractional order. It is shown that fractional order viscoelastic constitutive relations are superior to conventional integer order models. This knowledge is critical for transition to control of legged robotic structures that exhibit advanced mobility.

  3. Mechanically compliant electrodes and dielectric elastomers from PEG-PDMS copolymers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    2016-01-01

    Soft conducting elastomers have been prepared from polydimethylsiloxane-polyethyleneglycol (PDMS-PEG) copolymer and surfactant-stabilized multi-walled carbon nanotubes (MWCNTs). The copolymer was chain-extended with PDMS of molecular weight 17.2 kg mol-1 in order to obtain a crosslinkable PDMS...... showed high conductivity combined with inherent softness. The high conductivity and softness, PDMS-PEG copolymers with incorporated MWCNTs hold great promises as compliant and highly stretchable electrodes for stretchable devices such as electro-mechanical transducers....

  4. Alignment engineering in liquid crystalline elastomers: Free-form microstructures with multiple functionalities

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Hao; Cerretti, Giacomo; Wiersma, Diederik S., E-mail: camilla.parmeggiani@lens.unifi.it, E-mail: wiersma@lens.unifi.it [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Wasylczyk, Piotr [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Faculty of Physics, Institute of Experimental Physics, University of Warsaw, ul. Hoza 69, Warszawa 00-681 (Poland); Martella, Daniele [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Dipartimento di Chimica “Ugo Schiff,” University of Florence, via della Lastruccia 3-13, 50019 Sesto Fiorentino (Italy); Parmeggiani, Camilla, E-mail: camilla.parmeggiani@lens.unifi.it, E-mail: wiersma@lens.unifi.it [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); CNR-INO, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy)

    2015-03-16

    We report a method to fabricate polymer microstructures with local control over the molecular orientation. Alignment control is achieved on molecular level in a structure of arbitrary form that can be from 1 to 100 μm in size, by fixing the local boundary conditions with micro-grating patterns. The method makes use of two-photon polymerization (Direct Laser Writing) and is demonstrated specifically in liquid-crystalline elastomers. This concept allows for the realization of free-form polymeric structures with multiple functionalities which are not possible to realize with existing techniques and which can be locally controlled by light in the micrometer scale.

  5. Simulation study of electromagnetic circuit design in laminated magnetorheological elastomer isolator

    Science.gov (United States)

    Wahab, N. A. A.; Mazlan, S. A.; Hairuddin, K.; Zamzuri, H.

    2015-12-01

    This paper presents a simulation study of magnetic flux density distribution in a laminated magnetorheological elastomer (MRE) isolator. The performance of laminated MRE isolator depends on the particular magnetic properties of materials. Therefore, the electromagnetic simulation using Finite Element Method Magnetic (FEMM) had been carried out in designing and optimizing the MRE isolator. It is apparent that the capability of magnetic flux penetrated through the MRE depends on the design parameters approach including the selection of the materials, shape of MRE, thickness of MRE and steel sheet.

  6. A direct product decomposition of QMV algebras

    Institute of Scientific and Technical Information of China (English)

    LU Xian; SHANG Yun; LU RuQian

    2012-01-01

    We study the direct product decomposition of quantum many-valued algebras (QMV algebras)which generalizes the decomposition theorem of ortholattices (orthomodular lattices).In detail,for an idempotent element of a given QMV algebra,if it commutes with every element of the QMV algebra,it can induce a direct product decomposition of the QMV algebra.At the same time,we introduce the commutant C(S) of a set S in a QMV algebra,and prove that when S consists of idempotent elements,C(S) is a subalgebra of the QMV algebra.This also generalizes the cases of orthomodular lattices.

  7. On a Decomposition Model for Optical Flow

    Science.gov (United States)

    Abhau, Jochen; Belhachmi, Zakaria; Scherzer, Otmar

    In this paper we present a variational method for determining cartoon and texture components of the optical flow of a noisy image sequence. The method is realized by reformulating the optical flow problem first as a variational denoising problem for multi-channel data and then by applying decomposition methods. Thanks to the general formulation, several norms can be used for the decomposition. We study a decomposition for the optical flow into bounded variation and oscillating component in greater detail. Numerical examples demonstrate the capabilities of the proposed approach.

  8. Solid state exchange reactions and thermal decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Albarran, G.; Archundia, C.; Maddock, A.G.

    1982-01-01

    A further study of exchange of the cobalt atoms in solid Co(H/sub 2/O)/sub 6/(Co EDTA)/sub 2/ x 4H/sub 2/O has been made. The exchange is more easily measured when the compound has been ..gamma.. irradiated before heating. Without irradiation the exchange is complicated by substantial concurrent thermal decomposition. Vacuum dehydration to the tetrahydrate can be effected at 366 K without appreciable exchange. A relation between exchange, annealing of radiolytic decomposition and thermal decomposition in such compounds is suggested.

  9. Domain decomposition algorithms and computational fluid dynamics

    Science.gov (United States)

    Chan, Tony F.

    1988-01-01

    Some of the new domain decomposition algorithms are applied to two model problems in computational fluid dynamics: the two-dimensional convection-diffusion problem and the incompressible driven cavity flow problem. First, a brief introduction to the various approaches of domain decomposition is given, and a survey of domain decomposition preconditioners for the operator on the interface separating the subdomains is then presented. For the convection-diffusion problem, the effect of the convection term and its discretization on the performance of some of the preconditioners is discussed. For the driven cavity problem, the effectiveness of a class of boundary probe preconditioners is examined.

  10. Unimolecular thermal decomposition of dimethoxybenzenes

    Science.gov (United States)

    Robichaud, David J.; Scheer, Adam M.; Mukarakate, Calvin; Ormond, Thomas K.; Buckingham, Grant T.; Ellison, G. Barney; Nimlos, Mark R.

    2014-06-01

    The unimolecular thermal decomposition mechanisms of o-, m-, and p-dimethoxybenzene (CH3O-C6H4-OCH3) have been studied using a high temperature, microtubular (μtubular) SiC reactor with a residence time of 100 μs. Product detection was carried out using single photon ionization (SPI, 10.487 eV) and resonance enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry and matrix infrared absorption spectroscopy from 400 K to 1600 K. The initial pyrolytic step for each isomer is methoxy bond homolysis to eliminate methyl radical. Subsequent thermolysis is unique for each isomer. In the case of o-CH3O-C6H4-OCH3, intramolecular H-transfer dominates leading to the formation of o-hydroxybenzaldehyde (o-HO-C6H4-CHO) and phenol (C6H5OH). Para-CH3O-C6H4-OCH3 immediately breaks the second methoxy bond to form p-benzoquinone, which decomposes further to cyclopentadienone (C5H4=O). Finally, the m-CH3O-C6H4-OCH3 isomer will predominantly follow a ring-reduction/CO-elimination mechanism to form C5H4=O. Electronic structure calculations and transition state theory are used to confirm mechanisms and comment on kinetics. Implications for lignin pyrolysis are discussed.

  11. Geometric decompositions of collective motion

    Science.gov (United States)

    Mischiati, Matteo; Krishnaprasad, P. S.

    2017-04-01

    Collective motion in nature is a captivating phenomenon. Revealing the underlying mechanisms, which are of biological and theoretical interest, will require empirical data, modelling and analysis techniques. Here, we contribute a geometric viewpoint, yielding a novel method of analysing movement. Snapshots of collective motion are portrayed as tangent vectors on configuration space, with length determined by the total kinetic energy. Using the geometry of fibre bundles and connections, this portrait is split into orthogonal components each tangential to a lower dimensional manifold derived from configuration space. The resulting decomposition, when interleaved with classical shape space construction, is categorized into a family of kinematic modes-including rigid translations, rigid rotations, inertia tensor transformations, expansions and compressions. Snapshots of empirical data from natural collectives can be allocated to these modes and weighted by fractions of total kinetic energy. Such quantitative measures can provide insight into the variation of the driving goals of a collective, as illustrated by applying these methods to a publicly available dataset of pigeon flocking. The geometric framework may also be profitably employed in the control of artificial systems of interacting agents such as robots.

  12. Thermal Decomposition Kinetics of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Burnham, A K; Weese, R K

    2004-11-18

    Nucleation-growth kinetic expressions are derived for thermal decomposition of HMX from a variety of thermal analysis data types, including mass loss for isothermal and constant rate heating in an open pan and heat flow for isothermal and constant rate heating in open and closed pans. Conditions are identified in which thermal runaway is small to nonexistent, which typically means temperatures less than 255 C and heating rates less than 1 C/min. Activation energies are typically in the 140 to 165 kJ/mol range for open pan experiments and about 150 to 165 kJ/mol for sealed pan experiments. Our activation energies tend to be slightly lower than those derived from data supplied by the University of Utah, which we consider the best previous thermal analysis work. The reaction clearly displays more than one process, and most likely three processes, which are most clearly evident in open pan experiments. The reaction is accelerated in closed pan experiments, and one global reaction appears to fit the data well. Comparison of our rate measurements with additional literature sources for open and closed low temperature pyrolysis from Sandia gives a likely activation energy of 165 kJ/mol at 10% conversion.

  13. Thermal Decomposition Kinetics of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Burnham, A K; Weese, R K

    2004-05-05

    Nucleation-growth kinetic expressions are derived for thermal decomposition of HMX from a variety of types of data, including mass loss for isothermal and constant rate heating in an open pan, and heat flow for isothermal and constant rate heating in open and closed pans. Conditions are identified in which thermal runaway is small to nonexistent, which typically means temperatures less than 255 C and heating rates less than 1 C/min. Activation energies are typically in the 140 to 150 kJ/mol regime for open pan experiments and about 160 kJ/mol for sealed pan experiments. Our activation energies are about 10% lower than those derived from data supplied by the University of Utah, which we consider the best previous work. The reaction clearly displays more than one process, and most likely three processes, which are most clearly evident in open pan experiments. The reaction is accelerated for closed pan experiments, and one global reaction appears to fit the data well.

  14. Thermal Decomposition Kinetics of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Burnham, A K; Weese, R K

    2005-03-17

    Nucleation-growth kinetic expressions are derived for thermal decomposition of HMX from a variety of types of data, including mass loss for isothermal and constant rate heating in an open pan, and heat flow for isothermal and constant rate heating in open and closed pans. Conditions are identified in which thermal runaway is small to nonexistent, which typically means temperatures less than 255 C and heating rates less than 1 C/min. Activation energies are typically in the 140 to 165 kJ/mol regime for open pan experiments and about 150-165 kJ/mol for sealed-pan experiments. The reaction clearly displays more than one process, and most likely three processes, which are most clearly evident in open pan experiments. The reaction is accelerated for closed pan experiments, and one global reaction fits the data fairly well. Our A-E values lie in the middle of the values given in a compensation-law plot by Brill et al. (1994). Comparison with additional open and closed low temperature pyrolysis experiments support an activation energy of 165 kJ/mol at 10% conversion.

  15. Principais copolímeros elastoméricos à base de butadieno utilizados na indústria automobilística The most important butadiene based elastomers employed in the automotive industry

    Directory of Open Access Journals (Sweden)

    Tereza C. J. Rocha

    2007-12-01

    Full Text Available Copolímeros elastoméricos à base de butadieno são amplamente utilizados na indústria automobilística. Dentre esses destacam-se os copolímeros de butadieno-estireno (SBR e butadieno-acrilonitrila (NBR. O SBR apresenta maior importância comercial, devido a sua aplicação na produção de pneus. Quando SBR é utilizado juntamente com o homopolímero de butadieno BR-alto cis, excelentes propriedades são obtidas para sua aplicação na banda de rodagem de pneus. O copolímero elastomérico NBR é empregado em artefatos em que é necessária boa resistência a solventes orgânicos e a óleos. Nos últimos anos, as empresas automobilísticas e produtoras de pneumáticos vêm se preocupando com o meio-ambiente e, conseqüentemente, têm investido em novos processos de síntese, mais limpos, para a produção desses elastômeros. Assim, o objetivo deste artigo é apresentar uma revisão sobre dois importantes copolímeros elastoméricos à base de butadieno, SBR e NBR, abordando os processos de síntese, características principais, processamento e aplicações.Elastomer copolymers based on butadiene are widely applied in the automotive industry. Among those copolymers the most important ones are styrene-butadiene (SBR and nitrile-butadiene (NBR. SBR presents higher commercial interest, due to its application in the tire production. When SBR is mixed with high cis-1,4 polybutadiene, excellent properties are attained for application on the pneumatics treads. NBR can be used in a wide variety of application areas requiring oil, fuel, and chemical resistance. In the last years, the automotive and pneumatic industries have been increasingly concerned with environmental issues, and have invested in synthesis processes for elastomers that are less aggressive to the environment. Thus, the purpose of this article is to present a review on two important butadiene elastomer copolymers, SBR and NBR, with emphasis on the polymerization processes. The main

  16. The decomposition of estuarine macrophytes under different ...

    African Journals Online (AJOL)

    2013-04-29

    Apr 29, 2013 ... versity and recreational value (Hanisak, 1993; Pedersen and. Borum, 1996 ... in providing organic matter to detrital food chains, or alter- natively ..... Moreover, when assessing the SRP released during decomposition for each.

  17. Directional Filters for Cartoon + Texture Image Decomposition

    Directory of Open Access Journals (Sweden)

    Antoni Buades

    2016-05-01

    Full Text Available We present in this article a detailed analysis and implementation of the cartoon+texture decomposition algorithm proposed in [A. Buades, J.L. Lisani, 'Directional filters for color cartoon + texture image and video decomposition', Journal of Mathematical Imaging and Vision, 2015]. This method follows the approach proposed by [A. Buades, T. Le, J-M. Morel, L. Vese, 'Cartoon+Texture Image Decomposition', IPOL 2011], based on low/high-pass filtering, but replaces the isotropic filters by a bank of low-pass directional filters. The cartoon image is obtained by filtering in the direction that leads to the largest local total variation rate reduction. This permits to improve the performance of the decomposition near image discontinuities, where an halo effect was produced by the previous method.

  18. Thomas Decomposition of Algebraic and Differential Systems

    CERN Document Server

    Bächler, Thomas; Lange-Hegermann, Markus; Robertz, Daniel

    2010-01-01

    In this paper we consider disjoint decomposition of algebraic and non-linear partial differential systems of equations and inequations into so-called simple subsystems. We exploit Thomas decomposition ideas and develop them into a new algorithm. For algebraic systems simplicity means triangularity, squarefreeness and non-vanishing initials. For differential systems the algorithm provides not only algebraic simplicity but also involutivity. The algorithm has been implemented in Maple.

  19. Partial differential equations possessing Frobenius integrable decompositions

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Wen-Xiu [Department of Mathematics, University of South Florida, Tampa, FL 33620-5700 (United States)]. E-mail: mawx@cas.usf.edu; Wu, Hongyou [Department of Mathematical Sciences, Northern Illinois University, DeKalb, IL 60115-2888 (United States)]. E-mail: wu@math.niu.edu; He, Jingsong [Department of Mathematics, University of Science and Technology of China, Hefei, Anhui 230026 (China)]. E-mail: jshe@ustc.edu.cn

    2007-04-16

    Frobenius integrable decompositions are introduced for partial differential equations. A procedure is provided for determining a class of partial differential equations of polynomial type, which possess specified Frobenius integrable decompositions. Two concrete examples with logarithmic derivative Baecklund transformations are given, and the presented partial differential equations are transformed into Frobenius integrable ordinary differential equations with cubic nonlinearity. The resulting solutions are illustrated to describe the solution phenomena shared with the KdV and potential KdV equations.

  20. Decomposition of forging dies for machining planning

    CERN Document Server

    Tapie, Laurent; Anselmetti, Bernard

    2009-01-01

    This paper will provide a method to decompose forging dies for machining planning in the case of high speed machining finishing operations. This method lies on a machining feature approach model presented in the following paper. The two main decomposition phases, called Basic Machining Features Extraction and Process Planning Generation, are presented. These two decomposition phases integrates machining resources models and expert machining knowledge to provide an outstanding process planning.