WorldWideScience
1

Degradation of elastomeric gasket materials in PEM fuel cells  

International Nuclear Information System (INIS)

Polymer electrolyte membrane (PEM) fuel cell stack requires gaskets in each cell to keep the reactant gases within their respective regions. Long-term durability of the fuel cell stacks depends heavily on the functionality of the gaskets. Both the leachants from the seal materials and the cracking of the seals are of great concern to the overall durability of the fuel cell stacks. The degradation of four commercially available gasket materials was investigated in a PEM fuel cell environment in this study. Optical microscopy reveals that the degradation starts with surface roughness from the early stage of exposure and finally results in cracks over time. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to study the surface chemistry of the gasket materials before and after exposure to the PEM fuel cell environment over time. Results from these analyses indicate that the surface chemistry changed initially as a manifestation of the chemical degradation and proceeded via de-cross-linking and chain scission in the backbone. Atomic adsorption spectrometry analysis was used to identify the leachants in the soaking solution from the gasket materials. The effect due to applied stress is reported as well

2

Fluorinated elastomeric materials  

Science.gov (United States)

This invention relates to a method of making perfluorinated elastomeric materials, and to materials made by such methods. In the full synthetic scheme, a partially fluorinated polymeric compound, with moieties to prevent crystallization, is created. It is then crosslinked to a desired degree, then perfluorinated. Various intermediate materials, such as partially fluorinated crosslinked polymers, have useful properties, and are or may become commercially available. One embodiment of this invention therefore relates to perfluorination of a selected partially fluorinated, crosslinked material, which is one step of the full synthetic scheme.

Lagow, Richard J. (6204 Shadow Mountain, Austin, TX 78731); Dumitru, Earl T. (10116 Aspen St., Austin, TX 78758)

1990-02-13

3

46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...  

Science.gov (United States)

...weathertight covers of steel or other equivalent material fitted with gaskets and clamping...weathertight covers of steel or other equivalent material fitted with gaskets and clamping...hatch covers of steel or other equivalent material fitted with gaskets...

2010-10-01

4

Hydrogen isotope permeation in elastomeric materials  

International Nuclear Information System (INIS)

The permeabilities of elastomeric and polymeric materials to hydrogen isotopes were measured at room temperature. The technique for measuring permeation rates is based on the following constant-volume method: a fixed pressure of gas is applied to one side of the specimen to be studied and the permeability constant is determined from the observed rate of pressure increase in an initially evacuated volume on the other side of the specimen. Permeability constants for hydrogen, deuterium, and tritium were measured for Mylar, Teflon, Kapton, Saran, Buna-N, and latex rubber. Results were compared with literature values for hydrogen and deuterium where available and showed excellent agreement

5

A guide to the suitability of elastomeric seal materials for use in radioactive material transport packages  

Energy Technology Data Exchange (ETDEWEB)

Elastomeric seals are a frequently favoured method of sealing Radioactive Material Transport (RMT) packages. The sealing technology has been proven for many years in a wide range of industrial applications. The requirements of the RMT package applications, however, are significantly different from those commonly found in other industries. This guide outlines the Regulatory performance requirements placed on an RMT package sealing system by TS-R-1, and then summarises the material, environment and geometry characteristics of elastomeric seals relevant to RMT applications. Tables in the guide list typical material properties for a range of elastomeric materials commonly used in RMT packages.

Vince, D.J. [Department for Transport, London (United Kingdom)

2004-07-01

6

A guide to the suitability of elastomeric seal materials for use in radioactive material transport packages  

International Nuclear Information System (INIS)

Elastomeric seals are a frequently favoured method of sealing Radioactive Material Transport (RMT) packages. The sealing technology has been proven for many years in a wide range of industrial applications. The requirements of the RMT package applications, however, are significantly different from those commonly found in other industries. This guide outlines the Regulatory performance requirements placed on an RMT package sealing system by TS-R-1, and then summarises the material, environment and geometry characteristics of elastomeric seals relevant to RMT applications. Tables in the guide list typical material properties for a range of elastomeric materials commonly used in RMT packages

7

Evaluation of effective material properties of spiral wound gasket through homogenization  

International Nuclear Information System (INIS)

In this paper, a homogenization methodology is proposed to determine the material properties of spiral wound gaskets (SWGs) using finite element analysis through representative volume elements (RVE) of the gaskets. The constituents of this RVE are described by elasto-plastic material properties. The RVE are subjected to six load cases and the volume averaged responses are analyzed simultaneously to predict the anisotropic properties. The mechanical behaviour is simplified to an orthotropic material model with Hill's plasticity model and the properties are verified with micro-mechanical simulation and experimental results available in the literature. Reasonable agreement is obtained between the results. Formulae for elastic properties are also derived by a simplified analytical method based on lamination theory and compared with those obtained from homogenization.

8

Performance testing of elastomeric seal materials under low and high temperature conditions: Final report  

Energy Technology Data Exchange (ETDEWEB)

The US Department of Energy Offices of Defense Programs and Civilian Radioactive Waste Management jointly sponsored a program to evaluate elastomeric O-ring seal materials for radioactive material shipping containers. The report presents the results of low- and high-temperature tests conducted on 27 common elastomeric compounds.

BRONOWSKI,DAVID R.

2000-06-01

9

Performance testing of elastomeric seal materials under low and high temperature conditions: Final report  

International Nuclear Information System (INIS)

The US Department of Energy Offices of Defense Programs and Civilian Radioactive Waste Management jointly sponsored a program to evaluate elastomeric O-ring seal materials for radioactive material shipping containers. The report presents the results of low- and high-temperature tests conducted on 27 common elastomeric compounds

10

New Soft Polymeric Materials Applicable as Elastomeric Transducers  

DEFF Research Database (Denmark)

An elastomer is a material characterized by the capability to regain its original size and shape after being deformed (stretched or distorted). An ideal elastomer for electroactive polymer (EAP) applications is a system characterized by high extensibility, flexibility and a good mechanical fatigue. Dielectric elastomers (DEs) are part of electronic EAPs presenting a good combination of electromechanical properties such as high achievable strains and stresses, fast response speeds, long lifetime, high reliability and high efficiency1. Subjected to a voltage, a polymeric electroactive material sandwiched between two compliant electrodes will reduce its thickness and expand its area. The electrical energy transformed into mechanical energy is called actuation and it is studied in the technology of elastomeric transducers. While DEs deform under high voltage, the actuation varies for different materials (ceramics2, glassy polymers3 or soft polymeric networks4-6). The strain actuation for stiff materials such asglassy or semicrystalline polymers is limited by the electrical breakdown7, while the deformation upon actuation for soft materials is limited by the electromechanical breakdown8. This paper presents new soft polymeric materials based on silicone with improved mechanical properties. Silicone elastomers exhibit good characteristics including biocompatibility, oxidation resistance, thermal stability, fast mechanical response with good reproducibility and stable mechanical behaviour over a wide range of temperature10-13. However, silicone elastomer has weak intermolecular forces among polymeric chains, which limits its mechanical strength. Mechanical properties may be improved using different methods (adding fillers14, interpenetrating network synthesis15 or bimodal network synthesis16). In the present study hyperswollen silicone networks are synthesized and rheologically characterized. Their viscoelastic properties make them good candidates for elastomeric transducers. Silicone networks are synthesized using ahydrosilylation reaction at room temperature between vinyl-terminated polydimethyl siloxanes (PDMS), a 4-functional crosslinker and a platinum catalyst. A ‘one-step two-pot’ mixing procedure is applied and to each premix 70% solvent (heptane) is added. The use of solvent causes networks with fewer entanglements, thus giving the polymeric chains opportunity to act as undisturbed ideal springs. The viscoelastic behavior as function of the applied frequency (LVE diagram) is shown for different hyperswollen networks with varying stoichiometric imbalance (r). The results are compared with results of similar un-swollen networks. The hyperswollen networks are significantly softer and still easy to handle. From a mechanical point of view, the materials for EAPs use have to be soft with sufficient mechanical strength so the rupture of the material can be avoided at high strain actuation. Considering the EAP requirements and the experimental data for the hyperswollen networks based on silicone, these materials may be considered as good alternatives for the EAP application.

Bejenariu, Anca Gabriela; Skov, Anne Ladegaard

11

Successive mechanochemical activation and small molecule release in an elastomeric material.  

Science.gov (United States)

We have developed a mechanochemically responsive material capable of successively releasing small organic molecules from a cross-linked network upon repeated compressions. The use of a flex activated mechanophore that does not lead to main chain scission and an elastomeric polyurethane enabled consecutive compressions with incremental increases in the % mechanophore activation. Additionally, we examined the effect of multiple applications of compressive stress on both mechanophore activity and the mechanical behavior of the elastomeric matrix in which the mechanophore is embedded. PMID:24417375

Larsen, Michael B; Boydston, Andrew J

2014-01-29

12

Copper electroplating of non-aqueous elastomeric impression materials: a subjective appraisal of their platability.  

Science.gov (United States)

Electroplating of non-aqueous elastomeric impression materials is a well-documented technique. Electroplated silver or copper plated dies have many clinical advantages compared to other die systems. Silver electroplating appears to be used more frequently than copper electroplating. Utilization of silver for electroplating requires an appreciation of financial and biohazard considerations. Research on compatibility of copper electroplating with current non aqueous elastomeric impression materials is lacking. Samples of currently used non aqueous elastomeric impression materials were used to register impressions of conventional crown preparations on a typodont. These impressions were electroplated to form copper plated dies. The surface qualities of the dies were evaluated. Not all impression materials produced visually acceptable or workable copper plated dies. PMID:9582678

Payne, J A; Jeganathan, S

1994-01-01

13

Development of an impact noise reduction method by the adding of a small thickness elastomeric material  

Science.gov (United States)

The starting point of this Ph.D. is the industrial issue submitted to the ETS by the company Bombardier Recreational Products (BRP) of the noise reduction of the tracked drive mechanism of snowmobiles. The overall goal of is to develop a method to predict the impact noise reduction obtained by the adding of an elastomeric layer specimen of small thickness between the impacting body and the impacted structure which is a complex structure (i.e. a structure whose geometry is complex and whose composition involves several materials). To reach this overall goal, three specific goals have been fixed: (1) characterize the behavior under impact of different small thickness elastomeric layers; (2) predict the impact force generated when an elastomeric layer is added on a complex vibrating structure; and (3) validate experimentally the whole method by applying it to the impact noise reduction of a bar of the snowmobile track. To reach the first specific goal (characterize the behavior under impact of different small thickness elastomeric layers), a specific experimental characterization method has been developed. Firstly, an experimental device has been realized to submit the elastomeric layer specimens to the reproducible impact conditions of an impact hammer. The measurement of the penetration depth of the hammer into the elastomeric layer is achieved by recording its motion with a high-speed camera and by detecting its position by further analysis on the individual images. Secondly, the experimental curves obtained are analyzed to point out their main characteristics and choose an appropriate impact model. Thirdly, the contact force parameters are estimated from the experimental results and from the impact model. Using this method, eight impacted elastomeric specimens have been characterized. The results show that a more precise characterization than hardness is obtained. To reach the second specific goal (predict the impact force generated when an elastomeric layer is added on a complex vibrating structure), a simulation model of the impact on a structure whose vibrations are due to bending waves has been used. The physical model developed by the European project "Sounding Object" (Rocchesso et Fontana, 2003) has been chosen. From an analogy between the theory used in this model and the modal formulation used in vibration studies, some first modifications of the original program (MATLAB impact_modal.m script) have been made to simulate physically the impact of a mass on a vibrating structure. Some other modifications of the original program have been made in order to simulate the rigid body motion of the structure in the case of free boundary conditions (because the structure used for the validation of the method has free boundary conditions). To reach the third specific goal (validate experimentally the whole method by applying it to the impact noise reduction of a bar of the snowmobile track), the first step has been the measurement of the force and the acoustic pressure in two configurations: WITH and WITHOUT the elastomeric layer in the contact zone. The second step has been the simulation of the configuration WITH the elastomeric layer by applying the impact model of a mass on a vibrating structure (presented in Chapter 2). In order to estimate the value of the model parameters describing the track bar, the modal parameters of the six first bending modes of the bar have been measured using experimental modal analysis. Finally, validation of the method has been performed firstly by checking experimentally the hypothesis of linearity by comparisons between the reductions of force spectra obtained thanks to the adding of the elastomeric specimen and the reductions of noise spectra. Secondly, validations of the method in time and frequency domains have been performed by comparisons between simulated and measured force signals. These comparisons show that the discrepancies may be high enough for some specimens (especially because the rigid motion of the structure is more complicated than a pure translation) but that

Arz, Jean-Pierre

14

Unification of reactor elastomeric sealing based on material  

Energy Technology Data Exchange (ETDEWEB)

The unification of elastomeric sealing applications of Indian nuclear reactors based on a few qualified fluoroelastomer/perfluoroelastomer compounds and standardized approaches for finite element analysis (FEA) based design, manufacturing process and antifriction coatings is discussed. It is shown that the advance polymer architecture based Viton{sup Registered-Sign} formulation developed for inflatable seals of 500 MWe Prototype Fast Breeder Reactor (PFBR) and its four basic variations can encompass other sealing applications of PFBR with minimum additional efforts on development and validation. Changing the blend ratio of Viton{sup Registered-Sign} GBL 200S and 600S in inflatable seal formulation could extend its use to Pressurized Heavy Water Reactors (PHWRs). The higher operating temperature of Advanced Heavy Water Reactor (AHWR) seals expands the choice to perfluoroelastomers. FEA based on plane-strain/axisymmetric modeling (with Mooney-Rivlin as the basic constitutive model), seal manufacture by cold feed extrusion and injection molding as well as plasma Teflon-like coating belonging to two variations obtained from the development of inflatable seals provide the necessary standardization for unification. The gains in simplification of design, development and operation of seals along with the enhancements of safety and reliability are expected to be substantial.

Sinha, N.K., E-mail: nksinha@igcar.gov.in [Indira Gandhi Centre for Atomic Research (IGCAR), Department of Atomic Energy (DAE), Kalpakkam, Tamilnadu 603102 (India); Raj, Baldev [Indira Gandhi Centre for Atomic Research (IGCAR), Department of Atomic Energy (DAE), Kalpakkam, Tamilnadu 603102 (India)

2012-02-15

15

Unification of reactor elastomeric sealing based on material  

International Nuclear Information System (INIS)

The unification of elastomeric sealing applications of Indian nuclear reactors based on a few qualified fluoroelastomer/perfluoroelastomer compounds and standardized approaches for finite element analysis (FEA) based design, manufacturing process and antifriction coatings is discussed. It is shown that the advance polymer architecture based Viton® formulation developed for inflatable seals of 500 MWe Prototype Fast Breeder Reactor (PFBR) and its four basic variations can encompass other sealing applications of PFBR with minimum additional efforts on development and validation. Changing the blend ratio of Viton® GBL 200S and 600S in inflatable seal formulation could extend its use to Pressurized Heavy Water Reactors (PHWRs). The higher operating temperature of Advanced Heavy Water Reactor (AHWR) seals expands the choice to perfluoroelastomers. FEA based on plane-strain/axisymmetric modeling (with Mooney–Rivlin as the basic constitutive model), seal manufacture by cold feed extrusion and injection molding as well as plasma Teflon-like coating belonging to two variations obtained from the development of inflatable seals provide the necessary standardization for unification. The gains in simplification of design, development and operation of seals along with the enhancements of safety and reliability are expected to be substantial.

16

Elastomeric thermal interface materials with high through-plane thermal conductivity from carbon fiber fillers vertically aligned by electrostatic flocking.  

Science.gov (United States)

Electrostatic flocking is applied to create an array of aligned carbon fibers from which an elastomeric thermal interface material (TIM) can be fabricated with a high through-plane thermal conductivity of 23.3 W/mK. A high thermal conductivity can be achieved with a significantly low filler level (13.2 wt%). As a result, this material retains the intrinsic properties of the matrix, i.e., elastomeric behavior. PMID:25042211

Uetani, Kojiro; Ata, Seisuke; Tomonoh, Shigeki; Yamada, Takeo; Yumura, Motoo; Hata, Kenji

2014-09-01

17

Biodegradable and Elastomeric Poly(glycerol sebacate) as a Coating Material for Nitinol Bare Stent  

OpenAIRE

We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28?±?0.004?MPa, and Young's modulus was 0.122?±?0.0003?MPa. Elongation was as high a...

Min Ji Kim; Moon Young Hwang; JiHeung Kim; Dong June Chung

2014-01-01

18

Choice of Elastomeric Material for Buffer Devices of Metallurgical Equipment  

OpenAIRE

This study sheds light on the materials (elastomers) which are used for buffer equipment production. One of the unsolved problems concerning shock absorption is the problem of optimal material choice for the shock absorber. It is the main problem examined in this study. We conclude that the material should be chosen in accordance with such characteristics as energy intensity rate, internal friction and rheological characteristic.

Al-quran, Firas M. F.; Matarneh, M. E.; Artukh, V. G.

2012-01-01

19

Choice of Elastomeric Material for Buffer Devices of Metallurgical Equipment  

Directory of Open Access Journals (Sweden)

Full Text Available This study sheds light on the materials (elastomers which are used for buffer equipment production. One of the unsolved problems concerning shock absorption is the problem of optimal material choice for the shock absorber. It is the main problem examined in this study. We conclude that the material should be chosen in accordance with such characteristics as energy intensity rate, internal friction and rheological characteristic.

Firas M.F. Al-Quran

2012-06-01

20

Predicting the dynamic material constants of Mooney-Rivlin model in broad frequency range for elastomeric components  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english In this paper, dynamic material constants of 2-parameter Mooney-Rivlin model for elastomeric components are identified in broad frequency range. To consider more practical case, an elastomeric engine mount is used as the case study. Finite element model updating technique using Radial Basis Function [...] neural networks is implemented to predict the dynamic material constants. Material constants of 2-parameter Mooney-Rivlin model are obtained by curve fitting on uni-axial stress-strain curve. The initial estimations of the material constants are achieved by using uni-axial tension test data. To ensure of the consistency of dynamic response of a real component, frequency response function of three similar engine mounts are extracted from experimental modal data and average of them used in the procedure. The results showed that this technique can successfully predict dynamic material constants of Mooney-Rivlin model for elastomeric components.

Kamal, Jahani; Hossein, Mahmoodzade.

1983-19-01

21

Development and evaluation of elastomeric materials for geothermal applications  

Science.gov (United States)

A material for a casing packer for service for 24 hours in a geothermal environment was developed by synthesis of new elastomers and formulation of available materials. Formulation included use of commercial elastomer gumstocks and also crosslinking of plastic (high Tg) materials. Fibrous reinforcement of fluorocarbon rubbers was emphasized. Organic fiber reinforcement did not increase hot properties significantly. Glass fiber reinforcement gave significant increase in tensile properties. Elongation was reduced, and the glass-reinforced composition examined so far did not hold up well in the geothermal environment. Colloidal asbestos fibers were also investigated. A few experiments with polyphenyl ether gave material with low tensile and high compression set. Available high styrene SBR compositions were studied. Work to date suggests that new synthetic polymers will be required for service in geothermal environments.

Mueller, W. A.; Kalfayan, S. H.; Reilly, W. W.; Ingham, J. D.

1978-01-01

22

New Soft Polymeric Materials Applicable as Elastomeric Transducers  

OpenAIRE

An elastomer is a material characterized by the capability to regain its original size and shape after being deformed (stretched or distorted). An ideal elastomer for electroactive polymer (EAP) applications is a system characterized by high extensibility, flexibility and a good mechanical fatigue. Dielectric elastomers (DEs) are part of electronic EAPs presenting a good combination of electromechanical properties such as high achievable strains and stresses, fast response speeds, long l...

Bejenariu, Anca Gabriela; Skov, Anne Ladegaard

2011-01-01

23

High k dielectric elastomeric materials for low voltage applications  

Science.gov (United States)

In principle EAP technology could potentially replace common motion-generating mechanisms in positioning, valve control, pump and sensor applications, where designers are seeking quieter, power efficient devices to replace conventional electrical motors and drive trains. Their use as artificial muscles is of special interest due to their similar properties in terms of stress and strain, energy and power densities or efficiency. A broad application of dielectric elastomer actuators (DEA) is limited by the high voltage necessary to drive such devices. The development of novel elastomers offering better intrinsic electromechanical properties is one way to solve the problem. We prepared composites from cross-linked silicone elastomers or thermoplastic elastomers (TPE) by blending them with organic fillers exhibiting a high dielectric constant. Well characterized monomeric phthalocyanines and modified doped polyaniline (PANI) were used as filler materials. In addition, blends of TPE and an inorganic filler material PZT were characterized as well. We studied the influence of the filler materials onto the mechanical and electromechanical properties of the resulting mixtures. A hundredfold increase of the dielectric constant was already observed for blends of an olefin based thermoplastic elastomer and PANI.

Walder, C.; Molberg, M.; Opris, D. M.; Nüesch, F. A.; Löwe, C.; Plummer, C. J. G.; Leterrier, Y.; Månson, J.-A. E.

2009-03-01

24

A general approach for quantifying the heat-ageing of gaskets  

International Nuclear Information System (INIS)

A recurrent concern in the design of packaging for the transportation of radioactive material is to determine the elastomeric gaskets life at high temperature. Most gasket suppliers specify maximum allowable temperatures during ''continuous service'' and ''peak service'' (such as ''200 C in continuous service'' or ''250 C in peak'') but they do not specify the definition of ''continuous'' or ''peak'' service, what are the acceptance criteria and how these maximum temperatures are determined. Based on this type of data, it is difficult to assess the acceptability of a gasket submitted to fluctuating temperatures. COGEMA LOGISTICS has launched a test program on the different rubber grades used on its casks to determine, for different temperature levels (e.g. 200 C, 210 C,.., 250 C..), the maximum seal life based on clearly defined criteria. The goal is to establish, for each rubber grade, the seal life versus temperature curve. These curves can be used to know if a gasket exposed to any specified temperature profile can guarantee the leaktightness. The principle of the method is to calculate a sum of ''elementary damage rates'' on the temperature profile (split up into elementary time intervals) and to compare this sum (the ''global damage rate'') to a ''aximum permissible damage rate''. If the global damage rate is lower than the maximum permissible damage rate, the leaktightness of the packaging can be guaranteed for the given temperature profile

25

The thermal and mechanical properties of a low density elastomeric ablation material  

Science.gov (United States)

Thermal and mechanical properties data were obtained for a low density elastomeric resin based ablation material with phenolic-glass honeycomb reinforcement. Data were obtained for the material in the charred and uncharred state. Ablation material specimens were charred in a laboratory furnace at temperatures in the range from 600 K to 1700 K to obtain char specimens representative of the ablation char layer formed during reentry. These specimens were then used to obtain effective thermal conductivity, heat capacity, porosity, and permeability data at the char formation temperature. This provided a boxing of the data which enables the prediction of the transient response of the material during ablation. Limited comparisons were made between the furnace charred specimens and specimens which had been exposed to simulated reentry conditions.

Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

1973-01-01

26

Utilizing stretch-tunable thermochromic elastomeric opal films as novel reversible switchable photonic materials.  

Science.gov (United States)

In this work, the preparation of highly thermoresponsive and fully reversible stretch-tunable elastomeric opal films featuring switchable structural colors is reported. Novel particle architectures based on poly(diethylene glycol methylether methacrylate-co-ethyl acrylate) (PDEGMEMA-co-PEA) as shell polymer are synthesized via seeded and stepwise emulsion polymerization protocols. The use of DEGMEMA as comonomer and herein established synthetic strategies leads to monodisperse soft shell particles, which can be directly processed to opal films by using the feasible melt-shear organization technique. Subsequent UV crosslinking strategies open access to mechanically stable and homogeneous elastomeric opal films. The structural colors of the opal films feature mechano- and thermoresponsiveness, which is found to be fully reversible. Optical characterization shows that the combination of both stimuli provokes a photonic bandgap shift of more than 50 nm from 560 nm in the stretched state to 611 nm in the fully swollen state. In addition, versatile colorful patterns onto the colloidal crystal structure are produced by spatial UV-induced crosslinking by using a photomask. This facile approach enables the generation of spatially cross-linked switchable opal films with fascinating optical properties. Herein described strategies for the preparation of PDEGMEMA-containing colloidal architectures, application of the melt-shear ordering technique, and patterned crosslinking of the final opal films open access to novel stimuli-responsive colloidal crystal films, which are expected to be promising materials in the field of security and sensing applications. PMID:25243892

Schäfer, Christian G; Lederle, Christina; Zentel, Kristina; Stühn, Bernd; Gallei, Markus

2014-11-01

27

Elastomeric optical fiber sensors and method for detecting and measuring events occurring in elastic materials  

Science.gov (United States)

Fiber optic sensing means for the detection and measurement of events such as dynamic loadings imposed upon elastic materials including cementitious materials, elastomers, and animal body components and/or the attrition of such elastic materials are provided. One or more optical fibers each having a deformable core and cladding formed of an elastomeric material such as silicone rubber are embedded in the elastic material. Changes in light transmission through any of the optical fibers due the deformation of the optical fiber by the application of dynamic loads such as compression, tension, or bending loadings imposed on the elastic material or by the attrition of the elastic material such as by cracking, deterioration, aggregate break-up, and muscle, tendon, or organ atrophy provide a measurement of the dynamic loadings and attrition. The fiber optic sensors can be embedded in elastomers subject to dynamic loadings and attrition such as commonly used automobiles and in shoes for determining the amount and frequency of the dynamic loadings and the extent of attrition. The fiber optic sensors are also useable in cementitious material for determining the maturation thereof.

Muhs, Jeffrey D. (Lenoir City, TN); Capps, Gary J. (Knoxville, TN); Smith, David B. (Oak Ridge, TN); White, Clifford P. (Knoxville, TN)

1994-01-01

28

Nuclear power plant accident simulations of gasket materials under simultaneous radiation plus thermal plus mechanical stress conditions  

International Nuclear Information System (INIS)

In order to probe the response of silicone door gasket materials to a postulated severe accident in an Italian nuclear power plant, compression stress relaxation (CSR) and compression set (CS) measurements were conducted under combined radiation (approximately 6 kGy/h) and temperature (up to 230 degrees C) conditions. By making some reasonable initial assumptions, simplified constant temperature and dose rates were derived that should do a reasonable job of simulating the complex environments for worst-case severe events that combine overall aging plus accidents. Further simplification coupled with thermal-only experiments allowed us to derive thermal-only conditions that can be used to achieve CSR and CS responses similar to those expected from the combined environments that are more difficult to simulate. Although the thermal-only simulations should lead to sealing forces similar to those expected during a severe accident, modulus and density results indicate that significant differences in underlying chemistry are expected for the thermal-only and the combined environment simulations. 15 refs., 31 figs., 15 tabs

29

Biodegradable and elastomeric poly(glycerol sebacate) as a coating material for nitinol bare stent.  

Science.gov (United States)

We synthesized and evaluated biodegradable and elastomeric polyesters (poly(glycerol sebacate) (PGS)) using polycondensation between glycerol and sebacic acid to form a cross-linked network structure without using exogenous catalysts. Synthesized materials possess good mechanical properties, elasticity, and surface erosion biodegradation behavior. The tensile strength of the PGS was as high as 0.28 ± 0.004 MPa, and Young's modulus was 0.122 ± 0.0003 MPa. Elongation was as high as 237.8 ± 0.64%, and repeated elongation behavior was also observed to at least three times the original length without rupture. The water-in-air contact angles of the PGS surfaces were about 60°. We also analyzed the properties of an electrospray coating of biodegradable PGS on a nitinol stent for the purpose of enhancing long-term patency for the therapeutic treatment of varicose veins disease. The surface morphology and thickness of coating layer could be controlled by adjusting the electrospraying conditions and solution parameters. PMID:24955369

Kim, Min Ji; Hwang, Moon Young; Kim, JiHeung; Chung, Dong June

2014-01-01

30

Linear dimensional changes in plaster die models using different elastomeric materials  

Directory of Open Access Journals (Sweden)

Full Text Available Dental impression is an important step in the preparation of prostheses since it provides the reproduction of anatomic and surface details of teeth and adjacent structures. The objective of this study was to evaluate the linear dimensional alterations in gypsum dies obtained with different elastomeric materials, using a resin coping impression technique with individual shells. A master cast made of stainless steel with fixed prosthesis characteristics with two prepared abutment teeth was used to obtain the impressions. References points (A, B, C, D, E and F were recorded on the occlusal and buccal surfaces of abutments to register the distances. The impressions were obtained using the following materials: polyether, mercaptan-polysulfide, addition silicone, and condensation silicone. The transfer impressions were made with custom trays and an irreversible hydrocolloid material and were poured with type IV gypsum. The distances between identified points in gypsum dies were measured using an optical microscope and the results were statistically analyzed by ANOVA (p < 0.05 and Tukey's test. The mean of the distances were registered as follows: addition silicone (AB = 13.6 µm, CD=15.0 µm, EF = 14.6 µm, GH=15.2 µm, mercaptan-polysulfide (AB = 36.0 µm, CD = 36.0 µm, EF = 39.6 µm, GH = 40.6 µm, polyether (AB = 35.2 µm, CD = 35.6 µm, EF = 39.4 µm, GH = 41.4 µm and condensation silicone (AB = 69.2 µm, CD = 71.0 µm, EF = 80.6 µm, GH = 81.2 µm. All of the measurements found in gypsum dies were compared to those of a master cast. The results demonstrated that the addition silicone provides the best stability of the compounds tested, followed by polyether, polysulfide and condensation silicone. No statistical differences were obtained between polyether and mercaptan-polysulfide materials.

Jefferson Ricardo Pereira

2010-09-01

31

The thermal and mechanical properties of a low-density glass-fiber-reinforced elastomeric ablation material  

Science.gov (United States)

An evaluation of the thermal and mechanical properties was performed on a molded low-density elastomeric ablation material designated as Material B. Both the virgin and charred states were examined to provide meaningful inputs to the design of a thermal protection system. Chars representative of the flight chars formed during ablation were prepared in a laboratory furnace from 600 K to 1700 K and properties of effective thermal conductivity, heat capacity, porosity and permeability were determined on the furnace chars formed at various temperature levels within the range. This provided a boxing of the data which will enable the prediction of the transient response of the material during flight ablation.

Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

1974-01-01

32

A Comparative Evaluation of the Dimensional Stability of Three Different Elastomeric Impression Materials after Autoclaving – An Invitro Study  

Science.gov (United States)

Aim of the Study: The purpose of the study was to determine the effect of autoclaving on the dimensional stability of three different elastomeric impression materials at three different time intervals. Materials and Methods: Standardized stainless steel master die as per ADA specification number 19 was fabricated. The impression materials used for the study were condensation silicone (GP1), addition silicone (GP2) and polyether (GP3). A total of 45 samples of the stainless steel die were made (n = 45), that is 15 samples for each group. Impression materials were mixed according to the manufacturer’s instructions and were loaded into the mold to make an impression of the die. Impressions were identified with the help of numerical coding system and measurements were made using stereomicroscope (MAGNUS MSZ-Bi) of 0.65x magnification with the help of image analysis software (IMACE PRO-INSIGHT VERSION.The results were subjected to statistical analysis using one way analysis of variance and student t-test for comparison between the groups. Results: Within the limitations of the study statistically significant dimensional changes were observed for all the three impression materials at three different time intervals but this change was not clinically significant. Conclusion: It is well-known fact that all impressions should be disinfected to avoid possible transmission of infectious diseases either by direct contact or cross contamination. Immersion and spray disinfection as well as various disinfection solutions have been tested and proven to be effective for this purpose. But for elastomeric impression materials these methods have proven to be ineffective as they do not prevent cross contamination among the dental team. So autoclaving was one of the most effective sterilization procedure for condensation silicone and addition silicone. Since polyether is hydrophilic it is better to disinfect the impressions as recommended by the manufacturer or by immersion or spray atomization. PMID:25478447

Thota, Kiran Kumar; Ravuri, Rajyalakshmi; Tella, Suchita

2014-01-01

33

Behavior of a New Elastomeric material used as polyolefinic geo membrane in waterproofing; Comportamiento de un nuevo material elastomerico utilizado como geomembrana poliolefinica en impermeabilizacion  

Energy Technology Data Exchange (ETDEWEB)

Two decades ago that Balsas de Tenerife (BALTEN) and the Centro de Estudios y Experimentacion de Obras Publicas (CEDEX), in its experimental field of the south of the Tenerife Island have installed a series of materials to known their behaviour over time. These products among which was placed over a dozen years ago, on an elastomeric polyolefin. This work presents the performance of this synthetic geo membrane, focusing on the evolution in the time of the tensile properties static puncture, low temperature folding, dynamic impact, joint strength (shear and peeling test), optical microscopy of reflection nd scanning electron microscopy. (Author) 11 refs.

Blanco, M.; Aguilar, E.; Vara, T. A; Soriano, J.; Garcia, F.; Castillo, F.

2011-07-01

34

30 CFR 18.27 - Gaskets.  

Science.gov (United States)

...ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Construction and Design Requirements § 18.27 Gaskets. A gasket(s) shall not be...

2010-07-01

35

Thermal performance of 625-kg/cu m elastomeric ablative materials on spherically blunted 0.44-radian cones  

Science.gov (United States)

Spherically blunted 0.44-radian (25 deg) half-angle conical models coated with elastomeric ablative materials were tested in supersonic arc-heated wind tunnels to evaluate performance of the ablators over a range of conditions typical of lifting entry. Four test conditions were combinations of stagnation point-heat transfer rates of 2.3 and 4.5 MW/m2 and stagnation pressures of 20 and 2kN/m2. Afterbody values of heat transfer rate and pressure were 0.05 to 0.20 of stagnation point values. Stagnation enthalpy varied from 4.4 to 25 MJ/kg (1900 to 11000 Btu/lbm) and free-stream Mach number was in a range from 3.5 to 4. Ablative materials retained the spherical nose shape throughout tests at the lower heat transfer level, but receded, assuming a flattened nose shape, during tests at the high heat transfer level. The residue layer that formed on the conical after-body was weak, friable, and extensively cracked. The reference ablative material, which contained phenolic microspheres, generally retained the conical shape on the model afterbody. However, a modified ablator, in which phenolic microspheres were replaced with silica microspheres, deformed and separated from the undegraded material, and thereby produced a very uneven surface. Substrate temperatures and ablator recession were in good agreement with values computed by a numerical analysis.

Champman, A. J.

1972-01-01

36

Airborne fiber exposure assessment of dry asbestos-containing gaskets and packings found in intact industrial and maritime fittings.  

Science.gov (United States)

This study assessed airborne fiber exposures from intact asbestos-containing gaskets and packings while activities representative of historical work practices were performed. The study design eliminated analytical interferences while systematically capturing information related to activity variables. A series of gasket and packing activities was conducted according to traditional methods while sampling was performed to determine the 8-hour time-weighted average (TWA). The fittings used during this study were obtained intact from a decommissioned industrial power plant and U.S. Navy destroyers. The activities tested included flat blade scraping, hand wire brushing, power wire brushing, making gaskets with a ball-peen hammer, and stem packing removal and replacement. All activities were performed dry. Results for every area and personal sample showed the 8-hour TWAs were well below the current Occupational Safety and Health Administration permissible exposure limit of 0.1 f/cc. A database of more than 400 points was developed to analyze information from variable factors related to the tests. These factors included, for example, type of gasket, composition of the gasket, percentage of gasket adhering to a flange surface, gasket surface area, and minutes elapsed for removal. The results demonstrate a very low rate of fiber exposure from routine activities associated with asbestos-containing elastomeric gaskets and impregnated packing. PMID:12570082

Boelter, Fred W; Crawford, Gary N; Podraza, Daniel M

2002-01-01

37

Embedded Strain Gauges for Condition Monitoring of Silicone Gaskets  

Directory of Open Access Journals (Sweden)

Full Text Available A miniaturized strain gauge with a thickness of 5 µm is molded into a silicone O-ring. This is a first step toward embedding sensors in gaskets for structural health monitoring. The signal of the integrated sensor exhibits a linear correlation with the contact pressure of the O-ring. This affords the opportunity to monitor the gasket condition during installation. Thus, damages caused by faulty assembly can be detected instantly, and early failures, with their associated consequences, can be prevented. Through the embedded strain gauge, the contact pressure applied to the gasket can be directly measured. Excessive pressure and incorrect positioning of the gasket can cause structural damage to the material of the gasket, which can lead to an early outage. A platinum strain gauge is fabricated on a thin polyimide layer and is contacted through gold connections. The measured resistance pressure response exhibits hysteresis for the first few strain cycles, followed by a linear behavior. The short-term impact of the embedded sensor on the stability of the gasket is investigated. Pull-tests with O-rings and test specimens have indicated that the integration of the miniaturized sensors has no negative impact on the stability in the short term.

Timo Schotzko

2014-07-01

38

Embedded strain gauges for condition monitoring of silicone gaskets.  

Science.gov (United States)

A miniaturized strain gauge with a thickness of 5 µm is molded into a silicone O-ring. This is a first step toward embedding sensors in gaskets for structural health monitoring. The signal of the integrated sensor exhibits a linear correlation with the contact pressure of the O-ring. This affords the opportunity to monitor the gasket condition during installation. Thus, damages caused by faulty assembly can be detected instantly, and early failures, with their associated consequences, can be prevented. Through the embedded strain gauge, the contact pressure applied to the gasket can be directly measured. Excessive pressure and incorrect positioning of the gasket can cause structural damage to the material of the gasket, which can lead to an early outage. A platinum strain gauge is fabricated on a thin polyimide layer and is contacted through gold connections. The measured resistance pressure response exhibits hysteresis for the first few strain cycles, followed by a linear behavior. The short-term impact of the embedded sensor on the stability of the gasket is investigated. Pull-tests with O-rings and test specimens have indicated that the integration of the miniaturized sensors has no negative impact on the stability in the short term. PMID:25014099

Schotzko, Timo; Lang, Walter

2014-01-01

39

An elastomeric material for facial prostheses: synthesis, experimental and numerical testing aspects.  

Science.gov (United States)

Current materials used for maxillofacial prostheses are far from ideal and there is a need for new improved materials which better simulate the tissues they are replacing. This study was based on a mixed experimental/analytical/numerical approach. A new polymeric material was developed to provide a better alternative to the materials currently used in maxillofacial prosthetics. A series of experimental tensile tests were performed in order to characterise the tensile properties of the material. A Mooney-Rivlin type hyperelastic formulation was chosen to describe the constitutive behaviour of the polymer which operates at the finite strain regime. The material parameters (two) of the constitutive law were identified with the experimental data. The Mooney-Rivlin material was found to be suitable to represent accurately the mechanical behaviour of the polymer up to 50% strain as shown by the excellent agreement between analytical and experimental results. An FE model reproducing all the characteristics of the experimental tensile tests was built and a series of three FE analyses were conducted and has proven the proper finite element implementation of the material model. This preliminary study will serve as a basis to introduce more complex features such as viscoelasticity and wrinkling of the soft polymeric structure in order to optimise the performances of the final prosthetic material. PMID:14559020

Bellamy, Kathryn; Limbert, G; Waters, Mark G; Middleton, J

2003-12-01

40

Application of gasket performance data for design and operation of low emissions, high-reliability gasketed joints  

Energy Technology Data Exchange (ETDEWEB)

The MTI project No. 47, Test Methods for Non-Asbestos Gasket Materials, opened everyone`s eyes to the breadth of performance and use information for gasket materials. What the MTI has started has resulted in a quiet revolution in gasketing, and just in time. Today`s emissions and reliability mandates have created a situation whereby gasket materials can no longer be selected and designed into systems simply through practicable experience and personnel judgment. A defined engineering approach is required. Based on the work initiated by the MTI and furthered by groups such as ASME and PVRC, there now exists extensive performance data for all gasketing materials. This presentation addresses the existence and usage of the various MTI and PVRC-type performance data as a tool for initial material selection. With this background, a novel simplification to the future ASME code procedure is introduced which allows for a simple yet accurate means of applying this widely available data to an emissions` control program at the plant level.

Waterland, A.F. III [W.L. Gore and Associates, Inc., Elkton, MD (United States)

1996-07-01

41

Performance of seals and gaskets under severe accident conditions  

International Nuclear Information System (INIS)

The US Nuclear Regulatory Commission (USNRC) is sponsoring a set of programs to examine the modes of failure of light-water reactor (LWR) containments subjected to severe accidents. Severe accidents, which were not considered in the design of the containments, can sometimes result in temperatures and pressures significantly above design-base conditions. Under such conditions, containment failure could occur in one or more ways: the containment building could be torn or breached; leak paths could open as a result of degraded seal and gasket materials in mechanical penetrations; sufficient deformation could occur at the sealing surfaces in mechanical penetrations to permit leakage; and leakage could occur in electrical penetrations. Programs are in place at Sandia to investigate each of these possibilities, with this paper limited to the program addressing the degradation of seal and gasket materials. As part of this program, tests are conducted on seals and gaskets to evaluate the effect of radiation aging, thermal aging, atmosphere, temperature, pressure, and seal and gasket geometries on the performance of different seal and gasket materials. The test matrix and procedures and techniques used to test these seals are discussed. Results of completed tests are reviewed. Based on the experimental data, hypotheses for leakage mechanisms in mechanical penetrations are formed

42

Linear dimensional changes in plaster die models using different elastomeric materials  

Scientific Electronic Library Online (English)

Full Text Available Dental impression is an important step in the preparation of prostheses since it provides the reproduction of anatomic and surface details of teeth and adjacent structures. The objective of this study was to evaluate the linear dimensional alterations in gypsum dies obtained with different elastomer [...] ic materials, using a resin coping impression technique with individual shells. A master cast made of stainless steel with fixed prosthesis characteristics with two prepared abutment teeth was used to obtain the impressions. References points (A, B, C, D, E and F) were recorded on the occlusal and buccal surfaces of abutments to register the distances. The impressions were obtained using the following materials: polyether, mercaptan-polysulfide, addition silicone, and condensation silicone. The transfer impressions were made with custom trays and an irreversible hydrocolloid material and were poured with type IV gypsum. The distances between identified points in gypsum dies were measured using an optical microscope and the results were statistically analyzed by ANOVA (p

Jefferson Ricardo, Pereira; Karina Yumi, Murata; Accácio Lins do, Valle; Janaina Salomon, Ghizoni; Fábio Kenji, Shiratori.

2010-09-01

43

Geothermal elastomeric materials. Twelve-months progress report, October 1, 1976--September 30, 1977  

Energy Technology Data Exchange (ETDEWEB)

Progress is reported on efforts to develop elastomers for packer seal element applications which will survive downhole geothermal well chemistry at 260/sup 0/C (500/sup 0/F) for 24 hours. To achieve this development, a three level elastomer testing and evaluation program was established. The first level Screening Tests is a broad screening of potential candidates and with the end objective to filter out the more promising candidates for more expensive subsequent testing. The battery of tests include standard ASTM tests and a special test developed to test extrusion resistance using specimens all made from sheet stock. The second level or Simulation Tests provide a laboratory equivalent of downhole conditions using synthetic geothermal fluid. Full scale packer seals are tested under simulated operational conditions by a test fixture. The third level or In-Situ Tests which are currently in the planning, provide for testing the most favored materials in-situ in the geothermal well. A test module provides for testing of the specimen without interfacing with the well casing. A test module freely hanging on a wireline has much lower probability of causing a problem, such as becoming lodged in the well, as compared to an operational casing packer. This maximizes the number of wells (hence geothermal environments) where access can be gained and In-Situ Testing performed. During this period commercially available polymers were investigated. Most of the work centered around formulating peroxide cured Vitons and some on EPDMs, butyls, and resin cured Vitons. Of the formulations tested to date the EPDMs appear most promising and the peroxide cured Vitons next most promising. However, data is too sparse to make any firm conclusions at this time. Minor tasks were performed evaluating current commercially available elastomers used in oil tools and conceptualization of casing packer for the geothermal application.

Hirasuna, A.R.; Bilyeu, G.D.; Davis, D.L.; Stephens, C.A.; Veal, G.R.

1977-12-01

44

Polycarbosilazane passivation on graphite foil used as gasket seal  

Science.gov (United States)

Gasket seals are often used in industry and laboratories where a leak-proof installation is needed in order to avoid loss of products or dangerous materials. Many of products transported inside tubes are at relatively high temperatures excluding polymeric gaskets. In the same line, many of transported materials contain solvents which can attack polymer sealings, therefore limiting their use. An alternative is to use graphite joints as sealings. These joints are a sandwich of graphite foil and stainless steel mesh as forming core. The problem that raises using graphite in contact with steel is that at temperatures of about 500 °C an interdiffusion of carbon on the steel structure occurs which produces adhesion of the graphite gasket on the metallic flange. Therefore this adhesion increases the time to change each gasket, since rests of previously adhered graphite has to be removed from the flange. In order to avoid the adhesion of the graphite on the flange, polycarbosilazane precursor was used as protective finishing on the graphite foil surface. After thermal transformation of the polymer into the corresponding PDC finishing, it acts in two manners: It avoids the direct contact between the carbon and the steel and it allows the sealing of liquids and gases. Adhesion tests were done and showed that the foils passivated with PDCs did not adhere to the steel flange. Moreover, the production methods and products are compatible to industrial environment and processes. The results found here show that the time to change the gasket in industry can be clearly reduced by using the PDC finishing on graphite gasket.

Prette, A. L. G.; Haage, T.; Will, A.; Kolb, M.; Flores, O.; Günthner, M.; Motz, G.

2013-12-01

45

Thermo-mechanical induced deformation simulation studies for metal gaskets for UHV application  

Science.gov (United States)

In vacuum technology, metal gasket seals are extensively employed to achieve a UHV with reduced contamination considering the pressure and temperature variations as it performs a static seal between two stationary members of a mechanical assembly. The optimum sealing is attained over the balancing of the forces effective, which are function of temperature, governs the surface deformation for the metal gasket seal follows into degradation in the leak tightness at elevated temperatures. The prime component exerting the most deformation force over metal gasket seals, gasket seating force is a constant value generated by the bolting of the stationary members of a mechanical assembly. The paper address to metal gasket seals, copper and aluminum, behavior under thermo-mechanical load is analyzed (simulation), with ANSYS platform, workbench. The major concern is to investigate the typical deformation behavior as a function of thermal variation, baking/ cooling. For copper and Aluminum gasket seals, 16mm to 250mm internal diameter, exposed to pre-established gasket seating force under wide temperatures range. The deformation, average and the deformation range, observed to move in a very specific manner and runs to a wide range for a given material and size. The data reported here deserves to be substantial enough to establish the prediction of thermal behavior of metal gasket seals for standardization.

Kumar, B. Ramesh; Purohit, S.

2012-11-01

46

Bulk metallic glass gasket for high pressure, in situ x-ray diffraction  

International Nuclear Information System (INIS)

Amorphous metallic alloys lack long-range atomic order and consequently exhibit excellent homogeneity, no microstructure discontinuities, and no sharp x-ray diffraction peaks. Moreover they have higher tensile fracture strength and hardness than those of traditional crystalline metals. These excellent physical properties make bulk metallic glasses good candidates for high pressure gaskets for in situ x-ray/neutron diffraction experiments. We tested the Pd40Ni40P20 amorphous alloy as a gasket material in three experiments. The behavior of the Pd40Ni40P20 amorphous alloy under a hydrostatic/nonhydrostatic pressure of over 100 GPa was investigated by in situ synchrotron x-ray diffraction. The pressure gradient of the amorphous metallic gasket in the diamond anvil cell was measured on the ruby fluorescence scale during compression and decompression. The results show that bulk metallic glasses are good high-pressure gasket materials for in situ x-ray diffraction experiments

47

Cytotoxic Evaluation of Elastomeric Dental Impression Materials on a Permanent Mouse Cell Line and on a Primary Human Gingival Fibroblast Culture  

Directory of Open Access Journals (Sweden)

Full Text Available The need for clinically relevant in vitro tests of dental materials is widely recognized. Nearly all dental impression materials are introduced into the mouth just after mixing and allowed to set in contact with the oral tissues. Under these conditions, the materials may be toxic to cells or may sensitize the tissues. The aim of the present study is to evaluate the potential cytotoxicity of new preparations of elastomeric dental impression materials: A four vinylpolysiloxanes: Elite H-D Putty and Elite H-D Light Body (Zhermack, Badia Polesine, Rovigo, Italy; Express Putty and Express Light Body (3M ESPE AG Seefeld, Germany and B two polyethers: Impregum Penta and Permadyne Penta L (3M ESPE AG Seefeld, Germany. The cytotoxicity of these impression materials were examined using two different cell lines: Balb/c 3T3 (permanent cell line and human gingival fibroblasts (primary cell line and their effects were studied by indirect and direct tests. The direct tests are performed by placing one sample of the impression materials in the centre of the Petri dishes at the time of the seeding of cells. The cell growth was evaluated at the 12th and 24th hours by cell number. The indirect tests were performed by incubating a square of 1 cm diameter impression material in 5 mL of medium at 37 °C for 24 hours (“eluates”. Subconfluent cultures are incubated with “eluates” for 24 hours. The MTT-formazan production is the method used for measuring the cell viability. The results indicate that: a polyether materials are cytotoxic under both experimental conditions; b among vinylpolysiloxanes, only Express Light Body (3M ESPE AG Seefeld, Germany induces clear inhibition of cellular viability of Balb/c 3T3 evaluated by direct and indirect tests and c the primary cell line is less sensitive to the toxic effect than the permanent cell line.

Roberta Tiozzo

2009-08-01

48

Silicone foam molding method for sealing timing belt cover gasket; Timing belt gasket no happo silicone gomu tofu gijutsu  

Energy Technology Data Exchange (ETDEWEB)

An automated assembly of a timing belt cover gasket succeeded by changing a gasket material from molding rubber to silicone foam rubber and making a coating application process with the change. Since a conventional molding rubber gasket was unstable to shape and difficult to integrate in the automation, a method was examined for applying a liquid silicone foam rubber, a building material. A silicone foam rubber as a building material had problems such that reaction was fast after two liquids were mixed, that hardening occurred in the mixed part, and that the viscosity was so low as to make a 3-dimensional application impossible. Consequently, a material was developed for a two-liquid heat setting type that commenced reaction by heating. An application process excellent in quality and yield was completed. In the system containing a device for mixing and discharging two liquids, by enlarging the bore diameter of a discharge nozzle, cutting liquid at the tip end of the nozzle, making a mixer with a small number of revolution and small capacity, using the material in which reaction starting temperature was raised to suppress the reaction inside the mixer, and so on. Thus, the automation was successfully carried out. 16 figs., 1 tab.

Kobayashi, Y.; Kagosaki, T.; Omura, S.; Yamaguchi, H. [Toyota Motor Corp., Aichi (Japan)

1995-04-20

49

Integrated-fin gasket for palm cubic-anvil high pressure apparatus  

Energy Technology Data Exchange (ETDEWEB)

We described an integrated-fin gasket technique for the palm cubic-anvil apparatus specialized for the high-pressure and low-temperature measurements. By using such a gasket made from the semi-sintered MgO ceramics and the tungsten-carbide anvils of 2.5 mm square top, we successfully generate pressures over 16 GPa at both room and cryogenic temperatures down to 0.5 K. We observed a pressure self-increment for this specific configuration and further characterized the thermally induced pressure variation by monitoring the antiferromagnetic transition temperature of chromium up to 12 GPa. In addition to enlarge the pressure capacity, such a modified gasket also improves greatly the surviving rate of electrical leads hanging the sample inside a Teflon capsule filled with the liquid pressure-transmitting medium. These improvements should be attributed to the reduced extrusion of gasket materials during the initial compression.

Cheng, J.-G. [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Matsubayashi, K.; Nagasaki, S.; Hisada, A.; Hirayama, T.; Uwatoko, Y. [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Hedo, M. [Faculty of Science, University of Ryukyus, Senbaru, Nishihara, Okinawa 903-0213 (Japan); Kagi, H. [Graduate School of Science, University of Tokyo, 7-3-1, Hongo Bunkyo-Ku, Tokyo 113-0033 (Japan)

2014-09-15

50

Hybrid Methods in Designing Sierpinski Gasket Antennas  

OpenAIRE

Sierpinki gasket antennas as example of fractal antennas show multiband characteristics. The computer simulation of Sierpinksi gasket monopole with finite ground needs prohibitively large computer memory and more computational time. Hybrid methods consist of surface integral equation method and physical optics or uniform geometrical theory of diffraction should alleviate this computational burdens. The so-called full hybridization of the different methods with modifying the incoming electroma...

Mudrik Alaydrus

2010-01-01

51

Force-Degradation Pattern of Six Different Orthodontic Elastomeric Chains  

OpenAIRE

Objective: An ideal orthodontic force system should exert continuous light force. Thus, many efforts have been made to improve the memory characteristics of elastomeric chains. The aim of this study was to compare elastomeric chains (ECs) claimed by their manufacturers to offer high memory with traditional ones according to their force-extension diagrams.Materials and Methods: In this in-vitro study, ECs were divided into six groups, each containing 40 pieces of chain, from three brands (Amer...

Ah, Mirhashemi; Safarshahroudi, A.; Sodagar, A.; Atai, M.

2012-01-01

52

Method for making an elastomeric member with end pieces  

Science.gov (United States)

A molding process for molding an elongated elastomeric member (60) with wire mesh sleeves (16) bonded to the ends (14). A molding preform (10) of elastomeric material is positioned within a seamless mold cylinder (26), and the open ends of the wire mesh sleeves (16) are mounted to end plug assemblies (30) slidably received into the mold cylinder (26) and positioned against the ends (14) of the preform (10). A specialized profile is formed into surfaces (44) of the respective end plug assemblies (30) and by heating of the mold (26), the ends (14) of the elastomeric preform (10) are molded to the profile, as well as bonded to the reinforcing wire mesh sleeves (16). Vacuum is applied to the interior of the mold to draw outgassing vapors through relief spaces therethrough. The completed elastomeric member (60) is removed from the mold cylinder (26) by stretching, the consequent reduction in diameter enabling ready separation from the mold cylinder (26) and removal thereof.

Hoppie, Lyle O. (Birmingham, MI); McNinch, Jr., Joseph H. (Livonia, MI); Nowell, Gregory C. (Livonia, MI)

1984-01-01

53

Hybrid Methods in Designing Sierpinski Gasket Antennas  

Directory of Open Access Journals (Sweden)

Full Text Available Sierpinki gasket antennas as example of fractal antennas show multiband characteristics. The computer simulation of Sierpinksi gasket monopole with finite ground needs prohibitively large computer memory and more computational time. Hybrid methods consist of surface integral equation method and physical optics or uniform geometrical theory of diffraction should alleviate this computational burdens. The so-called full hybridization of the different methods with modifying the incoming electromagnetic waves in case of hybrid method surface integral equation method and physical optics and modification of the Greens function for hybrid method surface integral equation method and uniform geometrical theory of diffraction plays the central role in the observation. Comparison between results of different methods are given and also measurements of three Sierpinksi gasket antennas. The multiband characteristics of the antennas still can be seen with some reduction and enhancement of resonances.

Mudrik Alaydrus

2010-12-01

54

Electrically conductive composites based on an elastomeric matrix filled with expanded graphite as a potential oil sensing material  

Science.gov (United States)

The preparation and properties of electrically conductive polymeric composites based on an elastomer matrix (styrene-isoprene styrene block copolymer) filled with expanded graphite are reported in this paper. The developed materials were tested as oil sensors in various modes. The operation of this sensor is based on changes in the electrical resistance R of the composites when exposed to oil. This phenomenon involves both simple geometrical changes and changes in inherent material characteristics such as the specific electrical conductivity (resistivity). An original method for the improvement of the sensors’ response rate based on the application of stretched sensing films was developed. Slightly stretched films (by 4% of the original length) showed a response that was 12.5 times faster with respect to oil absorption than an un-stretched film. The specific electrical conductivity of a material strongly depends on the extent to which it is stretched. For a composite filled with 10 wt.% of the filler, it was found that the electrical conductivity remained constant up to 11% of the sample extension before sharply decreasing. It was also found that an increase in the filler content reduced the response rate of the sensors.

Krupa, Igor; Prostredný, Martin; Špitalský, Zdenko; Kraj?i, Juraj; AlMaadeed, Mariam Ali S.

2014-12-01

55

Airborne asbestos exposures associated with gasket and packing replacement: a simulation study and meta-analysis.  

Science.gov (United States)

Exposures to airborne asbestos during the removal and installation of internal gaskets and packing associated with a valve overhaul were characterized and compared to published data according to different variables (e.g., product, equipment, task, tool, setting, duration). Personal breathing zone and area samples were collected during twelve events simulating gasket and packing replacement, clean-up and clothing handling. These samples were analyzed using PCM and TEM methods and PCM-equivalent (PCME) airborne asbestos concentrations were calculated. A meta-analysis was performed to compare these data with airborne asbestos concentrations measured in other studies involving gaskets and packing. Short-term mechanic and assistant airborne asbestos concentrations during valve work averaged 0.013f/cc and 0.008f/cc (PCME), respectively. Area samples averaged 0.008f/cc, 0.005f/cc, and 0.003f/cc (PCME) for center, bystander, and remote background, respectively. Assuming a tradesman conservatively performs 1-3 gasket and/or packing replacements daily, an average 8-h TWA was estimated to be 0.002-0.010f/cc (PCME). Combining these results in a meta-analysis of the published exposure data showed that the majority of airborne asbestos exposures during work with gaskets and packing fall within a consistent and low range. Significant differences in airborne concentrations were observed between power versus manual tools and removal versus installation tasks. Airborne asbestos concentrations resulting from gasket and packing work during a valve overhaul are consistent with historical exposure data on replacement of asbestos-containing gasket and packing materials involving multiple variables and, in nearly all plausible scenarios, result in average airborne asbestos concentrations below contemporaneous occupational exposure limits for asbestos. PMID:24768989

Madl, Amy K; Hollins, Dana M; Devlin, Kathryn D; Donovan, Ellen P; Dopart, Pamela J; Scott, Paul K; Perez, Angela L

2014-08-01

56

Compatibility Study for Plastic, Elastomeric, and Metallic Fueling Infrastructure Materials Exposed to Aggressive Formulations of Ethanol-blended Gasoline  

Energy Technology Data Exchange (ETDEWEB)

In 2008 Oak Ridge National Laboratory began a series of experiments to evaluate the compatibility of fueling infrastructure materials with intermediate levels of ethanol-blended gasoline. Initially, the focus was elastomers, metals, and sealants, and the test fuels were Fuel C, CE10a, CE17a and CE25a. The results of these studies were published in 2010. Follow-on studies were performed with an emphasis on plastic (thermoplastic and thermoset) materials used in underground storage and dispenser systems. These materials were exposed to test fuels of Fuel C and CE25a. Upon completion of this effort, it was felt that additional compatibility data with higher ethanol blends was needed and another round of experimentation was performed on elastomers, metals, and plastics with CE50a and CE85a test fuels. Compatibility of polymers typically relates to the solubility of the solid polymer with a solvent. It can also mean susceptibility to chemical attack, but the polymers and test fuels evaluated in this study are not considered to be chemically reactive with each other. Solubility in polymers is typically assessed by measuring the volume swell of the polymer exposed to the solvent of interest. Elastomers are a class of polymers that are predominantly used as seals, and most o-ring and seal manufacturers provide compatibility tables of their products with various solvents including ethanol, toluene, and isooctane, which are components of aggressive oxygenated gasoline as described by the Society of Automotive Engineers (SAE) J1681. These tables include a ranking based on the level of volume swell in the elastomer associated with exposure to a particular solvent. Swell is usually accompanied by a decrease in hardness (softening) that also affects performance. For seal applications, shrinkage of the elastomer upon drying is also a critical parameter since a contraction of volume can conceivably enable leakage to occur. Shrinkage is also indicative of the removal of one or more components of the elastomers (by the solvent). This extraction of additives can negatively change the properties of the elastomer, leading to reduced performance and durability. For a seal application, some level of volume swell is acceptable, since the expansion will serve to maintain a seal. However, the acceptable level of swell is dependent on the particular application of the elastomer product. It is known that excessive swell can lead to unacceptable extrusion of the elastomer beyond the sealed interface, where it becomes susceptible to damage. Also, since high swell is indicative of high solubility, there is a heightened potential for fluid to seep through the seal and into the environment. Plastics, on the other hand, are used primarily in structural applications, such as solid components, including piping and fluid containment. Volume change, especially in a rigid system, will create internal stresses that may negatively affect performance. In order to better understand and predict the compatibility for a given polymer type and fuel composition, an analysis based on Hansen solubility theory was performed for each plastic and elastomer material. From this study, the solubility distance was calculated for each polymer material and test fuel combination. Using the calculated solubility distance, the ethanol concentration associated with peak swell and overall extent of swell can be predicted for each polymer. The bulk of the material discussion centers on the plastic materials, and their compatibility with Fuel C, CE25a, CE50a, and CE85a. The next section of this paper focuses on the elastomer compatibility with the higher ethanol concentrations with comparison to results obtained previously for the lower ethanol levels. The elastomers were identical to those used in the earlier study. Hansen solubility theory is also applied to the elastomers to provide added interpretation of the results. The final section summarizes the performance of the metal coupons.

Kass, Michael D [ORNL; Pawel, Steven J [ORNL; Theiss, Timothy J [ORNL; Janke, Christopher James [ORNL

2012-07-01

57

COMPARACIÓN DE MODELOS DINÁMICOS DEL COMPORTAMIENTO DE UN MATERIAL ELASTOMÉRICO BAJO TASAS DE DEFORMACIÓN MEDIAS / COMPARISON OF AN ELASTOMERIC MATERIAL BEHAVIOR’S DYNAMIC MODELS UNDER INTERMEDIATE STRAIN RATES  

Scientific Electronic Library Online (English)

Full Text Available El presente trabajo estudia dos modelos dinámicos del comportamiento de un material elastomérico cuando se somete a tasas de deformación medias. Los modelos a estudiar fueron los modelos constitutivos de Maxwell y Cowper & Symonds. Se realizó una comparación analítica entre los dos modelos. Se tomar [...] on resultados de pruebas de caracterización dinámica de materiales y se identificaron los parámetros de cada modelo mediante un proceso de identificación multi-variable. Se estudió el nivel de representatividad obtenido en los dos casos, analizando los resultados de la identificación multivariable. Abstract in english This paper studies two dynamic models of an elastomeric material behavior when it is subjected to intermediate strain rates. The studied models were the constitutive Maxwell model and the constitutive Cowper & Symonds model. An analytical comparison of each model was performed. Test results were tak [...] en from a dynamic material’s characterization and the parameters of each model were identified through a process of multi-variable identification. The level of representation obtained in both cases was studied, in order to analyze the analytical comparison with the results of the multi-variable identification.

Andrés Felipe, Ramírez; Luis Ernesto, Muñoz.

2014-06-01

58

Effect of Commonly Used Beverage, Soft Drink, and Mouthwash on Force Delivered by Elastomeric Chain: A Comparative In Vitro Study  

OpenAIRE

Background: The objective was to evaluate and compare the effect of Coca-Cola®, tea, Listerine® mouthwash on the force delivered by elastomeric chain in vitro. Materials and Methods: Four specimen groups (distilled water, Coca-Cola®, tea, Listerine® mouthwash) with a total sample size of 480 specimens. A specimen is described as a four link grey close elastomeric chain. Jigs, each with a series of pins set 25 mm apart, was used to hold stretched elastomeric chains ...

Kumar, Kiran; Shetty, Sharath; Krithika, M. J.; Cyriac, Bobby

2014-01-01

59

Electropolishing of aluminum gasket for linear accelerator  

International Nuclear Information System (INIS)

We developed electropolishing process of aluminum using vibrating blade agitator that can provide pit-free surface. The vibrating blade agitator is such an agitator that has blades vertically attached to an axis vibrating up and down at dozens of cycles a second. Pitting is caused by hydrogen gas bubbles generated at cathode during electropolishing. Those bubbles often stick on the parts' surface and make pits there. They stick more heavily when larger plane parts are electropolished in viscous electrolytes. We electropolished aluminum gasket for linear accelerator. The gasket is 135 mm in diameter, 2 mm thick and has some holes. Pulsating stream produced by vibrating blades kept hydrogen gas bubbles away from the gasket and avoided them sticking on the surface during electropolishing. Polished surface was highly smooth and pit-free. Surface roughness was diminished from Ra=0.09 ?m to Ra=0.03 ?m, and oxide layer of 200 nm thick was formed on the surface after electropolishing. (author)

60

Dimer Coverings on the Sierpinski Gasket  

Science.gov (United States)

We present the number of dimer coverings N d ( n) on the Sierpinski gasket SG d ( n) at stage n with dimension d equal to two, three, four or five. When the number of vertices, denoted as v( n), of the Sierpinski gasket is an even number, N d ( n) is the number of close-packed dimers. When the number of vertices is an odd number, no close-packed configurations are possible and we allow one of the outmost vertices uncovered. The entropy of absorption of diatomic molecules per site, defined as S_{SGd}=lim_{ntoinfty}ln Nd(n)/v(n) , is calculated to be ln (2)/3 exactly for SG 2. The numbers of dimers on the generalized Sierpinski gasket SG d, b ( n) with d=2 and b=3,4,5 are also obtained exactly with entropies equal to ln (6)/7, ln (28)/12, ln (200)/18, respectively. The number of dimer coverings for SG 3 is given by an exact product expression, such that its entropy is given by an exact summation expression. The upper and lower bounds for the entropy are derived in terms of the results at a certain stage for SG d ( n) with d=3,4,5. As the difference between these bounds converges quickly to zero as the calculated stage increases, the numerical value of S_{SGd} with d=3,4,5 can be evaluated with more than a hundred significant figures accurate.

Chang, Shu-Chiuan; Chen, Lung-Chi

2008-05-01

61

Development of high energy radiation resistant elastomeric composites  

International Nuclear Information System (INIS)

Stabilizer formulations are developed for the elastomeric composites which can withstand high energy radiations to the total dose of 200 MRads. The elastomeric materials used are general purpose formulations based on Ethylene propylene diene (EPDM) and Chlorosulfonated polyethylene (CSP). The stabilizers are synthesized from highly aromatic ring compounds in the oligomeric and polymeric form, in the laboratory. The polymeric stabilizers are found to have better radiation resistance compared to the former one when the performance was evaluated using standard methodology. Dielectric analysis, FTIR and wide angle x-ray diffraction are used to follow the physico-chemical changes taking place in the bulk when subjected to the performance test

62

Actuating dielectric elastomers in pure shear deformation by elastomeric conductors  

Energy Technology Data Exchange (ETDEWEB)

Pure shear experiments are commonly used to characterize dielectric elastomer (DE) material properties and to evaluate DE actuator/generator performance. It is increasingly important for many applications to replace conventional carbon grease electrodes with stretchable elastomeric conductors. We formulate a theory for DE with elastomeric conductors, synthesize transparent hydrogel as ionic conductors, and measure actuation of DE in pure shear deformation. Maximum 67% actuation strain is demonstrated. The theory agrees well with our measurement and also correlates well with reported experiments on DE with electronic conductors.

Wang, Yin; Chen, Baohong; 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); Bai, Yuanyuan; Wang, Hong [Electronic Materials Research Laboratory, School of Electronics and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)

2014-02-10

63

Luminescent elastomeric Janus particles.  

Science.gov (United States)

We report on a low-cost and low-tech method for the preparation of luminescent micro- and millimeter elastomeric particles with asymmetric morphology. The method of fabrication consists in UV-irradiating soft urethane/urea fluorescent spheres, which are then extracted in toluene and dried. Wrinkles appear on the irradiated portions of the particles surfaces, and the spatial periodicity can be controlled with variation in UV irradiation time and the amount of the luminescent compound. The spheres are thus composed of an urethane/urea network in which the tris(8-hydroxyquinolinato)aluminum (Alq3) fluorescent compound was incorporated. The asymmetric morphology and the optical properties of the resultant particles have been confirmed by scanning electron microscopy, atomic force microscopy, optical microscopy, and UV-Vis spectrophotometry. The system shows negligible leaching, and the encapsulation of the Alq3 without recourse to covalent bonding to the polymeric matrix has the advantage of allowing the tuning of the spheres morphology and fluorescence. PMID:24011562

Faita, F L; Trindade, A C; Godinho, M H; Bechtold, I H

2013-11-15

64

In situ evaluation of orthodontic elastomeric chains  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A hipótese testada foi que a exposição dos elásticos em cadeia ao meio bucal altera sua força de tensão. Portanto, o objetivo deste estudo foi avaliar o comportamento, in situ, de diferentes cadeias elastoméricas quando tensionadas durante 3 semanas. Três tipos de elásticos em cadeia Plastic Chain ( [...] PC), Memory Chain (MC) e Super Slick Chain (SSC) foram inseridos aleatoriamente em 3 dos quadrantes de 13 pacientes com distância fixa de 16 mm e força inicial de 180 g. Foi realizado ensaio de tração em uma máquina de ensaio universal EMIC nos seguintes intervalos: inicial, 1 h, 24 h, 1 semana, 2 semanas e 3 semanas. O teste ANOVA a dois critérios foi aplicado para verificar a influência do material e do tempo na degradação da força. Subsequentemente, foi utilizado o teste ANOVA a um critério e pós-teste de Tukey para identificar diferenças estatísticas (p Abstract in english The hypothesis tested in this study was that intraoral exposure of elastomeric chains alters their tensile strength. For such purpose, it was evaluated the in situ behavior of different elastomeric chains stretched for 3 weeks. Three kinds of elastomeric chains, Plastic chain (PC), Memory chain (MC) [...] and Super slick chain (SSC), were randomly placed in 3 quadrants of 13 patient in a fixed distance of 16 mm and mean initial force of 180 g. Tensile testing was performed in an universal testing machine at different intervals: initial, 1 h, 24 h, 1 week, 2 weeks and 3 weeks. A two-way ANOVA test was performed to identify the influence of both material and time on the force decrease. A subsequent one-way ANOVAtest with the Tukey's post hoc test was used to identify statistically significant intragroup and intergroup remaining force (g and %) differences at 5% significance level. The effect of both the material and the time factors were significant. All groups showed significant force decrease after the 1-h period (23% for PC and 14% for MC and SSC). At the end of the 3-week period, the remaining force was 57% (96 g), 67% (129 g) and 71% (125 g) for PC, MC and SSC, respectively. In conclusion, intraoral exposure of elastomeric chains altered their tensile strength. In general, the greater force decrease occurred within the first hour. The remaining force of the enhanced chains measured at each time interval was greater than the conventional one (PC). After 3 weeks, only the enhanced chains maintained the force applied over 100 g.

Carolina, Baratieri; Cláudia Trindade, Mattos; Matheus, Alves Jr; Thiago Chon Leon, Lau; Lincoln Issamu, Nojima; Margareth Maria Gomes de, Souza; Monica Tirre, Araujo; Matilde da Cunha Gonçalves, Nojima.

65

Magnet coil electrical gaskets of high compliance and ampacity  

International Nuclear Information System (INIS)

Coils employed in the magnets of the PHENIX Detector, presently under construction for RHIC (Relativistic Heavy Ion Collider) at the Brookhaven National Laboratory, are massive (weight ? 8000 kG each). For that reason we subdivided them into a series of manageable subcoils that we will subsequent bolt together. Electrical terminals attached to the subcoils conductors are rigidly embedded and precisely located during vacuum impregnation. However; we anticipate some misalignment and nonuniform gaping to occur between terminals at assembly. We have elected to use electrical gaskets of compliance and ampacity between the bolted terminals to enhance the current carrying capability of the electrical joints. This paper describes the material candidates selected, the tests performed, and the relative ranking of the materials tested

66

Magnet coil electrical gaskets of high compliance and ampacity  

Energy Technology Data Exchange (ETDEWEB)

Coils employed in the magnets of the PHENIX Detector, presently under construction for RHIC (Relativistic Heavy Ion Collider) at the Brookhaven National Laboratory, are massive (weight {approximately} 8000 kG each). For that reason we subdivided them into a series of manageable subcoils that we will subsequent bolt together. Electrical terminals attached to the subcoils conductors are rigidly embedded and precisely located during vacuum impregnation. However; we anticipate some misalignment and nonuniform gaping to occur between terminals at assembly. We have elected to use electrical gaskets of compliance and ampacity between the bolted terminals to enhance the current carrying capability of the electrical joints. This paper describes the material candidates selected, the tests performed, and the relative ranking of the materials tested.

Harvey, A.R.; Yamamoto, R.M.

1995-05-17

67

Reinforcement Of Elastomeric Rubber Using Carbon Fiber Laminates  

Directory of Open Access Journals (Sweden)

Full Text Available The Elastomeric rubber is a good energy absorbing device with spring back effect. The effectiveness of any form of rubber depends on its strength and stiffness which cannot be varied beyond a certain limit by using chemical additives alone. So, the elastomeric rubber has to be reinforced by adding a material that is normally stronger and stiffer than rubber. In this paper, the usual problem of vulcanization of rubber was overcome by selecting carbon fibers as the filler material. The unidirectional property of carbon fibers gives it the ability to be oriented in any desired direction, thus imparting required properties. The material was modeled as a composite beam structure initially using the ANSYS software and dynamic analysis was performed to find out the fundamental mode of vibration. A Test specimen was then fabricated according to ASTM standards and experimental investigations were carried out. Mechanical properties of the material such as tensile strength, compression strength, flexure strength and impact strength were obtained from the experimental investigation. The test results of the carbon fiber laminated elastomeric rubber were then compared with ordinary elastomeric rubber with usual additives and it was found to be superior in all aspects.

SIVARAMAN R, ROSEENID TERESA A, SIDDANTH S

2013-07-01

68

Adhesive, elastomeric gel impregnating composition  

Science.gov (United States)

An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

Shaw, David Glenn (Tucson, AZ); Pollard, John Randolph (Tucson, AZ); Brooks, Robert Aubrey (Tijeras, NM)

2002-01-01

69

An exposure study of bystanders and workers during the installation and removal of asbestos gaskets and packing.  

Science.gov (United States)

From 1982 until 1991, a series of studies was performed to evaluate the airborne concentration of chrysotile asbestos associated with replacing gaskets and packing materials. These studies were conducted by the senior author in response to concerns raised by a report from the Navy in 1978 on asbestos exposures associated with gasket work. A series of studies was conducted because results of those who worked with gaskets within the Navy study did not address the background concentrations of asbestos in the work areas, which may have been significant due to the presence of asbestos insulation in the ships and shipyards. The intent of the studies performed from 1982 through 1991 was to re-create the Navy's work practices in a contaminant-free environment during an 8-hour workday (so the data could be compared with the OSHA permissible exposure limit [PEL]). Samples were collected to characterize personal and area airborne asbestos concentrations associated with the formation, removal, and storage of gaskets, as well as the scraping of flanges and the replacement of valve packing. The results indicate that the 8-hour time-weighted average (TWA) exposures of pipefitters and other tradesmen who performed these activities were below the current PEL and all previous PELs. Specifically, the highest average 8-hour TWA concentration measured for workers manipulating asbestos gaskets during this study was 0.030 f/cc (during gasket removal and flange face scraping onboard a naval ship). Likewise, the 8-hour TWA breathing zone concentrations of a worker removing and replacing asbestos valve packing did not exceed 0.016 f/cc. In most cases, the concentrations were not distinguishable from ambient levels of asbestos in the ships or the general environment. These results are not surprising given that asbestos fibers in gasket materials are encapsulated within a binder. PMID:16418082

Mangold, Carl; Clark, Katherine; Madl, Amy; Paustenbach, Dennis

2006-02-01

70

Spectral triples for the Sierpinski Gasket  

OpenAIRE

We construct a family of spectral triples for the Sierpinski Gasket $K$. For suitable values of the parameters, we determine the dimensional spectrum and recover the Hausdorff measure of $K$ in terms of the residue of the volume functional $a\\to$ tr$(a\\,|D|^{-s})$ at its abscissa of convergence $d_D$, which coincides with the Hausdorff dimension $d_H$ of the fractal. We determine the associated Connes' distance showing that it is bi-Lipschitz equivalent to the distance on $K...

Cipriani, F.; Guido, D.; Isola, T.; Sauvageot, J-l

2011-01-01

71

Effect of storage period on the accuracy of elastomeric impressions  

OpenAIRE

AIMS: To investigate the effect of the storage period on the accuracy of recently developed elastomeric materials. METHODS: Simultaneous impressions of a steel die were taken using a polyether (I: Impregum Soft Heavy and Light body, 3M ESPE) and vinyl polysiloxane (P: Perfectim Blue Velvet and Flexi-Velvet, J.Morita). The trays were loaded with the heavy-bodied impression materials while the light-bodied impression materials were simultaneously spread on the steel die. The impressions were po...

Eduardo Batista Franco; Leonardo Fernandes da Cunha; Ana Raquel Benetti

2007-01-01

72

Influence of surface roughness on leakage of new metal gasket  

International Nuclear Information System (INIS)

Previous studies of new metal gaskets have established that the contact width, contact stress, and simulation process are important design parameters for optimizing the metal gasket performance. Optimum designs are thus realized based on the elastic and plastic contact stress. However, the influence of the flange surface roughness has not been investigated thoroughly. In this study, we developed a gasket model that includes the flange surface roughness effect. A flange can have different surface roughness levels. A finite element method was employed to develop the simulation solution. The contact width, contact stress, and force per unit length for gasket in contact with a flange having different surface roughness levels were obtained through the simulation. The leakage performance improved with an increase in the contact width and contact stress. The slope of the force per unit length increased with a decrease in the surface roughness level. Furthermore, the slope of the force per unit length for a gasket in 400-MPa mode was higher than that for one in 0-MPa mode. The higher slope suggests that the gasket and flange are pressed together strongly. Finally, the helium leakage quantity was determined to evaluate the leakage performance. The experimental result shows that the gasket in 400-MPa mode shows better sealing performance than the gasket in 0-MPa mode. For a low axial force, changes in the surface roughness caused significant changes in the leakage; the same was not observed for a high axial force. -- Highlights: • Leakage is a function of surface roughness, it increases with the surface roughness. • The average contact stress increases significantly with the axial force. • The contact width increases with the axial force. • The gasket in 400-MPa mode is better sealing performances than the gasket in 0-MPa mode

73

Exposure to airborne asbestos during removal and installation of gaskets and packings: a review of published and unpublished studies.  

Science.gov (United States)

In recent years, questions have been raised about the health risks to persons who have been occupationally exposed to asbestos-containing gaskets and packing materials used in pipes, valves, and machinery (pumps, autos, etc.). Up until the late 1970s, these materials were widely used throughout industrial and maritime operations, refineries, chemical plants, naval ships, and energy plants. Seven simulation studies and four work-site industrial hygiene studies of industrial and maritime settings involving the collection of more than 300 air samples were evaluated to determine the likely airborne fiber concentrations to which a worker may have been exposed while working with encapsulated asbestos-containing gaskets and packing materials. Each study was evaluated for the representativeness of work practices, analytical methods, sample size, and potential for asbestos contamination (e.g., insulation on valves or pipes used in the study). Specific activities evaluated included the removal and installation of gaskets and packings, flange cleaning, and gasket formation. In all but one of the studies relating to the replacement of gaskets and packing using hand-held tools, the short-term average exposures were less than the current 30-min OSHA excursion limit of 1 fiber per cubic centimeter (f/cc) and all of the long-term average exposures were less than the current 8-h permissible exposure limit time-weighted average (PEL-TWA) of 0.1 f/cc. The weight of evidence indicates that the use of hand tools and hand-operated power tools to remove or install gaskets or packing as performed by pipefitters or other tradesmen in nearly all plausible situations would not have produced airborne concentrations in excess of contemporaneous regulatory levels. PMID:17620202

Madl, Amy K; Clark, Katherine; Paustenbach, Dennis J

2007-01-01

74

Development Of Remote Hanford Connector Gasket Replacement Tooling For DWPF  

International Nuclear Information System (INIS)

The Defense Waste Processing Facility (DWPF) requested the Savannah River National Laboratory (SRNL) to develop tooling and equipment to remotely replace gaskets in mechanical Hanford connectors to reduce personnel radiation exposure as compared to the current hands-on method. It is also expected that radiation levels will continually increase with future waste streams. The equipment is operated in the Remote Equipment Decontamination Cell (REDC), which is equipped with compressed air, two master-slave manipulators (MSM's) and an electro-mechanical manipulator (EMM) arm for operation of the remote tools. The REDC does not provide access to electrical power, so the equipment must be manually or pneumatically operated. The MSM's have a load limit at full extension of ten pounds, which limited the weight of the installation tool. In order to remotely replace Hanford connector gaskets several operations must be performed remotely, these include: removal of the spent gasket and retaining ring (retaining ring is also called snap ring), loading the new snap ring and gasket into the installation tool and installation of the new gasket into the Hanford connector. SRNL developed and tested tools that successfully perform all of the necessary tasks. Removal of snap rings from horizontal and vertical connectors is performed by separate air actuated retaining ring removal tools and is manipulated in the cell by the MSM. In order install a new gasket, the snap ring loader is used tnew gasket, the snap ring loader is used to load a new snap ring into a groove in the gasket installation tool. A new gasket is placed on the installation tool and retained by custom springs. An MSM lifts the installation tool and presses the mounted gasket against the connector block. Once the installation tool is in position, the gasket and snap ring are installed onto the connector by pneumatic actuation. All of the tools are located on a custom work table with a pneumatic valve station that directs compressed air to the desired tool and vents the tools as needed. Extensive testing of tooling operation was performed in the DWPF manipulator repair shop. This testing allowed the operators to gain confidence before the equipment was exposed to radioactive contamination. The testing also led to multiple design improvements. On July 17 and 29, 2008 the Remote Gasket Replacement Tooling was successfully demonstrated in the REDC at the DWPF of The Savannah River Site.

75

Experimental Study on the Ultimate Shear Performance of Elastomeric Bearings of Doublefold Elastomeric Layer  

Directory of Open Access Journals (Sweden)

Full Text Available The elastomeric bearings shall not fail nor degrade the durability of the bridge due to the loss of its properties during its service life. Since the elastomeric bearings can be used in the seismic design complementarily to seismic devices, even if it is not a seismic isolator, they particularly should secure high shear performance. For elastomeric bearings to behave monolithically, the internal rubber which is located between the steel plates should be single rubber layer. In this study, a series of elastomeric bearings were fabricated and ultimate shear performance was investigated. Some specimens are of single elastomeric layer, the other are of doublefold elastomeric layer. Shear fatigue tests and ultimate shear tests were carried out. Tests results show that the elastomeric bearings whose internal rubber layer is formed by agglomeration of several rubber pads is likely to experience significant loss of its shear performance or early failure.

Hyejin Yoon

2013-01-01

76

Seal Materials Compatible with the Electroplating Solvent Used in Constellation-X Mirrors  

Science.gov (United States)

The existing gasket seals used in electroplating of the Constellation-X mirrors are difficult to assemble, and the current seal material is hydrophobic and too thick. The combination of the above problems result in: 1) non-uniform plating; 2) defect sites such as pits on the mirror edges; 3) "bear claws" on the edges of the mandrels and mirrors causing difficulties in shell-mirror separations; and 4) leakage of the plating solution past the seals into the mandrel causing chemical etching of the mandrel interior. This paper reports the results of this summer study in searching for alternate seal materials chemically compatible with the electroplating solvent. Fifteen common elastomeric rubber seal materials made-by Parker Seals were investigated including butyl, ethylene propylene, fluorosilicone, nitrile, Viton fluorocarbon, and silicone. Test results showed that Viton fluorocarbon compounds as a group were superior to the other tested compounds for chemical compatibility with the plating bath.

Pei, Xiong-Skiba

1999-01-01

77

46 CFR 56.30-35 - Gasketed mechanical couplings.  

Science.gov (United States)

...HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES...satisfaction of the Officer in Charge, Marine Inspection. (b) Gasketed mechanical...couplings may be used within the service limitations of pressure,...

2010-10-01

78

DEVELOPMENT OF REMOTE HANFORD CONNECTOR GASKET REPLACEMENT TOOLING FOR DWPF  

Energy Technology Data Exchange (ETDEWEB)

The Defense Waste Processing Facility (DWPF) requested the Savannah River National Laboratory (SRNL) to develop tooling and equipment to remotely replace gaskets in mechanical Hanford connectors to reduce personnel radiation exposure as compared to the current hands-on method. It is also expected that radiation levels will continually increase with future waste streams. The equipment is operated in the Remote Equipment Decontamination Cell (REDC), which is equipped with compressed air, two master-slave manipulators (MSM's) and an electro-mechanical manipulator (EMM) arm for operation of the remote tools. The REDC does not provide access to electrical power, so the equipment must be manually or pneumatically operated. The MSM's have a load limit at full extension of ten pounds, which limited the weight of the installation tool. In order to remotely replace Hanford connector gaskets several operations must be performed remotely, these include: removal of the spent gasket and retaining ring (retaining ring is also called snap ring), loading the new snap ring and gasket into the installation tool and installation of the new gasket into the Hanford connector. SRNL developed and tested tools that successfully perform all of the necessary tasks. Removal of snap rings from horizontal and vertical connectors is performed by separate air actuated retaining ring removal tools and is manipulated in the cell by the MSM. In order install a new gasket, the snap ring loader is used to load a new snap ring into a groove in the gasket installation tool. A new gasket is placed on the installation tool and retained by custom springs. An MSM lifts the installation tool and presses the mounted gasket against the connector block. Once the installation tool is in position, the gasket and snap ring are installed onto the connector by pneumatic actuation. All of the tools are located on a custom work table with a pneumatic valve station that directs compressed air to the desired tool and vents the tools as needed. Extensive testing of tooling operation was performed in the DWPF manipulator repair shop. This testing allowed the operators to gain confidence before the equipment was exposed to radioactive contamination. The testing also led to multiple design improvements. On July 17 and 29, 2008 the Remote Gasket Replacement Tooling was successfully demonstrated in the REDC at the DWPF of The Savannah River Site.

Krementz, D.; Coughlin, Jeffrey

2009-05-05

79

Airborne asbestos exposures associated with gasket and packing replacement: a simulation study of flange and valve repair work and an assessment of exposure variables.  

Science.gov (United States)

A simulation study was conducted to evaluate worker and area exposure to airborne asbestos associated with the replacement of asbestos-containing gaskets and packing materials from flanges and valves and assess the influence of several variables previously not investigated. Additionally, potential of take home exposures from clothing worn during the study was characterized. Our data showed that product type, ventilation type, gasket location, flange or bonnet size, number of flanges involved, surface characteristics, gasket surface adherence, and even activity type did not have a significant effect on worker exposures. Average worker asbestos exposures during flange gasket work (PCME=0.166 f/cc, 12-59 min) were similar to average worker asbestos exposures during valve overhaul work (PCME=0.165 f/cc, 7-76 min). Average 8-h TWA asbestos exposures were estimated to range from 0.010 to 0.062 f/cc. Handling clothes worn during gasket and packing replacement activities demonstrated exposures that were 0.71% (0.0009 f/cc 40-h TWA) of the airborne asbestos concentration experienced during the 5 days of the study. Despite the many variables considered in this study, exposures during gasket and packing replacement occur within a relatively narrow range, are below current and historical occupational exposure limits for asbestos, and are consistent with previously published data. PMID:25445297

Madl, Amy K; Devlin, Kathryn D; Perez, Angela L; Hollins, Dana M; Cowan, Dallas M; Scott, Paul K; White, Katherine; Cheng, Thales J; Henshaw, John L

2015-02-01

80

Fiber release during the removal of asbestos-containing gaskets: a work practice simulation.  

Science.gov (United States)

Work practice studies were conducted involving the removal of asbestos-containing sheet gaskets from steam flanges. These studies were performed to determine potential exposure levels to individuals who have worked with these types of materials in the past and may still work with these products today. The work practices were conducted inside an exposure characterization laboratory (ECL) and were performed by scraping and wire brushing, chrysotile-containing (65% to 85%) sheet gaskets from a number of used steam flanges. Airborne asbestos levels were measured by phase contrast microscopy (PCM) and transmission electron microscopy (TEM) for the personnel and area air samples collected during the study. These workplace simulations showed substantial asbestos fiber release using scraping, hand wire brushing, and power wire brushing techniques during the gasket removal process. The range of concentration was 2.1 to 31.0 fibers/cc greater than 5 micrometers when measured by PCM. These results contrasted with the few reported results in the published literature where lower airborne asbestos levels were reported. In these studies the airborne asbestos fiber levels measured in many of the samples exceeded all current and historical Occupational Safety and Health Administration (OSHA) excursion limits (15-30 minutes) and some previous permissible exposure limits (PEL) based on eight-hour time-weighted average (TWA) standards. Also, individuals who performed this type of work in the past may have had exposures higher than previously suspected. The results demonstrated that employees who remove dry asbestos-containing gaskets with no localized ventilation should wear a full face supplied air respirator with a HEPA escape canister and the work area should be designated a regulated area. PMID:11800407

Longo, William E; Egeland, William B; Hatfield, Richard L; Newton, Larry R

2002-01-01

81

The comparison of System 1000 analysis and type testing for neoprene gasket environmental qualification  

International Nuclear Information System (INIS)

The typical environmental qualification is to ensure that equipment will operate on demand to meet system performance requirements during normal and abnormal service conditions. There are four environmental qualification methods, type testing, operating experience, analysis and combined method. Generally, the American EQ do not contain the mechanical equipment like pumps and valves in their EQ equipment list because their EQ standard 10CFR50.49 limits EQ equipment as electrical equipment. On the other hand, Canadian EQ contain the mechanical equipment like pumps and valves in their EQ components list, Canadians usually call American 'equipment' as 'components', because their EQ standard CSA N290.13-05 do not limits EQ equipment as electrical equipment. System 1000 program is typical Canadian EQ analysis method using mathematical modeling and comparison with established engineering information and manufacturers' data. Most of Canadian nuclear power utilities like NB Power, Hydro Quebec and OPG use the System 1000 program to evaluate the design life for their EQ components. To qualify a pump, I had to list all the non-metallic parts in the pump and found there are lots of gaskets made by neoprene material. I tried to qualify these neoprene gaskets by analysis using System 1000 program and by type testing. In this paper, I'd like to introduce the qualification results of neoprene gasket both type testing and analysis using System 1000 program 1000 program

82

Statistical study of static gasket conductance  

International Nuclear Information System (INIS)

This work is motivated by tightness technological problems associated with metallic gasket. The objective is a better understanding of leakage mechanisms, through the development of new computational tools. In this study, the aperture field between two rough surfaces in contact is described by a short correlated isotropic random Gaussian process. The system is studied as a set of independent elementary surfaces. Joint conductances are evaluated from a statistical study on those elementary surfaces. A computational code is developed using a network approach based on lubrication theory estimation of local conductances. The global conductance computation becomes analogous to an electrical problem for which the resistances are distributed on a random network. The network is built from the identification of the aperture field critical points. Maxima are linked through saddle points. Bond conductances are estimated at the aperture field saddle points. First, a purely plastic model of deformations is considered. Near percolation threshold the conductances display a power behaviour. Far from percolation threshold, numerical results are favourably compared with an effective medium approximation. Secondly, we study the impact of elastic deformations. A computational code based on Boussinesq approximation is coupled to the network approach. The results indicate a significant impact of elastic deformations on conductances. Finally, the network approach is adapted to simulate quasi-static drainage thanks to a classical invasion percolation algorithm. A good comparison between previous experiments and numerical predictions is obtained. (author)

83

Coevolutionary extremal dynamics on gasket fractal  

Energy Technology Data Exchange (ETDEWEB)

We considered a Bak-Sneppen model on a Sierpinski gasket fractal. We calculated the avalanche size distribution and the distribution of distances between subsequent minimal sites. To observe the temporal correlations of the avalanche, we estimated the return time distribution, the first-return time, and the all-return time distribution. The avalanche size distribution follows the power law, P(s)approxs{sup -tau}, with the exponent tau=1.004(7). The distribution of jumping sites also follows the power law, P(r)approxr{sup -pi}, with the critical exponent pi=4.12(4). We observe the periodic oscillation of the distribution of the jumping distances which originated from the jumps of the level when the minimal site crosses the stage of the fractal. The first-return time distribution shows the power law, P{sub f}(t)approxt{sup -tau}{sub f}, with the critical exponent tau{sub f}=1.418(7). The all-return time distribution is also characterized by the power law, P{sub a}(t)approxt{sup -tau}{sub a}, with the exponent tau{sub a}=0.522(4). The exponents of the return time satisfy the scaling relation tau{sub f}+tau{sub a}=2 for tau{sub f}<=2.

Lee, Kyoung Eun [Department of Physics, Inha University, Incheon 402-751 (Korea, Republic of)] [Computational Physics, IfB, ETH-Honggerberg, Schafmattstrasse 6, 8093 Zurich (Switzerland); Sung, Joo Yup; Cha, Moon-Yong; Maeng, Seong Eun; Bang, Yu Sik [Department of Physics, Inha University, Incheon 402-751 (Korea, Republic of); Lee, Jae Woo, E-mail: jaewlee@inha.ac.k [Department of Physics, Inha University, Incheon 402-751 (Korea, Republic of)

2009-11-09

84

Coevolutionary extremal dynamics on gasket fractal  

International Nuclear Information System (INIS)

We considered a Bak-Sneppen model on a Sierpinski gasket fractal. We calculated the avalanche size distribution and the distribution of distances between subsequent minimal sites. To observe the temporal correlations of the avalanche, we estimated the return time distribution, the first-return time, and the all-return time distribution. The avalanche size distribution follows the power law, P(s)?s-?, with the exponent ?=1.004(7). The distribution of jumping sites also follows the power law, P(r)?r-?, with the critical exponent ?=4.12(4). We observe the periodic oscillation of the distribution of the jumping distances which originated from the jumps of the level when the minimal site crosses the stage of the fractal. The first-return time distribution shows the power law, Pf(t)?t-?f, with the critical exponent ?f=1.418(7). The all-return time distribution is also characterized by the power law, Pa(t)?t-?a, with the exponent ?a=0.522(4). The exponents of the return time satisfy the scaling relation ?f+?a=2 for ?f?2.

85

Reduction of molecular gas diffusion through gaskets in leaf gas exchange cuvettes by leaf?mediated pores  

DEFF Research Database (Denmark)

There is an ongoing debate on how to correct leaf gas exchange measurements for the unavoidable diffusion leakage that occurs when measurements are done in non?ambient CO2 concentrations. In this study, we present a theory on how the CO2 diffusion gradient over the gasket is affected by leaf?mediated pores (LMP) and how LMP reduce diffusive exchange across the gaskets. Recent discussions have so far neglected the processes in the quasi?laminar boundary layer around the gasket. Counter intuitively, LMP reduce the leakage through gaskets, which can be explained by assuming that the boundary layer at the exterior of the cuvette is enriched with air from the inside of the cuvette. The effect can thus be reduced by reducing the boundary layer thickness. The theory clarifies conflicting results from earlier studies. We developed leaf adaptor frames that eliminate LMP during measurements on delicate plant material such as grass leaves with circular cross section, and the effectiveness is shown with respiration measurements on a harp of Deschampsia flexuosa leaves. We conclude that the best solution for measurements with portable photosynthesis systems is to avoid LMP rather than trying to correct for the effects.

Boesgaard, Kristine Stove; Mikkelsen, Teis NØrgaard

2013-01-01

86

Behaviour of elastomeric seals at low temperature  

International Nuclear Information System (INIS)

The properties of elastomer O-ring seals (Viton, silicone rubber, EPDM) at low temperature have been investigated by measuring the gas leakage rate and the sealing force during thermal cycling between +20degC and -70degC. For all materials it has been found that at a well defined (critical) temperature the leakage rate sharply rises from permeation level to a high value which is determined by gas streaming through the leak path between the O-ring and the flange surfaces arising from thermal contraction of the elastomer in the glassy state. At the critical temperature the sealing force has been found to be zero or even negative due to adhesion between the elastomer material and the flanges. For all seals the critical temperature is well below the glass transition of the elastomer and also significantly below the temperature where the compression set becomes 100 %. Warming up the sealing system restores leak tightness. Low temperature cycle of elastomeric seals have been found to be entirely reversible. (author)

87

Efficiency of insulative gaskets in bimetal corrosion protection  

International Nuclear Information System (INIS)

Problems of evaluationg efficiency of isolation elements (filters, washers, etc.) used for electric insulation of heterogeneous metallic structures operating in corrosive media are considered. Using solution fo the problem of current distribution in case of contact corrosion during electrochemical interaction fo disk and circular coplanar concentric electrodes by way of example, basic regularities of corrosion rate decrease depending on parameters of insulative gaskets in case of incomplete electric separation of metal parts, were revealed. The optimal ratios between the gaskets thickness and characteristic dimensions of interacting parts were ascertained

88

Improved fibre optic acoustic sensors for partial discharge in elastomeric insulations  

Science.gov (United States)

Partial discharge in elastomeric high voltage insulations is a major reason for device failure. The special challenges of the high voltage environment limit the use of conventional acoustic emission sensors. Fibre-optic sensors can cope with these challenges thanks to their optical sensing principle and the use of all-dielectric materials. In this contribution, improvements to a previously introduced design of ultrasonic fibre-optic acoustic partial discharge sensors for elastomeric insulations are presented. The improved performance of fibre-optic acoustic sensors in detecting AC partial discharge is demonstrated. Furthermore, their ability to detect low-level damage processes in elastomeric insulation under DC dielectric stress is shown to outperform the highly sensitive electrical detection method.

Rohwetter, Philipp; Lothongkam, Chaiyaporn; Habel, Wolfgang; Heidmann, Gerd; Pepper, Daniel

2014-05-01

89

Elastomeric organic material for switching application  

Science.gov (United States)

Organic Electronic devices like OLED, Organic Solar Cells etc are promising as, cost effective alternatives to their inorganic counterparts due to various reasons. However the organic semiconductors currently available are not attractive with respect to their high cost and intricate synthesis protocols. Here we demonstrate that Natural Rubber has the potential to become a cost effective solution to this. Here an attempt has been made to fabricate iodine doped poly isoprene based switching device. In this work Poly methyl methacrylate is used as dielectric layer and Aluminium are employed as electrodes.

Shiju, K.; Praveen, T.; Preedep, P.

2014-10-01

90

Elastomeric organic material for switching application  

Energy Technology Data Exchange (ETDEWEB)

Organic Electronic devices like OLED, Organic Solar Cells etc are promising as, cost effective alternatives to their inorganic counterparts due to various reasons. However the organic semiconductors currently available are not attractive with respect to their high cost and intricate synthesis protocols. Here we demonstrate that Natural Rubber has the potential to become a cost effective solution to this. Here an attempt has been made to fabricate iodine doped poly isoprene based switching device. In this work Poly methyl methacrylate is used as dielectric layer and Aluminium are employed as electrodes.

Shiju, K., E-mail: shijuvenus@gmail.com, E-mail: pravymon@gmail.com, E-mail: ppredeep@gmail.com; Praveen, T., E-mail: shijuvenus@gmail.com, E-mail: pravymon@gmail.com, E-mail: ppredeep@gmail.com; Preedep, P., E-mail: shijuvenus@gmail.com, E-mail: pravymon@gmail.com, E-mail: ppredeep@gmail.com [Laboratory for Molecular Photonics and Electronics (LAMP), Department of Physics, National Institute of Technology, Calicut, Kerala, 673601 (India)

2014-10-15

91

Elastomeric organic material for switching application  

International Nuclear Information System (INIS)

Organic Electronic devices like OLED, Organic Solar Cells etc are promising as, cost effective alternatives to their inorganic counterparts due to various reasons. However the organic semiconductors currently available are not attractive with respect to their high cost and intricate synthesis protocols. Here we demonstrate that Natural Rubber has the potential to become a cost effective solution to this. Here an attempt has been made to fabricate iodine doped poly isoprene based switching device. In this work Poly methyl methacrylate is used as dielectric layer and Aluminium are employed as electrodes

92

Description of gasket failure in a 7 cell PEMFC stack  

Energy Technology Data Exchange (ETDEWEB)

This article presents the data and the description of a fuel cell stack that failed due to gasket degradation. The fuel cell under study is a 7 cell stack. The unexpected change in several variables such as temperature, pressure and voltage indicated the possible failure of the stack. The stack was monitored over a 6 h period in which data was collected and consequently analyzed to conclude that the fuel cell stack failed due to a crossover leak on the anode inlet port located on the cathode side gasket of cell 2. This stack failure analysis revealed a series of indicators that could be used by a super visional controller in order to initiate a shutdown procedure. (author)

Husar, Attila; Serra, Maria [Institut de Robotica i Informatica Industrial, Parc Tecnologic de Barcelona, Edifici U, C. Llorens i Artigas, 4-6, 2a Planta, 08028 Barcelona (Spain); Kunusch, Cristian [Laboratorio de Electronica Industrial Control e Instrumentacion, Facultad de Ingenieria, UNLP (Argentina)

2007-06-10

93

Analytical method of nonlinear gasket contact stress along width direction on bolted flanged connections  

International Nuclear Information System (INIS)

In order to evaluate the tightness of bolted flanged connections accurately, the deformation and the contact stress along the radial direction of nonlinear gaskets have been researched using analytical method. The analytical results obtained by analytical method were compared with those by finite element analysis (FEA), which shows that the results calculated by two methods are fundamentally coincident, but the former is smaller than the latter. The results indicate that both the deformation and the contact stress of gaskets distribute non-uniformly along the gasket radial direction, and they all increase from gasket inner margin to its outer margin. (authors)

94

Influence of thermally induced chemorheological changes on the torsion of elastomeric circular cylinders  

Science.gov (United States)

When an elastomeric material is deformed and subjected to temperatures above some characteristic value T cr (near 100?C for natural rubber), its macromolecular structure undergoes time and temperature-dependent chemical changes. The process continues until the temperature decreases below T cr. Compared to the virgin material, the new material system has modified properties (reduced stiffness) and permanent set on removal of the applied load. A new constitutive theory is used to study the influence of the changes of macromolecular structure on the torsion of an initially homogenous elastomeric cylinder. The cylinder is held at its initial length and given a fixed twist while at a temperature below T cr. The twist is then held fixed and the temperature of the outer radial surface is increased above T cr for a period of time and then returned to its original value. Assuming radial heat conduction, each material element undergoes a different chemical change. After enough time has elapsed such that the temperature field is again uniform and at its initial value, the cylinder properties are now inhomogeneous. Expressions for the time variation of the twisting moment and axial force are determined, and related to assumptions about material properties. Assuming the elastomeric networks to act as Mooney-Rivlin materials, expressions are developed for the permanent twist on release of torque, residual stress, and the new torsional stiffness in terms of the kinetics of the chemical changes.

Wineman, Alan; Shaw, John

2006-05-01

95

ISI of elastomeric components in nuclear reactors  

International Nuclear Information System (INIS)

On irradiation, polymers undergo chemical changes in their back bone/side chain. If the chemical structure is altered, the basic characteristic of parent polymer also changes, hence the property of the component also changes over the period of exposure to any type of radiation. This paper gives an idea about the main properties to be checked for assuring the quality of elastomeric components in view for radiation applications

96

Investigations of different types of gaskets for ILC cavity flanges  

International Nuclear Information System (INIS)

The paper describes the procedures adopted to carefully test the He leak rate of several types of vacuum seals. All the tests were performed at room temperature and at liquid nitrogen (LN2) temperature (77 K), and after thermal cycles between these two temperature levels. The paper also reports the test results in the INFN-Pisa clean room aimed to measure particle contamination while assembling the flange connections. The tests of the Quick Disconnect System using a new conical flange design and an external clamp were carried out. Two types of gaskets: the Helicoflex and the Ultra-Flex, were tested with this system

97

Analytical and Experimental Studies of Liquid and Gas Leaks through Micro and Nano-Porous Gaskets  

Directory of Open Access Journals (Sweden)

Full Text Available The reliability of industrial installation requires minimum leakage of pressurized sealed joints during operation. At the design stage, the leakage behavior of the gasket must be one of the most important parameter in the gasket selection. The objective of the work presented in this paper is to develop an analytical leak rate prediction methodology used in gasketed joints. A pseudo analytical-experimental innovative approach was used to estimate the characteristics of the porous structure for the purpose of predicting accurate leak rate through gaskets with different fluids under conditions similar to those of operation. The analytical model assumes the flow to be continuum but employs a slip boundary condition on the leak path wall to determine the porosity parameters of the gasket. The analytical model results are validated and confronted against experimental data which were conducted under various conditions of fluid media, pressure, gasket stress and temperature. Two experimental test rigs fully automate that accurately reproduces the real leakage behavior of the gasketed joint have been developed to analyze the mechanical and thermal effects on the gasket flow regime. The gas leaks were measured with multi-gas mass spectrometers while liquid leaks were measure using a sophisticated detection system based on the pressure rise method.

Lotfi Grine

2013-08-01

98

PERL - European research project on characterization of gaskets for bolted flange connections  

International Nuclear Information System (INIS)

Great progress was observed in the European standardization in the last years in the field of the design of floating type bolted flange connections. New design rules were developed (EN 1591) which include new definitions of gasket characteristics for the calculation of floating type flanged joints. In addition a new gasket testing standard was drafted (prEN 13555) which assures a comprehensive characterization of gaskets for bolted flanged joints. This draft standard contains some new features which were examined and validated within the European research project PERL (Pressure Equipment - Reduction of Leak Rate). The gasket testing strategy laid down in prEN 13555 is presented in this paper. Some testing results highlighten the measuring procedures and the evaluation of the gasket characteristics. (orig.)

99

PERL - European research project on characterization of gaskets for bolted flange connections  

Energy Technology Data Exchange (ETDEWEB)

Great progress was observed in the European standardization in the last years in the field of the design of floating type bolted flange connections. New design rules were developed (EN 1591) which include new definitions of gasket characteristics for the calculation of floating type flanged joints. In addition a new gasket testing standard was drafted (prEN 13555) which assures a comprehensive characterization of gaskets for bolted flanged joints. This draft standard contains some new features which were examined and validated within the European research project PERL (Pressure Equipment - Reduction of Leak Rate). The gasket testing strategy laid down in prEN 13555 is presented in this paper. Some testing results highlighten the measuring procedures and the evaluation of the gasket characteristics. (orig.)

Kockelmann, H.; Hahn, R. [Materials Testing Inst., Univ. of Stuttgart, Stuttgart (Germany)

2004-07-01

100

Gasket performance of SWG in ROTT and short term estimation at elevated temperature  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with the sealability at room temperature and the durability at elevated temperature of SWG (spiral wound gasket). The fillers in the gasket specimens are chosen as newly developed non-asbestos, asbestos and flexible graphite. The effects of inner and outer rings inserted in the gasket specimens on the new PVRC gaskets constants are examined by using the ROTT test procedure (room temperature tightness test). The durability of SWG at elevated temperature is estimated by using the weight loss of filler and the stress-deflection curve of SWG obtained after aging at elevated temperatures. As a result, the sealability and the durability of newly developed non-asbestos SWG is the same as asbestos SWG, and the durability of flexible graphite SWG at elevated temperatures in this method conform to the boundary temperature in field and it is shown that this method is available to estimate the durability of gaskets at elevated temperatures.

Asahina, M.; Nishida, T.; Yamanaka, Y. [Nippon Valqua Industries, Ltd., Yao, Osaka (Japan)

1996-12-01

101

Modelling leaktightness in a sealing system using elastomeric seal  

International Nuclear Information System (INIS)

The container of radioactive gases in a transport cask is governed by the efficiency of the sealing system. The gas release of an elastomeric seal can have two causes: 1) the permeation through the elastomer which is an intrinsic characteristic for the material. 2) the leakage through geometrical defects (cracks, gaps, capillaries...) which are of a random nature. The purpose of this study is to develop representative models of these two leakage processes. In order to validate these models, experimental measurements were performed with a specific equipment ('LISE' test rig), to carry out tests with O-ring in a trapezoidal groove within a temperature range from -50degC to +300degC. The leakage rate was measured with a mass spectrometer using pure gases or gas mixtures. (J.P.N.)

102

Three-Dimensional Elastomeric Scaffolds Designed with Cardiac-Mimetic Structural and Mechanical Features  

OpenAIRE

Tissue-engineered constructs, at the interface of material science, biology, engineering, and medicine, have the capacity to improve outcomes for cardiac patients by providing living cells and degradable biomaterials that can regenerate the native myocardium. With an ultimate goal of both delivering cells and providing mechanical support to the healing heart, we designed three-dimensional (3D) elastomeric scaffolds with (1) stiffnesses and anisotropy mimicking explanted myocardial specimens a...

Neal, Rebekah A.; Jean, Aure?lie; Park, Hyoungshin; Wu, Patrick B.; Hsiao, James; Engelmayr, George C.; Langer, Robert; Freed, Lisa E.

2012-01-01

103

The Effect of Prestretching on Force Degradation of Synthetic Elastomeric Chains  

OpenAIRE

Statement of Problems: The main disadvantage of elastic chains is their rapid force decay. Thus, pre-stretching has been recommended as a method to overcome this ever existing problem. However, the information regarding the magnitude and the method of its performance are still obscure or varied. Purpose: This study was designed to evaluate the effect of pre-stretching on force degradation of the synthetic elastomeric chains. Materials and Method: This experimental study had two categories ...

Hr, Fattahi; Poursayah A.

2011-01-01

104

Experimental and numerical study of damage initiation mechanism in elastomeric composites  

OpenAIRE

Purpose: Experimental and Finite Element Analysis (FEA) of the damage initiation mechanisms in elastomeric composites were carried out under static loading at room temperature. Double Cantilever Beam (DCB) specimens from natural rubber (NR) vulcanised and reinforced with other materials such as carbon black, silica, fibres and textiles or metals (rubber composites).Design/methodology/approach: Very huge experimental results were compared with that of the Finite Element Analysis (FEA). Damage ...

Silva Botelho, T. D.; Bayraktar, E.

2009-01-01

105

Force-Degradation Pattern of Six Different Orthodontic Elastomeric Chains  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: An ideal orthodontic force system should exert continuous light force. Thus, many efforts have been made to improve the memory characteristics of elastomeric chains. The aim of this study was to compare elastomeric chains (ECs claimed by their manufacturers to offer high memory with traditional ones according to their force-extension diagrams.Materials and Methods: In this in-vitro study, ECs were divided into six groups, each containing 40 pieces of chain, from three brands (American Orthodontics, GAC and Ortho-Technology. Each brand was divided into two groups with respect to their claimed characteristics (with or without memory. Each sample was stretched to twice its original length and kept constant in 37°C distilled water. Force-extension diagrams were drawn by universal testing machine at 0,1,8,24,72 hours and 1, 2, 4-week intervals. Additionally, the amounts of elongation required to deliver 200 g force were calculated. To compare the results, ANOVA and Tukey tests were performed.Results: Force-decay rate was significantly different between traditional and memory chains (p<0.05. For traditional chains, there was a substantial decay in force in the first hour and 30-40% of the force was retained at 4 weeeks. The memory chains demonstrated more constant force and retained 60% of the force. The maximum amount of elongation required to deliver 200 g force belonged to American Orthodontics memory chains (61.9% after 24hr and the minimum to Ortho-Technology ECs (23.4% initially.Conclusion: Memory chains exhibited superior mechanical properties compared to traditional ones. For delivering the same force, memory chains required more elongation. Memory chains of GAC and American Orthodontics showed better characteristics among all chains.

AH Mirhashemi

2012-01-01

106

A Digital Image Steganography using Sierpinski Gasket Fractal and PLSB  

Science.gov (United States)

Information attacks are caused due to the weaknesses in the information security. These attacks affect the non-repudiation and integrity of the security services. In this paper, a novel security approach that can defend the message from information attacks is proposed. In this new approach the original message is encrypted by Fractal Sierpinski Gasket (FSG) cryptographic algorithm, that result is hidden into an image using penultimate and least significant bit (PLSB) embedding method. This method makes the security more robust than conventional approach. Important properties of fractals are sensitivity and self similarity. These can be exploited to produce avalanche effect. Stegoanalysis of the proposed method shows that it is resistant to various attacks and stronger than the existed steganographic approaches.

Rupa, Ch.

2013-09-01

107

Random walks on Sierpinski gaskets of different dimensions.  

Science.gov (United States)

We study random walks (RWs) on classical and dual Sierpinski gaskets (SG and DSG), naturally embedded in d-dimensional Euclidian spaces (ESs). For large d the spectral dimension d(s) approaches 2, the marginal RW dimension. In contrast to RW over two-dimensional ES, RWs over SG and DSG show a very rich behavior. First, the time discrete scale invariance leads to logarithmic-periodic (log-periodic) oscillations in the RW properties monitored, which increase in amplitude with d. Second, the asymptotic approach to the theoretically predicted RW power laws is significantly altered depending on d and on the variant of the fractal (SG or DSG) under study. In addition, we discuss the suitability of standard RW properties to determine d(s), a question of great practical relevance. PMID:21230459

Weber, Sebastian; Klafter, Joseph; Blumen, Alexander

2010-11-01

108

Sensitivity improvement of a fibre Bragg grating pH sensor with elastomeric coating  

International Nuclear Information System (INIS)

A new optical pH sensor based on fibre Bragg grating (FBG) is demonstrated. The sensor consists of a FBG coated with pH sensitive hydrogel. The sensing was performed through the detection of wavelength shifts resulting from the induced strain on the FBG due to mechanical expansion of the hydrogel. An elastomeric coating was applied before the hydrogel coating to improve the sensitivity. The sensor performance was investigated by simulating the hydrogel swelling and the strain induced on the FBG. The swelling of hydrogel due to pH change was modelled using a free-energy function and was solved using the finite element method. With silicone rubber as the elastomer material, the results show that the sensitivity was improved by up to 66% compared to that of the FBG pH sensor without elastomeric coating

109

Fractal dimension of a quasi-two-dimensional Sierpinski gasket as a conductor  

International Nuclear Information System (INIS)

It is shown that the fractal dimension of Sierpinski gasket as a conductor is different from that for its geometry. The fractal dimension of Sierpinski gasket can be defined as D = D? + iDR. D? and DR are the fractal dimensions determined from its conductance and resistance, respectively. For 2-d Sierpinski gasket DR = 3.8 and D? = 1/DR = 0.263, while for 3-d Sierpinski tetrahedron DR = 2.41 and D? = 0.415. (author). 4 refs, 5 figs

110

FEM analysis of ultra-flex gasket for ILC cavity flanges  

International Nuclear Information System (INIS)

Numerical simulation of a new kind of metallic gasket by Garlock company, the Ultra-Flex, has been carried out using the ANSYS code for finite element analysis. The main purpose was to determine the optimal geometrical parameters of the seal for our application in ILC cavity flanges. The FEA model shows that if the gasket tore diameter is increased from 4.65 to 8 mm and its thickness is increased from 0.5 to 0.65 mm, the useful elastic recovery (spring-back) of the gasket will drastically increase, from 0.05 to 0.2 mm

111

The Effect of Prestretching on Force Degradation of Synthetic Elastomeric Chains  

Directory of Open Access Journals (Sweden)

Full Text Available Statement of Problems: The main disadvantage of elastic chains is their rapid force decay. Thus, pre-stretching has been recommended as a method to overcome this ever existing problem. However, the information regarding the magnitude and the method of its performance are still obscure or varied. Purpose: This study was designed to evaluate the effect of pre-stretching on force degradation of the synthetic elastomeric chains. Materials and Method: This experimental study had two categories of synthetic elastomeric chains: 1. Control (unprestretched 2. Test (prestretched. The test groups were pre-stretched to 33%, 100% and 200% of the original length. We evaluated 4 control and 16 test groups from four manufacturers. In a period of 5 seconds, each specimen was pre-stretched in the rate of 30 mm per minute. Then, all the specimens were stretched to 25 mm and fixed in this distance on the frames and were merged in 37 degree water. Their forces were measured at 0 hour, 1 hour, 24 hours, 1 week, and 3 weeks. Data were analyzed using Friedman, ANOVA and Green house-Geisser test.Results: All the 20 groups had force degradation in the study period ( p <001. The highest rate of force degradation (about half of the total force degradation occurred at the first hour. But the rate of force degradation declined over time. In all brands, force degradation was smaller in pre-stretching 200% than the control group ( p <0.01-0.001. Conclusion: Synthetic elastomeric chains from several companies have different effects from different distances of pre-strectching, so the appropriate pre-stretching length must be defined for each kind of synthetic elastomeric chain.

Fattahi HR.

2011-02-01

112

Elastomeric composites based on carbon nanomaterials.  

Science.gov (United States)

Carbon nanomaterials including carbon black (CB), carbon nanotubes (CNTs) and graphene have attracted increasingly more interest in academia due to their fascinating properties. These nanomaterials can significantly improve the mechanical, electrical, thermal, barrier, and flame retardant properties of elastomers. The improvements are dependent on the molecular nature of the matrix, the intrinsic property, geometry and dispersion of the fillers, and the interface between the matrix and the fillers. In this article, we briefly described the fabrication processes of elastomer composites, illuminated the importance of keeping fillers at nanoscale in matrices, and critically reviewed the recent development of the elastomeric composites by incorporating CB, CNTs, and graphene and its derivatives. Attention has been paid to the mechanical properties and electrical and thermal conductivity. Challenges and further research are discussed at the end of the article. PMID:25705981

Araby, Sherif; Meng, Qingshi; Zhang, Liqun; Zaman, Izzuddin; Majewski, Peter; Ma, Jun

2015-03-20

113

Solvent-resistant elastomeric microfluidic devices and applications  

Science.gov (United States)

Microfluidics is increasingly being used in many areas of biotechnology and chemistry to achieve reduced reagent volumes, improved performance, integration, and parallelism, among other advantages. Though early devices were based on rigid materials such as glass and silicon, elastomeric materials such as polydiznethylsiloxane (PDMS) are rapidly emerging as a ubiquitous platform for applications in biotechnology. This is due, in part, to simpler fabrication procedures and to the ability to integrate mechanical microvalves at vastly greater densities. For many applications in the areas of chemical synthesis and analysis, however, PDMS cannot replace glass and silicon due to its incompatibility with many solvents and reagents. Such areas could benefit tremendously from the development of an elastomeric microfluidic device technology that combines the advantages of PDMS with the property of solvent resistance. Simplified fabrication could increase the accessibility of microfluidics, and the possibility of dense valve integration could lead to significant advances in device sophistication. Applications could be more rapidly developed by design re-use due to the independence of mechanical valves on fluid properties (unlike electrokinetic pumping), and the property of permeability could enable novel fluidic functions for accessing a broader range of reactions than is possible in glass and silicon. The first half of this thesis describes our strategies and efforts to develop this new enabling technology. Several approaches are presented in Chapter 3, and two particularly successful ones, based on new elastomers (FNB and PFPE), are described in Chapters 4 and 5. Chapter 6 describes a novel method of fabricating devices from 3D molds that could expand the range of useful clastomers. The second half of this thesis discusses microfluidic combinatorial synthesis and high throughput screening-applications that take particular advantage of the ability to integrate thousands of individual valves and reaction chambers. Chapter 7 introduces several scalable device architectures and presents results of preliminary steps toward the synthesis of combinatorial DNA and peptide arrays. A novel method of performing universal gene expression analysis with combinatorial DNA arrays is described in Chapter 8 and an algorithm for predicting relationships among genes from gene expression array data is presented in Chapter 9.

van Dam, Robert Michael

114

Steady-state sinusoidal behavior of elastomeric dampers  

Science.gov (United States)

This paper presents an experimental and analytical investigation of an elastomeric damping material and assesses its potential application to stability augmentation of hingeless and bearingless helicopter rotors. Double lap shear specimens were tested on a servo-hydraulic testing machine. Single frequency sinusoidal tests were conducted over a strain amplitude range of 0 - 30% at three frequencies (lag/rev, 1/rev and a lower harmonic of the rotor). The frequencies were chosen such that the effect of the damper in mitigating instability phenomena, like ground and air resonance, could be analyzed. The effects of frequency, amplitude, pre-load and material self-heating were studied. A three-element mechanisms-based damper model was developed that accurately captures the energy dissipation and hysteresis behavior of the damper. The model incorporates a linear stiffness, viscous damping and a non-linear slip element that are placed in parallel to each other. The parameters of the model were identified using an LMS technique. The model was validated by reconstructing measured hysteresis cycles using these parameters.

Madhavan, Vijay; Wereley, Norman M.; Sieg, Thierry

1999-06-01

115

Magnetron sputtering of metallic coatings onto elastomeric substrates for a decrease in fuel permeation rate  

Science.gov (United States)

The purpose of this research was to investigate the application of a metallic coating by magnetron sputtering onto elastomeric substrates, as an inhibiting layer to permeation transport. The metallic coatings which were deposited were aluminum, titanium, and copper. The substrates used were NBR, FVMQ, and FKM elastomers. The permeating fluids were ASTM Fuel C, isooctane, and toluene. The magnetron sputtering properties of these metallic elements were unique to each material, with the titanium sputtering rate being very low. The sputtering rates of these materials correlated well with their sublimation temperature. It was found that some of the metallic particles which were sputtered onto the substrates, implanted into the surface of the elastomeric membranes, with the total amount and distance of implantation being related to the density of the substrate material. The permeation of these solvents through the composite materials was reduced by the presence of these coatings with the reduction in permeation rate ranging from 12 to 25% for Fuel C. The pervaporation properties of these substrates were also evaluated. It was found from this analysis that for the FVMQ and NBR substrates, the permeation rate of the permeating solute molecules was proportional to the size of the permeation molecule. The substrate materials were not significantly stiffened by the addition of the thin metallic coatings. The coated materials were cohesive and well adhered, as determined by stretching of the substrate materials with the metallic layer in place. Upon stretching, there was no evidence of damage to the metallic coating.

Myntti, Matthew F.

116

Nonthrombogenic, biodegradable elastomeric polyurethanes with variable sulfobetaine content.  

Science.gov (United States)

For applications where degradable polymers are likely to have extended blood contact, it is often important for these materials to exhibit high levels of thromboresistance. This can be achieved with surface modification approaches, but such modifications may be transient with degradation. Alternatively, polymer design can be altered such that the bulk polymer is thromboresistant and this is maintained with degradation. Toward this end a series of biodegradable, elastic polyurethanes (PESBUUs) containing different zwitterionic sulfobetaine (SB) content were synthesized from a polycaprolactone-diol (PCL-diol):SB-diol mixture (100:0, 75:25, 50:50, 25:75 and 0:100) reacted with diisocyanatobutane and chain extended with putrescine. The chemical structure, tensile mechanical properties, thermal properties, hydrophilicity, biodegradability, fibrinogen adsorption and thrombogenicity of the resulting polymers was characterized. With increased SB content some weakening in tensile properties occurred in wet conditions and enzymatic degradation also decreased. However, at higher zwitterionic molar ratios (50% and 75%) wet tensile strength exceeded 15 MPa and breaking strain was >500%. Markedly reduced thrombotic deposition was observed both before and after substantial degradation for both of these PESBUUs and they could be processed by electrospinning into a vascular conduit format with appropriate compliance properties. The mechanical and degradation properties as well as the acute in vitro thrombogenicity assessment suggest that these tunable polyurethanes could provide options appropriate for use in blood contacting applications where a degradable, elastomeric component with enduring thromboresistance is desired. PMID:25415875

Ye, Sang-Ho; Hong, Yi; Sakaguchi, Hirokazu; Shankarraman, Venkat; Luketich, Samuel K; D'Amore, Antonio; Wagner, William R

2014-12-24

117

Mechanical-property changes of structural composite materials after low-temperature proton irradiation: Implications for use in SSC magnet systems  

International Nuclear Information System (INIS)

Longterm physical, mechanical, electrical, and other properties of advanced composites, plastics, and other polymer materials are greatly affected by high-energy proton, neutron, electron, and gamma radiation. The effects of high-energy particles on materials is a critical design parameter to consider when choosing polymeric structural, nonstructural, and elastomeric matrix resin systems. Polymer materials used for filled resins, laminates, seals, gaskets, coatings, insulation and other nonmetallic components must be chosen carefully, and reference data viewed with caution. Most reference data collected in the high-energy physics community to date reflects material property degradation using other than proton irradiations. In most instances, the data were collected for room-temperature irradiations, not 4.2 K or other cryogenic temperatures, and at doses less than 108--109 Rad. Energetic proton (and the accompanying spallation-product particles) provide good simulation fidelity to the expected radiation fields predicted for the cold-mass regions of the SSC magnets, especially the corrector magnets. The authors present here results for some structural composite materials which were part of a larger irradiation-characterization of polymeric materials for SSC applications

118

Effect of storage period on the accuracy of elastomeric impressions  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english AIMS: To investigate the effect of the storage period on the accuracy of recently developed elastomeric materials. METHODS: Simultaneous impressions of a steel die were taken using a polyether (I: Impregum Soft Heavy and Light body, 3M ESPE) and vinyl polysiloxane (P: Perfectim Blue Velvet and Flexi [...] -Velvet, J.Morita). The trays were loaded with the heavy-bodied impression materials while the light-bodied impression materials were simultaneously spread on the steel die. The impressions were poured after 2 hours, 24 hours, and 7 days. Impressions were stored at approximately 55% relative humidity and room temperature. Ten replicas were produced for each experimental condition (n=60). Accuracy of the stone dies was assessed with a depth-measuring microscope. The difference in height between the surface of the stone die and a standard metallic ring was recorded in micrometers at four demarcated points, by two independent examiners. Data were submitted to two-way ANOVA and Tukey test (a = 0.05). RESULTS: Significant differences were found among the groups. Smaller discrepancies were observed when pouring was performed up to 24 hours (I-2h= 65.0 ± 15.68 µm; I-24h= 81.6 ± 11.13 µm) for the polyether, and up to 7 days for the vinyl polysiloxane (P-2h= 79.1 ± 13.82 µm; P-24h= 96.8 ± 6.02 µm; P-7d= 81.4 ± 4.3 µm). Significant dimensional discrepancies, however, were observed when polyether was stored for 7 days (I-7d= 295.3 ± 17.4 µm). CONCLUSION: Storage may significantly affect the dimensional accuracy of impressions and, thus, a maximum period and storage condition should be specified for the recently developed materials.

Eduardo Batista, Franco; Leonardo Fernandes da, Cunha; Ana Raquel, Benetti.

2007-06-01

119

Dimensional crossover and hidden incommensurability in Josephson junction arrays of periodically repeated Sierpinski gaskets  

CERN Document Server

We report a study of overdamped Josephson junction arrays with the geometry of periodically repeated Sierpinski gaskets. These model superconductors share essential geometrical features with truly random (percolative) systems. When exposed to a perpendicular magnetic field B, their euclidian or fractal behavior depends on the relation between the intervortex distance (imposed by B) and the size of a constituent gasket, and was explored with high-resolution measurements of the sample magnetoinductance L(B). In terms of the frustration parameter f expressing (in units of the superconducting flux quantum) the magnetic flux threading an elementary triangular cell of a gasket, the crossover between the two regimes occurs at f_{cN}=1/(2*4^{N}), where N is the gasket order. In the fractal regime (f>f_{cN}) a sequence of equally spaced structures corresponding to the set of states with unit cells not larger than a single gasket is observed at multiples of f_{cN}, as predicted by theory. The fine structure of L(f) rad...

Meyer, R; Leemann, C; Martinoli, P; Leemann, Ch.

2002-01-01

120

Magnetic resonance imaging evaluation of remodeling by cardiac elastomeric tissue scaffold biomaterials in a rat model of myocardial infarction.  

OpenAIRE

Grafting of elastomeric biomaterial scaffolds may offer a radical strategy for the prevention of heart failure after myocardial infarction by increasing efficacy of stem cell delivery as well as acting as mechanical restraint devices to constrain scar expansion. Biomaterials can be partially optimized in vitro, but their in vivo performance is most critical and should ideally be monitored serially and noninvasively. We used magnetic resonance imaging (MRI) to assess three scaffold materials w...

Stuckey, Dj; Ishii, H.; Chen, Qz; Boccaccini, Ar; Hansen, U.; Carr, Ca; Roether, Ja; Jawad, H.; Tyler, Dj; Ali, Nn; Clarke, K.; Harding, Se

2010-01-01

121

Reactions in elastomeric nanoreactors reveal the role of force on the kinetics of the Huisgen reaction on surfaces.  

Science.gov (United States)

The force dependence of the copper-free Huisgen cycloaddition between an alkyne and a surface-bound azide was examined in elastomeric nanoreactors. These studies revealed that pressure and chain length are critical factors that determine the reaction rate. These experiments demonstrate the central role of pressure and surface structure on interfacial processes that are increasingly important in biology, materials science, and nanotechnology. PMID:25028773

Han, Xu; Bian, Shudan; Liang, Yong; Houk, K N; Braunschweig, Adam B

2014-07-30

122

New elastomeric silicone based networks applicable as electroactive systems  

DEFF Research Database (Denmark)

Commercial elastomer materials are available for dielectric electroactive polymer (DEAP) purposes but the applied commercial elastomers have not been developed with the specific application in mind. It is therefore obvious that optimization of the elastomer material should be possible. In this study we focus on optimization of the mechanical properties of the elastomer and show that it is possible to lower the elastic modulus and still not compromise the other required mechanical properties such as fast response, stability, low degree of viscous dissipation and high extensibility. The elastomers are prepared from a vinyl-terminated polydimethyl siloxane (PDMS) and a 4-functional crosslinker by a platinum-catalyzed hydrosilylation reaction between the two reactants. Traditionally, elastomers based on hydrosilylation are prepared via a ‘one-step two-pot’ procedure (with a mix A and a mix B mixed in a given ratio). An alternative network formulation method is adopted in this study in order to obtain an elastomeric system with controlled topology – a so-called bimodal network. Bimodal networks are synthesized using a ‘two-step four-pot’ mixing procedure which results in a nonhomogeneous network structure which is shown to lead to novel mechanical properties due to the low extensibility of the short chains and the high extensibility of the long chains. The first ensures stability and the last retards the rupture process thereby combining two desired properties for DEAP purposes without necessarily compromising the viscous dissipation. Several elastomers are prepared and tested for the linear viscoelastic behaviour, i.e. behaviour in the small-strain limit (up to approximately 10% strain). The bimodal networks are, however, capable of extensions up to several times their initial length but the focus here is the small-strain limit.

Bejenariu, Anca Gabriela; Boll, Mads

2011-01-01

123

Thin graphite bipolar plate with associated gaskets and carbon cloth flow-field for use in an ionomer membrane fuel cell  

Science.gov (United States)

The present invention comprises a thin graphite plate with associated gaskets and pieces of carbon cloth that comprise a flow-field. The plate, gaskets and flow-field comprise a "plate and gasket assembly" for use in an ionomer membrane fuel cell, fuel cell stack or battery.

Marchetti, George A. (Western Springs, IL)

2003-01-03

124

EFFICIENCY OF VIBRATION-DAMPING GASKETS WITH DRY FRICTION FOR REDUCTION NOISE OF CIRCULAR WOODWORKING MACHINES ????????????? ????????????????? ????????? ? ????? ??????? ??? ???????? ???? ?? ????????????? ???????????????????? ???????  

Directory of Open Access Journals (Sweden)

Full Text Available Reasonable new design for reduction noise for saw disks of woodworking machines, in which gaskets with the dry friction, placed under clamping flange are used, is shown. Experimentally received results, characterizing dissipative and acoustic properties of this design

Osmolovsky D. S.

2011-06-01

125

Assessment of airborne asbestos exposure during the servicing and handling of automobile asbestos-containing gaskets.  

Science.gov (United States)

Five test sessions were conducted to assess asbestos exposure during the removal or installation of asbestos-containing gaskets on vehicles. All testing took place within an operative automotive repair facility involving passenger cars and a pickup truck ranging in vintage from late 1960s through 1970s. A professional mechanic performed all shop work including engine disassembly and reassembly, gasket manipulation and parts cleaning. Bulk sample analysis of removed gaskets through polarized light microscopy (PLM) revealed asbestos fiber concentrations ranging between 0 and 75%. Personal and area air samples were collected and analyzed using National Institute of Occupational Safety Health (NIOSH) methods 7400 [phase contrast microscopy (PCM)] and 7402 [transmission electron microscopy (TEM)]. Among all air samples collected, approximately 21% (n = 11) contained chrysotile fibers. The mean PCM and phase contrast microscopy equivalent (PCME) 8-h time weighted average (TWA) concentrations for these samples were 0.0031 fibers/cubic centimeters (f/cc) and 0.0017 f/cc, respectively. Based on these findings, automobile mechanics who worked with asbestos-containing gaskets may have been exposed to concentrations of airborne asbestos concentrations approximately 100 times lower than the current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 0.1 f/cc. PMID:16730109

Blake, Charles L; Dotson, G Scott; Harbison, Raymond D

2006-07-01

126

Thermal stress analysis of pipe flange connections with gaskets subjected to heat conduction  

International Nuclear Information System (INIS)

This paper deals with thermal stress analysis of a pipe flange connection with a full-face gasket subjected to heat conduction. In the analysis, pipe flange, hubs of the flanges and a gasket are replaced by finite hollow cylinders. When the inner surface is subjected to heat conduction due to contained fluid and the outer surfaces are held at a constant temperature, temperature distribution of the connection is analyzed. Using the temperature distribution, thermoelastic displacement potential is determined. Thermal stresses and displacements are analyzed by using the thermoelastic displacement potential and axisymmetrical theory of elasticity. In the numerical calculations, the effects of the ratio of Young's moduli and linear thermal expansion coefficients between pipe flanges and gasket on the contact stress distribution are examined. As the results, it is seen that the thermal stress at the inner surface increases with a decrease of the ratio of Young's modulus and that it increases with a decrease of the gasket thickness. In addition, it is found that the thermal stress is substantial at the corner of hubs. (author)

127

Long-term Confinement Test using Two Full-Scale Lid Models of Cask with Metal Gaskets for Interim Storage  

International Nuclear Information System (INIS)

The typical containment system of the lid of the metal cask consists of primary and secondary parts. The containment function is secured by inserting gaskets between the cask body and the lids, and then bolting them together. Metal gaskets are used for long-term durability. Therefore, it is very important to clarify the influence of the stress relaxation of the gaskets on the containment performance of the metallic gaskets for a long-term usage. Two kinds of cask lid structure models are being tasted for more than 17 years. In the I-type model, the cask body and lid are made of forged carbon steel. The sealing surface is overlaid with stainless steel welding, and a double metal gasket (enveloped with aluminum) is installed. In the other type model, the cask body is made of ductile cast iron, and the lid is made of stainless steel. The sealing surface of the body is plated with nickel. In this model, an inner metal gasket (enveloped with silver), and an outer rubber gasket (silicone rubber) were installed. In both models, the test temperature was maintained with the electrical heats installed in the cask cavities. Containment of the secondary lid has been tested using a helium leak detector about twice a month. The very reliable containment performance has been demonstrated. Moreover, by applying the Larson-Miller Parameter, the results indicate the containment performance taking account of the decay heat of the spent nuclear fuel. (authors)uel. (authors)

128

Development of Remote Hanford Connector Gasket Replacement Tooling for the Savannah River Site's Defense Waste Processing Facility  

International Nuclear Information System (INIS)

The Savannah River Site's (SRS) Defense Waste Processing Facility (DWPF) requested development of tooling and equipment to remotely replace gaskets in mechanical Hanford connectors to reduce personnel radiation exposure as compared to the current hands-on method. It is also expected that radiation levels will continually increase As future higher activity waste streams are treated. The facility is well equipped with compressed air, two master-slave manipulators (MSM's) and an electro-mechanical manipulator (EMM) arm for operation of the remote tools in the work cell proposed for remotely changing the gaskets. In order to perform all of the tasks required to remotely replace Hanford connector gaskets several operations must be performed remotely, including removal of the spent gasket and retaining ring, loading the new retaining ring and gasket into the installation tool and installation of the new gasket into the Hanford connector. The Savannah River National Laboratory, SRNL developed and tested multiple tools to perform all of the necessary tasks. Removal of retaining rings from horizontal and vertical connectors is performed by separate air actuated retaining ring removal tools and is manipulated in the cell by the MSM. A new retaining ring is then placed on a platform, rotated under the conical loading tool and raised and compressed into the gasket installation tool by two linear slides actuated by air cylinders. The gasket installation tool is then pressed against installation tool is then pressed against the gasket sealing surface of the Hanford connector using an MSM. Actuation of a custom air cylinder overcomes the force of several different springs to align and fix the installation tool relative to the Hanford connector and seats the retaining ring and gasket. All of the tools are located on a custom work table with a pneumatic valve station that directs compressed air to the desired tool and vents the tools as needed. On July 17 and 29, 2008 the Remote Gasket Replacement Tooling was successfully demonstrated in the Remote Equipment Decontamination Cell, REDC at the DWPF of The Savannah River Site. (authors)

129

Combined Technologies for Microfabricating Elastomeric Cardiac Tissue Engineering Scaffolds  

OpenAIRE

Polymer scaffolds that direct elongation and orientation of cultured cells can enable tissue engineered muscle to act as a mechanically functional unit. We combined micromolding and microablation technologies to create muscle tissue engineering scaffolds from the biodegradable elastomer poly(glycerol sebacate). These scaffolds exhibited well defined surface patterns and pores and robust elastomeric tensile mechanical properties. Cultured C2C12 muscle cells penetrated the pores to form spatial...

Guillemette, Maxime D.; Park, Hyoungshin; Hsiao, James C.; Jain, Saloni R.; Larson, Benjamin L.; Langer, Robert; Freed, Lisa E.

2010-01-01

130

Microintegrating smooth muscle cells into a biodegradable, elastomeric fiber matrix  

OpenAIRE

Electrospinning permits fabrication of biodegradable elastomers into matrices that can resemble the scale and mechanical behavior of the native extracellular matrix. However, achieving high-cellular density and infiltration with this technique remains challenging and time consuming. We have overcome this limitation by electrospraying vascular smooth muscle cells (SMCs) concurrently with electrospinning a biodegradable, elastomeric poly(ester urethane)urea (PEUU). Trypan blue staining revealed...

Stankus, John J.; Guan, Jianjun; Fujimoto, Kazuro; Wagner, William R.

2005-01-01

131

Fabrication of aligned microstructures with a single elastomeric stamp  

OpenAIRE

The fabrication of complex patterns of aligned microstructures has required the use of multiple applications of lithography. Here we describe an approach for microfabrication that encodes the two-dimensional spatial information of several photomasks onto a single elastomeric stamp by mapping each photomask onto distinct heights on the surface of the stamp. Pressing the stamp against a surface collapses the topography of the stamp such that each recessed layer contacts the surface in stepwise ...

Tien, Joe; Nelson, Celeste M.; Chen, Christopher S.

2002-01-01

132

Pigment effect on the long term elasticity of elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english OBJECTIVE: To evaluate the response of elastomeric ligatures in several colors for a 4 mm traction over time. METHODS: Morelli® elastomeric ligatures, were submitted to traction forces using two rods of circular cross section, until a 4 mm distance was reached, matching the approximate diameter of a [...] n upper central incisor bracket of the same manufacturer. The ligatures were kept in artificial saliva immersion at 37 ºC. Forces levels were measured immediately (0 h), 2, 4, 6, 8, 10, 12, 24, 48, 72, 96 hours, 1, 2, 3, 4 weeks and results were submitted to two-way repeated-measures ANOVA statistical analysis. RESULTS: The gray samples showed the higher initial values of tensile strength. The lowest values were presented by purple, light pink, green, black and red groups. The greater tensile strength instability was presented by red, black, silver, green and gray groups. The greater tensile strength stability was presented by deep pink, dark blue, blue, purple and light pink groups. CONCLUSION: Elastomeric ligatures do not present stable behavior when suffering traction forces over time and different colors display different behaviors. Deep pink, dark blue, blue, purple and light pink groups, displayed the most stable forces, suggesting that they should be used during the treatment to obtain constant forces.

Érika de Oliveira Dias de, Macêdo; Fabrício Mezzomo, Collares; Vicente Castelo Branco, Leitune; Susana Maria Werner, Samuel; Carmen Beatriz Borges, Fortes.

2012-06-01

133

Citotoxicity of nonlatex elastomeric ligatures of orthodontic use  

Scientific Electronic Library Online (English)

Full Text Available The aim of this study is to evaluate cytotoxicity between polyurethane and non-latex orthodontic elastomeric ligatures. Seven elastomeric ligatures of black-coloured from different manufactures (3 non-latex, 3 polyurethane and 1 latex) were divided into 7 groups of 10 elastics each: Group UK (nonlat [...] ex, 3M Unitek), Group TP (nonlatex, TP Orthodontics), Group AO (nonlatex, American Orthodontics), Group O (Polyurethane, OrthoSource), Group M (Polyurethane, Morelli), Group TD (Polyurethane, Tecnident) and Group TC (latex - Control, TP Orthodontics). The cytotoxicity essay was performed using cell cultures (L-929 line cells, mouse fibroblast) that were submitted to the cell viability test with neutral red ("dye-uptake") at 1, 2, 3, 7 and 28 days. Analysis of variance (ANOVA) with 1-way analysis followed by the Tukey post hoc test were employed (p.05). There was a statistically differences (p.05) between the groups O, M and TD at in all experimental times. It can be concluded that the nonlatex elastomeric ligatures of Unitek, TP Orthodontics, and American Orthodontics showed higher cell viability compared to others ligatures.

Rogério, Lacerda-Santos; Alane Sonally Benício do, Nascimento; Allana Roberta Bandeira, Pereira; Paulyana Pryscilla de Melo, Freire; Matheus Melo, Pithon; Maria Teresa Villela, Romanos.

2015-03-01

134

Response of elastomeric packaging components to a corrosive simulant mixed waste  

Energy Technology Data Exchange (ETDEWEB)

The purpose of hazardous and radioactive materials packaging is to enable these materials to be transported without posing a threat to the health or property of the general public. To achieve this aim, regulations in the US have been written establishing general design requirements for such packagings. While no regulations have been written specifically for mixed waste packaging, regulations for the constituents of mixed wastes, i.e., hazardous and radioactive substances, have been codified by the US Department of Transportation and the US Nuclear Regulatory Commission. Based on these national requirements, a Chemical Compatibility Testing Program was developed in the Transportation Systems Department at SNL. In this paper, the authors present the results of Part B of the second phase of this testing program. The first phase screened five liner materials and six seal materials towards four simulant mixed wastes. Part A of the second phase involved the comprehensive testing of five candidate liner materials to an aqueous Hanford Tank simulant mixed waste. Part B involved similar testing on elastomeric materials, ethylene-propylene and butadiene-acrylonitrile rubber. The comprehensive testing protocol involved exposing the respective materials to a matrix of four gamma radiation doses ({approximately}1, 3, 6, and 40 kGy), three temperatures (18, 50, and 60 C), and four exposure times (7, 14, 28, and 180 days). Following their exposure to these combinations of conditions, the materials were evaluated by measuring six material properties. These properties were specific gravity, dimensional changes, hardness, vapor transport rates, compression set, and mechanical properties.

Nigrey, P.J.; Dickens, T.G.

1997-10-01

135

Response of elastomeric packaging components to a corrosive simulant mixed waste  

International Nuclear Information System (INIS)

The purpose of hazardous and radioactive materials packaging is to enable these materials to be transported without posing a threat to the health or property of the general public. To achieve this aim, regulations in the US have been written establishing general design requirements for such packagings. While no regulations have been written specifically for mixed waste packaging, regulations for the constituents of mixed wastes, i.e., hazardous and radioactive substances, have been codified by the US Department of Transportation and the US Nuclear Regulatory Commission. Based on these national requirements, a Chemical Compatibility Testing Program was developed in the Transportation Systems Department at SNL. In this paper, the authors present the results of Part B of the second phase of this testing program. The first phase screened five liner materials and six seal materials towards four simulant mixed wastes. Part A of the second phase involved the comprehensive testing of five candidate liner materials to an aqueous Hanford Tank simulant mixed waste. Part B involved similar testing on elastomeric materials, ethylene-propylene and butadiene-acrylonitrile rubber. The comprehensive testing protocol involved exposing the respective materials to a matrix of four gamma radiation doses (?1, 3, 6, and 40 kGy), three temperatures (18, 50, and 60 C), and four exposure times (7, 14, 28, and 180 days). Following their exposure to these combinations of conditions, the materials were evaluated by measuring six material properties. These properties were specific gravity, dimensional changes, hardness, vapor transport rates, compression set, and mechanical properties

136

Practical identification of non-linear characteristics of elastomeric couplings in engine assemblies  

Science.gov (United States)

In many engineering applications, the connection between a combustion engine and the load is often done using elastomeric materials. However, these couplings far from behaving in a linear way, show a complex behavior that sometimes is difficult to evaluate. In this sense, with the present work it is intended to develop an easy methodology to identify the coupling characteristics to validate dynamic models of engine assemblies with this kind of connections, as well as to identify possible malfunction or damage behavior in a future. The method is based on static and dynamic tests, non-linear models and techniques for parameter identification. The process has been applied using two different couplings, mounted on a single-cylinder diesel engine (DE) and a three-cylinder spark ignition engine (SIE). Results demonstrate the validity of the method for any kind of engine (DE or SIE) and number of cylinders.

Cruz-Peragón, F.; Palomar, J. M.; Díaz, F. A.; Jiménez-Espadafor, F. J.

2009-04-01

137

Seismic response analysis of base isolated structures with high damping elastomeric bearings  

International Nuclear Information System (INIS)

Seismic response analysis of base-isolated structures with high damping elastomeric bearings is described in this paper. Emphasis is placed on the adaptation of a nonlinear constitutive model for the isolation bearing together with the treatment of foundation embedment for the soil-structure-interaction analysis. The constitutive model requires six input parameters derived from bearing experimental data under sinusoidal loading. The characteristic behavior of bearing, such as the variation of shear modulus and material damping with the change of maximum shear deformation, can be captured closely by the formulation. In the treatment of soil embedment a spring method is utilized to evaluate the foundation input motion as well as soil stiffness and damping. The above features have been incorporated into a three-dimensional system response program, SISEC, developed at Argonne National Laboratory. Sample problems are presented to illustrate the relative response of isolated and unisolated structures

138

Optimization of fractional composition of the excipient in the elastomeric covering for asphalt highways  

Directory of Open Access Journals (Sweden)

Full Text Available The computational method of optimum fractional composition of a dispersible filler of polymeric composite on the basis of three-dimensionally linked elastomer is developed according to non-linear programming. The coefficient of dynamic viscosity of polymeric suspension or the initial module of a viscoelasticity of the join solidification low-molecular rubbers with the final functional groups, filled by many fractional dioxide of silicon are considered as criteria of optimization. Influence of the limiting volume filling on energy of mechanical destruction was investigated. The elastomeric material is offered for use as a covering of asphalt highways in the form of a frost-proof waterproofing layer, which allowing multiply to increase operating properties.

E. M. Nurullaev

2013-04-01

139

The flow rate of the elastomeric balloon infusor is influenced by the internal pressure of the infusor.  

OpenAIRE

The purpose of this study was to evaluate the flow rate of elastomeric balloon infusor composed of rubber or silicone materials. Two models were studied: the Baxter Twoday Infusor and Advance Silicone Infusor. Each infusion device has a preset flow rate of 2 mL/hr. Fifteen units of each device were filled with 100 mL of normal saline. The flow rate was measured gravimetically using an electronic balance. The internal pressure of the balloon infusor was measured with a Digital pressure meter v...

Chung, I. S.; Cho, H. S.; Kim, J. A.; Lee, K. H.

2001-01-01

140

In vitro study of cytotoxicity of orthodontic elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english This study investigated the cytotoxicity of crystal-coloured orthodontic elastomeric ligatures of polyurethane. Six ligatures from distinct manufactures were divided into 6 groups of 10 elastics each: Groups P1, P2, P3, P4, P5 and P6 (Polyurethane). The cytotoxicity essay was performed using L-929 l [...] ine cells, which were submitted to the cell viability test with neutral red ("dye-uptake") at time intervals of 1, 2, 3, 7 and 28 days. Analysis of variance (ANOVA) with multiple comparisons and Tukey's test were used (p

Rogério Lacerda dos, Santos; Matheus Melo, Pithon; Paulyana Pryscilla de Melo, Freire; Maria Teresa Villela, Romanos.

2012-08-01

141

Increasing the durability of elastomeric compositions by introducing carbon nanomaterials  

International Nuclear Information System (INIS)

For the first time the effect of carbon nanomaterial (CNM) obtained in high-voltage discharge plasma on the durability of elastomeric compositions is investigated. The data on the durability go with the results obtained while determining kinetic parameters of curing, tensile strength, elongation at break, resistance to thermal aging and swelling in liquid hydrocarbon highly filled rubbers based on butadiene-nitrile rubbers. To confirm the proposed mechanism of action of nanomaterials, by the method of equilibrium swelling the parameters of vulcanization network of the samples are determined. It is shown that the introduction of CNM allows increasing the performance characteristics and the durability of rubber-based polar rubber. (authors)

142

Elastomeric gradients: a hedge against stress concentration in marine holdfasts?  

OpenAIRE

The byssal threads of marine mussels are elastomeric fibres with a great capacity for absorbing and dissipating energy. Up to 70% of the total absorbed energy can be dissipated in the byssus. Because byssal threads attach the mussel to hard inert surfaces in its habitat, they must combine the need to be good shock absorbers with appropriate matching of Young's modulus between living tissue and a hard sub-stratum such as stone - stiffnesses that can differ by five orders of magnitude. Recent d...

Waite, J. Herbert; Vaccaro, Eleonora; Sun, Chengjun; Lucas, Jared M.

2002-01-01

143

A New Modified Sloted Sierpinksi Gasket Fractal Microstrip Antenna for WLAN and RFID Applications  

Directory of Open Access Journals (Sweden)

Full Text Available A sierpinkski gasket fractal antenna for WLAN ,RFID ISM band applications proposed ,designed and simulated .The proposed modified sierpinksi slotted fractal patch designed in order to achieve radiation characteristics. The simulated antenna has a total dimensions of 25*25 ,simulated results of an antenna is -18 dB return loss for 2.4 GHz to 2.256 GHz with 56% .This frequency bands cover the IEEE 802.11 (WALAN and RFID ISM bands ,the simulated return loss ,radiation ,patterns and directivity ,gain of the antenna are presented.

P.PRABHU

2013-04-01

144

A New Modified Sloted Sierpinksi Gasket Fractal Microstrip Antenna for WLAN and RFID Applications  

OpenAIRE

A sierpinkski gasket fractal antenna for WLAN ,RFID ISM band applications proposed ,designed and simulated .The proposed modified sierpinksi slotted fractal patch designed in order to achieve radiation characteristics. The simulated antenna has a total dimensions of 25*25 ,simulated results of an antenna is -18 dB return loss for 2.4 GHz to 2.256 GHz with 56% .This frequency bands cover the IEEE 802.11 (WALAN) and RFID ISM bands ,the simulated return loss ,radiation ,patterns and directivity ...

Prabhu, P.; Ranjith Kumar, R.; Yogapriya, S.; Rajalakshmi, R.; Ahamedu Nisha, N.

2013-01-01

145

The Diameter of a Long-Range Percolation Cluster on Pre-Sierpinski Gasket  

Science.gov (United States)

We give several bounds for a graph diameter of a random graph created by a stochastic model called the long-range percolation, in which any pair of two distinct points is connected by a random bond independently. Such a problem is well studied on a finite subset of the -dimensional square lattice, where is a positive integer. In this manuscript, we consider the problem on a finite subset of a fractal lattice which is called the pre-Sierpinski gasket. We can observe that the Hausdorff dimension of the fractal lattice appears in the critical parameters of , where is a value determining the order of probabilities that random bonds exist.

Misumi, Jun

2015-03-01

146

A discrete model on Sierpinski gasket substrate for a conserved current equation with a conservative noise  

International Nuclear Information System (INIS)

A conserved discrete model on the Sierpinski gasket substrate is studied. The interface width W in the model follows the Family–Vicsek dynamic scaling form with growth exponent ? ? 0.0542, roughness exponent ? ? 0.240 and dynamic exponent z ? 4.42. They satisfy a scaling relation ? + z = 2zrw, where zrw is the random walk exponent of the fractal substrate. Also, they are in a good agreement with the predicted values of a fractional Langevin equation where ?c is a conservative noise. (paper)

147

Permeation through elastomeric O-ring seals  

International Nuclear Information System (INIS)

Permeation of He, Ne, Ar, Kr, Xe and D2 through O-ring seals of fluorocarbon rubber (e.g. Viton), ethylene-propylene rubber (EPDM) and silicone rubber (VMQ) has been measured at temperatures from 290 K up to the destruction of the materials, at about 600 to 700 K. Test gas pressures ?p up to 2 bar were applied. The quantity of the test gas that permeated was detected using high sensitivity quadrupole mass spectrometry. To investigate the influence of seal geometry, permeation through VMQ O-rings was measured as a function of their compression and compared with measurements of sheet geometry for the same material. The measured time dependence of the permeation gas flow is well described by theoretical predictions, when the flow through the O-ring is considered as the sum of flows through a number of rectangular slabs approximating the shape of the compressed O-ring. Equilibrium gas flow, the permeation coefficient, solubility, the diffusion coefficient, the activation energy of diffusion and the heat of solution are derived from the measurements and are compared with values given in the literature, where available. By extrapolating the results for rare gases He to Xe, permeation parameters for Rn are estimated for the three elastomers under investigation. (author)

148

DEVELOPMENT OF REMOTE HANFORD CONNECTOR GASKET REPLACEMENT TOOLING FOR THE SAVANNAH RIVER SITE'S DEFENSE WASTE PROCESSING FACILITY  

International Nuclear Information System (INIS)

The Savannah River Site's (SRS) Defense Waste Processing Facility (DWPF) requested development of tooling for remote replacement of gaskets in mechanical Hanford connectors. The facility has compressed air supply, two master-slave manipulators (MSM's) and a lightweight robotic arm for operation of the remote tools. The Savannah River National Laboratory (SRNL) developed and tested multiple tools to perform the gasket replacement tasks. Separate pneumatic snap-ring removal tools that use the connector skirt as a reaction surface were developed for removal of the snap ring and spent gasket on both vertical and horizontal Hanford connectors. A pneumatic tool that clamps and centers on the jumper pipe ID was developed to simultaneously install the new gasket and snap ring. A pneumatic snap-ring-loading tool was developed that compresses the snap ring and places it in a groove in the installation tool. All of the tools are located on a custom work table with a pneumatic valve station that directs compressed air to the desired tool and vents the tools as needed. The entire system has been successfully tested using MSM's to manipulate the various tools. Deployment of the entire system is expected during FY08. The Hanford connector gasket replacement tooling has been successfully tested using MSM's to manipulate the various tools. Nitric acid is used in many of the decontamination processes performed in the REDC, where the tooling will be deployed. Although most of the tool cl be deployed. Although most of the tool components were fabricated/purchased with nitric acid and radioactive service in mind, some of the prototype parts must be replaced with parts that are more compatible with nitric acid/radioactive service. Several modifications to the various tools are needed to facilitate maintenance and replacement of failed components. Development of installation tools for replacement of 1-inch, 2-inch and multi-hole gaskets is being considered. Deployment of the existing system in the DWPF REDC is expected during FY08

149

Fabrication of sub-20 nm nano-gap structures through the elastomeric nano-stamp assisted secondary sputtering phenomenon  

Science.gov (United States)

We describe a highly efficient method for fabricating controllable and reliable sub-20 nm scale nano-gap structures through an elastomeric nano-stamp with an embedded ultra-thin pattern. The stamp consists of ultrahigh resolution (approximately 10 nm) and high aspect ratio (ca. 15) metal nano-structures, which are obtained by secondary sputtering lithography (SSL). The nano-gap structures fabricated in this fashion achieve a high resolution and meet the requirements of minimal cost, high reliability, controllability, reproducibility, and applicability to different materials. Further, we demonstrate that this method enables the fabrication of SERS substrates for detection at the single-molecule level.We describe a highly efficient method for fabricating controllable and reliable sub-20 nm scale nano-gap structures through an elastomeric nano-stamp with an embedded ultra-thin pattern. The stamp consists of ultrahigh resolution (approximately 10 nm) and high aspect ratio (ca. 15) metal nano-structures, which are obtained by secondary sputtering lithography (SSL). The nano-gap structures fabricated in this fashion achieve a high resolution and meet the requirements of minimal cost, high reliability, controllability, reproducibility, and applicability to different materials. Further, we demonstrate that this method enables the fabrication of SERS substrates for detection at the single-molecule level. Electronic supplementary information (ESI) available: Descriptions of experimental scheme for fabrication of hole-cylinder pattern. See DOI: 10.1039/c3nr06346a

Jeon, Hwan-Jin; Lee, Eun Hyung; Yoo, Hae-Wook; Kim, Kyoung Hwan; Jung, Hee-Tae

2014-05-01

150

Mitigation of hypertrophic scar contraction via an elastomeric biodegradable scaffold.  

Science.gov (United States)

Hypertrophic scar (HSc) occurs in 40-70% of patients treated for third degree burn injuries. Current burn therapies rely upon the use of bioengineered skin equivalents (BSEs), which assist in wound healing but do not prevent HSc contraction. HSc contraction leads to formation of a fixed, inelastic skin deformity. We propose that BSEs should maintain their architecture in the wound bed throughout the remodeling phase of repair to prevent HSc contraction. In this work we study a degradable, elastomeric, randomly oriented, electrospun micro-fibrous scaffold fabricated from the copolymer poly(l-lactide-co-?-caprolactone) (PLCL). PLCL scaffolds displayed appropriate elastomeric and tensile characteristics for implantation beneath a human skin graft. In vitro analysis using human dermal fibroblasts demonstrated that PLCL scaffolds decreased myofibroblast formation as compared to an in vitro HSc contraction model. Using a validated immune-competent murine HSc contraction model, we found that HSc contraction was significantly greater in animals treated with standard of care, Integra, as compared to those treated with collagen coated-PLCL (ccPLCL) scaffolds. Finally, wounds treated with ccPLCL were significantly less stiff than control wounds at d30 in vivo. Together, these data suggest that scaffolds which persist throughout the remodeling phase of repair may represent a clinically translatable method to prevent HSc contraction. PMID:25591962

Lorden, Elizabeth R; Miller, Kyle J; Bashirov, Latif; Ibrahim, Mohamed M; Hammett, Ellen; Jung, Youngmee; Medina, Manuel A; Rastegarpour, Ali; Selim, Maria A; Leong, Kam W; Levinson, Howard

2015-03-01

151

In vitro study of cytotoxicity of orthodontic elastomeric ligatures  

Directory of Open Access Journals (Sweden)

Full Text Available This study investigated the cytotoxicity of crystal-coloured orthodontic elastomeric ligatures of polyurethane. Six ligatures from distinct manufactures were divided into 6 groups of 10 elastics each: Groups P1, P2, P3, P4, P5 and P6 (Polyurethane. The cytotoxicity essay was performed using L-929 line cells, which were submitted to the cell viability test with neutral red ("dye-uptake" at time intervals of 1, 2, 3, 7 and 28 days. Analysis of variance (ANOVA with multiple comparisons and Tukey's test were used (p < .05. There were statistical differences (p < .05 in cell viability between Groups P1, P4, P2 and P3, and Groups P5 and P6 at 1 and 2 days. All elastomeric ligatures were considered suitable for clinical use. The hypothesis was accepted, the P5 and P6 elastomers and the processing route of injection molding for these ligatures showed the lowest cell viability, due the temperature and pressure distinct in the processing of these elastomers.

Rogério Lacerda dos Santos

2012-08-01

152

Elastically stretchable thin film conductors on an elastomeric substrate  

Science.gov (United States)

Imagine a large, flat screen television that can be rolled into a small cylinder after purchase in the store and then unrolled and mounted onto the wall of a home. The electronic devices within the television must be able to withstand large deformation and tensile strain. Consider a robot that is covered with an electronic skin that simulates human skin. The skin would enable the machine to lift an elderly person with care and sensitivity. The skin will endure repeated deformation with the highest tensile strains being experienced at the robot's joints. These applications and many others will benefit from stretchable electronic circuitry. While several different methods have been employed to create stretchable electronics, all methods use a common tool -- stretchable conductors. Therefore, the goal of this thesis work was to fabricate elastically stretchable conductors that can be used in stretchable electronics. We deposited Au thin films on an elastomeric substrate, and the resulting conductors remained electrically continuous when stretched by 30% and more. We developed photolithographic processes that can be used to pattern elastically stretchable conductors with a 10 mum resolution. We fabricated bi-level stretchable conductors that are separated by an elastomeric insulator and are electrically connected through via holes in the insulator. We applied our bi-level conductors to create a stretchable resistor-inductor-capacitor (RLC) circuit with a tunable resonant frequency. We also used stretchable conductors to measure action potentials in biological samples. This thesis describes the fabrication and application of our elastically stretchable conductors.

Jones Harris, Joyelle Elizabeth

153

Development of improved gaskets, sealants and cables for use in geothermal well logging equipment. Final summary report  

Energy Technology Data Exchange (ETDEWEB)

The inventigation of materials which could be used for fabricating elastomeric seals for geothermal well logging equipment is described. The seals were to be made either from a methylphenylcarborane-siloxane base gum stock, or from new fluoroelastomer compounds synthesized at Hughes Aircraft Company. A literature search was made to obtain data on carborane-siloxane polymers, synthesis routes for fluorinated elastomers and high temperature hydrolytic stability tests of elastomers. Information was obtained on the first two topics, but very little was available on hydrolysis testing. A number of compounds, based on carborane-siloxane, were formulated and cured. Compression set, hardness and shrinkage tests with postcure variations were made on the most promising formulations. A simple hydrolytic stability test at 275/sup 0/C (525/sup 0/F) and 830 psi was developed which indicated that both the carborane and siloxane bonds were easily broken after short exposure periods. Thermodynamic calculatons indicated that this result could be expected. Because of the agreement between empirical and theoretical data, work on the carborane-siloxanes was discontinued after approximately the first year. Synthesis efforts to produce a highly fluorinated elastomer based on perfluorolkylene oxide were continued through the entrie program. None of these routes produced a satisfactory elastomer.

Schwartz, S.; Basiulis, D.; Leyden, R.; Landis, A.

1978-10-01

154

Avaliação das tensões liberadas por elásticos ortodônticos em cadeia: estudo in vitro / Assessment of force decay in orthodontic elastomeric chains: an in vitro study  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Languages: English, Portuguese Abstract in portuguese INTRODUÇÃO: os materiais elastoméricos são considerados importantes fontes de força para a movimentação ortodôntica. OBJETIVO: avaliar a liberação de tensões de quatro marcas comerciais de elásticos ortodônticos em cadeia (Morelli, Ormco, TP e Unitek), em função do tempo, quando mantidas tensionadas [...] por uma força inicial de 150g e imersas em saliva artificial a 37ºC. MÉTODOS: os elásticos em cadeia foram tensionados entre pinos de aço, fixados em uma placa de resina acrílica à distância de 15mm (Morelli e TP) e de 16mm (Unitek e Ormco), ambas medidas correspondendo a uma força de 150g. A leitura da quantidade de tensão liberada pelos elásticos foi realizada com um dinamômetro nos intervalos 30 minutos, 7, 14 e 21 dias. Os dados obtidos foram submetidos à análise de variância (ANOVA) (p Abstract in english INTRODUCTION: Elastomeric materials are considered important sources of orthodontic forces. OBJECTIVE: To assess force degradation over time of four commercially available orthodontic elastomeric chains (Morelli, Ormco, TP and Unitek). METHODS: The synthetic elastics were submerged in 37 ºC syntheti [...] c saliva and stretched by a force of 150 g (15 mm - Morelli and TP; 16mm - Unitek and Ormco). With a dynamometer, the delivered force was evaluated at different intervals: 30 minutes, 7 days, 14 days and 21 days. The results were subjected to ANOVA and Tukey's test. RESULTS: There was a force decay between 19% to 26.67% after 30 minutes, and 36.67% to 57% after 21 days of activation. CONCLUSIONS: TP elastomeric chains exhibited the smallest percentage of force decay, with greater stability at all time intervals tested. Meanwhile, the Unitek chains displayed the highest percentage of force degradation, and no statically significant difference was found in force decay between Ormco and Morelli elastomeric chains during the study period.

Claudia, Kochenborger; Dayanne Lopes da, Silva; Ernani Menezes, Marchioro; Diogo Antunes, Vargas; Luciane, Hahn.

2011-12-01

155

Avaliação das tensões liberadas por elásticos ortodônticos em cadeia: estudo in vitro Assessment of force decay in orthodontic elastomeric chains: an in vitro study  

Directory of Open Access Journals (Sweden)

Full Text Available INTRODUÇÃO: os materiais elastoméricos são considerados importantes fontes de força para a movimentação ortodôntica. OBJETIVO: avaliar a liberação de tensões de quatro marcas comerciais de elásticos ortodônticos em cadeia (Morelli, Ormco, TP e Unitek, em função do tempo, quando mantidas tensionadas por uma força inicial de 150g e imersas em saliva artificial a 37ºC. MÉTODOS: os elásticos em cadeia foram tensionados entre pinos de aço, fixados em uma placa de resina acrílica à distância de 15mm (Morelli e TP e de 16mm (Unitek e Ormco, ambas medidas correspondendo a uma força de 150g. A leitura da quantidade de tensão liberada pelos elásticos foi realizada com um dinamômetro nos intervalos 30 minutos, 7, 14 e 21 dias. Os dados obtidos foram submetidos à análise de variância (ANOVA (pINTRODUCTION: Elastomeric materials are considered important sources of orthodontic forces. OBJECTIVE: To assess force degradation over time of four commercially available orthodontic elastomeric chains (Morelli, Ormco, TP and Unitek. METHODS: The synthetic elastics were submerged in 37 ºC synthetic saliva and stretched by a force of 150 g (15 mm - Morelli and TP; 16mm - Unitek and Ormco. With a dynamometer, the delivered force was evaluated at different intervals: 30 minutes, 7 days, 14 days and 21 days. The results were subjected to ANOVA and Tukey's test. RESULTS: There was a force decay between 19% to 26.67% after 30 minutes, and 36.67% to 57% after 21 days of activation. CONCLUSIONS: TP elastomeric chains exhibited the smallest percentage of force decay, with greater stability at all time intervals tested. Meanwhile, the Unitek chains displayed the highest percentage of force degradation, and no statically significant difference was found in force decay between Ormco and Morelli elastomeric chains during the study period.

Claudia Kochenborger

2011-12-01

156

Elastomeric Structural Attachment Concepts for Aircraft Flap Noise Reduction - Challenges and Approaches to Hyperelastic Structural Modeling and Analysis  

Science.gov (United States)

Airframe noise is a significant part of the overall noise of transport aircraft during the approach and landing phases of flight. Airframe noise reduction is currently emphasized under the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) Project goals of NASA. A promising concept for trailing-edge-flap noise reduction is a flexible structural element or link that connects the side edges of the deployable flap to the adjacent main-wing structure. The proposed solution is distinguished by minimization of the span-wise extent of the structural link, thereby minimizing the aerodynamic load on the link structure at the expense of increased deformation requirement. Development of such a flexible structural link necessitated application of hyperelastic materials, atypical structural configurations and novel interface hardware. The resulting highly-deformable structural concept was termed the FLEXible Side Edge Link (FLEXSEL) concept. Prediction of atypical elastomeric deformation responses from detailed structural analysis was essential for evaluating feasible concepts that met the design constraints. The focus of this paper is to describe the many challenges encountered with hyperelastic finite element modeling and the nonlinear structural analysis of evolving FLEXSEL concepts. Detailed herein is the nonlinear analysis of FLEXSEL concepts that emerged during the project which include solid-section, foamcore, hollow, extended-span and pre-stressed concepts. Coupon-level analysis performed on elastomeric interface joints, which form a part of the FLEXSEL topology development, are also presented.

Sreekantamurthy, Thammaiah; Turner, Travis L.; Moore, James B.; Su, Ji

2014-01-01

157

Microfluidic fabrication and micromechanics of permeable and impermeable elastomeric microbubbles.  

Science.gov (United States)

We use droplet microfluidics to produce monodisperse elastomeric microbubbles consisting of gas encapsulated in a polydimethylsiloxane shell. These microbubbles withstand large, repeated deformations without rupture. We perform ?N-scale compression tests on individual microbubbles and find their response to be highly dependent on the shell permeability; during deformation, the pressure inside impermeable microbubbles increases, resulting in an exponential increase in the applied force. Finite element models are used to interpret and extend these experimental results enabling the design and development of deformable microbubbles with a predictable mechanical response. Such microbubbles can be designed to repeatedly transit through the narrow constrictions found in a porous medium functioning as probes of the local pressure. PMID:25730159

Duncanson, Wynter J; Kodger, Thomas E; Babaee, Sahab; Gonzalez, Grant; Weitz, David A; Bertoldi, Katia

2015-03-24

158

In vitro evaluation of force degradation of elastomeric chains used in Orthodontics  

OpenAIRE

OBJECTIVE: To analyze the in vitro force degradation of four different brands of elastomeric chains: American Orthodontics, Morelli, Ormco and TP Orthodontics. METHODS: The sample consisted of 80 gray elastomeric chains that were divided into four groups according to their respective manufacturers. Chain stretching was standardized at 21 mm with initial force release ranging from 300 g to 370 g. The samples were kept in artificial saliva at a constant temperature of 37°C and the degradation ...

André Weissheimer; Arno Locks; Luciane Macedo de Menezes; Adriano Ferreti Borgatto; Agostini Derech, Carla D.

2013-01-01

159

In vitro evaluation of force degradation of elastomeric chains used in Orthodontics  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: analisar, in vitro, a degradação de força, ao longo do tempo, de elastômeros das marcas comerciais American Orthodontics, Morelli, Ormco e TP Orthodontics. MÉTODOS: a amostra constituiu-se de 80 segmentos de elastômeros em cadeia fechada na cor cinza, divididos em quatro grupos, conforme o [...] fabricante. A distensão foi padronizada em 21mm, com liberação de força inicial variando de 300 a 370g de força. As amostras foram mantidas em saliva artificial em temperatura constante de 37ºC, e a força avaliada nos seguintes intervalos: inicial, 1h, 3h, 5h, 7h, 9h, 1 dia, 7 dias, 14 dias, 21 dias, 28 dias e 35 dias. RESULTADOS: houve diferença estatisticamente significativa na degradação de força entre os grupos avaliados, sendo que no primeiro dia houve perda de 50 a 55% em relação à força inicial. Os valores médios de força em 35 dias variaram de 122 a 148g. CONCLUSÃO: todas as marcas comerciais apresentaram degradação de força ao longo do tempo, sendo que na primeira hora a perda de força esteve entre 59 e 69% da força inicial. Porém, como existe variação dessa degradação dependendo da marca comercial, estudos como esses são importantes para orientação do uso desses elastômeros. Abstract in english OBJECTIVE: To analyze the in vitro force degradation of four different brands of elastomeric chains: American Orthodontics, Morelli, Ormco and TP Orthodontics. METHODS: The sample consisted of 80 gray elastomeric chains that were divided into four groups according to their respective manufacturers. [...] Chain stretching was standardized at 21 mm with initial force release ranging from 300 g to 370 g. The samples were kept in artificial saliva at a constant temperature of 37°C and the degradation force was recorded at the following time intervals: initial, 1, 3, 5, 7 and 9 hours, and 1, 7, 14, 21, 28, and 35 days. RESULTS: There was a statistically significant difference between the groups regarding the force degradation, mainly within the first day, as a force loss of 50-55% was observed during that time in relation to the initial force. The force delivered at 35 days ranged from 122 g to 148 g. CONCLUSION: All groups showed force degradation over time, regardless of their trademarks, a force loss of 59-69% was observed in the first hour compared to baseline. However, because the variation in force degradation depends on the trademark, studies such as the present one are important for guiding the clinical use of these materials.

André, Weissheimer; Arno, Locks; Luciane Macedo de, Menezes; Adriano Ferreti, Borgatto; Carla D' Agostini, Derech.

2013-02-01

160

In vitro evaluation of force degradation of elastomeric chains used in Orthodontics  

Directory of Open Access Journals (Sweden)

Full Text Available OBJECTIVE: To analyze the in vitro force degradation of four different brands of elastomeric chains: American Orthodontics, Morelli, Ormco and TP Orthodontics. METHODS: The sample consisted of 80 gray elastomeric chains that were divided into four groups according to their respective manufacturers. Chain stretching was standardized at 21 mm with initial force release ranging from 300 g to 370 g. The samples were kept in artificial saliva at a constant temperature of 37°C and the degradation force was recorded at the following time intervals: initial, 1, 3, 5, 7 and 9 hours, and 1, 7, 14, 21, 28, and 35 days. RESULTS: There was a statistically significant difference between the groups regarding the force degradation, mainly within the first day, as a force loss of 50-55% was observed during that time in relation to the initial force. The force delivered at 35 days ranged from 122 g to 148 g. CONCLUSION: All groups showed force degradation over time, regardless of their trademarks, a force loss of 59-69% was observed in the first hour compared to baseline. However, because the variation in force degradation depends on the trademark, studies such as the present one are important for guiding the clinical use of these materials.OBJETIVO: analisar, in vitro, a degradação de força, ao longo do tempo, de elastômeros das marcas comerciais American Orthodontics, Morelli, Ormco e TP Orthodontics. MÉTODOS: a amostra constituiu-se de 80 segmentos de elastômeros em cadeia fechada na cor cinza, divididos em quatro grupos, conforme o fabricante. A distensão foi padronizada em 21mm, com liberação de força inicial variando de 300 a 370g de força. As amostras foram mantidas em saliva artificial em temperatura constante de 37ºC, e a força avaliada nos seguintes intervalos: inicial, 1h, 3h, 5h, 7h, 9h, 1 dia, 7 dias, 14 dias, 21 dias, 28 dias e 35 dias. RESULTADOS: houve diferença estatisticamente significativa na degradação de força entre os grupos avaliados, sendo que no primeiro dia houve perda de 50 a 55% em relação à força inicial. Os valores médios de força em 35 dias variaram de 122 a 148g. CONCLUSÃO: todas as marcas comerciais apresentaram degradação de força ao longo do tempo, sendo que na primeira hora a perda de força esteve entre 59 e 69% da força inicial. Porém, como existe variação dessa degradação dependendo da marca comercial, estudos como esses são importantes para orientação do uso desses elastômeros.

André Weissheimer

2013-02-01

161

Modification of PVC compounds with butadiene-acrylonitrile elastomers  

OpenAIRE

Purpose: The purpose of the paper is to present the research programme on influence of acrylonitrile-butadiene copolymers on properties of plasticized polyvinylchloride as window gaskets material.Design/methodology/approach: Short literature review concerning application of modified PVC as gasket material was presented. In experimental part two types of acrylonitrile-butadiene copolymers were used as elastomeric plasticizers. Compounds with fifteen different levels of modifiers content (up to...

Stabik, J.; Rojek, M.

2006-01-01

162

Butadiene-acrylonitrile elastomers as PVC modifiers  

OpenAIRE

Purpose: The purpose of the paper is to present the results of research programme on influence of acrylonitrile-butadiene copolymers on plasticized polyvinylchloride compounds used as window gasket material.Design/methodology/approach: Short review concerning application of modified plasticized PVC compounds as gasket material was presented. In experimental part two types of acrylonitrile-butadiene copolymers were used as elastomeric plasticizers for PVC. Formulations with fifteen dif...

Rojek, M.; Stabik, J.

2007-01-01

163

Fabrication of micropored elastomeric film-covered stents and acute-phase performances.  

Science.gov (United States)

To prevent thrombus formation in the acute phase and restenosis in the subacute to chronic phase after stenting of atherosclerotic arteries, we developed a covered stent with a micropored elastomeric film, the blood-contacting surface of which was coated with a photocured gelatin layer immobilized with heparin. Segmented polyurethane (SPU) film (30 microm in wall thickness) as a cover material was multiply micropored by excimer laser-directed microprocessing (pore diameter, 30 microm; interpore distance, 125 microm). An aqueous mixed solution of benzophenone-derivatized gelatin and heparin was coated on the micropored SPU film. Upon ultraviolet light irradiation, a thin layer of a gelatin gel immobilized with heparin was formed and simultaneously fixed on the SPU film. The fully covered stents were assembled by wrapping a balloon-expandable stent with gelatin/heparin gel-layered SPU film and subsequently suturing and then gluing. To assess the validity of this covered stent in vivo, "half-covered" stents, in which half at the distal side was covered with the gel-layered SPU film, was implanted in rabbit common carotid arteries (about 3 mm in diameter). After 3 months of implantation, all the half-covered stents (n = 7) were patent. Regardless of the covered or noncovered region of the stents, the entire luminal surface of the stents was fully endothelialized and a thin neointimal tissue was formed. The potential advantages of a covered stent as designed above are discussed. PMID:12483696

Nakayama, Yasuhide; Nishi, Shogo; Ueda-Ishibashi, Hatsue; Matsuda, Takehisa

2003-01-01

164

Asymptotically one-dimensional diffusion on the Sierpinski gasket and multi-type branching processes with varying environment  

OpenAIRE

Asymptotically one-dimensional diffusions on the Sierpinski gasket constitute a one parameter family of processes with significantly different behaviour to the Brownian motion. Due to homogenization effects they behave globally like the Brownian motion, yet locally they have a preferred direction of motion. We calculate the spectral dimension for these processes and obtain short time heat kernel estimates in the Euclidean metric. The results are derived using branching process techniques, and...

Hambly, Bm; Jones, Od

2002-01-01

165

Dynamic analysis of fiber-reinforced elastomeric isolation structures  

International Nuclear Information System (INIS)

This paper presents an analysis of seismically isolated buildings using fiber-reinforced elastomeric structures that are subject to excitations caused by earthquakes. In analyzing the vibrations, the buildings are modeled by lumped mass systems. The fundamental equations of motion are derived for base isolated structures, and the hysteretic and nonlinear- elastic characteristics are included in the numerical calculations. The earthquake waves used as the excitation forces are those that have been recorded during strong earthquake motions in order to examine the dynamic stability of building structures. The seismic (nonlinear) responses of the building are compared for each restoring force type and, as a result, it is shown that the building's motions are not so large from a seismic design standpoint. Isolating structures are shown to reduce the responses sufficiently allowing the building's motions to be controlled to within a practical range. By increasing the acceleration of the earthquake, the yielding forces in the concrete and steel frames can be determined, which shows the advantages of performing nonlinear dynamic analysis in such applications

166

Biocide squirting from an elastomeric tri-layer film  

Science.gov (United States)

Protective layers typically act in a passive way by simply separating two sides. Protection is only efficient as long as the layers are intact. If a high level of protection has to be achieved by thin layers, complementary measures need to be in place to ensure safety, even after breakage of the layer-an important issue in medical applications. Here, we present a novel approach for integrating a biocide liquid into a protective film (about 300-500 ?m thick), which guarantees that a sufficient amount of biocide is rapidly released when the film is punctured. The film is composed of a middle layer, containing the liquid in droplet-like compartments, sandwiched between two elastomeric boundary layers. When the film is punctured, the liquid squirts out of the middle layer. A theoretical model was used to determine the size and density of droplets that are necessary to ensure a sufficient quantity of biocide is expelled from an adequately elastic matrix to provide protection at the site of damage. We demonstrate the utility of this approach for the fabrication of surgical gloves.

Sonntag, Philippe; Hoerner, Pierre; Cheymol, André; Argy, Gilles; Riess, Gérard; Reiter, Günter

2004-05-01

167

Radiation scattering behaviour of IPNs formed from thermoplastic and conventional elastomeric systems  

International Nuclear Information System (INIS)

Interpenetrating polymer networks (IPNs) using thermoplastic elastomers (TPEs) as starting materials can form tough but strong composites. Such networks when optimally prepared can combine the advantages of blending and crosslinking that result in nanometer scale interpenetration between polystyrene and poly(styrene-butadiene-styrene) (SBS) phases and consequential synergistic properties. In this study IPNs of SBS and PS were prepared using sequential network formation with the SBS crosslinked thermally and the styrene network formed using gamma irradiation. This work produced tough transparent IPNs of PS/SBS. Thermal degradation of the butadiene segments was avoided. We have previously examined a range of both thermal and radiation crosslinked IPNs using time-independent small angle neutron scattering (SANS) facilities at ANSTO and NIST. New data on IPN precursors, comprising both time-independent and real-time patterns at typically 15 minute intervals, are given for the first time. This allows the development of nanostructure in bulk (?1 mm) samples to be measured, and compared to previous arduous time-independent transmission electron microscopy (TEM) results on thin (?100nm) sections. TEM, SANS and atomic force microscopy were used to determine the size and shape of the phase domains and investigate any variation with crosslinking level and irradiation dose. The primary SBS network morphology was found to control IPN morphology and the effects of varying the Sology and the effects of varying the SBS structure and crosslink density were examined. The phase domains in these materials are ?20-50 nm in size, which gives synergistic property enhancement. With linear SBS giving more oriented morphology than the radial (SB)n material which has more symmetric morphology. We briefly introduce new work on elastomeric IPNs based on epichlorohydrin rubber and copolymers of butadiene and acrylonitrile which can form semi- and full IPNs using independent crosslinking modes. The differences in data possible with small angle X-ray scattering and SANS will be illustrated

168

Measurement of oil film thickness for application to elastomeric Stirling engine rod seals  

Science.gov (United States)

The rod seal in the Stirling engine has the function of separating high pressure gas from low or ambient pressure oil. An experimental apparatus was designed to measure the oil film thickness distribution for an elastomeric seal in a reciprocating application. Tests were conducted on commercial elastomeric seals having a 76 mm rod and a 3.8 mm axial width. Test conditions included 70 and 90 seal durometers, a sliding velocity of 0.8 m/sec, and a zero pressure gradient across the seal. An acrylic cylinder and a typical synthetic base automotive lubricant were used. The experimental results showed that the effect of seal hardness on the oil film thickness is considerable. A comparison between analytical and experimental oil film profiles for an elastomeric seal during relatively high speed reciprocating motion showed an overall qualitative agreement.

Krauter, A. I.

1981-01-01

169

Experimental and numerical study of damage initiation mechanism in elastomeric composites  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: Experimental and Finite Element Analysis (FEA of the damage initiation mechanisms in elastomeric composites were carried out under static loading at room temperature. Double Cantilever Beam (DCB specimens from natural rubber (NR vulcanised and reinforced with other materials such as carbon black, silica, fibres and textiles or metals (rubber composites.Design/methodology/approach: Very huge experimental results were compared with that of the Finite Element Analysis (FEA. Damage mechanism has been described with a threshold criterion to identify damage. The damage was evaluated just at the beginning of the tearing by assuming large strain. A typical type of specimen geometry of Double Cantilever Beam (DCB specimens was considered under static tensile tests conducted on the notched specimens with variable depths.Findings: In this stage of this research, a finite element analysis (FEA has been applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results. The numerical modelling is a representation of a previous experimental study. The specimen is stretched more than once its initial size, so that large strains occur. A hyper elastic Moonley-Rivlin law and a Griffith criterion are chosen. The finite elements analysis was performed with ABAQUS code (V.6.4.4.Practical implications: A damage criterion was suggested in the case of simple tension conditions by assuming large strain levels. an effective finite elements model has been developed to evaluate notch size effects on the load-displacement elastic response of 3D-DCB type specimen.Originality/value: This study proposes a threshold criterion for the damage just at the beginning of the tearing for Double Cantilever Beam (DCB specimens from rubber composites and gives a detail discussion for explaining the damage mechanisms. Comparison of FEA results with those of experimental studies gives many facilities for the sake of simplicity in industrial applications.

T.D. Silva Botelho

2009-09-01

170

Using "click-e-bricks" to make 3D elastomeric structures.  

Science.gov (United States)

Soft, 3D elastomeric structures and composite structures are easy to fabricate using click-e-bricks, and the internal architecture of these structures together with the capabilities built into the bricks themselves provide mechanical, optical, electrical, and fluidic functions. PMID:25080193

Morin, Stephen A; Shevchenko, Yanina; Lessing, Joshua; Kwok, Sen Wai; Shepherd, Robert F; Stokes, Adam A; Whitesides, George M

2014-09-10

171

Force decay in orthodontic elastomeric chains after immersion in disinfection solutions  

Scientific Electronic Library Online (English)

Full Text Available Aim: To evaluate the force decay of orthodontic elastomeric chains after immersion in disinfecting solutions. Methods: One-hundred and fifty segments of elastomeric chains were divided in 3 groups: Control group - no disinfection; Chlorhexidine group - disinfection in 0.12% chlorhexidine digluconate [...] solution; and Peracetic acid group - disinfection in 0.2% peracetic acid solution. Elastomeric chains of 14 mm were stretched up to 20 mm and the given force (kgf) was evaluated in an Instron universal testing machine at the following intervals: 1 h, 1 day, 7, 14, 21 and 28 days after the immersion in the disinfecting solutions. Data (kgf) were analyzed statistically by Analysis of Variance and Tukey's test at a 5% significance level. Results: Both groups presented similar force decay along 7 days and remained stable up to 28 days. Force degradation was observed in the first hours of activation (~50%). Conclusions: It may be concluded that there were no significant differences among the investigated groups, in most interval times, indicating that both chemical solutions can be used for previous disinfection of orthodontic elastomeric chains.

Karina Andréa Branco, Losito; Adriana Simoni, Lucato; Carlos Alberto Malanconi, Tubel; Cristian Alexandre, Correa; Julio Cesar Bentos dos, Santos.

2014-12-01

172

Standard operating procedure (SOP) for the quantitative determination of organic silicon compounds at the surface of elastomeric sealants  

Science.gov (United States)

Elastomeric sealants may contain organic silicon compounds. The use of these sealants for housings for electronic components is harmful for the reliability of electric contacts inside. In order to prevent electronic components from malfunction, quality control of elastomeric sealants is required. An analytical procedure developed to fulfil this requirement was developed. It is based on electron spectroscopy for chemical analysis (ESCA). Information on the silicon compounds existing at the surface of elastomeric sealants is provided by this method. Silicon in organic and inorganic compounds can be differentiated with the help of Si 2p photoelectron spectra. Quantitative results can be obtained too. The uncertainty budget of the quantitative procedure is estimated.

Gross, Th; Treu, D.; Unger, W.

2001-07-01

173

Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: Performance and advantages for in situ analysis  

Science.gov (United States)

Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 ??m in diameter and ???50 ??m deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 ??C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 ??C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90?? angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 ??m, a pressure of 76 MPa at 500 ??C was maintained for 2 h with no change in the original fluid density. ?? 2008 American Institute of Physics.

Chou, I.-Ming; Bassett, William A.; Anderson, Alan J.; Mayanovic, Robert A.; Shang, L.

2008-01-01

174

Novel elastomeric fibrous networks produced from poly(xylitol sebacate)2:5 by core/shell electrospinning: fabrication and mechanical properties.  

Science.gov (United States)

Fabrication of nonlinear elastic materials that resemble biological tissues remains a challenge in biomaterials research. Here, a new fabrication protocol to produce elastomeric fibrous scaffolds was established, using the core/shell electrospinning technique. A prepolymer of poly(xylitol sebacate) with a 2:5mol ratio of xylitol:sebacic acid (PXS2:5) was first formulated, then co-electrospun with polyvinyl alcohol (PVA - 95,000Mw). After cross-linking of core polymer PXS2:5, the PVA shells were rinsed off in water, leaving a porous elastomeric network of PXS2:5 fibres. Under aqueous conditions, the PXS2:5 fibrous scaffolds exhibited stable, nonlinear J-shaped stress-strain curves, with large average rupture elongation (76%) and Young?s modulus (~1.0MPa), which were in the range of muscle tissue. Rupture elongation of PXS2:5 was also much higher when electrospun, compared to 2D solid sheets (45%). In direct contact with cell monolayers under physiological conditions, PXS2:5 scaffolds were as biocompatible as those made of poly-l-lactic acid (PLLA), with improvements over culture medium alone. In conclusion, the newly developed porous PXS2:5 scaffolds show tissue-like mechanical properties and excellent biocompatibility, making them very promising for bioengineering of soft tissues and organs. PMID:25243671

Li, Yuan; Thouas, George A; Chen, Qizhi

2014-12-01

175

Butadiene-acrylonitrile elastomers as PVC modifiers  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The purpose of the paper is to present the results of research programme on influence of acrylonitrile-butadiene copolymers on plasticized polyvinylchloride compounds used as window gasket material.Design/methodology/approach: Short review concerning application of modified plasticized PVC compounds as gasket material was presented. In experimental part two types of acrylonitrile-butadiene copolymers were used as elastomeric plasticizers for PVC. Formulations with fifteen different levels of elastomeric modifiers content (up to 25% by weight were prepared and tested. As reference formulations three commercial compounds were additionally tested. Shore hardness, short-term and long-term elastic recovery, tensile strength, elongation at break and migration of plasticizers from gasket material to unplasticized PVC were searched.Findings: Incorporation of acrylonitrile-butadiene copolymers into PVC enhanced many properties essential for its application as window gasket material. The most important changes occurred for long-term and short term elastic recovery, tensile strength and elongation at break. At the same time addition of these butadiene-acrylonitrile elastomers did not change migration of other plasticizers contained in gasket material into rigid PVC in being in contact with gasket. Obtained results showed that among tested compounds best properties as gasket material exhibited plasticized PVC with 23% of acrylonitrile-butadiene copolymer Chemigum P83. Reference commercial formulations exhibited worse performance properties than new compounds with this acrylonitrile-butadiene copolymer.Practical implications: Research programme allowed to elaborate plasticized PVC compounds modified with acrylonitrile-butadiene copolymer that can be industrially applied for PVC window gaskets.Originality/value: Obtained results are of scientific and practical value. Research programme allowed to investigate the influence of elastomeric modifiers on plasticized PVC properties. Research results are also of practical importance.

M. Rojek

2007-01-01

176

Determination of safe operating conditions for gasketed flange joint under combined internal pressure and temperature: A finite element approach  

Energy Technology Data Exchange (ETDEWEB)

Performance of a flange joint is characterised mainly by its 'strength' and 'sealing capability'. A number of analytical and experimental studies have been conducted to study these characteristics under internal pressure loading. However, with the advent of new technological trends for high temperature and pressure applications, an increased demand for analysis is recognized. The effect of steady-state thermal loading makes the problem more complex as it leads to combined application of internal pressure and temperature. The present design codes do not address the effects of temperature on the structural integrity and sealing ability. In addition, the available design solutions do not solve problems of failure of a gasketed flange joint even under bolt up and internal pressure loading conditions. To investigate joint strength and sealing capability under combined internal pressure and different steady-state thermal loading, a 3D nonlinear finite element analysis (FEA) of a gasketed flange joint is carried out and its behaviour is discussed. To determine the safe operating conditions or the actual joint load capacity, the joint is further analyzed for different internal pressures keeping the temperature constant.

Abid, Muhammad [Faculty of Mechanical Engineering, Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi-23460, NWFP (Pakistan)]. E-mail: abid@giki.edu.pk

2006-06-15

177

Determination of safe operating conditions for gasketed flange joint under combined internal pressure and temperature: A finite element approach  

International Nuclear Information System (INIS)

Performance of a flange joint is characterised mainly by its 'strength' and 'sealing capability'. A number of analytical and experimental studies have been conducted to study these characteristics under internal pressure loading. However, with the advent of new technological trends for high temperature and pressure applications, an increased demand for analysis is recognized. The effect of steady-state thermal loading makes the problem more complex as it leads to combined application of internal pressure and temperature. The present design codes do not address the effects of temperature on the structural integrity and sealing ability. In addition, the available design solutions do not solve problems of failure of a gasketed flange joint even under bolt up and internal pressure loading conditions. To investigate joint strength and sealing capability under combined internal pressure and different steady-state thermal loading, a 3D nonlinear finite element analysis (FEA) of a gasketed flange joint is carried out and its behaviour is discussed. To determine the safe operating conditions or the actual joint load capacity, the joint is further analyzed for different internal pressures keeping the temperature constant

178

Modelling the Self-Assembly of Elastomeric Proteins Provides Insights into the Evolution of Their Domain Architectures  

OpenAIRE

Elastomeric proteins have evolved independently multiple times through evolution. Produced as monomers, they self-assemble into polymeric structures that impart properties of stretch and recoil. They are composed of an alternating domain architecture of elastomeric domains interspersed with cross-linking elements. While the former provide the elasticity as well as help drive the assembly process, the latter serve to stabilise the polymer. Changes in the number and arrangement of the elastomer...

Song, Hongyan; Parkinson, John

2012-01-01

179

Increasing pumping efficiency in a micro throttle pump by enhancing displacement amplification in an elastomeric substrate  

Science.gov (United States)

Fluid transport is accomplished in a micro throttle pump (MTP) by alternating deformation of a micro channel cast into a polydimethylsiloxane (PDMS) elastomeric substrate. The active deformation is achieved using a bimorph PZT piezoelectric disc actuator bonded to a glass diaphragm. The bimorph PZT deflects the diaphragm as well as alternately pushing and pulling the elastomer layer providing displacement amplification in the PDMS directly surrounding the micro channel. In order to improve pumping rates we have embedded a polymethylmethacrylate (PMMA) ring into the PMDS substrate which increases the magnitude of the displacement amplification achieved. FEM simulation of the elastomeric substrate deformation predicts that the inclusion of the PMMA ring should increase the channel deformation. We experimentally demonstrate that inclusion of a PMMA ring, having a diameter equal to that of the circular node of the PZT/glass/PDMS composite, increases in the throttle resistance ratio by 40% and the maximum pumping rate by 90% compared to an MTP with no ring.

Fujiwara, T.; Johnston, I. D.; Tracey, M. C.; Tan, C. K. L.

2010-06-01

180

Increasing pumping efficiency in a micro throttle pump by enhancing displacement amplification in an elastomeric substrate  

International Nuclear Information System (INIS)

Fluid transport is accomplished in a micro throttle pump (MTP) by alternating deformation of a micro channel cast into a polydimethylsiloxane (PDMS) elastomeric substrate. The active deformation is achieved using a bimorph PZT piezoelectric disc actuator bonded to a glass diaphragm. The bimorph PZT deflects the diaphragm as well as alternately pushing and pulling the elastomer layer providing displacement amplification in the PDMS directly surrounding the micro channel. In order to improve pumping rates we have embedded a polymethylmethacrylate (PMMA) ring into the PMDS substrate which increases the magnitude of the displacement amplification achieved. FEM simulation of the elastomeric substrate deformation predicts that the inclusion of the PMMA ring should increase the channel deformation. We experimentally demonstrate that inclusion of a PMMA ring, having a diameter equal to that of the circular node of the PZT/glass/PDMS composite, increases in the throttle resistance ratio by 40% and the maximum pumping rate by 90% compared to an MTP with no ring.

181

Pattern transfer printing by kinetic control of adhesion to an elastomeric stamp  

Science.gov (United States)

The present invention provides methods, systems and system components for transferring, assembling and integrating features and arrays of features having selected nanosized and/or microsized physical dimensions, shapes and spatial orientations. Methods of the present invention utilize principles of `soft adhesion` to guide the transfer, assembly and/or integration of features, such as printable semiconductor elements or other components of electronic devices. Methods of the present invention are useful for transferring features from a donor substrate to the transfer surface of an elastomeric transfer device and, optionally, from the transfer surface of an elastomeric transfer device to the receiving surface of a receiving substrate. The present methods and systems provide highly efficient, registered transfer of features and arrays of features, such as printable semiconductor element, in a concerted manner that maintains the relative spatial orientations of transferred features.

Nuzzo, Ralph G. (Champaign, IL); Rogers, John A. (Champaign, IL); Menard, Etienne (Urbana, IL); Lee, Keon Jae (Tokyo, JP); Khang, Dahl-Young (Urbana, IL); Sun, Yugang (Champaign, IL); Meitl, Matthew (Champaign, IL); Zhu, Zhengtao (Urbana, IL)

2011-05-17

182

Pre-treatment of synthetic elastomeric scaffolds by cardiac fibroblasts improves engineered heart tissue  

OpenAIRE

Native myocardium consists of several cell types, of which approximately one-third are myocytes and most of the nonmyocytes are fibroblasts. By analogy with monolayer culture in which fibroblasts were removed to prevent overgrowth, early attempts to engineer myocardium utilized cell populations enriched for cardiac myocytes (CMs; ~80–90% of total cells). We hypothesized that the pre-treatment of synthetic elastomeric scaffolds with cardiac fibroblasts (CFs) will enhance the functional assem...

Radisic, Milica; Park, Hyoungshin; Martens, Timothy P.; Salazar-lazaro, Johanna E.; Geng, Wenliang; Wang, Yadong; Langer, Robert; Freed, Lisa E.; Vunjak-novakovic, Gordana

2008-01-01

183

Physiologic Compliance in Engineered Small-diameter Arterial Constructs Based on an Elastomeric Substrate  

OpenAIRE

Compliance mismatch is a significant challenge to long-term patency in small-diameter bypass grafts because it causes intimal hyperplasia and ultimately graft occlusion. Current engineered grafts are typically stiff with high burst pressure but low compliance and low elastin expression. We postulated that engineering small arteries on elastomeric scaffolds under dynamic mechanical stimulation would result in strong and compliant arterial constructs. Compare properties of engineered arterial c...

Crapo, Peter M.; Wang, Yadong

2009-01-01

184

Numerical study of effect of elastomeric stress absorbers on stress reduction in bone-dental implant interface  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Objective This paper focused on optimal stress distribution in the mandibular bone surrounding a dental implant and is devoted to the development of a modified Osteoplant® implant type in order to minimize stress concentration in the bone-implant interface. Material and Methods This study investiga [...] ted 0.4 mm thick layers of two elastomeric stress barriers incorporated into the dental implant using 3-D finite element analysis. Results Overall, this proposed implant provoked lower load transfer in bone-implant interface due to the effect of the elastomers as stress absorbers. The stress level in the bone was reduced between 28% and 42% for three load cases: 75 N, 60 N and 27 N in corono-apical, linguo-buccal and disto-mesial direction, respectively. Conclusion The proposed model provided an acceptable solution for load transfer reduction to the mandible. This investigation also permitted to choose how to incorporate two elastomers into the Osteoplant® implant system.

Ghalem, MEHDI; Abderrahmane, BELARBI; Bensmaine, MANSOURI; Zitouni, AZARI.

2015-02-01

185

Evaluation of the influence of the polymer-filler interaction on compounds based on epoxidized elastomeric matrix and precipitated silica  

Directory of Open Access Journals (Sweden)

Full Text Available The introduction of epoxy groups into the main chain of elastomers has emerged as a promising alternative, considering the monitoring of polymer-filler interaction leading to changes in the properties of vulcanizates. The epoxidation reaction (in situ was chosen to modify elastomers, such as polybutadiene (BR and copolymer of styrene-butadiene-rubber (SBR, because it is a simple, easily controlled reaction, even considering the small epoxidation degree. The modification degree of the polymeric chain was studied with FT-IR and ¹H-NMR. The shift of the Tg to high temperatures with the increase of the epoxy group in the polymer chain was monitored through differential scanning calorimetry (DSC. An analysis of the dynamic modulus of the material in relation to its dependence on the amplitude and temperature was carried out. The interaction between epoxidized elastomeric matrix and silica as filler was extremely improved, even in the presence of very low content of epoxy groups into the polymer chain.

Tatiana L. A. C. Rocha

2006-06-01

186

Evaluation of the influence of the polymer-filler interaction on compounds based on epoxidized elastomeric matrix and precipitated silica  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The introduction of epoxy groups into the main chain of elastomers has emerged as a promising alternative, considering the monitoring of polymer-filler interaction leading to changes in the properties of vulcanizates. The epoxidation reaction (in situ) was chosen to modify elastomers, such as polybu [...] tadiene (BR) and copolymer of styrene-butadiene-rubber (SBR), because it is a simple, easily controlled reaction, even considering the small epoxidation degree. The modification degree of the polymeric chain was studied with FT-IR and ¹H-NMR. The shift of the Tg to high temperatures with the increase of the epoxy group in the polymer chain was monitored through differential scanning calorimetry (DSC). An analysis of the dynamic modulus of the material in relation to its dependence on the amplitude and temperature was carried out. The interaction between epoxidized elastomeric matrix and silica as filler was extremely improved, even in the presence of very low content of epoxy groups into the polymer chain.

Tatiana L. A. C., Rocha; Marly M., Jacobi; Dimitrios, Samios; Robert H., Schuster.

2006-06-01

187

New elastomeric silicone based networks applicable as electroactive systems  

OpenAIRE

Commercial elastomer materials are available for dielectric electroactive polymer (DEAP) purposes but the applied commercial elastomers have not been developed with the specific application in mind. It is therefore obvious that optimization of the elastomer material should be possible. In this study we focus on optimization of the mechanical properties of the elastomer and show that it is possible to lower the elastic modulus and still not compromise the other required mechanical properties s...

Bejenariu, Anca Gabriela; Boll, Mads; Lotz, Mikkel R.; Vraa, Christoffer; Skov, Anne Ladegaard

2011-01-01

188

Baseline and Lifetime Assessments for DC745U Elastomeric Components  

Energy Technology Data Exchange (ETDEWEB)

The silicone elastomer Dow Corning DC 745U is used in two major components in the W80. We have investigated a number of issues concerning this material. Our studies have accomplished a baseline study of the chemical composition of DC745 and LLNL now has a good understanding of the chemical composition of this material. DC745 crystallizes within the system STS. Two potential means identified to mitigate the risk associated with this phenomenon are to (1) change material formulation and (2) predose the parts to {approx} 25 MRad {gamma}-radiation. A candidate material identified by Gordon Spellman has been studied for composition and the lack of crystallization within the STS has been verified. A sensitivity study of the effects of relevant aging mechanisms also has been performed. The extent of aging due to radiation exposure or elevated temperatures is minimal over the expected course of the LEP. In addition, since the DC745 parts are expected to be replaced at rebuild, the aging clock is essentially being reset. No significant aging issues seem likely to develop for these parts. DC745 parts are also subject to permanent deformation in service. Our studies have shown that the deformation is likely due to incomplete mixing of the raw gum stock and the curing agent at production. This results in areas of low crosslink density that are subject to a higher degree of compression set in service. We have identified two production diagnostic tools based on Nuclear Magnetic Resonance spectroscopy to prescreen the parts at production at KCP. These studies are concluded with specific recommendation for changes to core surveillance for this part based on the chemical knowledge we have gained from this study.

Maxwell, R S; Chinn, S C; Herberg, J; Harvey, C; Alviso, C; Vance, A; Cohenour, R; Wilson, M; Solyom, D

2004-12-20

189

Baseline and Lifetime Assessments for DC745U Elastomeric Components  

International Nuclear Information System (INIS)

The silicone elastomer Dow Corning DC 745U is used in two major components in the W80. We have investigated a number of issues concerning this material. Our studies have accomplished a baseline study of the chemical composition of DC745 and LLNL now has a good understanding of the chemical composition of this material. DC745 crystallizes within the system STS. Two potential means identified to mitigate the risk associated with this phenomenon are to (1) change material formulation and (2) predose the parts to ? 25 MRad ?-radiation. A candidate material identified by Gordon Spellman has been studied for composition and the lack of crystallization within the STS has been verified. A sensitivity study of the effects of relevant aging mechanisms also has been performed. The extent of aging due to radiation exposure or elevated temperatures is minimal over the expected course of the LEP. In addition, since the DC745 parts are expected to be replaced at rebuild, the aging clock is essentially being reset. No significant aging issues seem likely to develop for these parts. DC745 parts are also subject to permanent deformation in service. Our studies have shown that the deformation is likely due to incomplete mixing of the raw gum stock and the curing agent at production. This results in areas of low crosslink density that are subject to a higher degree of compression set in service. We have identified two production diagnostic tools based on Nuclear Magnetic Resonance spebased on Nuclear Magnetic Resonance spectroscopy to prescreen the parts at production at KCP. These studies are concluded with specific recommendation for changes to core surveillance for this part based on the chemical knowledge we have gained from this study

190

Multiple refraction switches realized by stretching elastomeric scatterers in sonic crystals  

Science.gov (United States)

The effect of out-of-plane pre-stretch on the 2D sonic crystal with stretchable elastomeric scatterers is explored. The hyperelastic scatterers are characterized by a compressible neo-Hookean model. The Dirichlet-to-Neumann (DtN) map is adopted to obtain the band structure and equi-frequency contours. We focus on the first passband and find that a variety of switching functionalities for refraction behaviors can be realized in selected frequencies under a specific pre-stretch range. These refraction switches enable an active control of wave propagation and are applicable in advanced technologies where switchable and multifunctional sonic crystals are required.

Huang, Y.; Chen, W. Q.; Wang, Y. S.; Yang, W.

2015-02-01

191

Assessment of gas leakage performance for elastomeric seals during a thermal transient  

International Nuclear Information System (INIS)

To assess elastomeric seal leakage variation during a thermal transient, permeation losses and those past the seal need to be considered separately. Approximate methods of leakage assessment and their limitations for both flow components are defined. If seal leakage is low so that permeation losses are significant compared to leakage past the seal, an upper bound to the leakage change is given by scaling according to permeation laws. In general this requires computational methods for solution, and simplified procedures based on linear approximations to the pressure and temperature profiles are suggested. Such simplification enables graphical presentation of these solutions, and a specific application is discussed. (author)

192

Optical Manipulation of Shape-Morphing Elastomeric Liquid Crystal Microparticles Doped with Gold Nanocrystals  

Energy Technology Data Exchange (ETDEWEB)

We demonstrate facile optical manipulation of shape of birefringent colloidal microparticles made from liquid crystal elastomers. Using soft lithography and polymerization, we fabricate elastomeric microcylinders with weakly undulating director oriented on average along their long axes. These particles are infiltrated with gold nanospheres acting as heat transducers that allow for an efficient localized transfer of heat from a focused infrared laser beam to a submicrometer region within a microparticle. Photothermal control of ordering in the liquid crystal elastomer using scanned beams allows for a robust control of colloidal particles, enabling both reversible and irreversible changes of shape. Possible applications include optomechanics, microfluidics, and reconfigurable colloidal composites with shape-dependent self-assembly.

Sun, Y. R.; Evans, J. S.; Lee, T.; Senyuk, B.; Keller, P.; He, S. L.; Smalyukh, I. I.

2012-06-11

193

Development of a CAE-based procedure for the acoustic optimization of gaskets between engine structure and add-on parts; Entwicklung eines rechnergestuetzten Verfahrens zur akustischen Optimierung von Dichtungen zwischen Motorstruktur und Anbauteilen  

Energy Technology Data Exchange (ETDEWEB)

The current status for calculation of structure born noise flow via elastomer gaskets is not sufficient. A simulation method developed in this project which is based on MSC Nastran shows accurate results compared to measurements. The calculation results were significantly better than those which were conducted using the state-of-the-art modal calculation approach. The key for getting good simulation results is to include the frequency dependent shear modulus of the sealing material in the calculation. The optimisation of the sealing geometry regarding to it's NVH behaviour showed that no general statement concerning the best geometry is possible. The best geometry for acoustics strongly depends on the given boundaries. Depending on the utilized sealing material different physical effects like damping or insulation come into operation. The improved acoustic behaviour of the optimised geometry was verified in an experimental analysis. In order to confirm the methodology the calculation approach was transferred to a second engine structure and verified with experimental results. (orig.)

Pischinger, S.; Pilath, Ch. [RWTH Aachen (Germany). Lehrstuhl Verbrennungskraftmaschinen

2005-07-01

194

TN trademark FLEX: a new generation of fluorocarbon o-rings developed by COGEMA logistics with enhanced characteristics at low temperature (-40 C)  

International Nuclear Information System (INIS)

Three main types of elastomers are used for the sealing of radioactive material transport casks with elastomeric gaskets: EPDM, fluorocarbons type Viton registered (standard designation: FKM) and silicon rubbers. Each rubber has specific characteristics in terms of temperature range, permeability, coefficient of expansion.. For the casks where high temperatures can be reached (200 C in continuous using), FKM gaskets are generally used. The problem is that this type of gasket does not guarantee the leaktightness at -40 C, which is a regulatory requirement. Two solutions are generally used: to specify a minimum heat load or a minimum ambient temperature. The direct consequence is that it is impossible to get B(U) approvals on the new concepts when FKM gaskets are used but only B(M) approvals, which generate significant additional justification costs (multiple submittals of Safety Analysis Reports, calculation of the minimum heat load or of the minimum ambient temperature..). Thus, it is important to develop gaskets with the same performance as FKM gaskets at high temperature but with enhanced performance at low temperature (and mainly, which guarantee the leaktightness at -40 C). COGEMA LOGISTICS has qualified a new generation of fluorocarbon O-rings (TN trademark FLEX gaskets) which can be used in continuous service on a -47 C/+200 C temperature range. TN trademark FLEX gaskets will be implemented on new casks designs

195

TN trademark FLEX: a new generation of fluorocarbon o-rings developed by COGEMA logistics with enhanced characteristics at low temperature (-40 C)  

Energy Technology Data Exchange (ETDEWEB)

Three main types of elastomers are used for the sealing of radioactive material transport casks with elastomeric gaskets: EPDM, fluorocarbons type Viton {sup registered} (standard designation: FKM) and silicon rubbers. Each rubber has specific characteristics in terms of temperature range, permeability, coefficient of expansion.. For the casks where high temperatures can be reached (200 C in continuous using), FKM gaskets are generally used. The problem is that this type of gasket does not guarantee the leaktightness at -40 C, which is a regulatory requirement. Two solutions are generally used: to specify a minimum heat load or a minimum ambient temperature. The direct consequence is that it is impossible to get B(U) approvals on the new concepts when FKM gaskets are used but only B(M) approvals, which generate significant additional justification costs (multiple submittals of Safety Analysis Reports, calculation of the minimum heat load or of the minimum ambient temperature..). Thus, it is important to develop gaskets with the same performance as FKM gaskets at high temperature but with enhanced performance at low temperature (and mainly, which guarantee the leaktightness at -40 C). COGEMA LOGISTICS has qualified a new generation of fluorocarbon O-rings (TN trademark FLEX gaskets) which can be used in continuous service on a -47 C/+200 C temperature range. TN trademark FLEX gaskets will be implemented on new casks designs.

Issard, H.; Andre, R. [COGEMA Logistics, Saint-Quentin-en-Yvelines (France)

2004-07-01

196

Biodegradabilite et proprietes energetiques d'elastomeres azotures  

Science.gov (United States)

The interest for polymer materials has steadily increased in the last decades and the use of polymer materials has been increasing ever since. These polymers are used in a vast range of applications from civil to military (Colclough et al., 1994; Nair & Laurencin, 2007; Sansone et al., 2012). This demand for polymer materials resulted in the development of various polymers with a wide range of properties depending on the desired application. In the field of propellants, this interest led to the development of glycidyl azide polymer (GAP) and other similar materials. Growing environmental concerns has led to a demand for more environmentally friendly polymers. This demand so far has been increasing and shows no sign of following a different trend for the next years. This demand is in part due to the presence of non-recyclable polymers, for which end of life can be problematic. At the same time, another problematic arose: the soil contamination originating from repeated military training as well as the subsequent contamination of water supplies by rain water seeping into the ground absorbing part of the contaminants (Dontsova, Pennington, Hayes, imunek, & Williford, 2009; M. R. Walsh, Thiboutot, Walsh, & Ampleman, 2012). This phenomenon incurs large decontamination costs and can result in the abandonment of training grounds due to contamination (Michael R. Walsh, Walsh, & Hewitt, 2010). The compounds responsible for the contamination of military training grounds are in part present in elastomers used as binders for propellants. The binders are non-biodegradable as well. In order to make greener propellants, it is not only necessary to replace the contaminants by non-contaminant materials, but also necessary to replace the binder by using new biodegradable materials. Glycidyl azide polymer, a commonly used energetic polymer in binders is non-biodebradable and as such unburned residue will accumulate in the environment. The main objective of this work is to develop new biodegradable energetic binders in the form of polyurethane elastomers. These elastomers could be used as binders for propellants or as a gas generator. Biodegradable polyurethane elastomers have already garnered much attention in the field of biomedical research (Adhikari et al., 2008; He et al., 2012) and some preliminary work has been done towards the development of biodegradable energetic binders (Cossu, 2009). In order to fulfil this objective, three pre-polymers have been synthesised from sebacoyl chloride by polycondensation with polyepichlorohydrin, 3-chloro-1, 2-propanediol and 2-bromo- 2-nitro-1,3-propanediol respectively. These pre-polymers were subsequently azided in order to add or increase the energetic content of the pre-polymers. ATR-FTIR, 1H-NMR and 13C-NMR were used to verify the success of the azidations. Success of the azidation reaction was confirmed for the pre-polymers synthesized from polyepichlorohydrin and 3-chloro-1,2-propanediol while the reaction did not occur properly for the pre-polymer made from 2-propanediol and 2-bromo-2-nitro-1,3-propanediol. The lack of energetic groups was confirmed and the reaction product was a solid powder rather than a viscous liquid. DSC was performed on the pre-polymers in order to evaluate the energetic content of the pre-polymers that were successfully azided. The degradation energy of the azide group measured are 1724 J/g for the pre-polymer derived from polyepichlorohydrin and 614 J/g for the pre-polymer synthesized from 3-chloro-1,2-propanediol. Polyurethane elastomers were synthesized from the azided pre-polymers using ethyl ester L-lysine triisocyanate and subsequently characterized. The glass transition temperature of the copoly(ether/ester/urethane) was evaluated at -43°C through DSC and DMA while the Tg of the copoly(ester/urethane) was evaluated at -50°C through DSC. The decomposition energy of the azide groups of the elastomers was also evaluated through DSC and the copoly(ether/ester/urethane) was found to have an azide degradation energy of 1688 J/g while this parameter

Lavoie, Jonathan

197

Effect of elastomeric ligatures on frictional forces between the archwire and orthodontic bracket  

Scientific Electronic Library Online (English)

Full Text Available AIM: To evaluate the frictional force between the archwire and orthodontic bracket generated by elastomeric ligatures with polymer coating (Super slick, TP Orthodontics) and conventional ligatures (Morelli) using two types of insertion techniques. METHODS: Forty elastomeric ligatures, 20 with polyme [...] r coating and 20 conventional, were evaluated. Each type of ligature was separated into two groups (n=10), according to the insertion mode: conventional or crossed (from mesial to distal region crossed in front). To analyze friction, 40 5-cm-long segments of stainless steel orthodontic archwire 0.019" x 0.025" (Morelli) and Edgewise brackets (slot 0.022" x 0.028"; Morelli) were used. Each set (bracket, wire and elastic) was submitted to frictional testing in a universal test machine (Instron 4411) at a crosshead speed of 5 mm/min. Each bracket was moved 5 mm on the wire, with maximum friction and mean friction being recorded by software. Three readouts were taken for each bracket. Data were submitted to two-way ANOVA and Tukey's test (p

Flávia Ramos, Venâncio; Sílvia Amélia Scudeler, Vedovello; Carlos Alberto Malanconi, Tubel; Viviane Veroni, Degan; Adriana Simone, Lucato; Letícia Nery, Lealdim.

2013-03-01

198

Assessmentof seismic stability of buildings that have seismicprotection in the form of elastomeric isolators ?????? ??????????????? ?????? ? ????????????? ? ???? ??????????????????? ????  

Directory of Open Access Journals (Sweden)

Full Text Available Nowadays, various systems of seismic protection are applied to assure seismic protection of buildings and structures, located in earthquake areas. The greatest prevalence and popularity has been attained by the systems of active seismic protection.In this article, the authors study the efficiency of application of an active seismic protection system by taking high-damping rubber elastomeric isolators as an example. Calculations and their comparative analysis were made for a high-rise reinforced concrete building, and their exposure to the seismic impact was examined. Those calculations were made both with and without the application of the active seismic isolation system. Calculations were carried out by means of the linearly-spectral method using Lira software. Maximum relative horizontal moments arising on the top of the building and forces applied to the elements of walls and columns were compared. On the basis of the results of the calculations and their comparative analysis, the conclusion is drawn that elastomeric isolators may be efficiently applied as an active seismic protection system.???????? ??????? ?????????? ????????? ?????? ???????? ????????????, ? ?.?. ??????????????????? ????? (???, ??? ?????? ?? ????????????? ?????? ? ??????????, ????????????? ? ??????????? ??????? ???????. ?????????? ???????-???????????? ?????? ??????????????? ?????? ? ??????????? ??????? ???????? ?????????????? ? ???? ??? ? ??? ??? ? ??????????? ????????? «????». ?????????? ????????????? ?????? ??????????? ???????.

Mkrtychev Oleg Vartanovich

2013-08-01

199

Applicability of base isolation made of elastomeric isolators for the protection of cultural heritage  

Directory of Open Access Journals (Sweden)

Full Text Available This article briefly presents the applicability of base isolation made of elastomeric isolators for the protection of heritage architecture. The first part of the article gives an illustrative overview on the use of base isolation throughout the world, together with an analysis of guidelines for the protection and management of places of heritage architecture. The guidelines which are given through international agreements and resolutions on the conservation of monuments have to be considered when designing the base isolation of existing monuments. Generally, interventions into such structures should be minimal or visible as little as possible and should minimally affect the aesthetics and functionality of the object. In the second part of the article the general and some special requirements for base isolation design with elastomeric isolators are presented. The influence of the slenderness of the structure is analysed in more detail. The analysis is based on the corresponding rocking prevention criterion, upon the condition that the isolators cannot bear any tensile forces. The article concludes with a presentation of the maximum height-to-width ratios for objects that can be mounted on isolators, fulfilling the given rocking prevention criterion for different soil conditions. The maximum aspect ratios have also been determined by considering 5 appropriately scaled ground motions from the 1998 Poso?je earthquake.

Vojko Kilar

2009-01-01

200

Safety assessment aspects of materials for radioactive waste containers  

International Nuclear Information System (INIS)

In design testing and research BAM had investigated various aspects of material behaviour to ensure safety of RAM waste packages under operating and accident conditions: Strength and fracture toughness of cubic ductile cast iron containers in handling accidents, thermal behaviour of ion exchanger resin material in a full-scale fire test of a cubic DCI container, long-term, high and low temperature behaviour of VITON gaskets. (orig.)

201

Highly stretchable electric circuits from a composite material of silver nanoparticles and elastomeric fibres  

Science.gov (United States)

Conductive electrodes and electric circuits that can remain active and electrically stable under large mechanical deformations are highly desirable for applications such as flexible displays, field-effect transistors, energy-related devices, smart clothing and actuators. However, high conductivity and stretchability seem to be mutually exclusive parameters. The most promising solution to this problem has been to use one-dimensional nanostructures such as carbon nanotubes and metal nanowires coated on a stretchable fabric, metal stripes with a wavy geometry, composite elastomers embedding conductive fillers and interpenetrating networks of a liquid metal and rubber. At present, the conductivity values at large strains remain too low to satisfy requirements for practical applications. Moreover, the ability to make arbitrary patterns over large areas is also desirable. Here, we introduce a conductive composite mat of silver nanoparticles and rubber fibres that allows the formation of highly stretchable circuits through a fabrication process that is compatible with any substrate and scalable for large-area applications. A silver nanoparticle precursor is absorbed in electrospun poly (styrene-block-butadiene-block-styrene) (SBS) rubber fibres and then converted into silver nanoparticles directly in the fibre mat. Percolation of the silver nanoparticles inside the fibres leads to a high bulk conductivity, which is preserved at large deformations (? ~ 2,200 S cm-1 at 100% strain for a 150-µm-thick mat). We design electric circuits directly on the electrospun fibre mat by nozzle printing, inkjet printing and spray printing of the precursor solution and fabricate a highly stretchable antenna, a strain sensor and a highly stretchable light-emitting diode as examples of applications.

Park, Minwoo; Im, Jungkyun; Shin, Minkwan; Min, Yuho; Park, Jaeyoon; Cho, Heesook; Park, Soojin; Shim, Mun-Bo; Jeon, Sanghun; Chung, Dae-Young; Bae, Jihyun; Park, Jongjin; Jeong, Unyong; Kim, Kinam

2012-12-01

202

Geothermal Elastomeric Materials Technology-Transfer (GEM-TT) Program. Final report  

Energy Technology Data Exchange (ETDEWEB)

The primary objective, to promote broad use of the earlier developed elastomers technology appears to have been successfully accomplished. The expertise was transferred to three rubber products manufacturers, and is currently commercially available. Significant substantiation of the viability of the technology was fostered through supporting and tracking numerous test efforts in various industry laboratories and out in the field. Numerous papers were presented on the technology and information was also disseminated verbally and by providing data packages. The formal and informal technology transfer effort are described. Several secondary spin-offs also resulted. Steps toward a better understanding of the complex technology transfer process were achieved. The experience provides a data point illustrating one way that technology transfer can be accomplished and a data point which can be used to evaluate its effectiveness. And finally studies were made assessing the potential of elastomers to perform at even higher temperatures.

Hirasuna, A.R.; Friese, G.J.; Stephens, C.A.

1982-12-01

203

Caracterisation de l'effet du vieillissement en milieu aqueux sur les proprietes mecaniques de composites a matrice elastomere  

Science.gov (United States)

Rubber composites are widely used in several engineering fields, such as automotive, and more recently for inflatable dams and other innovative underwater applications. These rubber materials are composed by an elastomeric matrix while the reinforcing phase is a synthetic fabric. Since these components are expected to operate several years in water environment, their durability must be guaranteed. The use of rubber materials immersed in water is not new, in fact, these materials have been studied for almost one century. However, the knowledge on reinforced rubber composites immersed several years in water is still limited. In this work, investigations on reinforced rubbers were carried out in the framework of a research project in partnership with Alstom and Hydro-Quebec. The objective of this study was to identify rubber composites that could be used under water for long periods. Various rubber composites with ethylene-propylene-diene monomer (EPDM), silicone, EPDM/silicone and polychloroprene (Neoprene) matrices reinforced with E-glass fabric were studied. Thus, these materials were exposed to an accelerated ageing at 85 °C underwater for periods varying from 14 to 365 days. For comparison purposes, they were also immersed and aged one year at room temperature (21 °C). The impact of accelerated aging was estimated through three different characterization methods. Scanning electron microscopy (SEM) was first used to assess the quality of fiber-matrix interface. Then, water absorption tests were performed to quantify the rate of water absorption during immersion. Finally the evolution of the mechanical properties was followed by the determination of Young's modulus (E) and ultimate stress (sigmau) using a dedicated traction test. This analysis allowed to point out that the quality of the fiber-matrix interface was the main factor influencing the drop of the mechanical properties and their durability. Moreover, it was noticed that this interface could be improved by using appropriate coupling agent as confirmed by the silicone composite with treated fabric. It was also observed that fiber-matrix interface could be a place where high stresses were localized because of differential swelling leading to an important loss of mechanical properties. The results revealed very different behaviors from one composite to another. The accelerated aging of EPDM/silicone and Neoprene composites led to a rapid diminution of mechanical properties in only 14 days. Conversely, silicone composites showed a 20 % increase of mechanical properties after 75 days of immersion. EPDM composites exhibited an important variability from one sample to another. It can be concluded from this study that composites made from silicone matrix with treated E-glass result in a better durability underwater. Keywords: composite elastomer, accelerated ageing, immersion in the water

Favre, Audrey

204

Comparison of frictional resistance between self-ligating and conventional brackets tied with elastomeric and metal ligature in orthodontic archwires  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: comparar a resistência ao atrito entre braquetes autoligáveis e braquetes convencionais, variando o tipo de fio. MÉTODOS: foram usados braquetes incisivos Abzil Kirium Capelozza e Easy Clip. Uma ligadura elastomérica ou um fio ligável de 0,010" foi usado para ligação do fio no braque [...] te Abzil. Três tipos de ligas de fio ortodôntico foram avaliadas: fio de NiTi de 0,016"; fio de NiTi de 0,016" x 0,022"; e fio de aço de 0,019" x 0,025". Dez observações foram feitas para cada combinação "braquete-fio-inclinação". Os braquetes foram montados em um aparelho especial, posicionados a 90° em relação ao fio, e testados em duas inclinações. O teste de atrito foi realizado na máquina universal de ensaios, a 5mm/min e com 10mm de deslocamento. As médias (em MPa) foram submetidas aos testes ANOVA e de Tukey, a 5% de significância. As superfícies dos fios e dos braquetes foram observadas no MEV. RESULTADOS: o braquete com amarrilhos metálicos (16,48 ± 8,31MPa) apresentou médias mais altas que o braquete com ligaduras elastoméricas (4,29 ± 2,16MPa) e o braquete autoligável (1,66 ± 1,57) (p 0,05). Nenhuma diferença estatística (p > 0,05) foi encontrada entre inclinações de zero (7,76 ± 8,46) e cinco (7,19 ± 7,93) graus. Concluão: o atrito foi influenciado pelo tipo de braquete e sistemas de ligaduras. Diferentes aspectos morfológicos foram observados para os braquetes e fios estudados. Abstract in english OBJECTIVE: To compare the frictional resistance between self-ligating and conventional brackets tied to different types of wire. MATERIAL AND METHODS : Abzil Kirium Capelozza (Pattern I) and Easy Clip (Roth prescription) incisor brackets were used. An elastomeric ligature or a ligating wire 0. [...] 10-in was used to ligate the wire to the Abzil bracket. Three types of orthodontic archwire alloys were assessed: 0.016-in NiTi wire, 0.016 x 0.021-in NiTi wire and 0.019 x 0.025-in steel wire. Ten observations were carried out for each bracket-archwire angulation combination. Brackets were mounted in a special appliance, positioned at 90 degrees in relation to the wire and tested in two angulations. Frictional test was performed in a Universal Testing Machine at 5 mm/min and 10 mm of displacement. The means (MPa) were submitted to ANOVA and Tukey's test set at 5% of significance. The surfaces of wires and brackets were observed at SEM. RESULTS: Steel-tied brackets (16.48 ± 8.31) showed higher means of frictional resistance than elastomeric-tied brackets (4.29 ± 2.16 ) and self-ligating brackets (1.66 ± 1.57) (P 0.05). No statistical differences (P > 0.05) were found between zero (7.76 ± 8.46) and five-degree (7.19 ± 7.93) angulations. CONCLUSIONS: Friction was influenced not only by the type of bracket, but also by the ligating systems. Different morphological aspects were observed for the brackets and wires studied

Vanessa Vieira, Leite; Murilo Baena, Lopes; Alcides, Gonini Júnior; Marcio Rodrigues de, Almeida; Sandra Kiss, Moura; Renato Rodrigues de, Almeida.

2014-06-01

205

Radiation data definitions and compilation for equipment qualification data bank  

International Nuclear Information System (INIS)

Dose definitions, physical properties, mechanical properties, electrical properties, and particle definitions are listed for insulators and dielectrics, elastomeric seals and gaskets, lubricants, adhesives, and coatings

206

Cytotoxicity of latex and non-latex orthodontic elastomeric ligatures on L929 mouse fibroblasts  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Este estudo investigou a citotoxicidade entre ligaduras elásticas ortodônticas de látex e não-látex. Seis ligaduras elásticas de diferentes fabricantes (1 látex, 2 não-látex e 3 poliuretano) foram divididos em 6 grupos de 15 elásticos cada: Grupo A (látex-free, American Orthodontics), M (Poliuretano [...] , Morelli), G (Poliuretano, GAC International), Te (Poliuretano, Tecnident), TP (látex natural, TP Orthodontics) e U (Látex-free, 3M Unitek). O ensaio de citotoxicidade foi realizado utilizando culturas de células (células da linhagem L929, fibroblastos de camundongo) que foram submetidos ao teste de viabilidade celular com vermelho neutro ("dye-uptake") em 1, 2, 3, 7 e 28 dias. A análise de variância (ANOVA), com comparações múltiplas e teste de Tukey foram empregados (?=0,05). Os resultados mostraram que não houve diferença estatisticamente significante entre os Grupos M e Te em todos os tempos experimentais (p>0,05), exceto em 2 dias. Não houve diferença estatisticamente (p>0,05) entre a viabilidade das células nos grupos A, G, TP e U ou entre os grupos M e Te em 24 h, ou entre os grupos CC, A, G, TP e U em 2 e 28 dias. Concluiu-se que as ligaduras elásticas látex-free das marcas American Orthodontics e Unitek induziram menor quantidade de lise celular comparado às ligaduras de látex ou poliuretano. Abstract in english This study investigated the cytotoxicity exists between latex and non-latex Orthodontic elastomeric ligatures. Six elastomeric ligatures (1 latex, 2 latex-free and 3 polyurethane) from different manufacturers were divided into 6 groups of 15 elastics each: A (Latex-free, American Orthodontics), M (P [...] olyurethane, Morelli), G (Polyurethane,GAC International), Te (Polyurethane, Tecnident), TP (Natural latex,TP Orthodontics) and U (Latex-free,3M Unitek). The cytotoxicity assay was performed using cell cultures (L929 mouse fibroblast cell line), which were subjected to the cell viability test with neutral red ("dye-uptake") at 1, 2, 3, 7 and 28 days. Data were analyzed statistically by ANOVA and Tukey's test (?=0.05). No statistically significant differences (p>0.05) were observed between Groups M and Te in all experimental periods, except at 2 days. No significant differences (p>0.05) in cell viability were found either among Groups A, G, TP and U or between Groups M and Te at 24 h or among Groups CC, A, G, TP and U at 2 and 28 days. It may be concluded that latex-free elastomeric ligatures from American Orthodontics and Unitek trademarks induced less cell lysis compared to latex and polyurethane ligatures.

Rogério Lacerda dos, Santos; Matheus Melo, Pithon; Fernanda Otaviano, Martins; Maria Teresa Villela, Romanos; Antônio Carlos de Oliveira, Ruellas.

207

Compilation of current literature on seals, closures, and leakage for radioactive material packagings  

Energy Technology Data Exchange (ETDEWEB)

This report presents an overview of the features that affect the sealing capability of radioactive material packagings currently certified by the US Nuclear Regulatory Commission. The report is based on a review of current literature on seals, closures, and leakage for radioactive material packagings. Federal regulations that relate to the sealing capability of radioactive material packagings, as well as basic equations for leakage calculations and some of the available leakage test procedures are presented. The factors which affect the sealing capability of a closure, including the properties of the sealing surfaces, the gasket material, the closure method and the contents are discussed in qualitative terms. Information on the general properties of both elastomer and metal gasket materials and some specific designs are presented. A summary of the seal material, closure method, and leakage tests for currently certified packagings with large diameter seals is provided. 18 figs., 9 tabs.

Warrant, M.M.; Ottinger, C.A.

1989-01-01

208

A highly sensitive and flexible pressure sensor with electrodes and elastomeric interlayer containing silver nanowires  

Science.gov (United States)

The next-generation application of pressure sensors is gradually being extended to include electronic artificial skin (e-skin), wearable devices, humanoid robotics and smart prosthetics. In these advanced applications, high sensing capability is an essential feature for high performance. Although surface patterning treatments and some special elastomeric interlayers have been applied to improve sensitivity, the process is complex and this inevitably raises the cost and is an obstacle to large-scale production. In the present study a simple printing process without complex patterning has been used for constructing the sensor, and an interlayer is employed comprising elastomeric composites filled with silver nanowires. By increasing the relative permittivity, ?r, of the composite interlayer induced by compression at high nanowire concentration, it has been possible to achieve a maximum sensitivity of 5.54 kPa-1. The improvement in sensitivity did not sacrifice or undermine the other features of the sensor. Thanks to the silver nanowire electrodes, the sensor is flexible and stable after 200 cycles at a bending radius of 2 mm, and exhibits outstanding reproducibility without hysteresis under similar pressure pulses. The sensor has been readily integrated onto an adhesive bandage and has been successful in detecting human movements. In addition to measuring pressure in direct contact, non-contact pressures such as air flow can also be detected.The next-generation application of pressure sensors is gradually being extended to include electronic artificial skin (e-skin), wearable devices, humanoid robotics and smart prosthetics. In these advanced applications, high sensing capability is an essential feature for high performance. Although surface patterning treatments and some special elastomeric interlayers have been applied to improve sensitivity, the process is complex and this inevitably raises the cost and is an obstacle to large-scale production. In the present study a simple printing process without complex patterning has been used for constructing the sensor, and an interlayer is employed comprising elastomeric composites filled with silver nanowires. By increasing the relative permittivity, ?r, of the composite interlayer induced by compression at high nanowire concentration, it has been possible to achieve a maximum sensitivity of 5.54 kPa-1. The improvement in sensitivity did not sacrifice or undermine the other features of the sensor. Thanks to the silver nanowire electrodes, the sensor is flexible and stable after 200 cycles at a bending radius of 2 mm, and exhibits outstanding reproducibility without hysteresis under similar pressure pulses. The sensor has been readily integrated onto an adhesive bandage and has been successful in detecting human movements. In addition to measuring pressure in direct contact, non-contact pressures such as air flow can also be detected. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06494a

Wang, Jun; Jiu, Jinting; Nogi, Masaya; Sugahara, Tohru; Nagao, Shijo; Koga, Hirotaka; He, Peng; Suganuma, Katsuaki

2015-02-01

209

Three-dimensional Curling of Pre-strained Elastomeric Strips: From Hemi-helix to Helix  

Science.gov (United States)

A variety of three dimensional curls can be produced by a simple generic process consisting of pre-straining one elastomeric strip, joining it to another and then releasing the bi-strip. In thin strips we observe the formation of hemi-helices, which consists of multiple, alternating helical sections of half wavelength in opposite chiralities, separated by perversions. By contrast, helical shapes with uniform handedness are found when the cross-section is wide and flat. Finally, in the transition region between helices and hemi-helices not only the geometry effects but also boundary conditions as well as dynamic effects severely contributes. The phase separation of hemi-helical and helical structures has similarities with coiled polymer molecules and plant tendrils.

Liu, Jia; Huang, Jiangshui; Su, Tianxiang; Bertoldi, Katia; Clarke, David

2013-03-01

210

Mechanics of nanowire/nanotube in-surface buckling on elastomeric substrates  

Energy Technology Data Exchange (ETDEWEB)

A continuum mechanics theory is established for the in-surface buckling of one-dimensional nanomaterials on compliant substrates, such as silicon nanowires on elastomeric substrates observed in experiments. Simple analytical expressions are obtained for the buckling wavelength, amplitude and critical buckling strain in terms of the bending and tension stiffness of the nanomaterial and the substrate elastic properties. The analysis is applied to silicon nanowires, single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanotube bundles. For silicon nanowires, the measured buckling wavelength gives Young's modulus to be 140 GPa, which agrees well with the prior experimental studies. It is shown that the energy for in-surface buckling is lower than that for normal (out-of-surface) buckling, and is therefore energetically favorable.

Xiao, J; Huang, Y [Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208 (United States); Ryu, S Y; Paik, U [Division of Materials Science and Engineering, Hanyang University, 17 Hangdang-dong, Sungdong-gu, Seoul 133-791 (Korea, Republic of); Hwang, K-C [Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Rogers, J A, E-mail: y-huang@northwestern.edu, E-mail: jrogers@uiuc.edu [Department of Materials Science and Engineering, Frederick-Seitz Materials Research Laboratory and Beckman Institute, University of Illinois at Urbana-Champaign, Illinois 61801 (United States)

2010-02-26

211

Elastomeric 2D Grating and Hemispherical Optofluidic Chamber for Multifunctional Fluidic Sensing  

CERN Document Server

We present an optofluidic sensor based on an elastomeric two-dimensional (2D) grating integrated inside a hemispherical fluid chamber. Laser beam is diffracted before (reflection) and after (transmission) going through the grating and liquid in the dome chamber. The sensing mechanism is investigated and simulated with a finite difference time domain (FDTD) based electromagnetic (EM) method. For experiment, by analyzing the size, power and shape of the 2D diffraction patterns, we can retrieve multiple parameters of the liquid including the refractive index, pressure and opacity with high sensitivity. We demonstrate that glucose concentration can be monitored when mixed in different concentrated phosphate buffered saline (PBS) solution. The free-solution binding of bovine serum albumin (BSA) and anti-BSA IgG is detected with this optical sensor. This low-cost, multifunctional and reliable optofluidic sensor has the potential to be used as monitor of biofluid such as blood in hemodialysis.

Xu, Zhida

2014-01-01

212

Active Shape-Morphing Elastomeric Colloids in Short-Pitch Cholesteric Liquid Crystals  

Science.gov (United States)

Active elastomeric liquid crystal particles with initial cylindrical shapes are obtained by means of soft lithography and polymerization in a strong magnetic field. Gold nanocrystals infiltrated into these particles mediate energy transfer from laser light to heat, so that the inherent coupling between the temperature-dependent order and shape allows for dynamic morphing of these particles and well-controlled stable shapes. Continuous changes of particle shapes are followed by their spontaneous realignment and transformations of director structures in the surrounding cholesteric host, as well as locomotion in the case of a nonreciprocal shape morphing. These findings bridge the fields of liquid crystal solids and active colloids, may enable shape-controlled self-assembly of adaptive composites and light-driven micromachines, and can be understood by employing simple symmetry considerations along with electrostatic analogies.

Evans, Julian S.; Sun, Yaoran; Senyuk, Bohdan; Keller, Patrick; Pergamenshchik, Victor M.; Lee, Taewoo; Smalyukh, Ivan I.

2013-05-01

213

Analytical and empirical modeling of multilayered elastomeric isolators from damping experiments  

Science.gov (United States)

Experimental studies have been performed on elastomeric layered composites to characterize the nonlinearity in dynamic stiffness and specific damping energy, so that their performance can be enhanced as isolators. The present study is divided into two parts: (a) analytical modeling of isolator samples, and (b) formulation for glue characteristics. Several samples of layered arrangement of elastomer and metal strips were used in the experiments. Dynamic and static loading experiments were performed. All these experimental results were used in developing nonlinear empirical models for the elastomer characteristics. Furthermore creep-fatigue test was performed to explain certain observed behavior in the elastomer characteristics. Concluding part of the paper discusses empirical formulation of the layered sample considering elastomer and adhesive layers as basic elements, thus evolving a method to calculate adhesive properties.

Dutta, G. S.; Venkatesan, C.

2013-12-01

214

Elastomeric friction  

Science.gov (United States)

This dissertation examines the tribology of PDMS (polydimethylsiloxane) elastomers from a practical and a fundamental perspective. We examine the adhesive, energetic, and tribological properties of several commercial biofouling release coatings, and show that adhesive (and bioadhesive) release from an elastomer depends on the friction of its surface. Having shown that friction is an obstacle to release, we lubricate a model PDMS network by incorporating linear unreactive PDMS oils varying in molecular weight (0.8--423 kg/mol). Surface segregation upon curing depends on molecular weight and mass percentage. Atomic Force Microscopy (AFM) is used to detect the thickness of the lubricant layer. Surprisingly, high-viscosity oils lubricate better than low-viscosity oils, indicating a non-hydrodynamic lubrication. Applying this technology to a commercial elastomer, we see an improvement in bioadhesive release capabilities, as evidenced by a reduced tenacity of mussel adhesive protein. In comparing entangled polymer melts to crosslinked elastomers, we encountered an opportunity to study the tribology of the latter. We studied the effects of molecular weight, velocity, and temperature on the friction of crosslinked PDMS elastomers sliding against two model surfaces: a self-assembled monolayer (SAM) of n-hexadecylsilane, and a thin (˜100mum) film of polystyrene (PS). The change from smooth to stick-slip (unstable) interfacial sliding occurs at a distinct velocity on each surface, implying that it's not necessarily attributable to a bulk glass transition of the PDMS, as popularly believed. The peak shear stress attained immediately before stick-slip sliding is found to be linear with the shear modulus raised to an exponent n of ¾, in contrast with the predictions of Chernyak and Leonov ( n = 1). Low-velocity behavior differs greatly between the SAM and the PS, implying a mechanistic difference. Whereas on the SAM, sliding likely proceeds purely by stochastic adsorption and desorption of polymer chains, on the PS it may also proceed by disentanglement of PDMS from the PS. Temperature-variant measurements allow us to estimate the activation energy of sliding, implying strongly that the velocity of instability depends on the van der Waals interfacial interaction.

Vorvolakos, Katherine

215

Modification of PVC compounds with butadiene-acrylonitrile elastomers  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The purpose of the paper is to present the research programme on influence of acrylonitrile-butadiene copolymers on properties of plasticized polyvinylchloride as window gaskets material.Design/methodology/approach: Short literature review concerning application of modified PVC as gasket material was presented. In experimental part two types of acrylonitrile-butadiene copolymers were used as elastomeric plasticizers. Compounds with fifteen different levels of modifiers content (up to 25% by weight were prepared and tested. Additionally three commercial compounds were tested as reference formulations. The following test were performed: Shore hardness, short-term and long-term elastic recovery, tensile strength, elongation at break and migration of plasticizers from gasket material to unplasticized PVC.Findings: Application of acrylonitrile-butadiene copolymers as PVC modifier enhanced many properties essential for window gasket materials such as long-term and short term elastic recovery, tensile strength and elongation at break. At the same time addition of these elastomers did not change migration of other plasticizers contained in gasket material. Obtained results indicated that among tested compounds best properties as gasket material exhibited plasticized PVC with 23% of acrylonitrile-butadiene copolymer Chemigum P83. Reference commercial compounds exhibited worse performance properties than compounds with this acrylonitrile-butadiene copolymer. Practical implications: Research programme allowed to elaborate plasticized PVC compounds modified with acrylonitrile-butadiene copolymer that can be industrially applied for PVC window gaskets.Originality/value: Obtained results are of scientific and practical value. Research programme allowed to investigate the influence of elastomeric modifiers on plasticized PVC properties. Research results are also of practical importance.

J. Stabik

2006-04-01

216

Effects of Strain-Induced Crystallization on Mechanical Properties of Elastomeric Composites Containing Carbon Nanotubes and Carbon Black  

International Nuclear Information System (INIS)

The effects of strain-induced crystallization (SIC) on the mechanical properties of elastomeric composites as functions of extension ratio (?), multi walled carbon nanotube (CNT) content, and carbon black (CB) content are investigated. The differential scanning calorimetry (DSC) analysis shows that the degree of crystallinity increases with the increase in the CB and CNT content. As ? increases, the glass transition temperature (Tg) of the composites increases, and the latent heat of crystallization (LHc) of the composites is maximum at ?=1.5. It is found that the mechanical properties have a linear relation with LHc, depending on the CNT content. According to the TGA (thermogravimetric analysis), the weight loss of the composite matrix is 94.3% and the weight of the composites decreases with the filler content. The ratio of tensile modulus (Ecomp/ Ematrix) is higher than that of tensile strength (?comp/ ?matrix) because of the CNT orientation inside the elastomeric composites

217

Rationale for the use of protective gaskets made of geotextiles and permeability evaluation of impervious coatings made of geomembranes  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this paper is to design rationale for the use of protective pads of geotextiles and geomembranes permeability of PD using these pads. In order to justify the use of protective pads made of geotextile for reducing the defectiveness geomembrane soil fractions, the existing formulas to determine the thickness of the film element of impervious devices were examined. The calculations according to the formulas show that HDPE geomembrane with a minimum thickness of 1,0 mm, the protective lining of the geotextile should be applied at the average diameter fractions of soil of more than 6,5 mm, and for geomembranes HDPE - at a diameter of soil fractions of over 15,5 mm. In order to estimate the permeability of the TFG geomembrane using additional protective linings of geotextile in the scientific article the basic design schemes of such coatings with one and two layers of protective linings of geotextiles were considered. The evaluation results of water permeability of impervious surfaces with geotextile and for comparison - without geotextiles are given in a table. As it is shown by the data presented for the design scheme with a single layer of geotextile geomembrane at the base (in the presence of small holes in the geomembrane the decrease the effectiveness of an anti-covering is more than 268,0 %, and for the settlement scheme covering with two layers of geotextile there will be a very large reduction in the efficiency, which almost completely reduces the effectiveness of the coating to the value of the geomembrane permeability of a soil layer without geomembrane with the filtration flow rate of 71,75 m /day, against water permeability of the geomembrane cover - 38,52 m /day. From the foregoing, it can be concluded that the application of a coating design of well filtering gaskets made of geotextile is justified in terms of protecting the geomembrane from mechanical damage, but greatly reduces the effectiveness of impervious cover in case of its damage.

Kosichenko Yuriy Mikhaylovich

2015-03-01

218

The Significance of Pore Microarchitecture in a Multi-Layered Elastomeric Scaffold for Contractile Cardiac Muscle Constructs  

OpenAIRE

Multi-layered poly(glycerol sebacate) (PGS) scaffolds with controlled pore microarchitectures were fabricated, combined with heart cells, and cultured with perfusion to engineer contractile cardiac muscle constructs. First, one-layered (1L) scaffolds with accordion-like honeycomb shaped pores and elastomeric mechanical properties were fabricated by laser microablation of PGS membranes. Second, two-layered (2L) scaffolds with fully interconnected three dimensional pore networks were fabricated...

Park, H.; Larson, B. L.; Guillemette, M. D.; Jain, S. R.; Hua, C.; Engelmayr, G. C.; Freed, L. E.

2010-01-01

219

Development and characterisation of elastomeric block copolymeric substrates for myocardial tissue engineering using embryonic stem cell derived cardiomyocytes  

OpenAIRE

Cardiac patches comprised of embryonic stem cell derived cardiomyocytes (ESC-CMs) attached to biodegradable polymeric substrates were developed for patients suffering from heart attacks. Cardiomyocytes were derived from mouse and human embryonic stem cell (ESC). Thermoplastic elastomeric (TPE) block co-polymers poly(ethylene terephthalate)/dilionic acid (PET/DLA), a relatively slow degrading biomaterial, served as substrates to deliver cardiomyocytes and to further support the ...

Jawad, Hedeer Zuhair

2009-01-01

220

Migration of epoxidised soybean oil from PVC gaskets of commercial lids: simulation of migration under various conditions and screening of food products from Czech markets.  

Science.gov (United States)

Previous studies have shown that a large number of polyvinylchloride (PVC) lid gaskets exceed the existing migration limits for epoxidised soybean oil (ESBO) and correct prediction of ESBO release into food therefore appears to be a difficult issue. ESBO migration from PVC gaskets of metal closures into food simulants and food products from the Czech market is evaluated during a survey in 2009 and subsequently one in 2012 to assess progress in lid manufacturing and official testing conditions. ESBO migration from lids into various food simulants was studied at various temperatures (25, 40 and 60°C) during storage times up to 12 months. ESBO released into food simulants or food products was transmethylated, derivatised and analysed by GC-MS. The levels of ESBO migration in foodstuffs in 2012 exceeded the specific migration limit (SML) in fewer products in comparison with the previous survey. However, most of the products were analysed at a time far from the expiry date and exceedance of the SML at the end of the product shelf life is not therefore excluded. More severe test conditions (60°C for 10 days) for specific migration given by the current European Union legislation (Regulation (EU) No. 10/2011) still seem to be insufficient for the simulation of ESBO migration during long-term storage. PMID:25685888

Hanušová, Kristýna; Vrbík, Karel; Rajchl, Aleš; Dobiáš, Jaroslav; Sosnovcová, Jitka

2015-03-01

221

Evaluation of the susceptibility to pigmentation of orthodontic esthetic elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available OBJETIVO: avaliar alterações da pigmentação de ligaduras elásticas estéticas após imersão em solução de pigmentação. MÉTODOS: Sessenta ligaduras foram selecionadas e divididas em doze grupos de acordo com a marca comercial utilizada e nas condições normal e distendida. Os grupos foram divididos em: [...] Morelli transparente, TP Orthodontics transparente, American Orthodontics transparente, Unitek/3M transparente, American Orthodontics pérola e Unitek/3M pérola, separados quanto à condição normal e distendida, totalizando 5 ligaduras em cada condição. A avaliação das mudanças de coloração foi realizada por meio de fotografia digital e análise computadorizada usando o programa Adobe Photoshop. Foram realizadas fotografias digitais padronizadas nos tempos T0 - antes do processo de pigmentação, com as ligaduras em estado normal; e T1 - após o processo de pigmentação, que durou cinco dias. A solução de pigmentação utilizada foi composta por saliva artificial e por alimentos que possuem potencial de coloração. No tempo T1, as ligaduras se encontravam em estado distendido e em estado normal (sem distensão). RESULTADO: os resultados do presente estudo demonstraram que ligaduras elásticas estéticas são suscetíveis à pigmentação. Dentre as marcas comerciais avaliadas a TP Orthodontics e American Orthodontics transparente foram as mais estáveis. Já a Unitek/3M pérola demonstrou alterações estatisticamente significativas em todas as variáveis avaliadas. CONCLUSÃO: ligaduras elásticas estéticas são suscetíveis à pigmentação, não havendo diferença estatisticamente significativa entre o estado normal e o estado distendido, com exceção na marca TP Orthodontics. A marca Unitek/3M pérola demonstrou ser a que apresenta maior potencial para pigmentação. Abstract in english OBJECTIVE: The purpose of this laboratory study was to evaluate changes in the pigmentation of esthetic elastomeric ligatures after immersion in a staining solution. METHODS: Sixty ligatures were selected and divided into 12 groups according to their brand and also considering their condition, i.e., [...] unstretched or stretched. The groups were divided into: Morelli (clear), TP Orthodontics (clear), American Orthodontics (clear), 3M/Unitek (clear), American Orthodontics (pearl color) and 3M/Unitek (pearl color), separated into groups of 5 unstretched and five stretched ligatures. Assessment of their color changes was performed by means of digital photograph and computer analysis using Adobe Photoshop. Standardized digital photographs were taken at T0 (before the staining process, with unstretched ligatures) and at T1 (following the 5-days staining process). The staining solution was composed of artificial saliva and foods with staining potential. At T1 the ligatures were either stretched or unstretched. RESULTS: The results of this study showed that esthetic elastomeric ligatures are prone to staining. Among the evaluated brands, TP Orthodontics and American Orthodontics clear ligatures were the most stable. Moreover, 3M/Unitek pearl ligatures demonstrated statistically significant changes in all variables. CONCLUSIONS: Esthetic elastomeric ligatures are susceptible to staining and no statistically significant difference was found between unstretched or stretched ligatures, with the sole exception of the TP Orthodontics brand. The 3M/Unitek's pearl color ligatures displayed the greatest staining potential.

Janine Soares, Cavalcante; Marcelo de Castellucci e, Barbosa; Marcio Costa, Sobral.

2013-04-01

222

Deformation of elastomeric chains related to the amount and time of stretching  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: verificar a possível relação entre o grau de estiramento e a consequente deformação permanente dos elásticos em cadeia, bem como se o fator tempo de estiramento tem influência sobre o grau de deformação permanente. MÉTODOS: segmentos de 5 elos de elásticos em cadeia curta da Unitek/3M fora [...] m estirados em de 10 a 100% de seu comprimento original, em dispositivos especialmente idealizados para essa finalidade, permanecendo submersos em saliva artificial a 37 ± 1°C e removidos, sequencialmente, após uma, duas, três e quatro semanas. Quando de sua remoção, para se avaliar o grau de deformação permanente, cada segmento era medido e os valores registrados submetidos à análise estatística. CONCLUSÃO: pode-se concluir que a deformação permanente foi diretamente proporcional ao grau de estiramento dos elásticos em cadeia avaliados, onde os percentuais médios encontrados foram de 8,4% com 10% de estiramento, ultrapassando o percentual de 20% (21,3%) quando distendidos em 40%, chegando a 56,6% de deformação permanente se estirados em 100% de seu comprimento original. Por fim, o maior percentual de deformação permanente ocorreu durante a primeira semana, não sendo estatisticamente significativo após esse período. Abstract in english OBJECTIVE: To investigate a potential relationship between degree of stretching and resulting permanent deformation of elastomeric chains (ECs) as well as whether or not stretching time has any bearing on the degree of permanent deformation. METHODS: Five-module segments of closed elastomeric chains [...] manufactured by 3M Unitek were stretched to 10-100% of their original length in devices especially designed for this purpose, remaining submerged in artificial saliva at 37 ± 1° C and were removed sequentially after 1, 2, 3 and 4 weeks. Upon removal, each segment was measured and, once recorded the values, were statistically analyzed with the purpose of assessing the degree of permanent deformation. CONCLUSIONS: It was concluded that permanent deformation is directly proportional to the degree of stretching of the ECs assessed. The mean percentages found were 8.4% to 10% of stretching, and exceeding 20% (21.3%) when stretched by 40%, and reaching 56.6% permanent deformation when stretched 100% of their original length. Finally, the highest percentage of permanent deformation occurred during the first week and was not statistically significant after this period.

Denise, Yagura; Paulo Eduardo, Baggio; Luiz Sérgio, Carreiro; Ricardo, Takahashi.

2013-06-01

223

Percentual de degradação das forças liberadas por ligaduras elásticas / Force decay rate of orthodontic elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: avaliar ligaduras elásticas da marca Morelli, dos tipos modular e bengala, nas cores cinza e cristal para determinação do percentual de degradação das forças geradas pelas mesmas. METODOLOGIA: as ligaduras elásticas foram estiradas em estiletes de aço inoxidável com diâmetro de 4mm, imersa [...] s em solução de saliva artificial a 37ºC, sendo a intensidade das forças liberadas medidas nos tempos de zero hora, 24 horas, 1 semana, 2 semanas, 3 semanas e 4 semanas, em máquina de ensaios de tração. RESULTADOS E CONCLUSÕES: as ligaduras do tipo bengala liberaram, em média e no período de 4 semanas, maior intensidade de força que as do tipo modular. O percentual de degradação das forças liberadas por todas as ligaduras aumentou de forma acentuada entre zero e 24 horas e de forma gradativa após este período, com exceção do 28º dia quando, provavelmente, houve perda das propriedades elásticas das ligaduras. Não foi observado um comportamento constante das ligaduras bengala e modular em relação às cores cinza e cristal. Abstract in english PURPOSE: to evaluate gray and clear module and cane-loaded elastomeric ligatures of the brand Morelli to determine the percentage of decay of the forces they deliver. METHODS: the elastomeric ligatures were stretched over 4mm diameter stainless steel dowels and placed in synthetic saliva bath at 37º [...] C. The intensity of the forces delivered were taken at start, after 24 hours, one week, two weeks, three weeks and four weeks at a tensile test machine. RESULTS AND CONCLUSIONS: the cane-loaded ligatures delivered, in a period of 4 weeks, in average, greater force intensity than the modules. The percentage of force decay of all ligatures increased rapidly between zero and 24 hours and gradually after that period, except for the 28th day, when probably there was a loss of elastic properties of the ligatures. The researchers did not note any constant behavior in the cane-loaded and module ligatures in relation to the colors: gray and clear.

Emanoela Volles de, Souza; Alvaro de Moraes, Mendes; Marco Antônio de Oliveira, Almeida; Cátia Cardoso Abdo, Quintão.

2008-04-01

224

Percentual de degradação das forças liberadas por ligaduras elásticas Force decay rate of orthodontic elastomeric ligatures  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: avaliar ligaduras elásticas da marca Morelli, dos tipos modular e bengala, nas cores cinza e cristal para determinação do percentual de degradação das forças geradas pelas mesmas. METODOLOGIA: as ligaduras elásticas foram estiradas em estiletes de aço inoxidável com diâmetro de 4mm, imersas em solução de saliva artificial a 37ºC, sendo a intensidade das forças liberadas medidas nos tempos de zero hora, 24 horas, 1 semana, 2 semanas, 3 semanas e 4 semanas, em máquina de ensaios de tração. RESULTADOS E CONCLUSÕES: as ligaduras do tipo bengala liberaram, em média e no período de 4 semanas, maior intensidade de força que as do tipo modular. O percentual de degradação das forças liberadas por todas as ligaduras aumentou de forma acentuada entre zero e 24 horas e de forma gradativa após este período, com exceção do 28º dia quando, provavelmente, houve perda das propriedades elásticas das ligaduras. Não foi observado um comportamento constante das ligaduras bengala e modular em relação às cores cinza e cristal.PURPOSE: to evaluate gray and clear module and cane-loaded elastomeric ligatures of the brand Morelli to determine the percentage of decay of the forces they deliver. METHODS: the elastomeric ligatures were stretched over 4mm diameter stainless steel dowels and placed in synthetic saliva bath at 37ºC. The intensity of the forces delivered were taken at start, after 24 hours, one week, two weeks, three weeks and four weeks at a tensile test machine. RESULTS AND CONCLUSIONS: the cane-loaded ligatures delivered, in a period of 4 weeks, in average, greater force intensity than the modules. The percentage of force decay of all ligatures increased rapidly between zero and 24 hours and gradually after that period, except for the 28th day, when probably there was a loss of elastic properties of the ligatures. The researchers did not note any constant behavior in the cane-loaded and module ligatures in relation to the colors: gray and clear.

Emanoela Volles de Souza

2008-04-01

225

Experimental characterization of small thickness elastomeric layers submitted to impact loading  

Science.gov (United States)

An experimental device has been developed to submit small thickness (test hammer is used as an impactor to measure directly the dynamic force applied on the specimen. As an alternative to classical methods in which position is measured by time integration(s) of accelerometers or velocity sensors, the measurement of the hammer position during impact is achieved by recording its motion with a high-speed camera (at a rate of 30,000 frames per second) and by detecting its position by further analysis on the individual images. Additionally, the initial impact velocity is determined from measurements of the hammer position on the images before contact. The impact model proposed only requires five parameters: two parameters for the impactor (its mass and initial impact velocity) and three parameters for the Hunt-Crossley contact force law describing the specimen. Using a relation issued from the force versus penetration depth diagrams, the estimation of these three contact force parameters can be reduced to the estimation of two independent parameters which roles are well defined and distinct; therefore this estimation can be accomplished with a straightforward trial and error procedure. The method is used to characterize eight impacted elastomeric specimens and is validated with comparisons between experimental and simulation results. These comparisons show that the model is appropriate to simulate with reasonable precision the main experimental characteristics of force and penetration depth signals.

Arz, Jean-Pierre; Laville, Frédéric

2009-09-01

226

Parallel near-field photolithography with metal-coated elastomeric masks.  

Science.gov (United States)

Developing a cost-effective nanolithography strategy that enables the production of subwavelength features with various shapes over large areas is a long-standing goal in the nanotechnology community. Herein, an inexpensive nanolithographic technique that combines the wafer-scale production capability of photolithography with the subwavelength feature size controllability of near-field photolithography was developed to fabricate centimeter-scale up to wafer-scale sub-100-nm variously shaped nanopatterns on surfaces. The wafer-scale elastomeric trench-based photomasks with subwavelength apertures created at the apexes were compatible with mask aligners, allowing for the production of wafer-scale subwavelength nanopatterns with adjustable feature sizes, shapes, and periodicities. The smallest feature sizes of 50 and 80 nm were achieved on positive tone and negative tone photoresist surfaces, respectively, which could be ascribed to a near-field optical effect. The fabricated centimeter-scale nanopatterns were functionalized to study cell-matrix adhesion and migration. Compared to currently developed nanolithographic methods that approach similar functionalities, this facile nanolithographic strategy combines the merits of low cost, subwavelength feature size, high throughput, and varied feature shapes, making it an affordable approach to be used in academic research for researchers at most institutions. PMID:25549246

Wu, Jin; Yu, Cheng-han; Li, Shaozhou; Zou, Binghua; Liu, Yayuan; Zhu, Xiaoqun; Guo, Yuanyuan; Xu, Hongbo; Zhang, Weina; Zhang, Liping; Liu, Bin; Tian, Danbi; Huang, Wei; Sheetz, Michael P; Huo, Fengwei

2015-01-27

227

Optomechanical tolerancing and lens alignment using elastomeric lens mount to efficiently meet optical requirements  

Science.gov (United States)

Lens positioning accuracy and manufacturing cost are two main concerns for optomechanical engineers looking for solutions to reduce costs while meeting stringent optical and environmental requirements. Minimizing optical component positioning errors generally translates into significant cost increases. To maximize the precision-to-cost ratio, there are significant advantages in having both an accurate optomechanical tolerance calculation method and an effective technique to mount and align lenses. This paper presents a tool that has been developed at INO to easily perform complex optomechanical statistical tolerancing using Monte Carlo simulation to reduce manufacturing and alignment costs. This tolerancing method provides a more realistic prediction of optical component errors compared to the classical worst case and root sum square calculations. In addition, precision alignment using elastomeric lens mounting is presented. Thermal stability and often overlooked factors for effective alignments are discussed. Results of tests performed on real optical assemblies are presented for tolerancing, thermal stability and alignment performance. The use of these methods can considerably reduce cost while efficiently ensuring compliance with requirements.

Lamontagne, Frédéric; Doucet, Michel; Savard, Maxime; Wang, Min

2013-09-01

228

Static characterization of a soft elastomeric capacitor for non destructive evaluation applications  

International Nuclear Information System (INIS)

A large and flexible strain transducer consisting of a soft elastomeric capacitor (SEC) has been proposed by the authors. Arranged in a network setup, the sensing strategy offers tremendous potential at conducting non-destructive evaluation of large-scale surfaces. In prior work, the authors have demonstrated the performance of the sensor at tracking strain history, localizing cracks, and detecting vibration signatures. In this paper, we characterize the static performance of the proposed SEC. The characterization includes sensitivity of the signal, and temperature and humidity dependences. Tests are conducted on a simply supported aluminum beam subjected to bending as well as on a free standing sensor. The performance of the SEC is compared against off-the-shelf resistance-based strain gauges with resolution of 1 ??. A sensitivity of 1190 pF/? is obtained experimentally, in agreement with theory. Results also show the sensor linearity over the given level of strain, showing the promise of the SEC at monitoring of surface strain

229

Patterning the Stiffness of Elastomeric Nanocomposites by Magnetophoretic Control of Cross-linking Impeder Distribution  

Directory of Open Access Journals (Sweden)

Full Text Available We report a novel method to pattern the stiffness of an elastomeric nanocomposite by selectively impeding the cross-linking reactions at desired locations while curing. This is accomplished by using a magnetic field to enforce a desired concentration distribution of colloidal magnetite nanoparticles (MNPs in the liquid precursor of polydimethysiloxane (PDMS elastomer. MNPs impede the cross-linking of PDMS; when they are dispersed in liquid PDMS, the cured elastomer exhibits lower stiffness in portions containing a higher nanoparticle concentration. Consequently, a desired stiffness pattern is produced by selecting the required magnetic field distribution a priori. Up to 200% variation in the reduced modulus is observed over a 2 mm length, and gradients of up to 12.6 MPa·mm?1 are obtained. This is a significant improvement over conventional nanocomposite systems where only small unidirectional variations can be achieved by varying nanoparticle concentration. The method has promising prospects in additive manufacturing; it can be integrated with existing systems thereby adding the capability to produce microscale heterogeneities in mechanical properties.

Suvojit Ghosh

2015-01-01

230

Mechanics and optics of stretchable elastomeric microlens array for artificial compound eye camera  

Science.gov (United States)

Compound eye-inspired imaging devices can find vast applications due to their remarkable imaging characteristics, such as extremely large field of view angle, low aberrations, high acuity to motion, and infinite depth of field. Recently, researchers have successfully developed a digital camera that resembles the structure and functions of apposition compound eyes of arthropod, by combining an elastic array of microlenses with a stretchable array of photodetectors in their planar form and then transforming into a hemispherical shape. Designing an elastomeric microlens array that can be mechanically stretched to very large extent without deteriorating the optical performance is critical to this development. In this study, mechanics and optics of the stretchable microlens array, in which each hemispherical microlens sits on top of a supporting post connected to a base membrane, are studied. The results show that proper designs of the microlenses, supporting posts and base membrane are critically important to meet both mechanical and optical requirements simultaneously. This study can have important implications in not only the design of artificial compound eye cameras, but also other developments that require stretchable optical elements.

Li, Zhengwei; Xiao, Jianliang

2015-01-01

231

Static characterization of a soft elastomeric capacitor for non destructive evaluation applications  

Energy Technology Data Exchange (ETDEWEB)

A large and flexible strain transducer consisting of a soft elastomeric capacitor (SEC) has been proposed by the authors. Arranged in a network setup, the sensing strategy offers tremendous potential at conducting non-destructive evaluation of large-scale surfaces. In prior work, the authors have demonstrated the performance of the sensor at tracking strain history, localizing cracks, and detecting vibration signatures. In this paper, we characterize the static performance of the proposed SEC. The characterization includes sensitivity of the signal, and temperature and humidity dependences. Tests are conducted on a simply supported aluminum beam subjected to bending as well as on a free standing sensor. The performance of the SEC is compared against off-the-shelf resistance-based strain gauges with resolution of 1 ??. A sensitivity of 1190 pF/? is obtained experimentally, in agreement with theory. Results also show the sensor linearity over the given level of strain, showing the promise of the SEC at monitoring of surface strain.

Saleem, Hussam [Civil, Construction and Environmental Engineering, Iowa State University (United States); Laflamme, Simon [Civil, Construction and Environmental Engineering, Iowa State University and Electrical and Computer Engineering, Iowa State University (United States); Zhang, Huanhuan; Geiger, Randall [Electrical and Computer Engineering, Iowa State University (United States); Kessler, Michael; Rajan, Krishna [Materials Science and Engineering, Iowa State University (United States)

2014-02-18

232

Probing Mechanoregulation of Neuronal Differentiation by Plasma Lithography Patterned Elastomeric Substrates  

Science.gov (United States)

Cells sense and interpret mechanical cues, including cell-cell and cell-substrate interactions, in the microenvironment to collectively regulate various physiological functions. Understanding the influences of these mechanical factors on cell behavior is critical for fundamental cell biology and for the development of novel strategies in regenerative medicine. Here, we demonstrate plasma lithography patterning on elastomeric substrates for elucidating the influences of mechanical cues on neuronal differentiation and neuritogenesis. The neuroblastoma cells form neuronal spheres on plasma-treated regions, which geometrically confine the cells over two weeks. The elastic modulus of the elastomer is controlled simultaneously by the crosslinker concentration. The cell-substrate mechanical interactions are also investigated by controlling the size of neuronal spheres with different cell seeding densities. These physical cues are shown to modulate with the formation of focal adhesions, neurite outgrowth, and the morphology of neuroblastoma. By systematic adjustment of these cues, along with computational biomechanical analysis, we demonstrate the interrelated mechanoregulatory effects of substrate elasticity and cell size. Taken together, our results reveal that the neuronal differentiation and neuritogenesis of neuroblastoma cells are collectively regulated via the cell-substrate mechanical interactions.

Nam, Ki-Hwan; Jamilpour, Nima; Mfoumou, Etienne; Wang, Fei-Yue; Zhang, Donna D.; Wong, Pak Kin

2014-11-01

233

Influence of root embedment material and periodontal ligament simulation on fracture resistance tests Influência do material de inclusão e da simulação do ligamento periodontal nos ensaios de resistência à fratura  

OpenAIRE

The aim of this study was to evaluate the influence of the embedment material and periodontal ligament simulation on fracture resistance of bovine teeth. Eighty bovine incisor teeth were randomized into 8 groups (n = 10), embedded in acrylic or polystyrene resin using 4 types of periodontal ligament simulation: 1 - absence of the ligament; 2 - polyether impression material; 3 - polysulfide impression material; 4 - polyurethane elastomeric material. The specimens were stored at 37°C and 100% ...

Carlos José Soares; Eliane Cristina Gava Pizi; Rodrigo Borges Fonseca; Luis Roberto Marcondes Martins

2005-01-01

234

Tensile Properties and Small-Angle Neutron Scattering Investigation of Stereoblock Elastomeric Polypropylene  

Energy Technology Data Exchange (ETDEWEB)

Elastomeric polypropylene (ePP) produced from unbridged 2-arylindene metallocene catalysts was studied by uniaxial tensile and small-angle neutron scattering (SANS) techniques. The ePP can be separated into three fractions by successive boiling-solvent fractionation method to yield: a low-tacticity fraction soluble in ether (ES), an intermediate-tacticity fraction soluble in heptane (HS), and a high-tacticity fraction insoluble in heptane (HI). Tensile properties of ePP were compared to its solvent fractions, and the role of each solvent fraction residing within ePP was investigated by blending 5 weight % deuterated fraction with ePP. The tensile properties of each fraction vary considerably, exhibiting properties from a weak gum elastomer for ES, to a semi-crystalline thermoplastic for HI. The intermediate-tacticity HS fraction exhibits elastic properties similar to the parent elastomer (ePP). In the melt at 160 C, SANS shows that all deuterated fractions are homogeneously mixed with ePP in a one-phase system. At 25 C upon a slow cooling from the melt, the low-tacticity fraction is preferentially segregated in the amorphous domains induced by different crystallization temperatures and kinetics of the deuterated ES and high-tacticity components. The high-tacticity component within ePP (dHI-ePP) retains its plastic properties in the blend. Despite its low crystallinity ({le} 2%), the low-tacticity fraction can co-crystallize with the crystalline matrix. The dES-ePP shows little or no relaxation when held under strain and recovers readily upon the release of stress.

Pople, John A

2002-08-06

235

Stability Test of Ampicillin Sodium Solutions in the Accufuser® Elastomeric Infusion Device Using HPLC: UV Method  

Directory of Open Access Journals (Sweden)

Full Text Available The stabilities of two kinds of solutions (30 mg/mL of Ampicillin sodium in 0.9% NaCl in water (NS, normal saline and in sterile water (SW in the intravenous elastomeric infusion device (Accufuser® were evaluated based on recommended solutions and storage periods. The injectable NS- and SW-Ampicillin solutions in the Accufuser® device were stored and evaluated at controlled temperature (room temperature, 25? ± 2? and cold temperature, 4? ± 2? during 7 days. Effects of the periods of storage (from 0 to 7 days and the temperatures of storage (RT and CT on the physico-chemical appearances and concentrations of active compounds were determined. The visual clarity, pH, and concentrations of Ampicillin were determined by stability-indicating high-performance liquid chromatography (HPLC-ultraviolet (UV detection. The results showed that the amount of Ampicillin in studied solutions gradually decreased with time. The Ampicillin in NS, which was stored in CT, was relatively stable, retaining 94% of its original amount up to 7 days. The solution that showed least stability was Ampicillin in SW, which was stored in RT, retaining 80% of its original amount. Generally, solutions that were stored in CT were more stable than the solutions that were stored in RT. No significant changes in physical appearance or color of the solutions were observed during the study. Particles were not detected in any solution samples. In summary, two kinds of solutions of Ampicillin sodium, in NS and SW, showed different chemical stabilities with time in intravenous infusion device without any significant physical changes and retained about 94% vs 89% and 83% vs 80% of initial concentrations after 7 days in CT and RT, respectively. We suggest that 30 mg/mL of Ampicillin sodium in NS solution in an Accufuser® infusion device which is stored in CT can be applicable for 7 days in clinical situations.

Min A Kang

2012-10-01

236

On the mobility of iron particles embedded in elastomeric silicone matrix  

International Nuclear Information System (INIS)

In this contribution the rheological and magnetorheological properties of different polydimethylsiloxane (PDMS) based magnetorheological elastomers (MRE) are presented and discussed. In order to investigate the mobility of the iron particles with respect to the rheological characteristics, the iron particles were silanized with vinyltrimethoxysilane to enable a reaction between the modified particle and the cross-linking agent of the silicone elastomer. In addition, the vinyl-functionalized particles were further modified by the coupling of the superficial vinyl groups with a long-chain hydride terminated PDMS, which enables a reaction pathway with the vinyl terminated PDMS. On the other hand, the iron particles were treated with surfactants such as fatty acids, calcium and aluminum soaps, respectively, prior to vulcanization in order to increase the mobility of the iron particles in the elastomeric matrix. It was found, that both, the modification with the long-chain hydride terminated PDMS as well as the treatment with surfactants lead to an increase of the storage modulus G', the loss modulus G'' and the loss factor tan ? in the magnetic field. It is concluded that both modifications, the coupling with long-chain hydride terminated PDMS as well as the treatment with surfactants, provide a greater mobility of the iron particles and hence a greater friction represented by the increase of the loss factor tan ?. Consequently it is assumed that untreated iron particle is assumed that untreated iron particles are less mobile in the rubber matrix due to covalent bonding with the silicone components, most likely due to the reaction of the hydroxyl groups on the metal surface with the silane groups of the cross-linking agent.

237

On the mobility of iron particles embedded in elastomeric silicone matrix  

Science.gov (United States)

In this contribution the rheological and magnetorheological properties of different polydimethylsiloxane (PDMS) based magnetorheological elastomers (MRE) are presented and discussed. In order to investigate the mobility of the iron particles with respect to the rheological characteristics, the iron particles were silanized with vinyltrimethoxysilane to enable a reaction between the modified particle and the cross-linking agent of the silicone elastomer. In addition, the vinyl-functionalized particles were further modified by the coupling of the superficial vinyl groups with a long-chain hydride terminated PDMS, which enables a reaction pathway with the vinyl terminated PDMS. On the other hand, the iron particles were treated with surfactants such as fatty acids, calcium and aluminum soaps, respectively, prior to vulcanization in order to increase the mobility of the iron particles in the elastomeric matrix. It was found, that both, the modification with the long-chain hydride terminated PDMS as well as the treatment with surfactants lead to an increase of the storage modulus G', the loss modulus G" and the loss factor tan ? in the magnetic field. It is concluded that both modifications, the coupling with long-chain hydride terminated PDMS as well as the treatment with surfactants, provide a greater mobility of the iron particles and hence a greater friction represented by the increase of the loss factor tan ?. Consequently it is assumed that untreated iron particles are less mobile in the rubber matrix due to covalent bonding with the silicone components, most likely due to the reaction of the hydroxyl groups on the metal surface with the silane groups of the cross-linking agent.

Rabindranath, R.; Böse, H.

2013-02-01

238

Study on domestic material purchasing in MSR manufacture of conventional island  

International Nuclear Information System (INIS)

Combining the real case of Dongfang Electric (Guangzhou) Heavy Machinery Co., Ltd. trying to purchase the domestic sealing gasket as needed in the MSR of the conventional island, this paper describes the trends and relevant experience about nuclear power equipment manufacturers purchasing materials in the domestic market, and provides a reference to broadening the procurement channels of the purchasing departments of nuclear equipment manufacturers. (author)

239

Effects of Strain-Induced Crystallization on Mechanical Properties of Elastomeric Composites Containing Carbon Nanotubes and Carbon Black  

Energy Technology Data Exchange (ETDEWEB)

The effects of strain-induced crystallization (SIC) on the mechanical properties of elastomeric composites as functions of extension ratio ({lambda}), multi walled carbon nanotube (CNT) content, and carbon black (CB) content are investigated. The differential scanning calorimetry (DSC) analysis shows that the degree of crystallinity increases with the increase in the CB and CNT content. As {lambda} increases, the glass transition temperature (Tg) of the composites increases, and the latent heat of crystallization (LHc) of the composites is maximum at {lambda}=1.5. It is found that the mechanical properties have a linear relation with LHc, depending on the CNT content. According to the TGA (thermogravimetric analysis), the weight loss of the composite matrix is 94.3% and the weight of the composites decreases with the filler content. The ratio of tensile modulus (E{sub comp}/ E{sub matrix}) is higher than that of tensile strength ({sigma}{sub comp}/ {sigma}{sub matrix}) because of the CNT orientation inside the elastomeric composites.

Sung, Jong Hwan; Ryu, Sang Ryeoul; Lee, Dong Joo [Yeungnam University, Gyeongsan (Korea, Republic of)

2011-09-15

240

Materials  

Science.gov (United States)

NASA Langley Research Center has successfully developed an electron beam freeform fabrication (EBF3) process, a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. The EBF3 process produces structural metallic parts with strengths comparable to that of wrought product forms and has been demonstrated on aluminum, titanium, and nickel-based alloys to date. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas. Advanced metal manufacturing methods such as EBF3 are being explored for fabrication and repair of aerospace structures, offering potential for improvements in cost, weight, and performance to enhance mission success for aircraft, launch vehicles, and spacecraft. Near-term applications of the EBF3 process are most likely to be implemented for cost reduction and lead time reduction through addition of details onto simplified preforms (casting or forging). This is particularly attractive for components with protruding details that would require a significantly large volume of material to be machined away from an oversized forging, offering significant reductions to the buy-to-fly ratio. Future far-term applications promise improved structural efficiency through reduced weight and improved performance by exploiting the layer-additive nature of the EBF3 process to fabricate tailored unitized structures with functionally graded microstructures and compositions.

Glaessgen, Edward H.; Schoeppner, Gregory A.

2006-01-01

241

Case files of the University of Massachusetts Fellowship in Medical Toxicology: Lethal dose of opioids contained in an elastomeric capsule labeled as vancomycin  

OpenAIRE

This case describes the adulteration of a vancomycin elastomeric capsule with opioids that likely arose from degradation of heroin [29–31]. Although the clinical management of patients suffering the effects of contaminated drugs may be straightforward, the public health risk associated with adulterated pharmaceuticals and drug delivery devices should mandate a brisk response from governmental regulatory agencies.

Courtney, James M.; Boyer, Edward W.

2008-01-01

242

Development of bus body rubber profiles with additives from renewable sources: Part I – Additives characterization and processing and cure properties of elastomeric compositions  

International Nuclear Information System (INIS)

Highlights: • Bus body rubber profiles with additives from renewable sources. • Soybean oil, vulcanization activator from ethanol production and cereal loading filler. • Physical, chemical and thermal characterization of the additives. • Processing and cure properties of elastomeric compositions. • Components commonly used by the rubber industry can be replaced by these additives. - Abstract: The goal of this work was to characterize additives from renewable sources aiming replace the components that are traditionally used by the rubber industry in a formulation with terpolymer of ethylene–propylene–diene (EPDM). Soybean oil (MD600®) was used as a plasticizer. The vulcanization activator (MDECR®) was a sub-product from cellulosic ethanol production, while the loading filler (MDCO®) was obtained from cereals. Firstly, the physical, chemical and thermal properties of these additives were investigated. Thus, a standard composition used for bus body rubber profiles and compositions containing varying proportions of these additives were prepared. The acceleration system was added in a laboratory two-roll mill after the elastomeric compositions were processed in a torque rheometer. The elastomeric compositions were characterized by their cure properties, Mooney viscosities, differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD). The addition of these additives led to a decrease in the viscosity, work, energy and Mooney viscosity of each composition, thus improving its processability. The curing characteristics of elastomeric compositions were affected by the addition of MD600® and MDECR®, leading to lower vulcanization time, while the cure properties were not affected by the addition of MDCO®

243

Statistical study of static gasket conductance; Etude statistique de la conductance d'un joint d'etancheite statique  

Energy Technology Data Exchange (ETDEWEB)

This work is motivated by tightness technological problems associated with metallic gasket. The objective is a better understanding of leakage mechanisms, through the development of new computational tools. In this study, the aperture field between two rough surfaces in contact is described by a short correlated isotropic random Gaussian process. The system is studied as a set of independent elementary surfaces. Joint conductances are evaluated from a statistical study on those elementary surfaces. A computational code is developed using a network approach based on lubrication theory estimation of local conductances. The global conductance computation becomes analogous to an electrical problem for which the resistances are distributed on a random network. The network is built from the identification of the aperture field critical points. Maxima are linked through saddle points. Bond conductances are estimated at the aperture field saddle points. First, a purely plastic model of deformations is considered. Near percolation threshold the conductances display a power behaviour. Far from percolation threshold, numerical results are favourably compared with an effective medium approximation. Secondly, we study the impact of elastic deformations. A computational code based on Boussinesq approximation is coupled to the network approach. The results indicate a significant impact of elastic deformations on conductances. Finally, the network approach is adapted to simulate quasi-static drainage thanks to a classical invasion percolation algorithm. A good comparison between previous experiments and numerical predictions is obtained. (author)

Flukiger, F

2005-10-15

244

Rapid identification of additives in poly(vinyl chloride) lid gaskets by direct analysis in real time ionisation and single-quadrupole mass spectrometry.  

Science.gov (United States)

Gaskets for lids of glass jars usually consist of poly(vinyl chloride) (PVC) containing plasticisers and additional additives, which may migrate into packed foodstuffs. To conform to legal regulations, any such migration has to be determined analytically, which is a big challenge due to the huge chemical variety of additives in use. Therefore, a rapid screening method by means of direct analysis in real time mass spectrometry (DART-MS), using a single-quadrupole mass spectrometer, was developed. On introducing a plastisol sample into the DART interface, protonated molecules and ammonium adducts were obtained as the typical ionisation products of any additives present, and cleavages of ester bonds as typical fragmentation processes. Generally, additives present in the 1% range could be directly and easily identified if ion suppressive effects deriving from specific molecules did not occur. These effects could be avoided by analysing toluene extracts of plastisol samples, and this also improved the sensitivity. Using this method, it was possible to identify phthalates, fatty acid amides, tributyl O-acetylcitrate, dibutyl sebacate, bis(2-ethylhexyl) adipate, 1,2-diisononyl 1,2-cyclohexanedicarboxylate, and even more complex additives like acetylated mono- and diacylglycerides, epoxidised soybean oil, and polyadipates, with a limit of detection of or = 5% required for identification. The detection of azodicarbonamide, used as a foaming agent within the manufacturing process, was possible in principle, but was not highly reproducible due to the very low concentrations in plastisols. PMID:19957297

Rothenbacher, Thorsten; Schwack, Wolfgang

2010-01-01

245

Spontaneous and Deterministic Three-dimensional Curling of Pre-strained Elastomeric Strips: From Hemi-helix to Helix  

Science.gov (United States)

A variety of three dimensional curls are produced by a simple generic process consisting of pre-straining one elastomeric strip, joining it to another and then releasing the bi-strip. The hemi-helix, one kind of three dimensional curls, consists of multiple, alternating helical sections of half wavelength in opposite chiralities and separated by perversions. The hemi-helix wavelength and the number of perversions are determined by the strip cross-section, the constitutive behavior of the elastomer and the value of the pre-strain. Topologically, the perversions also separate regions of the helix deforming principally by bending from those where twisting dominates. Changing the prestrain and the ratio between the thickness and the width induce a phase separation of hemi-helical structure, helical structure and hybrid structure which have similarities to coiled polymer molecules and plant tendrils.

Huang, Jiangshui; Liu, Jia; Kroll, Benedikt; Bertoldi, Katia; Suo, Zhigang; Clarke, David

2012-02-01

246

Controle sismique d'un batiment en acier de 1 etage par amortisseurs elastomeres et contreventements en Chevron  

Science.gov (United States)

Actuellement, le principe de dimensionnement a la capacite est fortement utilise dans le domaine du genie parasismique. De maniere simplifiee, cette methode de dimensionnement consiste a dissiper l'energie injectee a une structure lors d'une secousse sismique par la deformation inelastique d'un element structural sacrificiel. Cette methode de dimensionne-ment permet d'obtenir des structures economiques, car cette dissipation d'energie permet de reduire substantiellement les efforts qui se retrouvent a l'interieur de la structure. Or, la consequence de ce dimensionnement est la presence de degats importants a la structure qui suivent a la secousse sismique. Ces degats peuvent engendrer des couts superieurs aux couts d'erection de la structure. Bien entendu, sachant que les secousses sismiques d'importances sont des phenomenes rares, l'ingenieur est pret a accepter ce risque afin de diminuer les couts initiaux de construction. Malgre que cette methode ait permis d'obtenir des constructions economiques et securitaires, il serait interessant de developper un systeme qui permettrait d'obtenir des performances de controle des efforts sismiques comparables a un systeme dimensionne selon un principe de dimensionnement a la capacite sans les consequences negatives de ces systemes. En utilisant les principes d'isolation a la base, il a ete possible de developper un systeme de reprise des forces sismiques (SRFS). qui permet d'obtenir un controle des efforts sismiques concurrentiels tout en gardant une structure completement elastique. Ce systeme consiste u inserer un materiel elastomere entre l'assemblage de la poutre et des contreventements a l'interieur d'un cadre contrevente conventionnel. Cette insertion permet de diminuer substantiellement la rigidite laterale du batiment, ce qui a pour consequence d'augmenter la valeur de la periode fondamentale du batiment dans lequel ces cadres sont inseres. Ce phenomene est appele le saut de periode. Ce saut de periode permet de reduire grandement l'amplification dynamique essuyee lors d'un seisme du au contenu frequentiel particulier des secousses sismiques. Toutefois, la reduction de la rigidite globale a pour consequence d'augmenter grandement les deplacements de fonctionnement de la structure, ce phenomene etant mitige par les proprietes amortissantes de l'elastomere utilise. Le SRFS propose a ete etudie dans le cadre de la presente maitrise. Les objectifs de l'etude consistent a demontrer l'efficacite et la faisabilite du systeme propose ainsi que de developper une methode de dimensionnement efficace et securitaire pour ce genre de systeme. Afin de faciliter l'obtention des objectifs, l'approche qui a ete utilisee est l'etude comparative d'un meme batiment dimensionne selon deux principes. Le premier est le dimensionnement a la capacite. Le second est un dimensionnement employant le systeme propose. La presente etude a ete scindee en quatre parties distinctes. La premiere est l'etude du materiel elastomere afin de determiner les proprietes utiles lors d'un dimensionnement. La seconde est le dimensionnement et l'etude en laboratoire du comportement d'un cadre contrevente selon un principe de dimensionnement a la capacite. La troisieme partie est le dimensionnement et l'etude en laboratoire du comportement d'un cadre contrevente integrant des amortisseurs elastomeres. La quatrieme et derniere partie est l'etude comparative des performances sismiques d'un batiment qui emploie des cadres amortis avec des amortisseurs elastomeres avec les performances d'un batiment qui emploie un SRFS par contreventements classiques. A la suite des differentes analyses, il a ete possible de conclure sur les performances du systeme propose employant des amortisseurs elastomeres. Le systeme possede un excellent comportement quant aux sollicitations sismiques. Le controle des efforts sismiques est du meme ordre qu'un SRFS par contreventements de ductilite moderee (reduction des efforts elastiques par un facteur de 3). Bien que la demande en deplacement soit plus grande pour le systeme propose que pour un syst

Girard, Olivier

247

Remifentalino intravenoso mediante infusor elastomerico frente a meperidina intramuscular: Estudio comparativo en analgesia obstetrica Intravenous remifentanil delivered through an elastomeric device versus intramuscular meperidine comparative study for obstetric analgesia  

Directory of Open Access Journals (Sweden)

Full Text Available Objetivos: Evaluar la eficacia y seguridad de remifentanilo administrado mediante infusor elastomérico con PCA iv en analgesia obstétrica comparado con meperidina intramuscular en parturientas con contraindicación para analgesia epidural. Material y Método: Se seleccionaron aletoriamente 24 parturientas, se asoció infusor elastomérico Baxter® con 250 ml de suero fisiológico con 2,5 mg de remifentanilo y un ritmo de 12 ml·h ¹, lo que supone una infusión media de 0,025 ?g·kg-1·min-1 de remifentanilo, permitiendo la administración de bolos de 5 ml con un tiempo de cierre de 30 minutos (Grupo R o 1 mg·kg¹ de meperidina y 2,5 mg de haloperidol (Grupo M vía intramuscular cada 4 h. Valoramos la intensidad del dolor cada 30 min mediante una escala analógica visual (EVA, tiempo de infusión, bolos administrados, el nivel de sedación mediante escala del estado de alerta y sedación evaluada por el observador (OAA/S, efectos adversos y el test de Apgar del recién nacido al minuto y a los 5 min. Resultados: No hubo diferencias en los datos antropométricos de ambos grupos. La duración media de la infusión en el grupo R fue de 280 ± 55 min y las necesidades de bolos de rescate de 1,2 ± 1,5. La dosis media de meperidina intramuscular en el grupo M fue de 120 ± 25 mg. La intensidad del dolor durante el parto fue significativamente menor en el grupo R durante todo el periodo de dilatación y expulsivo (pObjectives: To evaluate the effectiveness and security of remifentanil administered by means of elastomeric infusor with PCA IV compared obstetrical analgesia with intramuscular meperidine in obstetric patients with contraindication for epidural analgesia, Material and Method: 24 patients were randomized, an elastomeric infusor Baxter® with a capacity of 250 ml was filled with 2.5 mg of remifentanil and a 12 mililiter·h-1, was satarted, (average infusion of 0.025·kg-1·min-1 of remifentanil, and boluses of 5 ml with a time of closing of 30 minutes (Group R or 1 mg/kg-1 of meperidine and 2.5 mg of haloperidol (Group M every 4 h by IM route. We valued the intensity of pain each 30 min by means of a visual analogical scale (EVA, time of infusion, boluses administered, level of sedatión by means of scale of the alert status and sedatión evaluated by observer (OAA/S, adverse effects and the Apgar test of new born to 1 and 5 min. Results: There were no differences in the anthropometric data of both groups. The average duration of the infusion in group R was of 280 ± 55 min and the necessities of boluses of 1.2 rescue of ± 1,5. The average dose of intramuscular meperidine in group M was of 120 ± 25 mg. The intensity of the pain during the childbirth was significantly smaller in group R (p<0,05 that group M. The sedatión level was similar in both groups (OAA/S 1-2. The hemodinámics parameters, cardiac rate and arterial pressure remained stable without significant differences between both groups. There was no case of respiratory depression. The satisfaction degree was significantly superior in group R. Conclusion: Remifentanil administered by means of elastomeric system PCA IV provides an analgesic effectiveness superior to the intramuscular meperidine and constitutes an alternative modality to the epidural analgesia without causing respiratory depression or excessive sedation, with an elevated level of maternal satisfaction.

E. Calderón

2006-10-01

248

Exposure data from multi-application, multi-industry maintenance of surfaces and joints sealed with asbestos-containing gaskets and packing.  

Science.gov (United States)

Fluid sealing devices (gaskets and packing) containing asbestos are manufactured and blended with binders such that the asbestos fibers are locked in a matrix that limits the potential for fiber release. Occasionally, fluid sealing devices fail and need to be replaced or are removed during preventive maintenance activities. This is the first study known to pool over a decade's worth of exposure assessments involving fluid sealing devices used in a variety of applications. Twenty-one assessments of work activities and air monitoring were performed under conditions with no mechanical ventilation and work scenarios described as "worst-case" conditions. Frequently, the work was conducted using aggressive techniques, along with dry removal practices. Personal and area samples were collected and analyzed in accordance with the National Institute for Occupational Safety and Health Methods 7400 and 7402. A total of 782 samples were analyzed by phase contrast microscopy, and 499 samples were analyzed by transmission electron microscopy. The statistical data analysis focused on the overall data sets which were personal full-shift time-weighted average (TWA) exposures, personal 30-min exposures, and area full-shift TWA values. Each data set contains three estimates of exposure: (1) total fibers; (2) asbestos fibers only but substituting a value of 0.0035 f/cc for censored data; and (3) asbestos fibers only but substituting the limit of quantification value for censored data. Censored data in the various data sets ranged from 7% to just over 95%. Because all the data sets were censored, the geometric mean and geometric standard deviation were estimated using the maximum likelihood estimation method. Nonparametric, Kaplan-Meier, and lognormal statistics were applied and found to be consistent and reinforcing. All three sets of statistics suggest that the mean and median exposures were less than 25% of 0.1 f/cc 8-hr TWA sample or 1.0 f/cc 30-min samples, and that there is at least 95% confidence that the true 95th percentile exposures are less than 0.1 f/cc as an 8-hr TWA. PMID:21391064

Boelter, Fred; Simmons, Catherine; Hewett, Paul

2011-04-01

249

Estudo comparativo entre as diferentes cores de ligaduras elásticas / Comparative study of different colors of molded elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available OBJETIVO: avaliar as diversas cores de ligaduras elásticas do tipo modular da marca Morelli. METODOLOGIA: estas ligaduras foram estiradas em cilindros de aço inoxidável com diâmetro aproximado de um braquete de incisivo central superior, imersas em saliva artificial a 37ºC e tiveram suas forças medi [...] das em uma máquina de ensaios de tração, antes da colocação nos estiletes (0h) e após 24 horas de imersão em saliva artificial. Os resultados foram obtidos através de um computador que opera conectado à máquina de tração e foram submetidos a testes estatísticos (ANOVA e Tuckey) com p Abstract in english AIM: the purpose of this study was to evaluate the different colors of molded elastomerics ligatures from Morelli trademark. METHODS: the ligatures were stretched over stainless dowels with a circumference approximating that of upper central incisor bracket. They were immersed in a synthetic saliva [...] bath at 37ºC and had force levels measured at initial (0h) and after 24 hours of immersion. The results were obtained from a computer connected to a traction machine and were submitted to statistical analysis (ANOVA e Tuckey) with p

Mariana Martins e, Martins; Álvaro de Moraes, Mendes; Marco Antônio de Oliveira, Almeida; Maria Teresa de Andrade, Goldner; Viviane Ferreira, Ramos; Sarita de Sá, Guimarães.

2006-08-01

250

NR/EPDM elastomeric rubber blend miscibility evaluation by two-level fractional factorial design of experiment  

Science.gov (United States)

Fractional 25 two-level factorial design of experiment (DOE) was applied to systematically prepare the NR/EPDM blend using Haake internal mixer set-up. The process model of rubber blend preparation that correlates the relationships between the mixer process input parameters and the output response of blend compatibility was developed. Model analysis of variance (ANOVA) and model fitting through curve evaluation finalized the R2 of 99.60% with proposed parametric combination of A = 30/70 NR/EPDM blend ratio; B = 70°C mixing temperature; C = 70 rpm of rotor speed; D = 5 minutes of mixing period and E = 1.30 phr EPDM-g-MAH compatibilizer addition, with overall 0.966 desirability. Model validation with small deviation at +2.09% confirmed the repeatability of the mixing strategy with valid maximum tensile strength output representing the blend miscibility. Theoretical calculation of NR/EPDM blend compatibility is also included and compared. In short, this study provides a brief insight on the utilization of DOE for experimental simplification and parameter inter-correlation studies, especially when dealing with multiple variables during elastomeric rubber blend preparation.

Razak, Jeefferie Abd; Ahmad, Sahrim Haji; Ratnam, Chantara Thevy; Mahamood, Mazlin Aida; Yaakub, Juliana; Mohamad, Noraiham

2014-09-01

251

Heat shrink ability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene  

International Nuclear Information System (INIS)

The heat shrink ability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0-500 kGy), multifunctional sensitizer levels (ditri methylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrink ability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrink ability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.

252

Heat shrink ability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene  

Energy Technology Data Exchange (ETDEWEB)

The heat shrink ability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0-500 kGy), multifunctional sensitizer levels (ditri methylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrink ability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrink ability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.

Chattopadhyay, S.; Chaki, T.K.; Bhowmick, Anil K. E-mail: anilkb@rtc.iitkgp.ernet.in

2000-11-01

253

Development of elastomeric lab-on-a-chip devices through Proton Beam Writing (PBW) based fabrication strategies  

International Nuclear Information System (INIS)

In recent years, one of the most exciting developments in fluidic device applications is the rapid evolution of miniaturized micro- and nanofluidic systems, the so called 'lab-on-a-chip' devices. These devices integrate laboratory functions into a single chip, and are capable of various biochemical analysis and synthesis, such as sample injection and preparation, single cell/molecule observation, bioparticle sequencing and sorting etc. The evolvement of lab-on-a-chip concept implies the use of novel fabrication techniques for the construction of versatile analytical components in a fast and reproducible manner. Endowed with unique three-dimensional fabrication abilities, Proton Beam Writing (PBW) , which is capable of producing nanometer scaled fluidic structures with smooth and straight side wall features, has a great potential to develop all sorts of polymer fluidic devices. In this paper, we describe the batch fabrication of Poly-dimethysiloxane (PDMS) elastomeric lab-on-a-chip devices utilizing PBW technique. A series of fabrication processes, involving PBW, nickel electroplating, soft lithography, polymer dynamic coating and hydrophilic treating, were modified and adopted in our work. Subsequent characterization of individual categories of channel devices was carried out for specific fluidic studies. Respective experimental procedures are presented and results are explained. The channel devices demonstrated good fluidic performance and functionality, suggesting terformance and functionality, suggesting their further application in more complex biological investigations, and the versatility of PBW in lab-on-a-chip development.

254

Electrical insulating materials - Determination of the effects of ionizing radiation - Part 5: Procedures for assessment of ageing in service  

CERN Document Server

Covers ageing assessment methods which can be applied to components based on polymeric materials (for example, cable insulation and jackets, elastomeric seals, polymeric coatings, gaiters) which are used in environments where they are exposed to radiation. The object of this part of IEC 60544 is to provide guidelines on the assessment of ageing in service. The approaches discussed cover ageing assessment programmes based on condition monitoring (CM), the use of equipment deposits in severe environments and sampling of real-time aged components.

International Electrotechnical Commission. Geneva

2003-01-01

255

Elastomeric degradable biomaterials by photopolymerization-based CAD-CAM for vascular tissue engineering  

Energy Technology Data Exchange (ETDEWEB)

A predominant portion of mortalities in industrial countries can be attributed to diseases of the cardiovascular system. In the last decades great efforts have been undertaken to develop materials for artificial vascular constructs. However, bio-inert materials like ePTFE or PET fail as material for narrow blood vessel replacements (coronary bypasses). Therefore, we aim to design new biocompatible materials to overcome this. In this paper we investigate the use of photoelastomers for artificial vascular constructs since they may be precisely structured by means of additive manufacturing technologies. Hence, 3D computer aided design and manufacturing technologies (CAD-CAM) offer the possibility of creating cellular structures within the grafts that might favour ingrowth of tissue. Different monomer formulations were screened concerning their suitability for this application but all had drawbacks, especially concerning the suture tear resistance. Therefore, we chose to modify the original network architecture by including dithiol chain transfer agents which effectively co-react with the acrylates and reduce crosslink density. A commercial urethane diacrylate was chosen as base monomer. In combination with reactive diluents and dithiols, the properties of the photopolymers could be tailored and degradability could be introduced. The optimized photoelastomers were in good mechanical accordance with native blood vessels, showed good biocompatibility in in vitro tests, degraded similar to poly(lactic acid) and were successfully manufactured with the 3D CAD-CAM technology.

Baudis, Stefan; Nehl, Franziska; Ligon, S Clark; Liska, Robert [Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163MC, A-1060 Vienna (Austria); Nigisch, Anneliese; Bernhard, David [Department of Surgery, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria); Bergmeister, Helga [Core Unit for Biomedical Research, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria); Stampfl, Juergen, E-mail: robert.liska@tuwien.ac.at [Institute of Material Science and Technology, Vienna University of Technology, Favoritenstrasse 9-11, A-1040 Vienna (Austria)

2011-10-15

256

Elastomeric degradable biomaterials by photopolymerization-based CAD-CAM for vascular tissue engineering  

International Nuclear Information System (INIS)

A predominant portion of mortalities in industrial countries can be attributed to diseases of the cardiovascular system. In the last decades great efforts have been undertaken to develop materials for artificial vascular constructs. However, bio-inert materials like ePTFE or PET fail as material for narrow blood vessel replacements (coronary bypasses). Therefore, we aim to design new biocompatible materials to overcome this. In this paper we investigate the use of photoelastomers for artificial vascular constructs since they may be precisely structured by means of additive manufacturing technologies. Hence, 3D computer aided design and manufacturing technologies (CAD-CAM) offer the possibility of creating cellular structures within the grafts that might favour ingrowth of tissue. Different monomer formulations were screened concerning their suitability for this application but all had drawbacks, especially concerning the suture tear resistance. Therefore, we chose to modify the original network architecture by including dithiol chain transfer agents which effectively co-react with the acrylates and reduce crosslink density. A commercial urethane diacrylate was chosen as base monomer. In combination with reactive diluents and dithiols, the properties of the photopolymers could be tailored and degradability could be introduced. The optimized photoelastomers were in good mechanical accordance with native blood vessels, showed good biocompatibility in in vitro tests, degrd biocompatibility in in vitro tests, degraded similar to poly(lactic acid) and were successfully manufactured with the 3D CAD-CAM technology.

257

Simulation of Payne effect of elastomeric isolators with a harmonic balance method  

OpenAIRE

In the presented work, a non linear effect of rubber referred as Fletcher-Gent effect or Payne effect is investigated. It leads to a change in the rubber dynamic modulus with vibration amplitudes and, consequently, modifies resonance frequencies of mechanical systems including non linear elastomers. In this study a new methodology is developed to take into account Payne effect in a linear viscoelastic rubber material. Small vibration amplitudes around a no-preloaded state are predicted by con...

Jaumouille?, Vincent; Sinou, Jean-jacques; Petitjean, Benoi?t

2012-01-01

258

Plate heat exchanger  

International Nuclear Information System (INIS)

In a plate heat exchanger required to handle corrosive, toxic or radioactive fluids, wherein each plate has a peripheral recess or like formation adapted for receiving an elastomeric gasket, the plates are welded together in pairs by the method comprising the steps of inserting into the gasket recess of a first plate of said pair a metal packing piece and welding the second place (e.g. by a laser or electron beam weld running along the base of the recess) superimposing a second plate on to the first in contact with the packing piece and welding the second plate to the packing piece (e.g. by a laser or electron beam weld). The packing piece may be of hollow or solid cross section and is preferably of the same material (e.g. titanium or stainless steel) as the plates. In use a service fluid in heat exchange with the said corrosive etc. fluid is confined by peripheral and normally elastomeric gaskets. (author)

259

Self-standing elastomeric composites based on lithium ferrites and their dielectric behavior  

Science.gov (United States)

Lithium ferrite (LiFe5O8) is an attractive material for technological applications due to its physical properties, which are significantly dependent on the preparation method and raw materials. In this work, LiFe5O8 crystallites were obtained by controlled heat-treatment process at 1100 °C, of a homogeneous mixture of Li2O-Fe2O3 powders, prepared by wet ball-milling and using lithium and iron nitrates as raw materials. The main goal was the preparation of a flexible and self-standing tick composite film by embedding lithium ferrite particles in a polymeric matrix, taking advantage of the good mechanical properties of the polymer and of the electrical and dielectric properties of the ferrite. The selected polymer matrix was styrene-b-isoprene-b-styrene copolymer. To prepare the composites, the lithium ferrite particles were chemically modified in order to functionalize their surface. To analyse the influence of the particles surface modification, different composites were made, with modified and unmodified particles. The structure of the obtained composites was studied by FTIR, XRD, TGA, and DSC techniques. The dielectric properties were analysed, in the frequency range between 10 Hz and 1 MHz and in function of temperature in the range between -73 °C and 127 °C. These properties were related with the structure and concentration of the particles in the matrix network. The composites with the modified particles present higher dielectric constant, maintaining values of loss tangent sufficiently low (<10-2) that can be considered interesting for technological applications.

Soreto Teixeira, S.; Graça, M. P. F.; Dionisio, M.; Ilcíkova, M.; Mosnacek, J.; Spitalsky, Z.; Krupa, I.; Costa, L. C.

2014-12-01

260

Cryogenic loading of large volume presses for high-pressure experimentation and synthesis of novel materials  

Energy Technology Data Exchange (ETDEWEB)

We present an efficient easily implemented method for loading cryogenic fluids in a large volume press. We specifically apply this method to the high-pressure synthesis of an extended solid derived from CO using a Paris-Edinburgh cell. This method employs cryogenic cooling of Bridgman type WC anvils well insulated from other press components, condensation of the load gas within a brass annulus surrounding the gasket between the Bridgman anvils. We demonstrate the viability of the described approach by synthesizing macroscopic amounts (several milligrams) of polymeric CO-derived material, which were recovered to ambient conditions after compression of pure CO to 5 GPa or above.

Lipp, M J; Evans, W J; Yoo, C S

2005-01-21

261

The mechanical properties of elastomeric poly(alkyl methacrylate)s.  

Science.gov (United States)

A range of poly(alkyl methacrylate)s in the range C5 to C13 with varying degrees of crosslinking, have been studied with respect to stress-strain behaviour. Where the extensions to break were sufficiently high, stress-strain properties conformed well to the statistical theory of rubber elasticity, the Mooney/Rivlin C2 term being sensibly zero. All materials studied were very elastic, exhibiting extremely little permanent set. The energy to break decreases very rapidly as the homologous series is ascended, and 0.5% crosslinking agent is perfectly adequate to give elastic properties. Hence either n-pentyl or hexyl methacrylates are to be preferred in soft prosthesis formulations on mechanical grounds. PMID:3315020

Davy, K W; Braden, M

1987-09-01

262

Buckling Instability of Dielectric Elastomeric Plates for Soft, Bio-Compatible Microfluidic Pumps  

Science.gov (United States)

Dielectric elastomers are well-known for their superior stretchability and permittivity. A fully-clamped thin elastomer will buckle when it is compressed by applying sufficient electric potentials to its sides. When embedded within soft, silicone rubbers, these advanced materials can provide a means for a bio-compatible pumping mechanism that can be used to inject bio-fluids with desired flow rates into microfluidic devices, tissues, and organs of interest. We have incorporated a dielectric film that is sandwiched between two thin, flexible, solid electrodes into a microfluidic device and utilized a voltage-induced out-of-plane buckling instability for pumping of fluids. We experimentally quantify the voltage-induced plate buckling and measure the fluid flow rate when the structure is embedded in a microchannel. Additionally, we offer an analytical prediction that uses plate buckling theory to estimate the flow rate as a function of applied voltage.

Tavakol, Behrouz; Bozlar, Michael; Froehlicher, Guillaume; Punckt, Christian; Stone, Howard A.; Aksay, Ilhan; Holmes, Douglas

2013-03-01

263

Rumen metabolism and absorption of a 14C-labelled elastomeric copolymer and its value as a roughage substitute for cattle  

International Nuclear Information System (INIS)

Several synthetic elastomeric and plastomeric polymers were tested for suitability as artificial roughages. They were fed to rumenfistulated cattle fed grain only. Several of the polymers were regurgitated, remasticated and reswallowed, and they formed thin strands of intermeshed fiber that produced a large, loosely woven hay-like mass that floated on the rumen contents. An elastomeric polymer consisting of copolymers of 80 to 90% ethylene and 10 to 20% propylene, with a tensile strength at yield of 45.7 kg/cm2, a hardness of 30 units (Shore D hardness scale) and a tensile strength at 300% elongation of 51.0 kg/cm2, was selected for further testing. The copolymer was fed at about 90 g/head daily for 127 days to cattle fed grain only. At slaughter, rumens contained an average of 8.0 kg copolymer (dry basis). Cattle fed the copolymer had healthier rumen papillae and epithelia of the abomasum and small intestines than did control animals fed grain only. Using 14C-labeled copolymer, we found that the copolymer was not degraded by rumen microorganisms or acid-pepsin solution. When 14C-labeled copolymer was fed to milking cows, no 14C activity was found in milk, blood or urine. Upon slaughter, about 100% of the 14C activity was recovered from digesta and feces. We concluded that the copolymer was not absorbed from the digestive tract

264

Bio-inspired structural bistability employing elastomeric origami for morphing applications  

Science.gov (United States)

A structural concept based upon the principles of adaptive morphing cells is presented whereby controlled bistability from a flat configuration into a textured arrangement is shown. The material consists of multiple cells made from silicone rubber with locally reinforced regions based upon kirigami principles. On pneumatic actuation these cells fold or unfold based on the fold lines created by the interaction of the geometry with the reinforced regions. Each cell is able to maintain its shape in either a retracted or deployed state, without the aid of mechanisms or sustained actuation, due to the existence of structural bistability. Mathematical quantification of the surface texture is introduced, based on out-of-plane deviations of a deployed structure compared to a reference plane. Additionally, finite element analysis is employed to characterize the geometry and stability of an individual cell during actuation and retraction. This investigation highlights the critical role that angular rotation, at the center of each cell, plays on the deployment angle as it transitions through the elastically deployed configuration. The analysis of this novel concept is presented and a pneumatically actuated proof-of-concept demonstrator is fabricated.

Daynes, Stephen; Trask, Richard S.; Weaver, Paul M.

2014-12-01

265

High friction on ice provided by elastomeric fiber composites with textured surfaces  

Science.gov (United States)

Two main applications requiring high friction on ice are automobile tires and footwear. The main motivation behind the use of soft rubbers in these applications is the relatively high friction force generated between a smooth rubber contacting smooth ice. Unfortunately, the friction force between rubber and ice is very low at temperatures near the melting point of ice and as a result we still experience automobile accidents and pedestrian slips and falls in the winter. Here, we report on a class of compliant fiber-composite materials with textured surfaces that provide outstanding coefficients of friction on wet ice. The fibrous composites consist of a hard glass-fiber phase reinforcing a compliant thermoplastic polyurethane matrix. The glass-fiber phase is textured such that it is aligned transversally and protruding out of the elastomer surface. Our analysis indicates that the exposed fiber phase exhibits a "micro-cleat" effect, allowing for it to fracture the ice and increase the interfacial contact area thereby requiring a high force to shear the interface.

Rizvi, R.; Naguib, H.; Fernie, G.; Dutta, T.

2015-03-01

266

Production of centimeter-scale gradient patterns by graded elastomeric tip array.  

Science.gov (United States)

Large-area patterned surfaces with chemical and/or morphological gradients have significant applications in biology, chemistry, and materials science. In this work, we developed a unique lithographic strategy to fabricate 2D and 3D gradient patterns with gradually varying feature size or height over centimeter-scale areas by utilizing a large-area polydimethylsiloxane (PDMS) tip array with programmable tip apex as a conformal photomask in near-field photolithography. Meanwhile, a new strategy was developed to create the PDMS tip array with graded apex size, which was employed to fabricate gradient patterns with the lateral feature sizes changing from sub-100 nm to several microns on one single substrate over macroscopic (square centimeter) areas. Furthermore, 3D gradient patterns with spatially varying feature height were enabled by employing gradient exposure dose. The formation of gradient feature size was ascribed either to gradient contact areas between tips and substrates or to exposure dose gradient. This lithography strategy combines the advantages of a wide range of feature sizes, simplicity, high-throughput, low-cost and diversified feature shapes, making it a facile and flexible approach to manufacture various functional gradient structures. PMID:25763938

Wu, Jin; Miao, Jianmin

2015-04-01

267

Enabling Desktop Nanofabrication with the Targeted Use of Soft Materials  

Science.gov (United States)

This thesis focuses on the application of soft materials to scanning probe-based molecular printing techniques, such as dip-pen nanolithography (DPN). The selective incorporation of soft materials in place of hard materials in traditional cantilever-based scanning probe lithography (SPL) systems not only enables the deposition of a broader range of materials, but also dramatically lowers the cost while simultaneously increasing the throughput of SPL. Chapter 1 introduces SPL and DPN, and highlights a few recent advances in using DPN to control surface chemical functionality at the nanoscale. In addition to introducing the material deposition capabilities of DPN, Chapter 1 introduces the development of the cantilever-free architecture, a relatively recent paradigm shift in high-throughput SPL. Furthermore, an in-depth synthetic methodology for making the most widely used cantilever-free tip arrays, consisting of elastomeric nanoscale pens adhered to an elastomeric backing layer on a glass slide, is included as an appendix. Chapter 2 discusses the synthesis of metal and metal oxide nanoparticles at specified locations by using DPN to deposit the precursors dispersed in a polymer matrix; after deposition, the precursors are annealed to form single nanoparticles. This work builds on previous soft material-based advances in DPN by utilizing the polymer as a "nanoreactor" to synthesize the desired nanoparticles, where the precursors can diffuse and coalesce into a single nanoparticle within each spot. The process of precursor aggregation and single nanoparticle formation is studied, and it is found that metal precursors follow one of three pathways based upon their reduction potential. Chapter 3 is the first of three chapters that highlights the power of soft materials in the cantilever-free architecture. In particular, Chapter 3 examines the role of the elastomeric backing layer as a compliant spring whose stiffness (as measured by the spring constant, k) can be tuned with a simple chemical change to the composition of the elastomer. In particular, the extent of cross-linking within the elastomer is found to dictate the k the backing layer, and arrays with spring constants tuned from 7 to 150 N/m are described. Furthermore, a simple geometric model is developed that explains the low variation of k within each cantilever-free array; this stands in contrast to arrays of cantilevers, which typically show large variations of k within an array. Chapter 4 addresses the problem of individual actuation in SPL by embedding resistive heaters directly beneath the elastomeric backing layer. This actuation scheme was chosen because the elastomer used in the cantilever-free tip arrays has extraordinary thermal expansion properties, and thorough exploration of their actuation behavior shows that the heater arrays are fast (> 100 microm/s) and powerful (> 4 microm) enough for actuation. After implementing several corrections for the tip height -- a problem that is intractable without the heaters, and has never been addressed before -- printing of alkanethiols onto Au is demonstrated with a 2D array of individually actuated probes. Chapter 5 examines the hypothesis that elastomeric tips can absorb solvent and be used to transport materials in the absence of environmental solvent. This is evaluated by first using tip arrays soaked in a nonpolar solvent to pattern a hydrophobic block copolymer that cannot be patterned by traditional DPN, and is subsequently explored for the case of water uptake into the pen arrays. Surprisingly, despite their poor water retention ability, the tip arrays can store enough water to pattern hydrophilic polymers in dry environments for over 2 hours. The dynamics of the solvent absorption are captured by a simple calculation that accounts for the dynamical behavior of water retention and the backing layer thickness, thereby allowing these results to be generalized to other solvents. This exploration of the subtle and dynamic role of absorbed solvent in cantilever-free pen arrays shows that proper pr

Eichelsdoerfer, Daniel James

268

High resolution PFPE-based molding High resolution PFPE-based molding High resolution PFPE-based molding techniques for nanofabrication of high pattern density sub-20 nm features: A fundamental materials approach  

Energy Technology Data Exchange (ETDEWEB)

ABSTRACT. Described herein is the development and investigation of PFPE-based elastomers for high resolution replica molding applications. The modulus of the elastomeric materials was increased through synthetic and additive approaches while maintaining relatively low surface energies (<25 mN/m). Using practically relevant large area master templates, we show that the resolution of the molds is strongly dependant upon the elastomeric mold modulus. A composite mold approach was used to form flexible molds out of stiff, high modulus materials that allow for replication of sub-20 nm post structures. Sub-100 nm line grating master templates, formed using e-beam lithography, were used to determine the experimental stability of the molding materials. It was observed that as the feature spacing decreased, high modulus composite molds were able to effectively replicate the nano-grating structures without cracking or tear-out defects that typically occur with high modulus elastomers.

Williams, Stuart S [University of North Carolina, Chapel Hill; Samulski, Edward [University of North Carolina, Chapel Hill; Lopez, Renee [University of North Carolina, Chapel Hill; Ruiz, Ricardo [Hitachi; DeSimone, Joseph [University of North Carolina, Chapel Hill; Retterer, Scott T [ORNL

2010-01-01

269

Estudo comparativo entre as diferentes cores de ligaduras elásticas Comparative study of different colors of molded elastomeric ligatures  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: avaliar as diversas cores de ligaduras elásticas do tipo modular da marca Morelli. METODOLOGIA: estas ligaduras foram estiradas em cilindros de aço inoxidável com diâmetro aproximado de um braquete de incisivo central superior, imersas em saliva artificial a 37ºC e tiveram suas forças medidas em uma máquina de ensaios de tração, antes da colocação nos estiletes (0h e após 24 horas de imersão em saliva artificial. Os resultados foram obtidos através de um computador que opera conectado à máquina de tração e foram submetidos a testes estatísticos (ANOVA e Tuckey com pAIM: the purpose of this study was to evaluate the different colors of molded elastomerics ligatures from Morelli trademark. METHODS: the ligatures were stretched over stainless dowels with a circumference approximating that of upper central incisor bracket. They were immersed in a synthetic saliva bath at 37ºC and had force levels measured at initial (0h and after 24 hours of immersion. The results were obtained from a computer connected to a traction machine and were submitted to statistical analysis (ANOVA e Tuckey with p<0.05. RESULTS AND CONCLUSION: the medium values were md=0.3792KgF for 0h and md=0.1286KgF for 24h and the percentage of force decay were 66.07% ± 2.31%. The results revealed statically differences between forces delivered in 0h and 24h. At 0h, there were differences statistically significance between some colors of ligatures before the action of the time and the immersion in artificial saliva bath, with higher values for the pearl (md=0.4024KgF and minors values for the slight green (md=0.3511KgF. At 24h, it was also find differences statistically significances between some colors, but the distribution was different than the observed at 0h. The slight green, red, yellow and white colors had the minor percentage of force decay, in which slight green showed the best behavior (62.60%. However, the pearl, silver and gray had the highest percentage of force decay, with pearl showing the worst behavior (69.23%.

Mariana Martins e Martins

2006-08-01

270

Optimization of the heavy metal (Bi-W-Gd-Sb) concentrations in the elastomeric shields for computer tomography (CT)  

International Nuclear Information System (INIS)

Eight elastomeric composites (NRU, GR1-GR4, NRBG08-NRBG24) containing mixtures of different proportions of heavy metal additives (Bi, W, Gd and Sb) have been synthesized and examined as protective shields. The NRU sample was a pure rubber matrix and served as a reference sample for heavy metal modified composites. Experimental procedure used for evaluation of the composite shields and their attenuation properties was based on the utilization of HPGe spectrometry and analysis of X-ray fluorescence radiation intensity of the heavy metal additives in the following energy ranges for: Sb (20-35 keV), Gd (35-55 keV), W (55-70 keV) and Bi (70-90 keV). The main contributor to the induced X-ray fluorescence radiation within the shield is Bi additive and the intensity of the X-ray radiation generated within the energy range of 70-90 keV strongly depends on its concentration. It was found that decreasing concentration of the Bi fraction from 0.35 (GR samples) to 0.15 (NRBG samples) results in significant lowering Bi X-ray fluorescence radiation within the 70-90 keV energy range. Secondary effect of decreasing Bi concentration was efficient diminishing excitation processes for lower Z heavy metal additives (W, Gd and Sb, GR vs. NRBG samples). As the final quality parameter of the shielding properties for the examined elastomers, dose reduction factor (DRF) coefficients were calculated for each shield. It was found, that the best shielding properties are observed for composites with lower Bi concentration (0.15 vs. 0.35 Bi mass fraction) with only slight further improvement of their parameters (DRF) with increasing of Gd concentration (Gd mass fraction 0.08, 0.16 and 0.24). The most efficient dose reduction composite was found to be NRBG24 elastomer with DRF value 0.47 (53 % dose reduction) for ca. 2 mm and 0.44 g/cm2 layer thickness. (author)

271

Compression and shear properties of elastomeric bearing using finite element analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Standard size samples of four natural rubber compounds, varying the amount of carbon black from 10 to 70 phr, were characterised under uniaxial compression and simple shear tests in order to obtain the strain energy function constants. These constants were then used as hyperelastic material constants for the Windows-based finite element package (COSMOS/M version 1.75. The investigated bearings, made with those NR compounds, had the approximate area and thickness of 50x106 mm2 and 50 mm respectively. Each compound of bearing consisted of four different values of shape factor ranging from about 0.33 to 1.70, according to the number of reinforcing plates in the bearing. Three deformation modes of compression, shear and compression-shear were predicted. Good agreement was found between twelve compression model predictions and the corresponding experimental values of bearings, containing 10, 20 and 40 phr of carbon black and each of which consisted of four different layers of reinforcing metal plates (0, 1, 2 and 3 layers. On the other hand, deviation from the predicted valve was clearly seen in the 70 phr black bearing case. The percentage difference increased with respect to the increasing number of reinforcing plates or the rising shape factor. Therefore, the improved FEA model was supplemented with an imaginary elastic glue layer between the rubber block and metal plate as glue failure compensation. The optimum value of the elastic layers modulus is 8 MPa while the thickness of the layer depends on the total thickness or total volume of rubber block. This model can predict the 70 phr carbon black bearings, having shape factor ranging from 0.5 to 2.35 for 11 cases. The FEA prediction of shear behaviour agrees well with the experimental data for all four bearing compounds and there is no effect of shape factor on shear stress. Moreover, shear stress does not depend on the compressive force applied to like bearing before shear and the FEA results agreed with the corresponding experimental results.

2Faculty of Science and Technology, Chiang Mai Rajabhat University, Muang, Chiang Mai, 50300 Thailand.

2006-09-01

272

Identifying target properties for the design of meta-material tank track pads  

Science.gov (United States)

On track vehicle systems, track pads are designed to provide traction and support the weight of the vehicle, they have limited service life due to common failure by blowout. According to the literature, blowout is a failure mode caused by overheating due to hysteresis in elastomeric materials during high speed operations. Elastomers are used primarily for their high compliance, which is essential to protect the suspension components and maintain structural integrity of the track pad. The objective of the work is to explore the use of linear elastic meta-materials with optimized topology to replace elastomers and reduce or eliminate the effect of hysteretic loss. This work presents a methodology to design an alternate meta-material that can provide some of the desired elastic properties of the track pads. To determine the requirements for linear elastic meta-materials, dynamic analyses of a rollover event were conducted. From these analyses the complex dependence of the strain history on different strain components is understood. Due to the non-linearity of elastomers, tangent stiffness matrices are required to update the stress states at different strain increments. The elasticity tensors (tangent operators) determined at a set of strain levels, are used as prescribed constitutive parameters to tailor the meta-material unit-cell topology. The optimal material properties according to which the elastomeric track pad is designed with linear elastic material are identified in this work.

Dangeti, Venkata Sampath

273

Bio-Inspired Wide-Angle Broad-Spectrum Cylindrical Lens Based on Reflections from Micro-Mirror Array on a Cylindrical Elastomeric Membrane  

Directory of Open Access Journals (Sweden)

Full Text Available We present a wide-angle, broad-spectrum cylindrical lens based on reflections from an array of three-dimensional, high-aspect-ratio micro-mirrors fabricated on a cylindrical elastomeric substrate, functionally inspired by natural reflecting superposition compound eyes. Our device can perform one-dimensional focusing and beam-shaping comparable to conventional refraction-based cylindrical lenses, while avoiding chromatic aberration. The focal length of our cylindrical lens is 1.035 mm, suitable for micro-optical systems. Moreover, it demonstrates a wide field of view of 152° without distortion, as well as modest spherical aberrations. Our work could be applied to diverse applications including laser diode collimation, barcode scanning, holography, digital projection display, microlens arrays, and optical microscopy.

Chi-Chieh Huang

2014-06-01

274

An in vitro comparison of the force decay generated by different commercially available elastomeric chains and NiTi closed coil springs Comparação in vitro da degradação da força gerada por cadeias elastoméricas e por molas fechadas de NiTi de diferentes marcas comerciais  

OpenAIRE

This in vitro study was designed to compare the forces generated by commercially available elastomeric chains and NiTi closed coil springs, and to determine their force decay pattern. Forty elastomeric chains and forty NiTi closed coil springs were divided into 4 groups according to the following manufacturers: (1) Morelli®, (2) Abzil®, (3) TP Orthodontics® and (4) American Orthodontics®. The specimens were extended to twice their original length and stored in artificial saliva at 37°...

Ana Cristina Soares Santos; André Tortamano; Sandra Regina Frazatto Naccarato; Gladys Cristina Dominguez-Rodriguez; Julio Wilson Vigorito

2007-01-01

275

Advanced process control and novel test methods for PVD silicon and elastomeric silicone coatings utilized on ion implant disks, heatsinks and selected platens  

Science.gov (United States)

Coatings play multiple key roles in the proper functioning of mature and current ion implanters. Batch and serial implanters require strategic control of elemental and particulate contamination which often includes scrutiny of the silicon surface coatings encountering direct beam contact. Elastomeric Silicone Coatings must accommodate wafer loading and unloading as well as direct backside contact during implant plus must maintain rigid elemental and particulate specifications. The semiconductor industry has had a significant and continuous effort to obtain ultra-pure silicon coatings with sustained process performance and long life. Low particles and reduced elemental levels for silicon coatings are a major requirement for process engineers, OEM manufacturers, and second source suppliers. Relevant data will be presented. Some emphasis and detail will be placed on the structure and characteristics of a relatively new PVD Silicon Coating process that is very dense and homogeneous. Wear rate under typical ion beam test conditions will be discussed. The PVD Silicon Coating that will be presented here is used on disk shields, wafer handling fingers/fences, exclusion zones of heat sinks, beam dumps and other beamline components. Older, legacy implanters can now provide extended process capability using this new generation PVD silicon - even on implanter systems that were shipped long before the advent of silicon coating for contamination control. Low particles and reduced elemental levels are critical performance criteria for the silicone elastomers used on disk heatsinks and serial implanter platens. Novel evaluation techniques and custom engineered tools are used to investigate the surface interaction characteristics of multiple Elastomeric Silicone Coatings currently in use by the industry - specifically, friction and perpendicular stiction. These parameters are presented as methods to investigate the critical wafer load and unload function. Unique tools and test methods have been developed that deliver accurate and repeatable data, which will be described.

Springer, J.; Allen, B.; Wriggins, W.; Kuzbyt, R.; Sinclair, R.

2012-11-01

276

Corrosion and stress corrosion cracking of bolting materials in light water reactors  

International Nuclear Information System (INIS)

The primary coolant of a pressurized water reactor contains dissolved boric acid added as a soluble neutron absorber. Corrosion and stress corrosion cracking of bolts on pumps and on primary system manways have occurred where gaskets leak this boric acid onto the low alloy steel bolting material. Laboratory experiments have shown that the concentration of the boric acid to a moist paste at approximately the boiling point of water can produce corrosion rates of the order of several tenths of an inch per year on bolting and piping materials, which values are consistent with service experience. Frequently molybdenum disulfide is used as a lubricant for tightening bolts on massive flanges. Laboratory experience has shown that when the primary coolant leaks through a gasket the molybdenum disulfide can react with the leaking steam to produce hydrogen sulfide and subsequent stress corrosion cracking of the bolts. Additionally, contaminants concentrating over significant time periods have caused stress corrosion cracking failures of reactor coolant pump internals. Failure analysis of cracked bolts from service and the results of laboratory tests that demonstrate these mechanisms of bolt cracking are presented

277

Thermal conductivity coefficient of materials for superconducting magnet system of the T-15 device  

International Nuclear Information System (INIS)

The results are presented of eXperimental determination of thermal conductivity of some materials used in one of the versions of the T-15 toroidal magnetic field superconducting coil. The material of the coil body (Kh18N10T stainless steel), electric insulating gaskets of fiberglass laminate, electric insulating material (several layers of varnished cloth impregnated with binding compound used as interturn electic insulation) and separate parts of the cuurrent-carrying busy As regards the bus, the data are obtained on the thermal conductivity coefficient for the coolant pipe (M2 copper), bus body material (electrolytical copper), superconducting cable of nine NT-50 wires with copper coating and for the bus cross section. The thermal conductivity coefficient measurements are carried out on experimental installations using the stationary method of axial heat flux in the 4-300 K temperature range. The measurement error does not exceed 6%

278

Outgassing tests on materials used in the DIII - D magnetic fusion tokamak  

International Nuclear Information System (INIS)

In order to achieve high performance plasma discharges in the DIII - D magnetic fusion tokamak, impurity levels must be carefully controlled. Since first wall materials can desorb volatile impurities during these discharges, it is important to characterize and control the outgassing of these materials. An outgassing chamber was built to measure the outgassing properties of various materials used in the DIII - D vessel. The results of pump-down tests performed on ATJ graphite, thin Grafoilreg-sign gaskets, and MgO coaxial cables will be presented. In addition to outgassing tests, it was desired to study the behavior of the materials at temperatures up to 400 degree C, which is the maximum temperature to which the DIII - D vessel is baked. The station was modified to include independent heating control of the sample and a simple load-lock chamber. copyright 1999 American Vacuum Society

279

Outgassing tests on materials used in the DIII-D magnetic fusion tokamak  

International Nuclear Information System (INIS)

In order to achieve high performance plasma discharges in the DIII-D magnetic fusion tokamak, impurity levels must be carefully controlled. Since first wall materials can desorb volatile impurities during these discharges, it is important to characterize and control the outgassing of these materials. An outgassing chamber was built to measure the outgassing properties of various materials used in the DIII-D vessel. The results of pump-down tests performed on ATJ graphite, thin Grafoil reg-sign gaskets, and MgO coaxial cables will be presented. In addition to pumpdown tests it was desired to study the behavior of the materials at temperatures up to 400 C, which is the maximum temperature to which the DIII-D vessel is baked. The station was modified to include independent heating control of the sample and a simple load-lock chamber

280

Materials aspects of solar energy use in buildings  

Energy Technology Data Exchange (ETDEWEB)

Advances in materials for solar energy utilization have the potential to produce large performance improvements (both present and future concepts) in use of solar energy or conservation. Because approximately 26 quads of the total national energy budget of 75 quads is consumed by buildings, solar and conservation improvements can have a large effect on our overall energy consumption. There have been a large number of materials research programs funded through the Department of Energy (DOE) in an attempt to expand the use of solar energy. These materials programs have covered the areas of sealants and gaskets, insulations, glazings, glazing-surface treatments, polymers, selective absorber surfaces, phase-change storage, and heat mirrors. In addition to developing the materials, a large effort has been directed toward determining the reliability and durability of solar materials. The present state of the art and status of these solar materials are discussed. Although much progress has been made in recent years, many improvements are still needed. For many of the more routine materials, simple cost reductions or durability improvements would suffice. For the more advanced concepts of controlling energy flow into or out of buildings, basic materials research remains a necessity. There are a large number of potentially viable concepts that appear promising but have not yet been developed into usable materials.

Moore, S.W.; McFarland, R.D.

1984-05-01

281

Investigation of test methods, material properties, and processes for solar cell encapsulants. Eighteenth quarterly progress report, August 12-November 12, 1980  

Energy Technology Data Exchange (ETDEWEB)

The goal of this program is to identify, evaluate, and recommend encapsulant materials and processes for the production of cost-effective, long-life solar cell modules. A survey was made of elastomers for use as gaskets for the photovoltaic module. Of the wide variety of materials examined EPDM offered the optimum combination of low compression set and low cost. The preference for EPDM is borne out by its long history of use as an automobile gasket. The commercial availability of materials that would be useful for sealants between the edge of the module and the gasket was investigated. Butyl sealants have the best combination of physical properties, low cost and a well-documented history of performance. A preferred composition has not yet been identified. One laminating type pottant ethylene/methyl acrylate copolymer (EMA), and two casting polymers, polybutyl acrylate and polyurethane, have been under investigation this past quarter. An EMA formulation has been developed which is easily extrudable and cures to a high gel content. So far only one commercial US source (Quinn) of aliphatic polyurethane has been located. Work is continuing to improve reaction rate as well as to eliminate source(s) of bubble formation during module fabrication. Considerable effort was spent in developing an improved polybutyl acrylate casting formulation providing high gel. Many viable curing systems are now available: however, the best formulation considering physical properties, freedom from bubbles as well as cure time utilizes Lupersol II (aliphatic peroxide) initiator. This initiator gives the desired gel after 20 minute cure at 45/sup 0/C or 12 minute cure at 55/sup 0/C.

Willis, P. B.; Baum, B.; Davis, M.

1980-12-01

282

The influence of filler on the properties of elastomeric materials based on poly(ethylene-co-propylene-co-2-ehylidene-5-norbornene rubber  

Directory of Open Access Journals (Sweden)

Full Text Available Crosslinked samples based on poly(ethylene-co-propylene-co-2-ehylidene5-norbornene EPDM rubber, carbon black as active filler and natural chalk as inactive filler were cured with sulphur. The content of carbon black was varied from 100 to 200 pph. The content of chalk was varied from 0 to 100 pph. The content of paraffin oil was also varied in some samples. The compounds were prepared by mixing ingredients on a laboratory two-roll mill. Vulcanizates were prepared by curing at 180°C. Various methods were used for the physical and mechanical characterizations. The dynamic mechanical properties of the elastomers were measured in the temperature range from -120 to 80°C.

Budinski-Simendi? Jaroslava

2006-01-01

283

Nanoprobe measurements of materials at megabar pressures  

Energy Technology Data Exchange (ETDEWEB)

The use of nanoscale x-ray probes overcomes several key limitations in the study of materials up to multimegabar (> 200) pressures, namely, the spatial resolution of measurements of multiple samples, stress gradients, and crystal domains in micron to submicron size samples in diamond-anvil cells. Mixtures of Fe, Pt, and W were studied up to 282 GPa with 250–600 nm size synchrotron x-ray absorption and diffraction probes. The probes readily resolve signals from individual materials, between sample and gasket, and peak pressures, in contrast to the 5-?m-sized x-ray beams that are now becoming routine. The use of nanoscale x-ray beams also enables single-crystal x-ray diffraction studies in nominally polycrystalline samples at ultrahigh pressures, as demonstrated in measurements of (Mg,Fe)SiO{sub 3} postperovskite. These capabilities have potential for driving a push toward higher maximum pressures and further miniaturization of high-pressure devices, in the process advancing studies at extreme conditions.

Wang, Lin; Ding, Yang; Yang, Wenge; Liu, Wenjun; Cai, Zhonghou; Kung, Jennifer; Shu, Jinfu; Hemley, Russell J.; Mao, Wendy L.; Mao, Ho-kwang

2010-01-01

284

Ultra-high-precision alignment of the elastomerically mounted elements of the science camera lenses for the Mars Science Laboratory (MSL) rover.  

Science.gov (United States)

Cameras built for space exploration are required to meet stringent environmental conditions, such as thermal and dynamic loads for both the optics (camera lens) and imaging electronics. On a multitude of spaceborne imaging instruments, optical elements are supported in their mounts via an elastomeric bonding approach using a room temperature vulcanizing silicone as the bonding agent. Employing this integration method, we achieved element-to-element alignment, measured as the total indicated runout, using a high-precision contact probe to be on the order of half a wavelength of He-Ne laser light, or 0.3??m, on the Malin Space Science Systems lenses for the Mars Science Laboratory (MSL) cameras. This is a higher precision than the current industry state-of-the-art, and it was achieved for the very challenging small diameter lens elements. This paper describes the design philosophy, implementation, and integration method that resulted in achieving this level of precision for interelement alignment. The results are based on actual measurements that were made during the process of building the MSL rover's science camera lenses, namely Mastcams, the Mars Hand Lens Imager, and the Mars Descent Imager. The optical designs of these cameras lenses are described in detail in [Opt. Eng.48, 103002 (2009)], while further information on the four science cameras can be found at http://www.msss.com. PMID:21946992

Ghaemi, F Tony

2011-09-10

285

Ultra-high-precision alignment of the elastomerically mounted elements of the science camera lenses for the Mars Science Laboratory (MSL) rover  

Energy Technology Data Exchange (ETDEWEB)

Cameras built for space exploration are required to meet stringent environmental conditions, such as thermal and dynamic loads for both the optics (camera lens) and imaging electronics. On a multitude of spaceborne imaging instruments, optical elements are supported in their mounts via an elastomeric bonding approach using a room temperature vulcanizing silicone as the bonding agent. Employing this integration method, we achieved element-to-element alignment, measured as the total indicated runout, using a high-precision contact probe to be on the order of half a wavelength of He-Ne laser light, or 0.3 {mu}m, on the Malin Space Science Systems lenses for the Mars Science Laboratory (MSL) cameras. This is a higher precision than the current industry state-of-the-art, and it was achieved for the very challenging small diameter lens elements. This paper describes the design philosophy, implementation, and integration method that resulted in achieving this level of precision for interelement alignment. The results are based on actual measurements that were made during the process of building the MSL rover's science camera lenses, namely Mastcams, the Mars Hand Lens Imager, and the Mars Descent Imager. The optical designs of these cameras lenses are described in detail in [Opt. Eng.48, 103002 (2009)10.1117/1.3251343], while further information on the four science cameras can be found at http://www.msss.com.

Ghaemi, F. Tony

2011-09-10

286

Ultra-high-precision alignment of the elastomerically mounted elements of the science camera lenses for the Mars Science Laboratory (MSL) rover  

International Nuclear Information System (INIS)

Cameras built for space exploration are required to meet stringent environmental conditions, such as thermal and dynamic loads for both the optics (camera lens) and imaging electronics. On a multitude of spaceborne imaging instruments, optical elements are supported in their mounts via an elastomeric bonding approach using a room temperature vulcanizing silicone as the bonding agent. Employing this integration method, we achieved element-to-element alignment, measured as the total indicated runout, using a high-precision contact probe to be on the order of half a wavelength of He-Ne laser light, or 0.3 ?m, on the Malin Space Science Systems lenses for the Mars Science Laboratory (MSL) cameras. This is a higher precision than the current industry state-of-the-art, and it was achieved for the very challenging small diameter lens elements. This paper describes the design philosophy, implementation, and integration method that resulted in achieving this level of precision for interelement alignment. The results are based on actual measurements that were made during the process of building the MSL rover's science camera lenses, namely Mastcams, the Mars Hand Lens Imager, and the Mars Descent Imager. The optical designs of these cameras lenses are described in detail in [Opt. Eng.48, 103002 (2009)10.1117/1.3251343], while further information on the four science cameras can be found at http://www.msss.com.

287

49 CFR 178.360-4 - Closure devices.  

Science.gov (United States)

...TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SPECIFICATIONS...for Class 7 (Radioactive) Materials § 178.360-4 Closure...the selected gasket. Gasket material must be capable of withstanding...The flange, whether of ferrous or nonferrous metal,...

2010-10-01

288

Laser 3D Printing with Sub-Microscale Resolution of Porous Elastomeric Scaffolds for Supporting Human Bone Stem Cells.  

Science.gov (United States)

A reproducible method is needed to fabricate 3D scaffold constructs that results in periodic and uniform structures with precise control at sub-micrometer and micrometer length scales. In this study, fabrication of scaffolds by two-photon polymerization (2PP) of a biodegradable urethane and acrylate-based photoelastomer is demonstrated. This material supports 2PP processing with sub-micrometer spatial resolution. The high photoreactivity of the biophotoelastomer permits 2PP processing at a scanning speed of 1000 mm s(-1) , facilitating rapid fabrication of relatively large structures (>5 mm(3) ). These structures are custom printed for in vitro assay screening in 96-well plates and are sufficiently flexible to enable facile handling and transplantation. These results indicate that stable scaffolds with porosities of greater than 60% can be produced using 2PP. Human bone marrow stromal cells grown on 3D scaffolds exhibit increased growth and proliferation compared to smooth 2D scaffold controls. 3D scaffolds adsorb larger amounts of protein than smooth 2D scaffolds due to their larger surface area; the scaffolds also allow cells to attach in multiple planes and to completely infiltrate the porous scaffolds. The flexible photoelastomer material is biocompatible in vitro and is associated with facile handling, making it a viable candidate for further study of complex 3D-printed scaffolds. PMID:25522214

Petrochenko, Peter E; Torgersen, Jan; Gruber, Peter; Hicks, Lucas A; Zheng, Jiwen; Kumar, Girish; Narayan, Roger J; Goering, Peter L; Liska, Robert; Stampfl, Jürgen; Ovsianikov, Aleksandr

2015-04-01

289

Golden gaskets: variations on the Sierpinski sieve  

Science.gov (United States)

We consider the iterated function systems (IFSs) that consist of three general similitudes in the plane with centres at three non-collinear points, with a common contraction factor lgr epsi (0, 1). As is well known, for lgr = ½ the attractor, \\mathcal{S}_\\lambda , is a fractal called the Sierpinski sieve and for lgr < ½ it is also a fractal. Our goal is to study \\mathcal{S}_\\lambda for this IFS for ½ < lgr < 2/3, i.e. when there are 'overlaps' in \\mathcal{S}_\\lambda as well as 'holes'. In this introductory paper we show that despite the overlaps (i.e. the breaking down of the open set condition (OSC)), the attractor can still be a totally self-similar fractal, although this happens only for a very special family of algebraic lgr (so-called multinacci numbers). We evaluate \\dim_{H}(\\mathcal{S}_\\lambda) for these special values by showing that \\mathcal{S}_\\lambda is essentially the attractor for an infinite IFS that does satisfy the OSC. We also show that the set of points in the attractor with a unique 'address' is self-similar and compute its dimension. For non-multinacci values of lgr we show that if lgr is close to 2/3, then \\mathcal{S}_\\lambda has a non-empty interior. Finally we discuss higher-dimensional analogues of the model in question.

Broomhead, Dave; Montaldi, James; Sidorov, Nikita

2004-07-01

290

Accuracy of stone casts obtained by different impression materials  

Scientific Electronic Library Online (English)

Full Text Available Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a part [...] ially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p .05) to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.

Adriana Cláudia Lapria, Faria; Renata Cristina Silveira, Rodrigues; Ana Paula, Macedo; Maria da Gloria Chiarello de, Mattos; Ricardo Faria, Ribeiro.

2008-12-01

291

Accuracy of stone casts obtained by different impression materials  

Directory of Open Access Journals (Sweden)

Full Text Available Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p .05 to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.

Adriana Cláudia Lapria Faria

2008-12-01

292

Propriedades reométricas e mecânicas e morfologia de compósitos desenvolvidos com resíduos elastoméricos vulcanizados Cure characteristics, mechanical properties and morphology of composites developed with addition of elastomeric vulcanized ground scraps  

Directory of Open Access Journals (Sweden)

Full Text Available Uma alternativa para as empresas geradoras de resíduos elastoméricos é a incorporação dos mesmos em suas formulações. Esse trabalho tem como objetivo preparar compósitos a partir da incorporação de resíduos industriais de SBR (copolímero de butadieno-estireno e de EPDM (terpolímero de etileno-propileno-dieno, em formulação ASTM específica para cada tipo de elastômero. Foram avaliadas as propriedades reométricas, mecânicas e morfológicas dos compósitos desenvolvidos. A incorporação do resíduo permitiu a obtenção de produtos que vulcanizam em menores tempos quando comparados a composições sem resíduo. A quantidade de resíduo, para o melhor resultado de resistência à tração foi de 37 e de 196 phr para os compósitos com SBR e EPDM, respectivamente. As micrografias de MEV corroboraram os resultados mecânicos dessas composições, indicando melhor homogeneidade do resíduo na respectiva matriz elastomérica.One alternative for elastomeric scraps generation is its incorporation in conventional formulations in the industry itself. In this work, compositions with incorporation of SBR (styrene butadiene rubber and EPDM (ethylene propylene diene rubber industrial scraps, in specific ASTM formulation for each elastomer, were prepared. Rheometric characteristics, mechanical properties and the morphology of the compounds developed were evaluated. With the ground scraps incorporation the vulcanization time decreases, comparing with compounds without ground scraps. The amount of scraps for the best tensile strength properties was 37 and 196 phr for SBR and EPDM compositions, respectively. Micrographs corroborated the mechanical results, indicating the best homogeneity of the scraps in the elastomeric matrix for these compositions.

Aline Zanchet

2007-03-01

293

Development of thermoradiation technology of making of aggressiveproof elastomer materials for oil industry  

International Nuclear Information System (INIS)

Full text: At present in oil industry is used elastomer materials (EM) on base of butadiene-nitrile caoutchouc (BNC). In most cases EM made from BNC, especially diaphragms, gasket rings and glands are destructed after shortly exploitation in aggressive liquid mediums, at result of the structure of EM contenting caoutchouc matter, accelerators plasticizer, antioxidant and other ingredients have some changes. So in factories of rubber and oil industry there are a lot of used EM on base of BNC. The problem of returning to balance expensive and deficit materials has a high economical, technological and ecological significance. At the Institute of radiation Problems of NAS of Azerbaijan is developed thermo radiation method of vulcanization of EM on base of BNC using ?-irradiation of Co60.This method has a significance advantage on comparison thermochemical method and allows to get the product of high quality. EM can be obtained with predicted properties by changing of absorbed dose of radiation, at this is ensured obtaining of C-C connection without application of sulfur and sulfur contenting accelerators. Instead is recommended polychalogenmethylcontenting (PCM) and epoxy compounds (EC) with oxides of metals. A wide laboratory testing of PCM and EC showed, that entering these structuring systems to gasket and gland mixtures is purposeful. On technological and exploitation properties the model are comparable with factory made products. It is suggested to use thermo radiation EM in engineering industry. The developed method allows to exclude environment pollution. Properties of thermo radiated vulcanizate depend on vulcanization structure and absorbed dose. The technological scheme of obtaining of use thermo radiation EM includes mixing heating in electropress during 2-4 min, radiation and other operations

294

Fabrication and characterization of elastomeric scaffolds comprised of a citric acid-based polyester/hydroxyapatite microcomposite  

International Nuclear Information System (INIS)

Highlights: • Porous scaffolds were prepared from polymer/hydroxyapatite (POC/HA) composite. • The pore size was designed to be uniform for all POC/HA composite scaffolds. • Compression strength and modulus are dependent on HA concentration within composite. - Abstract: In this paper we describe an effective technical route for the production of porous scaffolds from microcomposite material consistent of citric acid-based polyester elastomer and hydroxyapatite microparticles with potential use in tissue engineering applications. Fabricated scaffolds were characterized by field emission electron microscopy, Fourier-transform infra-red spectroscopy, thermal gravimetric analysis and mechanical tests. We demonstrate that the chemical composition, scaffold morphology, mechanical integrity and porosity of the produced microcomposite scaffolds are strongly affected by variation of the initial hydroxyapatite concentration in the mineral-polymer mixture during the fabrication process. This polyester/mineral scaffold exhibits versatility in compression modulus and strength in the range of 21.72–33.25 KPa and 49.92–101.48 KPa respectively, corresponding to the hydroxyapatite concentration in the composite (10–30 wt.%)

295

[First results of the investigation of the stability and tissue integration of a degradable, elastomeric copolymer in an animal model].  

Science.gov (United States)

The stability and tight integration into adjacent tissue of a novel, degradable, elastic copolymer were examined in an animal model. The biomaterial was used for the reconstruction of a gastric wall defect in Sprague-Dawley rats (n=42) to test the polymeric material under the extreme chemical, enzymatical and mechanical conditions of the stomach. In the control group (n=21) the same defect of the gastric wall was primarily closed without biomaterial implantation. In the baseline group (n=21) the animals were kept under standard conditions without any surgical procedure. The implantation periods were 1 week, 4 weeks and 6 months. The animals' weight was determined preoperatively and before explantation. After explantation, air was pumped into the stomach and the pressure was measured by using a pressure-gauge in order to test whether the surgically produced union of the stomach wall and the polymer patch was gas-tight. After 1 week of implantation time a statistically significant increase of the body weight of the animals was found only in the baseline group. Four weeks and 6 months after the abdominal surgical procedure, a statistically significant increase of the animals' weight was found in the implantation group, the control and the baseline group. Gastrointestinal complications like fistula, perforation or peritonitis did not occur in any of the animals. The measurement of the stomach pressure after maximal gas insufflation did not show significant differences between the implantation group, the control and the baseline group in any of the time periods investigated. Despite very high strains of the gastric wall, no gas leakage was detected. There was a tight connection between the polymer and the adjacent stomach wall in all animals investigated. An adequate mechanical stability of the biomaterial was detectable under the extreme pathophysiological conditions of the stomach milieu. A fast and unfavourable degradation of the degradable polymer was not found in any of the animals. Further investigations are needed to analyse the mechanisms of the tissue integration of the biomaterial as well as the degradation kinetic of the polymer and the process of the tissue remodeling. The knowledge of these processes is necessary to adapt the novel biomaterial and thus prepare it for the use and implantation in different body locations and to develop novel therapeutical options in medicine. PMID:16961454

Rickert, Dorothee; Scheithauer, Marc O; Coskun, Saadet; Lendlein, Andreas; Kelch, Steffen; Franke, Ralf-Peter

2006-09-01

296

High-resolution PFPE-based molding techniques for nanofabrication of high-pattern density, sub-20 nm features: a fundamental materials approach.  

Science.gov (United States)

Several perfluoropolyether (PFPE)-based elastomers for high-resolution replica molding applications are explored. The modulus of the elastomeric materials was increased through synthetic and additive approaches while maintaining relatively low surface tension values (4 in.(2)) master templates, we experimentally show the relationship between mold resolution and material properties such as modulus and surface tension for materials used in this study. A composite mold approach was used to form flexible molds out of stiff, high modulus materials that allow for replication of sub-20 nm post structures. Sub-100 nm line grating master templates, formed using e-beam lithography, were used to determine the experimental stability of the molding materials. It was observed that as the feature spacing decreased, high modulus PFPE tetramethacrylate (TMA) composite molds were able to effectively replicate the nanograting structures without cracking or tear-out defects that typically occur with high modulus elastomers. PMID:20178369

Williams, Stuart S; Retterer, Scott; Lopez, Rene; Ruiz, Ricardo; Samulski, Edward T; DeSimone, Joseph M

2010-04-14

297

High-Resolution PFPE-based Molding Techniques for Nanofabrication of High-Pattern Density, Sub-20nm Features: A Fundamental Materials Approach  

Energy Technology Data Exchange (ETDEWEB)

Several perfluoropolyether (PFPE)-based elastomers for high-resolution replica molding applications are explored. The modulus of the elastomeric materials was increased through synthetic and additive approaches while maintaining relatively low surface tension values (<25 mN/m). Using large area (>4 in.{sup 2}) master templates, we experimentally show the relationship between mold resolution and material properties such as modulus and surface tension for materials used in this study. A composite mold approach was used to form flexible molds out of stiff, high modulus materials that allow for replication of sub-20 nm post structures. Sub-100 nm line grating master templates, formed using e-beam lithography, were used to determine the experimental stability of the molding materials. It was observed that as the feature spacing decreased, high modulus PFPE tetramethacrylate (TMA) composite molds were able to effectively replicate the nanograting structures without cracking or tear-out defects that typically occur with high modulus elastomers.

Williams, Stuart S.; Retterer, Scott; Lopez, Rene; Ruiz, Ricardo; Samulski, Edward T.; DeSimone, Joseph M.

2010-01-01

298

Space Environment Effects on Silicone Seal Materials  

Science.gov (United States)

A docking system is being developed by the NASA to support future space missions. It is expected to use redundant elastomer seals to help contain cabin air during dockings between two spacecraft. The sealing surfaces are exposed to the space environment when vehicles are not docked. In space, the seals will be exposed to temperatures between 125 to -75 C, vacuum, atomic oxygen, particle and ultraviolet radiation, and micrometeoroid and orbital debris (MMOD). Silicone rubber is the only class of space flight-qualified elastomeric seal material that functions across the expected temperature range. NASA Glenn has tested three silicone elastomers for such seal applications: two provided by Parker (S0899-50 and S0383-70) and one from Esterline (ELA-SA-401). The effects of atomic oxygen (AO), UV and electron particle radiation, and vacuum on the properties of these three elastomers were examined. Critical seal properties such as leakage, adhesion, and compression set were measured before and after simulated space exposures. The S0899-50 silicone was determined to be inadequate for extended space seal applications due to high adhesion and intolerance to UV, but both S0383-70 and ELA-SA-401 seals were adequate.

deGroh, Henry C., III; Daniels, Christopher C.; Dever, Joyce A.; Miller, Sharon K.; Waters, Deborah L.; Finkbeiner, Joshua R.; Dunlap, Patrick H.; Steinetz, Bruce M.

2010-01-01

299

IE Information Notice No. 85-08: Industry experience on certain materials used in safety-related equipment  

International Nuclear Information System (INIS)

This information notice is being issued to provide licensees and construction permit holders with information pertaining to the behavior of certain materials used in safety-related equipment. The materials, as described below, were observed to have the potential of degrading the operability of safety-related equipment. These observations were made during environmental qualification testing and/or during routine inspection of in-service equipment. The notice describes the following: elastomeric seals used in personnel air locks for the reactor containment systems; epoxy phenolic coating applied to the lower portion of the interior surface of diesel oil storage tanks; the use of Viton elastomer as the seal material in hydrogen recombiner applications; and environmental qualification of ASCO NP valves with Viton and ethylene propylene parts

300

Materials selection guidelines for geothermal power systems. First edition  

Energy Technology Data Exchange (ETDEWEB)

Nine potential power cycles are defined and diagrammed for the generation of electricity from geothermal fluids. General fluid properties that influence the applicability of power cycles to a particular geothermal resource are discussed. The corrosivity of individual process streams in power cycles is described based on variations in chemical composition and temperature. Results of materials performance tests are analyzed based on the chemical composition of the corrosive medium and physical factors such as temperature, duration of exposure, and fluid velocity. The key chemical components in geothermal fluids that are significant in determining corrosivity are identified. Both summarized and detailed results of materials performance tests in U.S. liquid-dominated resources are given. Seven U.S. liquid-dominated KGRA's are classified according to relative corrosiveness and their key chemical components are defined. The various forms and mechanisms of corrosive attack that can occur in geothermal process streams are described. The application of nonmetallic materials in geothermal environments is discussed. The appendices contain information on (1) operating experience at geothermal power plants, (2) corrosion in desalination facilities, (3) reliability of geothermal plants, (4) elastomeric materials, (5) comparative alloy costs, and (6) geothermal equipment manufacturers. (MHR)

DeBerry, D.W.; Ellis, P.F.; Thomas, C.C.

1978-09-01

301

Orthodontic materials research and applications: part 2. Current status and projected future developments in materials and biocompatibility.  

Science.gov (United States)

The purpose of this 2-part opinion article was to project the developments expected to occur in the next few years in orthodontic materials research and applications. Part 1 reviewed developments in bonding to enamel. Part 2 looks at other orthodontic materials applications and explores emerging research strategies for probing the biological properties of materials. In the field of metallic brackets, expansion of the use of titanium alloys with improved hardness and nickel-free steels with better corrosion resistance and increased hardness is expected. Manufacturing techniques might be modified to include laser-welding methods and metal injection molding. Esthetic bracket research will involve the synthesis of high-crystallinity biomedical polymers with increased hardness and stiffness, decreased water sorption, and improved resistance to degradation. New plastic brackets might incorportate ceramic wings. Fiber-reinforced composite archwires, currently experimental, could soon be commercially available, and long-term applications of shape-memory plastics might become viable. Advancements in elastomeric materials will result in polymers with reduced relaxation, broader use of fluoride-releasing elastomers with decreased relaxation, and large-scale film coating of elastomers to decrease reactivity, water sorption, and degradation. Finally, biocompatibility assessments will incorporate testing of potential endocrinological action. New polymer formulations might be tested in adhesive and plastic bracket manufacturing, based on benzoic ring-free monomers to avoid the adverse effects of the estrogenic molecule bisphenol-A. PMID:17276868

Eliades, Theodore

2007-02-01

302

Compatibility of refrigerants and lubricants with elastomers  

Energy Technology Data Exchange (ETDEWEB)

Information contained in this reporters designed to assist the air-conditioning and refrigeration industry in the selection of suitable elastomeric gasket and seal materials that will prove useful in various refrigerant and refrigeration lubricant environments. Swell measurements have been made on approximately 50% of the proposed elastomers (94 total)in both the lubricant (7 total) and refrigerant (10 total) materials. Swell behavior in the these fluids have been determined using weight and in situ diameter measurements for the refrigerants and weight, diameter and thickness measurements for the lubricants. Weight and diameter measurements are repeated after 2 hours and 24 hours for samples removed from the refrigerant test fluids and 24 hours after removal from the lubricants.

Hamed, G.R.; Seiple, R.H.

1992-07-01

303

Compatibility of refrigerants and lubricants with elastomers. Quarterly report, 1 April 1992--30 June 1992  

Energy Technology Data Exchange (ETDEWEB)

Information contained in this reporters designed to assist the air-conditioning and refrigeration industry in the selection of suitable elastomeric gasket and seal materials that will prove useful in various refrigerant and refrigeration lubricant environments. Swell measurements have been made on approximately 50% of the proposed elastomers (94 total)in both the lubricant (7 total) and refrigerant (10 total) materials. Swell behavior in the these fluids have been determined using weight and in situ diameter measurements for the refrigerants and weight, diameter and thickness measurements for the lubricants. Weight and diameter measurements are repeated after 2 hours and 24 hours for samples removed from the refrigerant test fluids and 24 hours after removal from the lubricants.

Hamed, G.R.; Seiple, R.H.

1992-07-01

304

Propriedades reométricas e mecânicas e morfologia de compósitos desenvolvidos com resíduos elastoméricos vulcanizados / Cure characteristics, mechanical properties and morphology of composites developed with addition of elastomeric vulcanized ground scraps  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Uma alternativa para as empresas geradoras de resíduos elastoméricos é a incorporação dos mesmos em suas formulações. Esse trabalho tem como objetivo preparar compósitos a partir da incorporação de resíduos industriais de SBR (copolímero de butadieno-estireno) e de EPDM (terpolímero de etileno-propi [...] leno-dieno), em formulação ASTM específica para cada tipo de elastômero. Foram avaliadas as propriedades reométricas, mecânicas e morfológicas dos compósitos desenvolvidos. A incorporação do resíduo permitiu a obtenção de produtos que vulcanizam em menores tempos quando comparados a composições sem resíduo. A quantidade de resíduo, para o melhor resultado de resistência à tração foi de 37 e de 196 phr para os compósitos com SBR e EPDM, respectivamente. As micrografias de MEV corroboraram os resultados mecânicos dessas composições, indicando melhor homogeneidade do resíduo na respectiva matriz elastomérica. Abstract in english One alternative for elastomeric scraps generation is its incorporation in conventional formulations in the industry itself. In this work, compositions with incorporation of SBR (styrene butadiene rubber) and EPDM (ethylene propylene diene rubber) industrial scraps, in specific ASTM formulation for e [...] ach elastomer, were prepared. Rheometric characteristics, mechanical properties and the morphology of the compounds developed were evaluated. With the ground scraps incorporation the vulcanization time decreases, comparing with compounds without ground scraps. The amount of scraps for the best tensile strength properties was 37 and 196 phr for SBR and EPDM compositions, respectively. Micrographs corroborated the mechanical results, indicating the best homogeneity of the scraps in the elastomeric matrix for these compositions.

Aline, Zanchet; Nicolle, Dal’Acqua; Tatiana, Weber; Janaina S., Crespo; Rosmary N., Brandalise; Regina C. R., Nunes.

2007-03-01

305

Avaliação do desempenho de materiais absorvedores de radiação eletromagnética por guia de ondas / Performance of radar absorbing materials by waveguide measurements  

Scientific Electronic Library Online (English)

Full Text Available Neste trabalho, amostras elastoméricas contendo diferentes tipos de cargas absorvedoras de microondas, sob a forma de pós, foram obtidas para medidas de refletividade. Os materiais utilizados com diferentes composições percentuais em peso foram: ferrocarbonila, negro de fumo, polianilina e ferrita d [...] opadas. As medidas de refletividade foram determinadas com base nas propriedades magnéticas e dielétricas dos compósitos elastoméricos a partir de dados de espalhamento, através da inserção e fixação em um guia de ondas, para a faixa de freqüência de 8-16 GHz. Os melhores resultados foram apresentados pelo ferrocarbonila e negro de fumo para as freqüências mais baixas, enquanto a ferrita dopada absorveu em uma freqüência mais elevada. Abstract in english In this work, samples consisting of an elastomeric matrix containing different kinds of active material in particulate form were prepared for reflectivity measurements. The materials used in different contents were: carbonyl-iron, carbon black, doped polyaniline and doped ferrite. The microwave refl [...] ectivity levels were determined from the magnetic and dielectric properties of the elastomeric composites from scattering data, by fitting the samples in a waveguide, for measurements in the frequency range of 8-16 GHz. Better microwave absorption at low frequencies was obtained for carbonyl-iron and carbon black while doped ferrite absorbed at high frequencies.

Magali S., Pinho; Roberto C., Lima; Bluma G., Soares; Regina C. R., Nunes.

1999-12-01

306

Efecto de la composición del bloque elastomérico de SBS y SEBES en las propiedades reológicas de asfaltos modificados / On the effect of the composition of the elastomeric block of SBS and SEBES block polymers on the rheological properties of modified aphalts  

Scientific Electronic Library Online (English)

Full Text Available Se estudió el comportamiento de los asfaltos modificados (AMP) con polímeros SBS (Lote 416) y SEBES a fin de entender el efecto de la composición del bloque elastomérico de esos dos tipos de polímeros en la morfología y la reología de los AMP. Los polímeros SEBES fueron producidos por hidrogenación [...] homogénea de los SBS con diferente grado de saturación de las dobles ligaduras de polibutadieno (0%, 7%, 29% y 49%). Los asfaltos modificados (AMP) con un 10% de polímero fueron preparados por mezclado a altas temperaturas (1880 0C, 4 h, 5000 rpm). Los análisis de microscopia por fluorescencia indican que el AMP es un material heterogeneo con una fase rica en polímero y otra fase rica en asfalto. Los análisis reológicos en flujo oscilatorio para varias temperaturas (40 a 90ºC) indican que los AMP producidos con SEBES con alta saturación experimentan cambios estructurales dando un incremento de su respuesta con respecto a la frecuencia, y exhibiendo una mas alta elasticidad (G'>G"). Se empleó el modelo multimodal de Maxwell para reproducir G' y G" de las curvas maestras. Se observó que el número de modos para ajustar los datos de los AMP aumentan con el grado de saturación. Abstract in english The behaviour of asphalt (PMA) modified with SBS (lot 416) and SBEBS was studied to elucidate the effect of the composition of the elastomeric block of these two types of polymers on the morphology and rheology of PMAs. The SBEBS polymers were produced by homogeneous hydrogenation of the SBS having [...] different degree of saturation of poly-butadiene double bonds (0%), 7%, 29% and 49%). Asphalt modified samples (PMA) with 10 wt % of polymer were prepared by hot mixing proces j (180 °C, 4 hours, 5000 rpm). Fluorescence microscopic analysis indicated that PMA are heterogeneous materials exhibiting a polymer-rich and asphalts-rich phases. Oscillatory flow rheology analysis for various temperatures (40-90ºC) indicate that all PMA prepared with SBEBS with higher saturation degree undergo structural c h angei exhibiting a higher viscoelastic response, and higher elasticity (G'>G"). The Maxwell multimodal model was employed to reproduce G' and G" master curves. It was observed thai the number of relaxation modes required to fit the data of SBEBS modified asphalt increases with the degree of polybutadiene saturation, since 12 modes are need are for SBEBS with 49 % of saturation while 8 modes are enough to fit the data of SBEBS 7 % of saturation.

R., Herrera-Najera; G., García-Guzmán; H., Xicotencalt-Serrano; L., Medina-Torres.

2012-04-01

307

Photo-actuating materials based on elastomers and modified carbon nanotubes  

Science.gov (United States)

The photo-actuating behavior of new polymeric nanocomposite materials based on a commercial elastomer, an ethylene-vinylacetate copolymer (EVA), filled with multiwalled carbon nanotubes (MWCNT) was investigated. A good dispersion of the MWCNT within the elastomeric matrix was ensured by using a novel, specific compatibilizer consisting of pyrenyl and cholesteryl groups. A uniaxial orientation of the MWCNT within the matrix was induced with shear forces by employing a special custom-made punch/die system. Good dispergation and alignment of the MWCNT within the matrix were demonstrated by scanning electron microscopy. Transmission electron microscopy showed a good dispersion of the MWCNT within the composite. Photo-actuation was qualitatively characterized by atomic force microscopy and quantitatively characterized by nanoindentation. The samples prepared in the form of Braille element showed expansion upon illumination by light diodes. The maximal height deformation changes about 15% was detected when a blue diode was used.

Czaniková, Klaudia; Krupa, Igor; Il?íková, Markéta; Kasák, Peter; Chorvát, , Dušan; Valentin, Marian; Šlouf, Miroslav; Mosná?ek, Jaroslav; Mi?ušík, Matej; Omastová, Mária

2012-01-01

308

46 CFR 162.018-3 - Materials.  

Science.gov (United States)

...EQUIPMENT Safety Relief Valves, Liquefied Compressed...manufacture of safety relief valves shall conform to...compressed gas in the liquid or gas phase. (b...containing external parts of valves must be constructed...Flange gaskets shall be metal or spiral wound...

2010-10-01

309

30 CFR 20.9 - Class 2 lamps.  

Science.gov (United States)

...Gaskets, if adequate, may be used to obtain a firm seat for the glass but not elsewhere. Rubber, putty, and plaster of paris are not acceptable as material for gaskets. For enclosures having an unoccupied volume (air space) of more...

2010-07-01

310

Galvanic effects accelerate crevice corrosion of type 316L SS flanges coupled to 6% Mo alloy  

International Nuclear Information System (INIS)

A service water system underwent a material replacement program in recent years. The service was a once-through system fed from the Delaware River. The original type 316L stainless steel (SS) and cement-lined carbon steel were replaced with 6% Mo alloy AL-6XN (UNS N08367). The majority of the system was 6% Mo piping connected to type 316L SS valves via gasketed flanges. During several years of operation, plant personnel observed localized crevice corrosion on the flange-face areas of the type 316L SS (UNS S31603) flanges. This area typically contains an insulation gasket material (a fibrous bound elastomeric material) that is sandwiched between flange joints. Galvanic effects, caused by the mixed alloy construction (i.e., type 316L SS to alloy 6% Mo), may be accelerating the observed crevice corrosion of type 316L SS. This possibility was of significant concern, and flange isolation kits typically used for isolating cathodic protection systems or dissimilar metals were being used. However, the plant grounding system caused the isolated flanges to have zero electrical resistance between them

311

Mechanics of Re-Torquing in Bolted Flange Connections  

Science.gov (United States)

It has been widely accepted that the phenomenon of time-dependent loosening of flange connections is a strong consequence of the viscous nature of the compression seal material. Characterizing the coupled interaction between gasket creep and elastic bolt stiffness has been useful in predicting conditions that facilitate leakage. Prior advances on this sub-class of bolted joints has lead to the development of (1) constitutive models for elastomerics, (2) initial tightening strategies, (3) etc. The effect of re-torque, which is a major consideration for typical bolted flange seals used on the Space Shuttle fleet, has not been fully characterized, however. The current study presents a systematic approach to characterizing bolted joint behavior as the consequence of sequentially applied torques. Based on exprimenta1 and numerical results, the optimal re-torquing parameters have been identified that allow for the negligible load loss after pre-load application

Gordon, Ali P.; Drilling Brian; Weichman, Kyle; Kammerer, Catherine; Baldwin, Frank

2010-01-01

312

Compatibility of refrigerants and lubricants with elastomers. Final report  

Energy Technology Data Exchange (ETDEWEB)

The information contained in this report is designed to assist the air-conditioning and refrigeration industry in the selection of suitable elastomeric gasket and seal materials that will prove useful in various refrigerant and refrigeration lubricant environments. In part I of the program the swell behavior in the test fluids has been determined using weight and in situ diameter measurements for the refrigerants and weight, diameter and thickness measurements for the lubricants. Weight and diameter measurements are repeated after 2 and 24 hours for samples removed fro the refrigerant test fluids and 24 hours after removal from the lubricants. Part II of the testing program includes the evaluation of tensile strength, hardness, weight, and dimensional changes after immersion aging in refrigerant/lubricant mixtures of selected elastomer formulations at elevated temperature and pressure.

Hamed, G.R.; Seiple, R.H.; Taikum, Orawan

1994-01-01

313

Contrast Materials  

Science.gov (United States)

What are contrast materials and how do they work? Contrast materials, also called contrast agents or contrast media, are used to improve pictures ... top of page Which imaging exams use contrast materials? Oral Contrast Materials Barium-sulfate contrast materials that ...

314

Hazardous materials  

Science.gov (United States)

HazCom; Hazard communication; Material Safety Data Sheet; MSDS ... Hazardous materials are substances that could harm human health or the environment. Hazardous means dangerous, so these materials must ...

315

Characterisation of Materials used in Flex Bearings of Large Solid Rocket Motors  

Directory of Open Access Journals (Sweden)

Full Text Available Solid rocket motors are propulsion devices for both satellite launchers and missiles, which require guidance and steering to fly along a programmed trajectory and to compensate for flight disturbances. A typical solid rocket motor consists of motor case, solid propellant grain, motor insulation, igniter and nozzle. In most solid rocket motors, thrust vector control (TVC is required. One of the most efficient methods of TVC is by flex nozzle system. The flex nozzle consists of a flexible bearing made of an elastomeric material alternating with reinforcement rings of metallic or composite material. The material characterisation of AFNOR 15CDV6 steel and the natural rubber-based elastomer developed for use in flex nozzle are discussed. This includes testing, modelling of the material, selection of a material model suitable for analysis, and the validation of material model.Defence Science Journal, 2011, 61(3, pp.264-269, DOI:http://dx.doi.org/10.14429/dsj.61.52

CH.V. Ram Mohan

2011-04-01

316

Materials research  

International Nuclear Information System (INIS)

The information brochure first recapitulates the main goals of the BMFT-sponsored materials research programme launched in 1985, and then gives an interim account as of 1988, of results obtained in the subject fields of ceramics, powder metallurgy, metallic high-temperature materials and special materials, new polymers, and composite materials. (MM)

317

Understanding Materials  

Science.gov (United States)

Almost everything people have ever done has involved materials. Historical evidence indicates that "engineered materials" have been available and utilized for the benefit of humankind since the Neolithic period, beginning about 10,000 BC. Some of these materials have been in existence for thousands of years. At first, materials consisted of wood,…

Katsioloudis, Petros J.

2010-01-01

318

Material Properties  

Science.gov (United States)

In this online activity, learners investigate the material properties of wood, metal, plastic, glass, and wool. Learners investigate the strength, flexibility, transparency of these materials to determine which materials work best for different parts of a space shuttle. Use this activity to talk about how some materials are better for certain applications, depending on the requirements.

BBC

2012-01-01

319

Materials Chemistry  

CERN Document Server

The 2nd edition of Materials Chemistry builds on the strengths that were recognized by a 2008 Textbook Excellence Award from the Text and Academic Authors Association (TAA). Materials Chemistry addresses inorganic-, organic-, and nano-based materials from a structure vs. property treatment, providing a suitable breadth and depth coverage of the rapidly evolving materials field. The 2nd edition continues to offer innovative coverage and practical perspective throughout. After briefly defining materials chemistry and its history, seven chapters discuss solid-state chemistry, metals, semiconducting materials, organic "soft" materials, nanomaterials, and materials characterization. All chapters have been thoroughly updated and expanded with, for example, new sections on ‘soft lithographic’ patterning, ‘click chemistry’ polymerization, nanotoxicity, graphene, as well as many biomaterials applications. The polymer and ‘soft’ materials chapter represents the largest expansion for the 2nd edition. Each ch...

Fahlman, Bradley D

2011-01-01

320

Engineered materials  

Energy Technology Data Exchange (ETDEWEB)

The following topics are treated: Special alloys and metal matrix composites, processing and properties of polymers and composites, biomaterials, advanced analytical techniques for engineered materials; ceramics, glass-ceramics and ceramic-matrix composites and materials for electronic applications.

Hampshire, S. (ed.) (Limerick Univ. (Ireland)); Buggy, M. (ed.) (Limerick Univ. (Ireland)); Carr, A.J. (ed.) (University Coll., Dublin (Ireland))

1993-01-01

321

Nanoporous materials  

OpenAIRE

The current review article attempts to cover the eld of nanoporous materials, thereby materials with voids of the order of 1 nm to 100 nm or even larger. Concepts, that have an effect on a more general basis, are introduced and the common features among the different classes of nanoporous materials are demonstrated enabling understanding their formation and stability. It is seen that the most successful method to produce nanoporous materials made by design is to imprint a template structure...

Polarz, Sebastian; Smarsly, Bernd

2002-01-01

322

Material problems  

International Nuclear Information System (INIS)

For the development and realisation of HTR reactors, modern high-temperature materials must be adapted to nuclear demands, and special materials must be developed. The paper discusses some aspects of structural materials for core shutdown components with a special view to HTR reactors. (orig./ORU)

323

Long term integrity of spent fuel and construction materials for dry storage facilities  

International Nuclear Information System (INIS)

In Japan, two dry storage facilities at reactor sites have already been operating since 1995 and 2002, respectively. Additionally, a large scale dry storage facility away from reactor sites is under safety examination for license near the coast and desired to start its operation in 2010. Its final storage capacity is 5,000tU. It is therefore necessary to obtain and evaluate the related data on integrity of spent fuels loaded into and construction materials of casks during long term dry storage. The objectives are: - Spent fuel rod: To evaluate hydrogen migration along axial fuel direction on irradiated claddings stored for twenty years in air; To evaluate pellet oxidation behaviour for high burn-up UO2 fuels; - Construction materials for dry storage facilities: To evaluate long term reliability of welded stainless steel canister under stress corrosion cracking (SCC) environment; To evaluate long term integrity of concrete cask under carbonation and salt attack environment; To evaluate integrity of sealability of metal gasket under long term storage and short term accidental impact force.

324

Adsorption and Permeation Behavior of Tritium in Vacuum Storage Vessel Materials  

International Nuclear Information System (INIS)

Adsorption behaviour of tritium in 316 L stainless steel vacuum storage vessels and gaskets which used for tritium targets storage about 4 years and 20 years was investigated, and the permeation rate of tritium in the stainless steel vessels was analysed as well. The results showed that tritium on the surface of the stainless steel vessels was dozens Bq/cm2, and there was about 106 Bq/g tritium in stainless steel and ceramic materials. During thermal desorption to 1 273 K, about 99% tritium released from these materials, and the proportion of HTO in ceramic was more than stainless steel. The permeation rate of storage vessels in summer was about 4 times than that in winter. It indicated that tritium adsorbed on the inner surface of the storage vessels at first, some of it diffused to the matrix and remained in it, others permeate from storage vessels to environment,and the temperature is one of the key factors which affect tritium permeation. (authors)

325

Occurrence and implications of radiation dose-rate effects for material aging studies  

International Nuclear Information System (INIS)

A number of commercial cable materials, including ethylene propylene rubber and crosslinked polyolefin insulations and chloroprene and chlorosulfonated polyethylene jackets have been radiation aged in air and nitrogen at radiation dose rates ranging from approximately 103 to 106 rad/hr. Material degradation was followed using ultimate tensile properties (elongation and tensile strength), swelling measurements and infrared spectroscopy. The tensile results indicate that in air environments radiation dose rate effects are important for all four materials, with more mechanical damage occurring as the dose rate is lowered. These results are interpreted as coming from a competition between crosslinking and oxidative scission in which scission becomes more important as the dose rate is lowered. The swelling results offer direct evidence in support of this interpretation. In addition the infrared results show increased carbonyl content at lower dose rates, also indicative of increased oxidation. The conclusions of this study have important implications for the qualification of elastomeric materials for nuclear applications, since they clearly indicate that the mechanism of degradation is quite different (and the amount usually more severe) under low dose rate exposures compared to the mechanism occurring under the high dose rate exposures normally utilized for simulating the natural aging. (author)

326

An in vitro comparison of the force decay generated by different commercially available elastomeric chains and NiTi closed coil springs Comparação in vitro da degradação da força gerada por cadeias elastoméricas e por molas fechadas de NiTi de diferentes marcas comerciais  

Directory of Open Access Journals (Sweden)

Full Text Available This in vitro study was designed to compare the forces generated by commercially available elastomeric chains and NiTi closed coil springs, and to determine their force decay pattern. Forty elastomeric chains and forty NiTi closed coil springs were divided into 4 groups according to the following manufacturers: (1 Morelli®, (2 Abzil®, (3 TP Orthodontics® and (4 American Orthodontics®. The specimens were extended to twice their original length and stored in artificial saliva at 37°C. Initial force was measured by means of an Instron universal testing machine and then at 1, 4, 7, 14, 21, and 28 days. The results revealed that the elastomeric chains delivered a mean initial force of 347 g for Morelli®, 351 g for American Orthodontics®, 402 g for Abzil®, and 404 g for TP Orthodontics®. The NiTi closed coil springs generated a mean initial force of 196 g for American Orthodontics®, 208 g for TP Orthodontics®, 216 g for Abzil®, and 223 g for Morelli®. The mean percentage of force decay observed after 28 days for the elastomeric chains was 37.4% for TP Orthodontics®, 48.1% for American Orthodontics®, 65.4% for Morelli®, and 71.6% for Abzil®. After 28 days, the NiTi closed coil springs presented a mean percentage of force decay of 22.6% for American Orthodontics®, 29.8% for Abzil®, 30.6% for Morelli®, and 45.8% for TP Orthodontics®. At the end of the study, significant differences were observed between the elastomeric chains and the NiTi closed coil springs. The results indicated that the studied NiTi closed coil springs are more adequate for dental movement than the elastomeric chains.Este estudo in vitro foi delineado para comparar a força gerada por cadeias elastoméricas e por molas fechadas de NiTi comercialmente disponíveis e para determinar seu padrão de degradação de forças. Para tal, 40 segmentos de cadeia elastomérica e 40 molas fechadas de NiTi foram divididas em 4 grupos de acordo com a marca comercial: (1 Morelli®, (2 Abzil®, (3 TP Orthodontics® e (4 American Orthodontics®. As amostras foram distendidas ao dobro de seu comprimento original e imersas em solução de saliva artificial a 37°C. Uma máquina de ensaio (Instron foi utilizada para aferir a força inicial e em 1, 4, 7, 14, 21 e 28 dias. Os resultados mostraram que as cadeias elastoméricas liberaram uma força média inicial de 404 g para a marca TP Orthodontics®, 402 g para Abzil®, 351 g para American Orthodontics® e 347 g para Morelli®. As molas fechadas de NiTi geraram uma força média inicial de 223 g para a marca Morelli®, 216 g para Abzil®, 208 g para TP Orthodontics® e 196 g para American Orthodontics®. A percentagem média de degradação da força após 28 dias para as cadeias elastoméricas foi de 37,4% para TP Orthodontics®, 48,1% para American Orthodontics®, 65,4% para Morelli® e 71,6% para Abzil®. A percentagem média de degradação da força após 28 dias para as molas fechadas de NiTi foi de 22,6% para American Orthodontics®, 29,8% para Abzil®, 30,6% para Morelli® e 45,8% para TP Orthodontics®. Ao final do experimento, observaram-se diferenças significantes entre as cadeias elastoméricas e as molas fechadas de NiTi. Os resultados permitem recomendar as molas fechadas de NiTi estudadas como dispositivos mais adequados para movimentação dentária do que as cadeias elastoméricas.

Ana Cristina Soares Santos

2007-03-01

327

An in vitro comparison of the force decay generated by different commercially available elastomeric chains and NiTi closed coil springs / Comparação in vitro da degradação da força gerada por cadeias elastoméricas e por molas fechadas de NiTi de diferentes marcas comerciais  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Este estudo in vitro foi delineado para comparar a força gerada por cadeias elastoméricas e por molas fechadas de NiTi comercialmente disponíveis e para determinar seu padrão de degradação de forças. Para tal, 40 segmentos de cadeia elastomérica e 40 molas fechadas de NiTi foram divididas em 4 grupo [...] s de acordo com a marca comercial: (1) Morelli®, (2) Abzil®, (3) TP Orthodontics® e (4) American Orthodontics®. As amostras foram distendidas ao dobro de seu comprimento original e imersas em solução de saliva artificial a 37°C. Uma máquina de ensaio (Instron) foi utilizada para aferir a força inicial e em 1, 4, 7, 14, 21 e 28 dias. Os resultados mostraram que as cadeias elastoméricas liberaram uma força média inicial de 404 g para a marca TP Orthodontics®, 402 g para Abzil®, 351 g para American Orthodontics® e 347 g para Morelli®. As molas fechadas de NiTi geraram uma força média inicial de 223 g para a marca Morelli®, 216 g para Abzil®, 208 g para TP Orthodontics® e 196 g para American Orthodontics®. A percentagem média de degradação da força após 28 dias para as cadeias elastoméricas foi de 37,4% para TP Orthodontics®, 48,1% para American Orthodontics®, 65,4% para Morelli® e 71,6% para Abzil®. A percentagem média de degradação da força após 28 dias para as molas fechadas de NiTi foi de 22,6% para American Orthodontics®, 29,8% para Abzil®, 30,6% para Morelli® e 45,8% para TP Orthodontics®. Ao final do experimento, observaram-se diferenças significantes entre as cadeias elastoméricas e as molas fechadas de NiTi. Os resultados permitem recomendar as molas fechadas de NiTi estudadas como dispositivos mais adequados para movimentação dentária do que as cadeias elastoméricas. Abstract in english This in vitro study was designed to compare the forces generated by commercially available elastomeric chains and NiTi closed coil springs, and to determine their force decay pattern. Forty elastomeric chains and forty NiTi closed coil springs were divided into 4 groups according to the following ma [...] nufacturers: (1) Morelli®, (2) Abzil®, (3) TP Orthodontics® and (4) American Orthodontics®. The specimens were extended to twice their original length and stored in artificial saliva at 37°C. Initial force was measured by means of an Instron universal testing machine and then at 1, 4, 7, 14, 21, and 28 days. The results revealed that the elastomeric chains delivered a mean initial force of 347 g for Morelli®, 351 g for American Orthodontics®, 402 g for Abzil®, and 404 g for TP Orthodontics®. The NiTi closed coil springs generated a mean initial force of 196 g for American Orthodontics®, 208 g for TP Orthodontics®, 216 g for Abzil®, and 223 g for Morelli®. The mean percentage of force decay observed after 28 days for the elastomeric chains was 37.4% for TP Orthodontics®, 48.1% for American Orthodontics®, 65.4% for Morelli®, and 71.6% for Abzil®. After 28 days, the NiTi closed coil springs presented a mean percentage of force decay of 22.6% for American Orthodontics®, 29.8% for Abzil®, 30.6% for Morelli®, and 45.8% for TP Orthodontics®. At the end of the study, significant differences were observed between the elastomeric chains and the NiTi closed coil springs. The results indicated that the studied NiTi closed coil springs are more adequate for dental movement than the elastomeric chains.

Ana Cristina Soares, Santos; André, Tortamano; Sandra Regina Frazatto, Naccarato; Gladys Cristina, Dominguez-Rodriguez; Julio Wilson, Vigorito.

2007-03-01

328

Poliamidas, poliésteres e termoplásticos elastoméricos: uma perspectiva sustentável na indústria moderna / Polyamides, polyesters and elastomeric thermoplastics: a sustainable perspective in modern industry  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Polímeros extraídos de fontes fósseis, não biodegradáveis, são assunto cada vez mais em pauta. Seja por conta de descartes incorretos, do longo tempo que levam para se decompor no meio ambiente ou até mesmo pelo impacto socioambiental que esse tipo de material pode causar às gerações futuras. Isso n [...] os faz indagar: como as tecnologias utilizadas por empresas do setor de polímeros têm feito surgir novos materiais? É possível oferecer soluções de menor impacto ambiental, mais resistência, mais segurança e custo menor? Ao longo deste artigo, exibiremos novos produtos e modelos de fabricação que podem tornar mais saudável e sustentável todo o caminho, que leva das grandes empresas até o consumidor final, os elementos presentes no dia-a-dia de pessoas no mundo todo. Abstract in english Polymers extracted from fossile sources are an issue highlighted among debates in industry, for its incorrect discard, for the long period of time this material takes to decompose or even due to its unsustainable environmental footprint. This scenario makes the industry of polymers question how the [...] available technology can be used to create new materials, and if it would be possible to offer safer and cheaper solutions with less environmental impact and more resistance. This article will expose new products and new industrial development models that can make the chain that leads from the companies to the consumer the elements present into present-day society worldwide more sustainable.

Haroldo, Marcos.

329

Materials development  

International Nuclear Information System (INIS)

Objective of the materials program is the development of a structural material for the MSBR primary circuit which is resistant to irradiation embrittlement and intergranular attack by fission products. The bulk of the work was done on the development and study of modified Hastelloy N (Ti, Nb), including its interaction with salt and fission Te. Materials (Ta-10 percent W, Mo, graphite) are also being tested for corrosion resistance at 600 and 7000C to Bi--Li for use in fuel processing

330

AVALIAÇÃO DA CAPACIDADE DE CÓPIA DE MATERIAIS DE MOLDAGEM ELASTOMÉRICOS DE DIFERENTES SISTEMAS POR MEIO DE UMA TÉCNICA APLICÁVEL CLINICAMENTE EVALUATION OF THE COPYING ABILITY OF DIFFERENT ELASTOMERIC IMPRESSION MATERIALS USING A CLINICALLY APPLICABLE TECHNIQUE  

OpenAIRE

O objetivo deste trabalho foi realizar um estudo comparativo entre diferentes sistemas de materiais de moldagem, tais como o polissulfeto, a silicona de condensação e a silicona de adição, através de uma nova técnica de avaliação não destrutiva e, conseqüentemente, aplicável clinicamente. A partir da confecção de próteses fixas de três elementos, fundidas em liga de níquel-cromo, obtiveram-se réplicas tridimensionais do espaço entre a restauração e o preparo cavitário, ut...

Antunes, Rossana Pereira Almeida; Matsumoto, Wilson; Panzeri, Heitor

1997-01-01

331

Measuring the electrical resistance of metals to 40 GPa in the diamond-anvil cell  

International Nuclear Information System (INIS)

A four-probe technique is described for measuring the electrical resistance of metals in a diamond-anvil cell at pressures up to 40 GPa. The pressure range for electrical resistance measurements was extended by developing insulating gaskets that provide the necessary support for the diamonds and the electrical leads at the diamond edges. The various gasket materials and construction methods that were tested fall into two categories: (1) gaskets made entirely of insulating materials, and (2) gaskets made of metal coated with insulating materials. Gaskets developed in each category were used successfully in making resistance measurements up to 40 GPa. The most reliable gaskets were composites of sheet mica and MgO powder. This report describes the testing and development of the gaskets and presents electrical resistance data obtained for iron and beryllium to 40 GPa

332

Radiation application on some polymeric industrial waste materials  

International Nuclear Information System (INIS)

Polymer wastes of different kinds and magnitudes are produced as a result of manufacture of various polymeric articles. These kinds of waste materials would be expected to contribute to environmental pollution. polymeric waste discarded after industrial utilization of polytetrafluoroethylene (PTFE) in the form of scrap, was used in this investigation as a filler for preparation of rubber based composites, which have been vulcanized by gamma radiation. Before being used as filler, the scrap has been transformed at first into powder of particle size of 125 um through its irradiation with 50 kGy, followed by heating at 250 C and finally grinding. This study is divided into two main parts: The first is concerned with the effect of ionizing gamma rays on the PTFE scrap alone. The results obtained revealed that a maximum irradiation dose of 150 KGy was sufficient to attain the maximum change in properties of PTFE scrap, its molecular weight and degree of crystallization In the second part, the mechanical, physico - chemical , thermal and electrical properties of NBR based composites, filled with varying contents of PTFE powder. Have been followed up as a function of irradiation dose. Moreover, the effect of either pure gasoline fuel or gasoline containing different ratios of toluene, on swelling property of prepared composites as a function of PTFE filler content , has been carried out . The results obtained showed that composites prepared have gained the property of self lrepared have gained the property of self lubrication which shows its suitability for being mainly used as substitute for oil seal. Other applications are also possible such as rubber seal that may be used under static, i.e, gaskets, at room temperature as well as high temperature up to 100 C, lining of fuel tank and gears.10 tabs., 35 figs., 95 refs

333

Scintillator material  

International Nuclear Information System (INIS)

A scintillator material for detection and quantitative determination of ionizing radiation is discussed consisting of an acridone dissolved in a fluid or solid medium. Solvent mixtures with at least one protogenic component or polymers and copolymers are used. The scintillator material is distinguished by an excellent stability at high energy doses

334

Radioactive Material  

CERN Multimedia

The Radiation Protection Group of the Safety Commission is responsible for shipping of radioactive material from CERN to any external institute or organisation. The RP group is equally responsible for the reception of radioactive material shipped to any of the CERN sites. Anyone who needs to ship from or import into CERN radioactive material must contact the Radioactive Shipping Service of the RP group in advance. Instructions are available at: http://cern.ch/rp-shipping or in the Radiation Protection Procedure PRP13: https://edms.cern.ch/document/346823 Radiation Protection Group

2004-01-01

335

Thermoluminescent materials  

International Nuclear Information System (INIS)

Thermoluminescence is the emission of light from substances when they are heated. This phenomena is observed for many synthetic and natural substances. These thermoluminescent materials must be ionic crystals, covalent crystals, and molecular crystals - an insulator or a semiconductor, but metals do not exhibit luminescent properties because they could not storage radiation energy. Most research has been devoted to the discovery and development of materials suitable for thermoluminescence dosemeters, and some phosphors are used routinely in dosimetric applications. But for other purposes, many interesting materials have been suggested and investigated. (author)

336

Materials & Processes  

Science.gov (United States)

This resource, created by National Aerospace Technical Education Center (SpaceTEC), is centered on materials and processes. The document focuses on the material structure of metal. It mainly focuses on the properties, these being: hardness, brittleness, malleability, ductility, elasticity, toughness, density, fusibility, conductivity, contraction and expansion. After the initial discussion of properties, the topic shifts to metalworking, case hardening and corrosion. Corrosion dominates over half of the presentation. Overall, this is thorough examination of this material. It totals nearly seventy slides in length. Instructors could use this either as a study guide or simply to enhance existing curriculum.

337

Nuclear materials  

International Nuclear Information System (INIS)

Nuclear materials denotes all the materials implied in the construction and functioning of a nuclear reactor or, in a broader sense, all the materials participating in nuclear processes. The materials within a nuclear reactor are the nuclear fuel, the moderator, the reflector the coolant, the neutron absorbents, the materials for the biological shieldings and the structural materials. These materials are presented and accordingly the contents of the book is as follows: 1. Nuclear fuels; 1.1. Introduction; 1.2. Uranium extraction; 1.3. Uranium ore processing; 1.4. Uranium conversion; 1.5. Uranium enrichment; 1. 5.1. Theoretical aspects in isotope enrichment; 1.5.2. Gaseous diffusion; 1.5.3. Centrifuge enrichment; 1.5.4. Laser enrichment. The AVLIS procedure; 2. Building materials; 2.1. Mechanical and metallurgical properties; 2.2. Operation conditions. Specific aspects in the NPP primary and secondary circuits. Irradiation effects; 2.3. Selecting the nuclear materials; 3. Corrosion in nuclear materials; 3.1. Generals; 3.2. Generalized corrosion and primary circuit contamination; 3.3. Stress-crevice corrosion; 3.4. Local corrosion. Pitting denting and intercrystalline corrosion; 3.5. Electrochemical corrosion. Cathodic protection; 3.6. Corrosion-erosion; 3.7. Corrosion in steam generators, turbomachinery and their condensers; 4. Welding of nuclear materials; 4.1. Introductory notions; 4.2. Welding techniques. 4.3. Thermal aspects of welding; 4.4. Thermomechanical aspects of welding; 4.4. Thermomechanical aspects of welding; 4.5. Metallurgical aspects of welding; 4.5.1. Structural and phase modifications; 4.5.2. Welding modified properties; 4.6. Defects and cracks in welding areas; 4.7. Materials' weldability; 5. Nondestructive testing methods; 5.1. Radiography; 5.2. Ultrasonic testing; 5.3. Stress testing; 5.4. Electromagnetic testing; 6. Moderators and coolants; 6.1. Heavy water production; 6.2. Heavy water utilization; 6.2.1. Activation of heavy water; 6.2.2. Heavy water radiolysis; 6.2.3. Air radiolysis; 6.3. Control parameters; 6.3.1. Control parameters within the moderator; 6.3.2. Heat Transport Primary System (SPTC) control parameters; 7. Absorbent and shielding materials; 7.1. Absorbing materials; 7.2. Biological protection materials; 8. Problems concerning the pressure tubes; 8.1. Introduction; 8.2. Factors influencing the lifetime; 8.2.1. Modifications of size; 8.2.2. Modification of materials properties; 8.2.3. Corrosion and hydration; 8.3. Importance of fuel channel inspection; 8.4. Conclusions from testings; 8.4.1. Zr-2 tubes; 8.4.2. Zr-2.5%Nb tubes; 8.5. Problems occurring in pressure tubes; 8.6. Delayed Hydride Cracking. In the end the author presents measures to prevent or minimize the danger of occurrence of DHC

338

Basalt Materials  

International Science & Technology Center (ISTC)

Physicochemical Studies of Basalt Materials and Ceramic Chromite-Niobate Composites for the Purpose of the Immobilization of Ecologically Hazardous Actinides and the Making of Protective Barriers for a Long-term Safe Storage of Radwastes.

339

Nuclear materials  

International Nuclear Information System (INIS)

In 1998, Nuclear Regulatory Authority of the Slovak Republic (NRA SR) performed 38 inspections, 25 of them were performed in co-operation with IAEA inspectors. There is no fresh nuclear fuel at Bohunice A-1 NPP at present. Fresh fuel of Bohunice V-1 and V-2 NPPs is inspected in the fresh fuel storage.There are 327 fresh fuel assemblies in Mochovce NPP fresh fuel storage. In addition to that, are also 71 small users of nuclear materials in Slovakia. In most cases they use: covers made of depleted uranium for non-destructive works, detection of level in production plants, covers for therapeutical sources at medical facilities. In. 1995, NRA SR issued 4 new licences for nuclear material withdrawal. In the next part manipulation with nuclear materials, spent fuel stores and illegal trafficking in nuclear materials are reported

340

Magnetostrictive materials  

International Nuclear Information System (INIS)

The paper has been prepared on the basis of literature survey covering last 10 years. The article contains concise overview of the effect of magnetostriction and related effects such as Villarie effect, Young modulus change effect, Widemann and Birkhausen effects. Magnetostrictive materials (MM) covert reversibly magnetic energy into energy of elastic deformation. Traditional, as well as newest magnetostrictive materials, exhibiting effect of giant magnetostriction, e.g. containing rare earth metals (Tb,Dy) Terphenol-D, have been discussed. Interesting new groups of materials appear to be hybrid systems, which combine properties of magnetostrictive and magnetic shape memory materials. Processing methods of MM comprise rapid solidification of liquid alloy, monocrystallization, directional crystallization and powder metallurgy. Potential application areas of MM are generally related to their use as sensors and actuators. MM find applications in sonar devices, seismic sensors, geological tomography, hydraulic valves, sensors of motion, force and magnetic field, and many others. Interesting field of MM applications is related to systems for health monitoring of composite materials. Directions for further research in the field of MM should consider development of new materials having lower anisotropy and hysteresis, and development of a new technologies e.g. thin magnetostrictive films. (author)

341

New materials  

International Nuclear Information System (INIS)

This volume contains state-to-the-art lectures presented by distinguished scientists on important aspects of new materials covering diverse and varied aspects of the subject, such as: growth and characterization of ZnSe-based II-VI semiconductor quantum wells and superlattices for short wavelength semiconductor lasers; atomic layer and unit-cell layer growth of oxide superconductor thin films by laser molecular beam epitaxy; lattice engineering of ceramics for exploration of new high Tc superconductors; hydrogenated amorphous silicon, its alloys and their device applications; organic superconductors; occurrence of high-temperature ?-phase of AgI at room temperature in superionic AgI-Ag2O-MxOy glasses; gas sensor materials; diamond thin films; sol-gel technique for materials synthesis; computer applications to materials science and engineering; icosahedral quasicrystals; construction and functional properties of polymer/(liquid crystal) composite systems; novel method to prepare conducting polymer composites; membranes for gas separations; discontinuously reinforced metal matrix composites; tribological behaviour of new materials; development of carbon-carbon composites; ceramic composites by directed metal oxidation; biofunctional materials that initiate, excel and control the living body; and biomaterials host tissue interactions. (orig.)

342

Comparación de la resistencia al deslizamiento en brackets de autoligado y brackets convencionales ligados con ligadura elastomérica convencional y ligaduras de baja fricción Comparison of resistance to sliding produced by self-ligating Brackets and conventional brackets ligated with conventional Elastomeric ligature and low-friction ligatures  

Directory of Open Access Journals (Sweden)

Full Text Available INTRODUCCIÓN: es importante para el ortodoncista conocer la resistencia al deslizamiento (RD generada por el método de ligado usado durante la fase de cierre de espacio con mecánica de deslizamiento. El objetivo es comparar in vitro la RD de un tipo de bracket de autoligado con un tipo de bracket convencional combinado con ligaduras elastoméricas de baja fricción y ligadura elastomérica convencional. MÉTODOS: se utilizaronbrackets de autoligado SmartClip (3M® ybrackets convencionales Gemini (3M®, dos tipos de ligadura elastomérica de baja fricción Slide (Leone®, Synergy (RMO® y un tipo de ligadura elastomérica convencional Sani-Tie (GAC®. Los sistemas de ligación de los brackets fueron probados con alambre de acero inoxidable calibre 0,019 × 0,025?. La resistencia al deslizamiento de la combinación bracket/alambre/ligadura fue medida con un modelo experimental de tres brackets cementados en una placa acrílica, montada en una máquina Instron. Cada combinación fue probada 9 veces consecutivas en estado seco. RESULTADOS: losbrackets Gemini (3M® con ligadura convencional Sani-tie (GAC®, reportaron valores promedio de 67,3 g y los brackets Gemini (3M® con ligadura de baja fricción siliconada Synergy (RMO® de 84,6 g. Losbrackets SmartClip (3M® y Gemini (3M® con ligadura elastomérica de baja fricción Slide (Leone® tuvieron valores promedio similares de 5,0 y 5,4 g, respectivamente, sin diferencias significativas (p = 0,999. CONCLUSIONES: las ligaduras elastoméricas de baja fricción Slide (Leone®, mostraron fuerzas de resistencia al deslizamiento similares a los brackets de autoligado Smartclip (3M®.INTRODUCTION: It is important for the orthodontist to be familiar with the sliding resistance (SR generated by the ligation method used during the space closure phase with sliding mechanics. The objective of this article is to make an in vitro comparison of the SR produced by a self-ligating bracket and a conventional bracket in combination with low-friction and conventional elastomeric ligatures. METHODS:SmartClip (3M® self-ligatingbrackets and Gemini (3M® conventional brackets were used, as well as two types of low-friction elastomeric ligature: Slide (Leone® and Synergy (RMO®, and one type of conventional elastomeric ligature: Sani-Tie (GAC®.The brackets ligation systems were tested with stainless steel wire of 0.019 × 0.025'' caliber. Sliding resistance of the bracketwire- ligature combination was measured with an experimental model of three brackets bonded in an acrylic plate mounted on an Instron machine. Each combination was tested nine consecutive times in dry state. RESULTS: The Gemini (3M®brackets with a conventional Sani-Tie (GAC® ligature reported mean values of 67.3 g, while the Gemini (3M®brackets with low-friction Synergy (RMO® silicone ligature obtained mean values of 84.6 g. The SmartClip (3M® and Gemini (3M®brackets with low-friction Slide (Leone® elastomeric ligature had similar mean values of 5.0 and 5.4 g respectively, with no significant differences (p = 0.999. CONCLUSIONS: The Slide (Leone® low-friction elastomeric ligatures showed sliding resistance forces similar to the SmartClip (3M® self-ligatingbrackets.

Mileny Nieto Uribe

2012-06-01

343

Comparación de la resistencia al deslizamiento en brackets de autoligado y brackets convencionales ligados con ligadura elastomérica convencional y ligaduras de baja fricción / Comparison of resistance to sliding produced by self-ligating Brackets and conventional brackets ligated with conventional Elastomeric ligature and low-friction ligatures  

Scientific Electronic Library Online (English)

Full Text Available INTRODUCCIÓN: es importante para el ortodoncista conocer la resistencia al deslizamiento (RD) generada por el método de ligado usado durante la fase de cierre de espacio con mecánica de deslizamiento. El objetivo es comparar in vitro la RD de un tipo de bracket de autoligado con un tipo de bracket c [...] onvencional combinado con ligaduras elastoméricas de baja fricción y ligadura elastomérica convencional. MÉTODOS: se utilizaronbrackets de autoligado SmartClip (3M®) ybrackets convencionales Gemini (3M®), dos tipos de ligadura elastomérica de baja fricción Slide (Leone®), Synergy (RMO®) y un tipo de ligadura elastomérica convencional Sani-Tie (GAC®). Los sistemas de ligación de los brackets fueron probados con alambre de acero inoxidable calibre 0,019 × 0,025?. La resistencia al deslizamiento de la combinación bracket/alambre/ligadura fue medida con un modelo experimental de tres brackets cementados en una placa acrílica, montada en una máquina Instron. Cada combinación fue probada 9 veces consecutivas en estado seco. RESULTADOS: losbrackets Gemini (3M®) con ligadura convencional Sani-tie (GAC®), reportaron valores promedio de 67,3 g y los brackets Gemini (3M®) con ligadura de baja fricción siliconada Synergy (RMO®) de 84,6 g. Losbrackets SmartClip (3M®) y Gemini (3M®) con ligadura elastomérica de baja fricción Slide (Leone®) tuvieron valores promedio similares de 5,0 y 5,4 g, respectivamente, sin diferencias significativas (p = 0,999). CONCLUSIONES: las ligaduras elastoméricas de baja fricción Slide (Leone®), mostraron fuerzas de resistencia al deslizamiento similares a los brackets de autoligado Smartclip (3M®). Abstract in english INTRODUCTION: It is important for the orthodontist to be familiar with the sliding resistance (SR) generated by the ligation method used during the space closure phase with sliding mechanics. The objective of this article is to make an in vitro comparison of the SR produced by a self-ligating bracke [...] t and a conventional bracket in combination with low-friction and conventional elastomeric ligatures. METHODS:SmartClip (3M®) self-ligatingbrackets and Gemini (3M®) conventional brackets were used, as well as two types of low-friction elastomeric ligature: Slide (Leone®) and Synergy (RMO®), and one type of conventional elastomeric ligature: Sani-Tie (GAC®).The brackets ligation systems were tested with stainless steel wire of 0.019 × 0.025'' caliber. Sliding resistance of the bracketwire- ligature combination was measured with an experimental model of three brackets bonded in an acrylic plate mounted on an Instron machine. Each combination was tested nine consecutive times in dry state. RESULTS: The Gemini (3M®)brackets with a conventional Sani-Tie (GAC®) ligature reported mean values of 67.3 g, while the Gemini (3M®)brackets with low-friction Synergy (RMO®) silicone ligature obtained mean values of 84.6 g. The SmartClip (3M®) and Gemini (3M®)brackets with low-friction Slide (Leone®) elastomeric ligature had similar mean values of 5.0 and 5.4 g respectively, with no significant differences (p = 0.999). CONCLUSIONS: The Slide (Leone®) low-friction elastomeric ligatures showed sliding resistance forces similar to the SmartClip (3M®) self-ligatingbrackets.

Mileny, Nieto Uribe; Judith Patricia, Barrera Chaparro; Ernesto José, González Cáceres; Ivón Lilian, Parra Mazo; Aleida Cristina, Rodríguez Quijada.

2012-06-01

344

BOOK REVIEW: NMR Imaging of Materials  

Science.gov (United States)

Magnetic resonance imaging (MRI) of materials is a field of increasing importance. Applications extend from fundamental science like the characterization of fluid transport in porous rock, catalyst pellets and hemodialysers into various fields of engineering for process optimization and product quality control. While the results of MRI imaging are being appreciated by a growing community, the methods of imaging are far more diverse for materials applications than for medical imaging of human beings. Blümich has delivered the first book in this field. It was published in hardback three years ago and is now offered as a paperback for nearly half the price. The text provides an introduction to MRI imaging of materials covering solid-state NMR spectroscopy, imaging methods for liquid and solid samples, and unusual MRI in terms of specialized approaches to spatial resolution such as an MRI surface scanner. The book represents an excellent and thorough treatment which will help to grow research in materials MRI. Blümich developed the treatise over many years for his research students, graduates in chemistry, physics and engineering. But it may also be useful for medical students looking for a less formal discussion of solid-state NMR spectroscopy. The structure of this book is easy to perceive. The first three chapters cover an introduction, the fundamentals and methods of solid-state NMR spectroscopy. The book starts at the ground level where no previous knowledge about NMR is assumed. Chapter 4 discusses a wide variety of transformations beyond the Fourier transformation. In particular, the Hadamard transformation and the 'wavelet' transformation are missing from most related books. This chapter also includes a description of noise-correlation spectroscopy, which promises the imaging of large objects without the need for extremely powerful radio-frequency transmitters. Chapters 5 and 6 cover basic imaging methods. The following chapter about the use of relaxation and spectroscopic methods to weight or filter the spin signals represents the core of the book. This is a subject where Blümich is deeply involved with substantial contributions. The chapter includes a lot of ideas to provide MR contrast between different regions based on their mobility, diffusion, spin couplings or NMR spectra. After describing NMR imaging methods for solids with broad lines, Blümich spends time on applications in the last two chapters of the book. This part is really fun to read. It underlines the effort to bring NMR into many kinds of manufacturing. Car tyres and high-voltage cables are just two such areas. Elastomeric materials, green-state ceramics and food science represent other interesting fields of applications. This part of the book represents a personal but nevertheless extensive compilation of modern applications. As a matter of course the MOUSE is presented, a portable permanent-magnet based NMR developed by Blümich and his co-workers. Thus the book is not only of interest to NMR spectroscopists but also to people in material science and chemical engineering. The bibliography and indexing are excellent and may serve as an attractive reference source for NMR spectroscopists. The book is the first on the subject and likely to become the standard text for NMR imaging of materials as the books by Abragam, Slicher and Ernst et al are for NMR spectroscopy. The purchase of this beautiful book for people dealing with NMR spectroscopy or medical MRI is highly recommended. Ralf Ludwig

Blümich, Bernhard

2003-09-01

345

High-pressure, low-temperature optical and X-ray diffraction studies of semiconducting and incommensurate materials  

Science.gov (United States)

In order to investigate the effects of both high-pressure and low-temperature on materials, a new diamond anvil cell and gasket system has been developed which has increased stability over the previous design. In addition, a system has been designed to perform optical absorption measurements at high-pressure and low-temperature in a diamond anvil cell. Successful high-pressure, low-temperature Raman measurements have been performed on both Cs2MOS 4 and KTbP2Se6 using the newly designed cell. Two pressure induced phase transitions have been observed at 77 K in Cs 2MOS4 and a single pressure induced phase transition has been observed at 77 K in KTbP2Se6. High pressure, energy dispersive X-ray diffraction measurements of (NH4)2 ZnCl4 have also been performed at constant temperatures up to 150°C. Values of the calculated adiabatic bulk modulus and experimentally determined isothermal bulk modulus for (NH4)2 ZnCl4 and other materials in the A2BX4 have been compiled and discussed.

Burris, Jennifer L.

346

Material science and new materials  

International Nuclear Information System (INIS)

Comprehensive studies were made into the structure and properties of materials intended for nuclear and thermonuclear reactor applications. The influence of reactor irradiation on stainless steels, zirconium, vanadium and nickel base alloys. 44 refs., 50 figs., 23 tabs

347

Controle sismique d'un batiment en acier de 3 etages a l'echelle 1/3 par amortisseurs elastomeres et contreventements en chevron  

Science.gov (United States)

This study develops an innovative configuration of seismic natural rubber dampers for multistory low- and medium-rise steel braced frames. The dampers are directly integrated in an horizontal position in the seismic force resisting system of the structure. They are connected in a series with typical chevron brace systems. This control system provides not only additional structural damping to the structure but also a period shift, acting in the same way as a base isolation system. First, the fiber reinforced natural rubber used in the application was tested. It exhibited strong non linear dependance of its equivalent viscoelastic properties related to the shear strain. Then, a 1/3-scale 3-story chevron braced steel frame with and without dampers was considered. The structure was build and placed on the shaking table of the University of Sherbrooke Structures Laboratory. Numerical studies show that the efficiency of the control system reduces strongly the seismic induced forces of the undamped structure without any amplification of displacement or drift. Obtained seismic response reduction levels represent significant safety and economical benefits for the proposed application. Finally, the control system viability is experimentally demonstrated by shaking table tests at different reduced seismic intensities. Non linear behavior of the structure due to non linear behavior of the damping material is highlighted, and the dependance of seismic control performances is shown to be related to seismic intensities. Results allow an extrapolation of the experimental control peformances tending to the numerical results at higher intensities. Key-words : chevron braces, damper, multistory building, natural rubber, seismic control, shaking table.

Gauron, Olivier

348

Efeito da amarração em Ortodontia, com ligaduras elastoméricas e de aço inoxidável, na saúde periodontal Effects of orthodontic ligation-using elastomeric and stainless steel ligatures-on periodontal health  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: o presente estudo avaliou clinicamente as condições periodontais de um grupo teste e um grupo controle utilizando-se os seguintes três sistemas de indexação periodontal: índice de biofilme, índice de sangramento e profundidade de sondagem. MÉTODOS: o grupo teste foi composto por 20 indivíduos com média etária de 13,5 anos, submetido ao tratamento ortodôntico fixo, que recebeu duas formas de ligaduras: a elastomérica e a de aço inoxidável. Os resultados foram comparados entre si e com um grupo controle, sem tratamento ortodôntico, composto de 15 indivíduos com média etária de 15,3 anos. As mensurações foram realizadas previamente ao tratamento ortodôntico (T1 e seis meses após a colocação do aparelho ortodôntico fixo (T2; e, no grupo controle, após seis meses da mensuração inicial (T2. Ambos os grupos foram orientados quanto à higiene bucal, segundo a técnica de Bass, antes do início do tratamento. RESULTADOS E CONCLUSÕES: os resultados das análises das faces dentárias demonstraram um aumento estatisticamente significativo nos índices de biofilme (P=0,000, sangramento gengival (P=0,000 e profundidade de sondagem (P=0,000, quando T1 e T2 e os grupos foram comparados; entretanto, não foram encontradas diferenças estatisticamente significativas entre as ligaduras elastoméricas e de aço inoxidável na avaliação desses índices periodontais.OBJECTIVE: This study aimed to conduct a clinical evaluation of the periodontal conditions of a test group and a control group using three periodontal indexing systems, namely: dental biofilm index (DBI, bleeding index (BI and pocket probing depth (PPD. METHODS: The test group consisted of 20 subjects with a mean age of 13.5 years undergoing fixed orthodontic treatment involving the use of two types of ligature: elastomeric ligature (EL and stainless steel ligature (SSL. The results were compared with a control group without prior orthodontic treatment, comprising 15 subjects with a mean age of 15.3 years. The measurements were performed prior to orthodontic treatment (T1 and six months after placement of a fixed orthodontic appliance (T2; and in the control group, six months after the initial measurement (T2. Both groups were instructed about oral hygiene, according to the Bass technique, before treatment. RESULTS AND CONCLUSIONS: Dental surfaces showed a statistically significant increase in levels of biofilm (P=0.000, gingival bleeding (P=0.000 and probing depth (P=0.000. When the T1 and T2 groups were compared, however, no statistically significant differences were found between EL and SSL in terms of these periodontal indexes.

Clotilde Freitas Rodrigues

2011-02-01

349

Efeito da amarração em Ortodontia, com ligaduras elastoméricas e de aço inoxidável, na saúde periodontal / Effects of orthodontic ligation-using elastomeric and stainless steel ligatures-on periodontal health  

Scientific Electronic Library Online (English)

Full Text Available OBJETIVO: o presente estudo avaliou clinicamente as condições periodontais de um grupo teste e um grupo controle utilizando-se os seguintes três sistemas de indexação periodontal: índice de biofilme, índice de sangramento e profundidade de sondagem. MÉTODOS: o grupo teste foi composto por 20 indivíd [...] uos com média etária de 13,5 anos, submetido ao tratamento ortodôntico fixo, que recebeu duas formas de ligaduras: a elastomérica e a de aço inoxidável. Os resultados foram comparados entre si e com um grupo controle, sem tratamento ortodôntico, composto de 15 indivíduos com média etária de 15,3 anos. As mensurações foram realizadas previamente ao tratamento ortodôntico (T1) e seis meses após a colocação do aparelho ortodôntico fixo (T2); e, no grupo controle, após seis meses da mensuração inicial (T2). Ambos os grupos foram orientados quanto à higiene bucal, segundo a técnica de Bass, antes do início do tratamento. RESULTADOS E CONCLUSÕES: os resultados das análises das faces dentárias demonstraram um aumento estatisticamente significativo nos índices de biofilme (P=0,000), sangramento gengival (P=0,000) e profundidade de sondagem (P=0,000), quando T1 e T2 e os grupos foram comparados; entretanto, não foram encontradas diferenças estatisticamente significativas entre as ligaduras elastoméricas e de aço inoxidável na avaliação desses índices periodontais. Abstract in english OBJECTIVE: This study aimed to conduct a clinical evaluation of the periodontal conditions of a test group and a control group using three periodontal indexing systems, namely: dental biofilm index (DBI), bleeding index (BI) and pocket probing depth (PPD). METHODS: The test group consisted of 20 sub [...] jects with a mean age of 13.5 years undergoing fixed orthodontic treatment involving the use of two types of ligature: elastomeric ligature (EL) and stainless steel ligature (SSL). The results were compared with a control group without prior orthodontic treatment, comprising 15 subjects with a mean age of 15.3 years. The measurements were performed prior to orthodontic treatment (T1) and six months after placement of a fixed orthodontic appliance (T2); and in the control group, six months after the initial measurement (T2). Both groups were instructed about oral hygiene, according to the Bass technique, before treatment. RESULTS AND CONCLUSIONS: Dental surfaces showed a statistically significant increase in levels of biofilm (P=0.000), gingival bleeding (P=0.000) and probing depth (P=0.000). When the T1 and T2 groups were compared, however, no statistically significant differences were found between EL and SSL in terms of these periodontal indexes.

Clotilde Freitas, Rodrigues; Lígia de Araújo Ramos, Sales; Robert Willer Farinazzo, Vitral; Marcelo Reis, Fraga; Cátia Cardoso Abdo, Quintão.

2011-02-01

350

Nanostructured materials  

International Nuclear Information System (INIS)

Interest in the physics of condensed matter at size scales larger than that of atoms and smaller than that of bulk solids has grown rapidly over the past two decades owing to the increasing realization that the properties of these mesoscopic atomic ensembles are different than those of conventional solids. As a consequence, interest in artificially assembling materials from nanometer sized building blocks, whether layers or clusters of atoms, arose from discoveries that by controlling the sizes in the range of 1-100 nm and the assembly of such costituents one could begin to alter and prescribe the properties of the assembled nanostructures. Nature had already learned the value of nanostructuring, since many examples of naturally formed nanostructures can be found in biological systems from sea shells to the human body. Nanostructured materials are modulated over nanometer length scales in from zero to three dimensions. They can be assembled with modulation dimensionalities of zero (atom clusters or filaments), one (multilayers), two (ultrafine-grained overlayers or coatings or buried layers), and three (nanophase materials), or also with intermediate dimensionalities. Thus, nanocomposite materials containing multiple phases can range from the most conventional case in which a nanoscale phase is embedded in a phase of conventional sizes to the case in which all the constituent phases are of nanoscale dimensions. All nanostructured materials share three features: atomic domains (grains, layers or phases) spatially confined to less than 100 nm in at least one dimension, significant atom fractions associated with interfacial environments, and interactions between their constituent domains

351

Shielding material  

International Nuclear Information System (INIS)

The present invention effectively utilizes iron reinforced concrete wastes generated upon dismantling of concretes of nuclear facilities, to provide shielding material. That is, at least one of members selected from the group consisting of iron rods in iron-reinforced concretes and, regenerated aggregates regenerated from concrete wastes upon dismantling is charged in a predetermined mold. Cement pastes or cement mortars are charged therein, and solidified, cured and released from the mold. With such procedures, a block-formed shielding materials made of precast concretes can be obtained. In this case, the cements including much water of crystallization are used. Since iron reinforcing dusts and iron reinforcing dust chips are contained in the shielding materials, a great ?-ray shielding effect can be obtained. Further, since cements containing a great amount of water of crystallization are used, a great neutron shielding effect can be obtained. (I.S.)

352

Layered materials  

Science.gov (United States)

Layered compounds, materials with a large anisotropy to their bonding, electrical and/or magnetic properties, have been important in the development of solid state chemistry, physics and engineering applications. Layered materials were the initial test bed where chemists developed intercalation chemistry that evolved into the field of topochemical reactions where researchers are able to perform sequential steps to arrive at kinetically stable products that cannot be directly prepared by other approaches. Physicists have used layered compounds to discover and understand novel phenomena made more apparent through reduced dimensionality. The discovery of charge and spin density waves and more recently the remarkable discovery in condensed matter physics of the two-dimensional topological insulating state were discovered in two-dimensional materials. The understanding developed in two-dimensional materials enabled subsequent extension of these and other phenomena into three-dimensional materials. Layered compounds have also been used in many technologies as engineers and scientists used their unique properties to solve challenging technical problems (low temperature ion conduction for batteries, easy shear planes for lubrication in vacuum, edge decorated catalyst sites for catalytic removal of sulfur from oil, etc). The articles that are published in this issue provide an excellent overview of the spectrum of activities that are being pursued, as well as an introduction to some of the most established achievements in the field. Clusters of papers discussing thermoelectric properties, electronic structure and transport properties, growth of single two-dimensional layers, intercalation and more extensive topochemical reactions and the interleaving of two structures to form new materials highlight the breadth of current research in this area. These papers will hopefully serve as a useful guideline for the interested reader to different important aspects in this field and an overview of current areas of research interest.

Johnson, David; Clarke, Simon; Wiley, John; Koumoto, Kunihito

2014-06-01

353

Evaluation of seals for mechanical penetrations of containment buildings  

International Nuclear Information System (INIS)

This report describes tests of elastomeric seals that are used in the mechanical penetrations of nuclear power plant containments. These tests assessed the effects of thermal aging, radiation and thermal aging, sealing surface separation, and squeeze on the performance of several gasket designs: O-ring, gum drop, double dog ear, and tongue and groove. Both ethylene propylene rubber and silicone rubber gaskets were tested. The environment for testing enveloped a hypothetical severe seals is quantified in terms of the leakage onset point on the time-temperature curve

354

Utopian Materialities  

DEFF Research Database (Denmark)

In various ways, this paper makes the counter-intuitive claim that the utopian and the material are thoroughlyinterdependent, rather than worlds apart. First, through a reading of Thomas More's Utopia, it is argued thatUtopia is the product of particular kinds of relations, rather than merely a detachment from the known world.Second, the utopianism of a new economy firm is examined. It is argued that the physical set-up of the firm -in particular the distribution of tables and chairs - evoke a number of alternatives to ordinary work practice.In this way the materialities of the firm are crucial to its persuasive image of being the office of the future.The notion that utopia is achieved through material arrangements is finally related to the analysis of facts andfictions in ANT. It is argued, that even though Utopias are neither fact nor fiction, they are both material andeffective on the configuration of networks; Where facts tend to stabilise the network by `holding' others,Utopias tend to `push' the networkby evoking the possibility of others.

Elgaard-Jensen, Torben

2004-01-01

355

Friction Material Composites Materials Perspective  

CERN Document Server

Friction Material Composites is the first of the five volumes which strongly educates and updates engineers and other professionals in braking industries, research and test labs. It explains besides the formulation of design processes and its complete manufacturing input. This book gives an idea of mechanisms of friction and how to control them by designing .The book is  useful for designers  of automotive, rail and aero industries for designing the brake systems effectively with the integration of friction material composite design which is critical. It clearly  emphasizes the driving  safety and how serious designers should  select the design input. The significance of friction material component like brake pad or a liner as an integral part of the brake system of vehicles is explained. AFM pictures at nanolevel illustrate broadly the explanations given.

Sundarkrishnaa, K L

2012-01-01

356

Magnetocaloric materials  

Energy Technology Data Exchange (ETDEWEB)

New and improved magnetocaloric materials are one of the cornerstones in the development of room temperature magnetic refrigeration. Magnetic refrigeration has been used since the 1930ies in cryogenic applications, but has since the discovery of room temperature refrigerants received enormous attention. This Ph.D. work has been mainly concerned with developing a new technique to characterize the magnetocaloric effect (MCE) and using this technique in the investigations on new and improved magnetocaloric materials. For this purpose a novel differential scanning calorimeter (DSC) with applied magnetic fields was developed for measuring heat capacity as function of magnetic field. Measurements using the developed DSC demonstrate a very high sensitivity, fast measurements and good agreement with results obtained by other techniques. Furthermore, two material systems have been described in this work. Both systems take basis in the mixed-valence manganite system La{sub 1-x}Ca{sub x}MnO{sub 3} well known from research on colossal magnetoresistance (CMR). The mixed-valence manganite crystallizes in the perovskite structure of general formula ABO{sub 3}. The first material system is designed to investigate the influence of low level Cu doping on the B-site. Six different samples were prepared with over-stoichiometric compositions La{sub 0.67}Ca{sub 0.33}Mn{sub 1.05}Cu{sub x}O{sub 3}, x=0, 1, 2, 3, 4 and 5%. All compositions crystallized well in the same perovskite structure, but the morphology of the samples changed drastically with doping. Investigation on the magnetocaloric properties revealed that small levels of Cu up to around 3% could improve the magnetocaloric performance of the materials. Furthermore, Cu could be used to tune the temperature interval without deteriorating the MCE, which is a much desired characteristic for potential use in magnetic refrigerators. A less comprehensive part of the work has been concerned with the investigation of doping on the A-site in the structure. The possibility of substituting the lanthanum content of the material with a lanthanide mix (Ln) consisting of La, Ce, Nd and Pr was investigated due to the potential of making more cost-effective materials. Four samples with compositions (La{sub 1-x}Ln{sub x}){sub 0.67}Ca{sub 0.33}Mn{sub 1.05}O3 with x=0, 0.33, 0.67 and 1.00, were synthesized to investigate the effect on the magnetocaloric properties. It was found that the perovskite structure could be maintained even at the highest level of doping (x=1.00), and that the maximum magnetic entropy change, DELTAS{sub M}, quantifying the magnetocaloric effect was actually enhanced to an optimum at x=0.67. Furthermore, the relative cooling power (RCP) was calculated for this series, and it was demonstrated that RCP increases continuously with doping and reaches the highest value in the composition, where the entire lanthanum content has been replaced by the lanthanide mix. These observations make promise of compositions, which could be competitive both in terms of cost-effectiveness and MCE. The work on the latter materials have been disclosed in a US and UK patent application. (author)

Jeppesen, Stinus

2008-10-15

357

Material Beliefs  

OpenAIRE

Material Beliefs was a two-year research project, based at the Interaction Research Studio in the Department of Design at Goldsmiths, University of London, and funded by the Engineering and Physical Sciences Research Council. The project brought together a network of designers, engineers, scientists and social scientists to explore potential implications of emerging biomedical and cybernetic technologies. The ambition was to produce prototypes, exhibitions and debates that would move scientif...

2009-01-01

358

Prosthesis Material  

Science.gov (United States)

In this photograph, Amputee Amie Bradly uses a NASA-developed prosthesis to paint her fingernails. Derived from foam insulation technology used to protect the Space Shuttle External Tank from excessive heat, FAB/CAD, a subsidiary of the Harshberger Prosthetic and Orthotic Center, utilized the technology to replace the heavy, fragile plaster they used to produce master molds for prosthetics. The new material was lighter, cheaper and easier to manufacture than plaster, resulting in lower costs to the customer.

2004-01-01

359

Thermoelectric Materials  

Science.gov (United States)

Mg2(Si,Sn) compounds are promising candidate low-cost, lightweight, nontoxic thermoelectric materials made from abundant elements and are suited for power generation applications in the intermediate temperature range of 600 K to 800 K. Knowledge on the transport and mechanical properties of Mg2(Si,Sn) compounds is essential to the design of Mg2(Si,Sn)-based thermoelectric devices. In this work, such materials were synthesized using the molten-salt sealing method and were powder processed, followed by pulsed electric sintering densification. A set of Mg2.08Si0.4- x Sn0.6Sb x (0 ? x ? 0.072) compounds were investigated, and a peak ZT of 1.50 was obtained at 716 K in Mg2.08Si0.364Sn0.6Sb0.036. The high ZT is attributed to a high electrical conductivity in these samples, possibly caused by a magnesium deficiency in the final product. The mechanical response of the material to stresses is a function of the elastic moduli. The temperature-dependent Young's modulus, shear modulus, bulk modulus, Poisson's ratio, acoustic wave speeds, and acoustic Debye temperature of the undoped Mg2(Si,Sn) compounds were measured using resonant ultrasound spectroscopy from 295 K to 603 K. In addition, the hardness and fracture toughness were measured at room temperature.

Gao, Peng; Berkun, Isil; Schmidt, Robert D.; Luzenski, Matthew F.; Lu, Xu; Bordon Sarac, Patricia; Case, Eldon D.; Hogan, Timothy P.

2014-06-01

360

Golden gaskets: variations on the Sierpi\\'nski sieve  

CERN Document Server

We consider the iterated function systems (IFSs) that consist of three general similitudes in the plane with centres at three non-collinear points, and with a common contraction factor $\\la\\in(0,1)$. As is well known, for $\\la=1/2$ the invariant set, $\\S_\\la$, is a fractal called the Sierpi\\'nski sieve, and for $\\la<1/2$ it is also a fractal. Our goal is to study $\\S_\\la$ for this IFS for $1/2<\\la<2/3$, i.e., when there are "overlaps" in $\\S_\\la$ as well as "holes". In this introductory paper we show that despite the overlaps (i.e., the Open Set Condition breaking down completely), the attractor can still be a totally self-similar fractal, although this happens only for a very special family of algebraic $\\la$'s (so-called "multinacci numbers"). We evaluate $\\dim_H(\\S_\\la)$ for these special values by showing that $\\S_\\la$ is essentially the attractor for an infinite IFS which does satisfy the Open Set Condition. We also show that the set of points in the attractor with a unique ``address'' is self-s...

Broomhead, D; Sidorov, N; Broomhead, Dave; Montaldi, James; Sidorov, Nikita

2003-01-01

361

Golden gaskets: variations on the Sierpi\\'nski sieve  

OpenAIRE

We consider the iterated function systems (IFSs) that consist of three general similitudes in the plane with centres at three non-collinear points, and with a common contraction factor $\\la\\in(0,1)$. As is well known, for $\\la=1/2$ the invariant set, $\\S_\\la$, is a fractal called the Sierpi\\'nski sieve, and for $\\la

Broomhead, Dave; Montaldi, James; Sidorov, Nikita

2003-01-01

362

Investigations on helicoflex gaskets for ILC cavity flanges  

International Nuclear Information System (INIS)

A reliable joint of the Nb superconducting cavities is achieved due to the use of the conical Nb-Ti flanges together with a quick disconnect system (from the Garlock company). The joint was tested at room temperature and liquid nitrogen temperature (77 K), the measured leak level is -9 mbar·1/s. This flange assembly simplifies the design, reduces the assembly time by an order of magnitude, and is expected to decrease the accelerator vacuum chamber length

363

Influence of root embedment material and periodontal ligament simulation on fracture resistance tests / Influência do material de inclusão e da simulação do ligamento periodontal nos ensaios de resistência à fratura  

Scientific Electronic Library Online (English)

Full Text Available O objetivo deste estudo foi avaliar a influência do material de inclusão e da simulação de ligamento periodontal na resistência à fratura de dentes bovinos. Oitenta incisivos bovinos foram divididos em 8 grupos (n = 10) e, então, incluídos em cilindros com dois materiais, resina acrílica ou resina d [...] e poliestireno, usando-se quatro tipos de simulação do ligamento periodontal: 1 - ausência do ligamento; 2 - material de moldagem à base de poliéter; 3 - material de moldagem à base de polissulfeto; e 4 - material elastomérico à base de poliuretano. As amostras foram armazenadas em 100% de umidade a 37°C por 24 horas e então submetidas a carregamento tangencial na superfície palatina com velocidade de 0,5 mm/minuto até a fratura. Os padrões de fratura foram analisados de acordo com: 1 - fraturas coronais; 2 - fratura da junção esmalte-cemento; 3 - fratura parcial da raiz; 4 - fratura radicular total. A análise estatística empregou análise de variância fatorial e teste de Tukey (p Abstract in english The aim of this study was to evaluate the influence of the embedment material and periodontal ligament simulation on fracture resistance of bovine teeth. Eighty bovine incisor teeth were randomized into 8 groups (n = 10), embedded in acrylic or polystyrene resin using 4 types of periodontal ligament [...] simulation: 1 - absence of the ligament; 2 - polyether impression material; 3 - polysulfide impression material; 4 - polyurethane elastomeric material. The specimens were stored at 37°C and 100% humidity for 24 hours. Specimens were submitted to tangential load on the palatal surface at 0.5 mm/minute crosshead speed until fracture. The fracture modes were analyzed as follows: 1 - coronal fracture; 2 - cemento-enamel junction fracture; 3 - partial root fracture; 4 - total root fracture. Statistical analyses by two-way ANOVA and Tukey's test were applied (p

Carlos José, Soares; Eliane Cristina Gava, Pizi; Rodrigo Borges, Fonseca; Luis Roberto Marcondes, Martins.

2005-03-01

364

Materializing Superghosts  

CERN Document Server

We construct the off-shell BV realization of N=1, d=10 SYM with 7 auxillary fields. This becomes possible due to materialized ghost phenomenon. Namely, supersymmetry ghosts are coordinates on a manifold B of 10-dimensional spinors with pure spinors cut out. Auxillary fields are sections of a bundle over B, and supersymmetry transformations are nonlinear in ghosts. By integrating out axillary fields we obtain on-shell supersymmetric BV action with terms quadratic in antifields. Exactly this on-shell BV action was obtained in our previous paper after integration out of auxiliary fields in the framework of Pure Spinor Superfield Formalism.

Alexandrov, Victor; Losev, Andrei; Lysov, Vyacheslav

2007-01-01

365

Photographic materials  

International Nuclear Information System (INIS)

Radiographic films based on silver halides are normally handled under red or orange safelights to prevent fogging due to their sensitivity to white light. The present invention relates to ultraviolet radiation sensitive material which can be handled under virtually white light without significant fogging. The film material is comprised of a base having at least one layer of a photographic silver halide emulsion and a yellow filter dye screening the emulsion from visible radiation. The silver halide emulsion contains 50-100 mole % of silver chloride, the higher the silver chloride content, the lower the visible light sensitivity. The nature and properties of the yellow filter dye are described. When recording an X-ray image, the film is loaded into the camera under white safelight conditions from which light of wavelength shorter than 400 nm is excluded. The film is in contact with one or more phosphor screens capable when struck by X-rays of emitting ultraviolet radiation, the screens having a peak ultraviolet emission within the wavelength range of 250-380 nm. After X-ray exposure, the film is removed and developed. Two examples illustrating the invention are given. (U.K.)

366

Functional materials  

International Nuclear Information System (INIS)

Development of fabrication process of functional ceramic materials, evaluation of characteristics and experiments for understanding of irradiation behavior of ceramics were carried out for application of ceramics to the nuclear industry. The developed processes were the SiC surface coating technology with large area for improvement of wear resistance and corrosion resistance, the fabrication technology of SiC composites for excellent irradiation resistance, performance improvement technology of SiC fiber and nano-sized powder processing by combustion ignition and spray. Typical results were CVD SiC coating with diameter of 25cm and thickness of 100?m, highly dense SiC composite by F-CVI, heat-treating technology of SiC fiber using B4C power, and nano-sized powders of ODS-Cu, Li-based breeding materials, Ni-based metal powders with primary particle diameter of 20?50nm. Furthermore, test equipment, data productions and damage evaluations were performed to understand corrosion resistance and wear resistance of alumina, silicon carbide and silicon nitride under PWR or PHWR operation conditions. Experimental procedures and basic technologies for evaluation of irradiation behavior were also established. Additionally, highly reactive precursor powders were developed by various technologies and the powders were applied to the fabrication of 100 m long Ag/Bi-2223 multi-filamentary wires. High Tc magnets and fly wheel for energy storage were developed, as well

367

Recent laboratory tests with elastomeric revetments:  

OpenAIRE

A new construction method of Polyurethane (PUR)-bonded revetments (Elastocoast) has been tested successfully on various locations in Germany, in the Netherlands, in France, and in the UK. See also the presentation of Bijlsma on this conference. This year a series of large scale test in the GWK-facility in Hannover have been executed. This presentation will focus on the preliminary results, including a large failure due to liquefaction.

Verhagen, H. J.

2009-01-01

368

Dielectric elastomer actuators with elastomeric electrodes  

Science.gov (United States)

For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers of a conducting silicone elastomer to prestrained films of an acrylic dielectric elastomer and achieve voltage-actuated areal strains over 70%. The influence of the stiffness of the electrodes and the prestrain of the dielectric films is studied experimentally and theoretically.

Bozlar, Michael; Punckt, Christian; Korkut, Sibel; Zhu, Jian; Chiang Foo, Choon; Suo, Zhigang; Aksay, Ilhan A.

2012-08-01

369

Selecting elastomeric seals for nuclear service  

International Nuclear Information System (INIS)

In the early 1960s, the primary test used in selecting elastomers for reactor seals was a tensile test conducted on unstressed slabs of the compounds after they had been subjected to irradiation. These standard tests had the unfortunate ability to make compounds look very appealing to the nuclear engineer while completely failing the primary requirements of seal engineers. Today, a test has been developed which promises to satisfy the demands of both engineers. This is a test to determine the compression set of seals which are simultaneously squeezed (as they would be when installed) and irradiated (as they may be when in service) over prolonged periods. The new data provide criteria by which compounds may be selected for long life, normally requiring replacement only during conservatively scheduled five-year-reactor overhauls

370

Elastodynamic spot testing - assessing serviceability of aging elastomer parts  

International Nuclear Information System (INIS)

The properties of all polymers change with time as a function of their environment. Traditional practice has been to replace these parts according to generic time limits based on estimates of worst case material properties and conditions. This is overly-conservative in many cases, and creates unnecessary maintenance work and costs for replacement and disposal. Much of this could be avoided if the serviceability of elastomeric parts such as seals, diaphragms, gaskets, cable insulation and hoses could be reassessed on a routine basis. Elastodynamic spot testing offers a way to do this. Parts can be sampled while in service or storage to compare their as-new and used (or aged) elastodynamic properties. This data can usually be correlated with the results of functional tests to prove that material properties have not degraded to the point where the part could fail. This spot testing is similar to a micro-hardness test, but includes stress-relaxation and subsequent recovery. It provides a nondestructive means to assess the effective age of the material at a point, or several points, on a part. Sampling of hardness alone is rarely sufficient to know whether a part is still functional because this overlooks the material's viscoelastic and strength properties. An elastodynamic spot tester has been used to test different sizes, shapes and hardnesses of elastomeric parts at different levels of strain, i.e., indentation depths. An initial test program has given informative relaxation and recovery data, showing repeatability and comparing well with finite element analysis of the indentation process. Tests of aged 0-rings and diaphragms have revealed different elastodynamic properties, depending on the elastomer compound and aging conditions. (author)

371

Migration of epoxidised soya bean oil into foods from retail packaging materials and from plasticised PVC film used in the home.  

Science.gov (United States)

Epoxidised soya bean oil (ESBO) is used as a plasticiser and heat stabiliser in a number of feed contact materials, in particular in poly(vinyl chloride) (PVC) films and gaskets. The level of ESBO migration into foods has been determined using a combined gas chromatographic/mass spectrometric (GC/MS) analytical procedure. The study has included both the use of ESBO-containing materials for retail packaged foods and the domestic use of plasticised PVC films for applications such as wrapping food and covering food for re-heating in a microwave oven. Levels of ESBO in fresh retail meat samples wrapped in film ranged from less than 1 to 4 mg/kg, but were higher (max. 22 mg/kg) in retail cooked meat. Migration into sandwiches and rolls from 'take-away' outlets ranged from less than 1 to 27 mg/kg depending on factors such as the type of filling and the length of the contact time prior to analysis. The levels of migration of ESBO into cheese and cakes were consistent with previous experience with plasticiser migration--direct contact with fatty surfaces leading to the highest levels. When the film was used for microwave cooking in direct contact with food, levels of ESBO from 5 to 85 mg/kg were observed, whereas when the film was employed only as a splash cover for re-heating foods, ESBO levels ranged from 0.1 to 16 mg/kg. For a variety of baby foods there was no significant difference in ESBO levels between foods packaged in glass jars with PVC gaskets and foods in cans containing ESBO in the can lacquer. In both cases ESBO levels were low, ranging from less than 0.1 to 7.6 mg/kg. It is not clear for these retail samples, if the low levels observed (average 1.9 mg/kg) result solely from migration or contain some contribution from naturally occurring epoxides. PMID:2307263

Castle, L; Mayo, A; Gilbert, J

1990-01-01

372

Advanced materials for control of post-earthquake damage in bridges  

Science.gov (United States)

This paper presents analytical modeling to study the seismic response of bridge systems with conventional and advanced details. For validation, a 33 m quarter-scale model of a four-span bridge incorporating innovative materials and details seismically tested on the shake tables at the University of Nevada, Reno was taken. The bridge specimen involved use of advanced materials and details to reduce damage at plastic hinges and minimize residual displacements. A three-dimensional, nonlinear model incorporating the response of the innovative materials was developed to study the bridge response using the finite-element software OpenSees. Existing finite-element formulations were used to capture the response of the advanced materials used in the bridge. The analytical model was found to be able to reproduce comparable bent displacements and bent shear forces within reasonable accuracy. The validated model was further used to study different types of bridges under suite of scaled bi-directional near-fault ground motions. Comparisons were made on behavior of five different bridge types, first conventional reinforced concrete bridge, second post-tensioned column bridge, third bridge with elastomeric rubber elements at the plastic hinge zone, fourth bridge with nickel–titanium superelastic shape memory alloy (SMA) reinforcing bar and fifth bridge with CuAlMn superelastic SMA reinforcing bar. Both the SMA used bridges also utilized engineered cementitious composite element at the plastic hinge zone. The results showed effectiveness of the innovative interventions on the bridges in providing excellent recentering capabilities with minimal damage to the columns.

Shrestha, Kshitij C.; Saiid Saiidi, M.; Cruz, Carlos A.

2015-02-01

373

Photographic materials  

International Nuclear Information System (INIS)

Radiographic films based on silver halides are normally handled under red or orange safelights to prevent fogging due to their sensitivity to white light. The present invention relates to ultraviolet radiation sensitive material which can be handled under virtually white light without significant fogging. A photographic, chemically sensitised silver halide emulsion is described, containing 50-100 mole % of silver chloride, the higher the silver chloride content, the lower the visible light sensitivity. The remaining silver halide, if any, is silver bromide and/or silver iodide. The silver halide grains are grown in the presence of ammonia, an excess of chloride ions and tetraazaindene growth controller. Examples illustrating the invention are given. (U.K.)

374

Materializing superghosts  

Science.gov (United States)

The off-shell Batalin-Vilkovysky (BV) realization has been constructed for N = 1, d = 10 super-Yang-Mills theory with seven auxiliary fields. This becomes possible due to the materialized ghost phenomenon. Namely, supersymmetry ghosts are coordinates on a manifold B of ten-dimensional spinors with the pure spinors cut out. Auxiliary fields are sections of a bundle over B, and supersymmetry transformations are nonlinear in ghosts. By integrating out the auxiliary fields, we obtain an on-shell supersymmetric BV action with quadratic terms in the antifields. Exactly this on-shell BV action was obtained in our previous paper after integration out of auxiliary fields in the framework of a pure spinor superfield formalism.

Alexandrov, V.; Krotov, D.; Losev, A.; Lysov, V.

2007-12-01

375

PREFACE: Superconducting materials Superconducting materials  

Science.gov (United States)

The discovery of superconductivity in 1911 was a great milestone in condensed matter physics. This discovery has resulted in an enormous amount of research activity. Collaboration among chemists and physicists, as well as experimentalists and theoreticians has given rise to very rich physics with significant potential applications ranging from electric power transmission to quantum information. Several superconducting materials have been synthesized. Crucial progress was made in 1987 with the discovery of high temperature superconductivity in copper-based compounds (cuprates) which have revealed new fascinating properties. Innovative theoretical tools have been developed to understand the striking features of cuprates which have remained for three decades the 'blue-eyed boy' for researchers in superconductor physics. The history of superconducting materials has been notably marked by the discovery of other compounds, particularly organic superconductors which despite their low critical temperature continue to attract great interest regarding their exotic properties. Last but not least, the recent observation of superconductivity in iron-based materials (pnictides) has renewed hope in reaching room temperature superconductivity. However, despite intense worldwide studies, several features related to this phenomenon remain unveiled. One of the fundamental key questions is the mechanism by which superconductivity takes place. Superconductors continue to hide their 'secret garden'. The new trends in the physics of superconductivity have been one of the two basic topics of the International Conference on Conducting Materials (ICoCoM2010) held in Sousse,Tunisia on 3-7 November 2010 and organized by the Tunisian Physical Society. The conference was a nice opportunity to bring together participants from multidisciplinary domains in the physics of superconductivity. This special section contains papers submitted by participants who gave an oral contribution at ICoCoM2010 and by invited authors selected by the editor. We are grateful to IUPAP, ICTP and the European Office of Aerospace Research and Development, Air Force Office of Scientific Research, United States Air Force Laboratory. We would like to acknowledge the authors for their careful work, and finally we thank Dr L Smith the publisher of Journal of Physics: Condensed Matter for her patience and help. Superconducting materials contents Raman spectrum in the pseudogap phase of the underdoped cuprates: effect of phase coherence and the signature of the KT-type superconducting transitionTao Li and Haijun Liao Pressure effects on Dirac fermions in ?-(BEDT-TTF)2I3Takahiro Himura, Takao Morinari and Takami Tohyama Effect of Zn doping in hole-type 1111 phase (Pr, Sr)FeAsOXiao Lin, Chenyi Shen, Chen Lv, Jianjian Miao, Hao Tan, Guanghan Cao and Zhu-An Xu Superconductivity and ferromagnetism in EuFe2(As1 - xPx)2*Guanghan Cao, Shenggao Xu, Zhi Ren, Shuai Jiang, Chunmu Feng and Zhu'an Xu OInhomogeneous superconductivity in organic conductors: the role of disorder and magnetic fieldS Haddad, S Charfi-Kaddour and J-P Pouget

Charfi Kaddour, Samia; Singleton, John; Haddad, Sonia

2011-11-01

376

Synthesis, characterization, and efficacy of antimicrobial chlorhexidine hexametaphosphate nanoparticles for applications in biomedical materials and consumer products  

Directory of Open Access Journals (Sweden)

Full Text Available Michele E Barbour,1 Sarah E Maddocks,2 Natalie J Wood,1,3 Andrew M Collins3 1Oral Nanoscience, School of Oral and Dental Sciences, University of Bristol, Bristol, UK; 2Cardiff School of Health Sciences, Cardiff Metropolitan University, Cardiff, UK; 3Bristol Centre for Functional Nanomaterials, University of Bristol, Bristol, UK Abstract: Chlorhexidine (CHX is an antimicrobial agent that is efficacious against gram-negative and -positive bacteria and yeasts. Its mechanism of action is based on cell membrane disruption and, as such, it does not promote the development of bacterial resistance, which is associated with the widespread use of antibiotics. In this manuscript, we report the development of novel antimicrobial nanoparticles (NPs based on a hexametaphosphate salt of CHX. These are synthesized by instantaneous reaction between equimolar aqueous solutions of CHX digluconate and sodium hexametaphosphate, under room temperature and pressure. The reaction results in a stable colloid composed of highly negatively charged NPs (?50 mV, of size 20-160 nm. The NPs adhere rapidly to specimens of glass, titanium, and an elastomeric wound dressing, in a dose-dependent manner. The functionalized materials exhibit a gradual leaching of soluble CHX over a period of at least 50 days. The NP colloid is efficacious against methicillin-resistant Staphylococcus aureus (MRSA and Pseudomonas aeruginosa in both planktonic and biofilm conditions. These NPs may find application in a range of biomedical and consumer materials. Keywords: MRSA, biomaterials, chlorhexidine, drug delivery, slow release

Barbour ME

2013-09-01

377

Mechatronic systems and materials materials production technologies  

CERN Document Server

Mechatronics can be defined as being the synergistic integration of mechanical engineering with electronics and intelligent computer control in the manufacture of products and design of processes. Advanced engineering materials and related technologies increasingly rely upon multifunctional materials, materials resistant to extreme conditions and hybrid and multi-materials. The goal of this collection is to disseminate news of recent progress made in the area of mechatronic systems and materials production technologies, to discuss future development in mechatronics and materials science, to an

Marcinkevicius, Andrejus Henrikas

2010-01-01

378

Gas storage materials, including hydrogen storage materials  

Science.gov (United States)

A material for the storage and release of gases comprises a plurality of hollow elements, each hollow element comprising a porous wall enclosing an interior cavity, the interior cavity including structures of a solid-state storage material. In particular examples, the storage material is a hydrogen storage material, such as a solid state hydride. An improved method for forming such materials includes the solution diffusion of a storage material solution through a porous wall of a hollow element into an interior cavity.

Mohtadi, Rana F; Wicks, George G; Heung, Leung K; Nakamura, Kenji

2014-11-25

379

Phthalates and food-contact materials: enforcing the 2008 European Union plastics legislation  

DEFF Research Database (Denmark)

The migration of phthalates into foodstuffs from food-contact materials (FCM) is a well-known source of food contamination. In 2005, the European Food Safety Authority finalized its risk assessment for several of the classical phthalate plasticizers. In their risk management procedure the European Commission transformed the tolerable daily intakes established by the Authority into legislative limits for phthalates in both plastic and food simulants, while taking exposure from other sources into consideration. These limits have been into force since 1 July 2008. A detailed interpretation of the regulation of these substances was agreed upon in the European network of FCM reference laboratories. This paper reports results from a Danish control campaign of samples collected by official food inspectors and analysed by a newly validated analytical method run under accreditation. Samples were from FCM producers, FCM importers and importers of packed foodstuffs from third-party countries. Products containing phthalates above the current limits were found in several categories of FCM: conveyor belts (six of six), lids from packed foodstuffs in glasses (eight of 28), tubes for liquid foodstuffs (four of five) and gloves (five of 14). More than 20% of the samples analysed contained dibutylphthalate (DBP) or di-(2-ethylhexyl)phthalate (DEHP) above the compositional limits of 0.05% and 0.1%, respectively. Analysis of residual phthalates in metal lid gaskets instead of analysis of phthalates in the food when controlling foodstuffs packed outside the European Union proved to be an efficient and simple control method. All findings of phthalates were associated with the use of plasticized polyvinylchloride (PVC).

Petersen, Jens HØjslev; Jensen, Lisbeth Krüger

2010-01-01

380

Nuclear materials in Japan  

Science.gov (United States)

The incident at Fukushima Daiichi brought materials in the nuclear industry into the spotlight. Nature Materials talks to Tatsuo Shikama, Director of the International Research Centre for Nuclear Materials, Institute for Materials Research, Tohoku University, about the current situation.

2015-03-01

381

Reactor fuels and materials  

Energy Technology Data Exchange (ETDEWEB)

This book deals with reactor fuels and materials, introducing elementary knowledge of materials such as interaction between radiation and crystal lattice, damage of the crystal by the radiation and recovery, uranium enrichment and a nuclear fuel reprocessing, metal fuels, uranium silicide fuels, covering material fuels, uranium dioxide fuels, gas cooled reactor materials fast reactor materials, fusion of cell nuclear, control materials of neutron and moderator materials. This books explains how to deal with these materials and how to use them in right way.

Lee, Gi Sun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2012-08-15

382

Shielding techniques tackle EMI excesses. V - EMI shielding  

Science.gov (United States)

The utilization of shielding gaskets in EMI design is presented in terms of seam design, gasket design, groove design, and fastener spacing. The main function of seam design is to minimize the coupling efficiency of a seam, and for effective shielding, seam design should include mating surfaces which are as flat as possible, and a flange width at least five times the maximum anticipated separation between mating surfaces. Seam surface contact with a gasket should be firm, continuous, and uniform. Gasket height, closure pressure, and compression set as a function of the applied pressure parameters are determined using compression/deflection curves. Environmental seal requirements are given and the most common materials used are neoprene, silicone, butadiene-acrylonitrile, and natural rubber. Groove design is also discussed, considering gasket heights and cross-sectional areas. Finally, fastener spacing is considered, by examining deflection as a percentage of gasket height.

Grant, P.

1982-10-01

383

Method for forming materials  

Science.gov (United States)

A material-forming tool and a method for forming a material are described including a shank portion; a shoulder portion that releasably engages the shank portion; a pin that releasably engages the shoulder portion, wherein the pin defines a passageway; and a source of a material coupled in material flowing relation relative to the pin and wherein the material-forming tool is utilized in methodology that includes providing a first material; providing a second material, and placing the second material into contact with the first material; and locally plastically deforming the first material with the material-forming tool so as mix the first material and second material together to form a resulting material having characteristics different from the respective first and second materials.

Tolle, Charles R. (Idaho Falls, ID); Clark, Denis E. (Idaho Falls, ID); Smartt, Herschel B. (Idaho Falls, ID); Miller, Karen S. (Idaho Falls, ID)

2009-10-06

384

Materials Informatics: Fast Track to New Materials  

Energy Technology Data Exchange (ETDEWEB)

Current methods for new materials development focus on either deeper fundamental-level studies or generation of large quantities of data. The data challenge in materials science is not only the volume of data being generated by many independent investigators, but its heterogeneity and also its complexity that must be transformed, analyzed, correlated and communicated. Materials informatics addresses these issues. Materials informatics is an emerging information-based field combining computational, statistical, and mathematical approaches with materials sciences for accelerating discovery and development of new materials. Within the informatic framework, the various different forms of information form a system architecture, an iterative cycle for transforming data into knowledge.

Ferris, Kim F.; Peurrung, Loni M.; Marder, James M.

2007-01-01

385

Photorefractive Materials and Their Applications 2 Materials  

CERN Document Server

Photorefractive Materials and Their Applications 2: Materials is the second of three volumes within the Springer Series in Optical Sciences. The book gives a comprehensive review of the most important photorefractive materials and discusses the physical properties of organic and inorganic crystals as well as poled polymers. In this volume, photorefractive effects have been investigated at wavelengths covering the UV, visible and near infrared. Researchers in the field and graduate students of solid-state physics and engineering will gain a thorough understanding of the properties of materials in photorefractive applications. The other two volumes are: Photorefractive Materials and Their Applications 1: Basic Effects. Photorefractive Materials and Their Applications 3: Applications.

Günter, Peter

2007-01-01

386

Improvement and evaluation of thermal, electrical, sealing and mechanical contacts, and their interface materials  

Science.gov (United States)

Material contacts, including thermal, electrical, seating (fluid sealing and electromagnetic sealing) and mechanical (pressure) contacts, together with their interface materials, were, evaluated, and in some cases, improved beyond the state of the art. The evaluation involved the use of thermal, electrical and mechanical methods. For thermal contacts, this work evaluated and improved the heat transfer efficiency between two contacting components by developing various thermal interface pastes. Sodium silicate based thermal pastes (with boron nitride particles as the thermally conductive filler) as well as polyethylene glycol (PEG) based thermal pastes were developed and evaluated. The optimum volume fractions of BN in sodium silicate based pastes and PEG based pastes were 16% and 18% respectively. The contribution of Li+ ions to the thermal contact conductance in the PEG-based paste was confirmed. For electrical contacts, the relationship between the mechanical reliability and electrical reliability of solder/copper and silver-epoxy/copper joints was addressed. Mechanical pull-out testing was conducted on solder/copper and silver-epoxy/copper joints, while the contact electrical resistivity was measured. Cleansing of the copper surface was more effective for the reliability of silver-epoxy/copper joint than that of solder/copper joint. For sealing contacts, this work evaluated flexible graphite as an electromagnetic shielding gasket material. Flexible graphite was found to be at least comparable to conductive filled silicone (the state of the art) in terms of the shielding effectiveness. The conformability of flexible graphite with its mating metal surface under repeated compression was characterized by monitoring the contact electrical resistance, as the conformability is important to both electromagnetic scaling and fluid waling using flexible graphite. For mechanical contacts, this work focused on the correlation of the interface structure (such as elastic/plastic deformation, oxidation, strain hardening, passive layer damage, fracture, etc.) with the electrical contact resistance, which was measured in real time for contacts under dynamic compression, thus allowing both reversible and irreversible changes to be observed. The materials studied included metals (carbon steel, stainless steel, aluminum and copper), carbon fiber reinforced polymer-matrix composite (nylon-6), ceramic (mortar) and graphite, due to their relevance to fastening, concrete structures, electric brushes and electrical pressure contacts.

Luo, Xiangcheng

387

Transporting particulate material  

Energy Technology Data Exchange (ETDEWEB)

A material transporting system comprises a material transporting apparatus (100) including a material transporting apparatus hopper structure (200, 202), which comprises at least one rotary transporting apparatus; a stationary hub structure (900) constraining and assisting the at least one rotary transporting apparatus; an outlet duct configuration (700) configured to permit material to exit therefrom and comprising at least one diverging portion (702, 702'); an outlet abutment configuration (800) configured to direct material to the outlet duct configuration; an outlet valve assembly from the material transporting system venting the material transporting system; and a moving wall configuration in the material transporting apparatus capable of assisting the material transporting apparatus in transporting material in the material transporting system. Material can be moved from the material transporting apparatus hopper structure to the outlet duct configuration through the at least one rotary transporting apparatus, the outlet abutment configuration, and the outlet valve assembly.

Aldred, Derek Leslie (North Hollywood, CA); Rader, Jeffrey A. (North Hollywood, CA); Saunders, Timothy W. (North Hollywood, CA)

2011-08-30

388

Common Waste and Materials  

Science.gov (United States)

... Resource Conservation Common Wastes & Materials Common Waste and Materials Related Links Universal Waste Comprehensive Procurement Guidelines (CPG) ... Waste Composting Paper Scrap Tires Used Oil Additional Materials Aluminum Antifreeze Automotive Parts Batteries Disaster Debris Glass ...

389

Super Dielectric Materials  

OpenAIRE

Evidence is provided that a class of materials with dielectric constants greater than 100,000, herein called super dielectric materials (SDM), can be generated readily from common, inexpensive materials.

Fromille, Sam; Phillips, Jonathan

2014-01-01

390

Thermoelectric materials and devices  

Science.gov (United States)

New thermoelectric materials comprise highly [111]-oriented twinned group IV alloys on the basal plane of trigonal substrates, which exhibit a high thermoelectric figure of merit and good material performance, and devices made with these materials.

Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Talcott, Noel A. (Inventor)

2011-01-01

391

Fusion materials: insulators and plasma facing materials  

International Nuclear Information System (INIS)

Insulating materials: surface damage: Oxide materials will be extensively used in ITER in heating and current drive, and diagnostic systems where they will play important roles as electrical insulators, and RF and optical transmission components. These materials will be subjected to neutron and gamma radiation, and additionally to bombardment by low energy ions and neutral particles of energies between eV and keV as a consequence of neutron reactions and related sputtering at vacuum surfaces, as well as ionization and acceleration of the residual gas due to local electric fields. To assess the damage, SiO2 (KS-4V), Al2O3, AlN, and BeO, the main candidate ceramic insulators for ITER were implanted (bombarded) with light ions, and KS-4V and sapphire were also irradiated with electrons. In-situ surface electrical conductivity measurements in high vacuum during implantation or irradiation were carried out. In addition, before and after implantation or irradiation, both optical absorption measurements and SEM X-ray analysis were performed. It was found that the origin of the surface electrical and related optical degradation is radiolytic, i.e. the damage is caused by the electronic excitation induced during material irradiation. Plasma Wall Interaction: In fusion devices, in the region next to high temperature plasma (typically ?10 keV), material erodes from plasma-facing materials in one location and is transported to other, sometimes remote, locations throughout the device. The transported material may then be deposited on, or implanted into, other materials. If the plasma facing material in a device consists of more than a single element there is a high probability that the composition of the plasma-facing surfaces will evolve over time and may exhibit plasma interaction properties much different from the originally installed material. These plasma-created materials are so - called mixed materials. The creation of mixed-material surfaces will depend on many factors that determine the arrival and loss rate of material from those surfaces. Previous works carried out in the linear divertor plasma simulator PISCES-B on beryllium/carbon mixed-material effects revealed that both chemical and physical erosion of carbon was mitigated by beryllium impurities in the plasma. X-ray photoelectron spectroscopy (XPS) analyses of these targets subsequent to plasma exposure revealed the formation of beryllium carbide (Be2C), which is thought to play an important role in carbon erosion mitigation. Here, formation and evolution of mixed material in JET, in where both beryllium and carbon are used together as plasma-facing materials are discussed. (author)

392

Physically Functional Materials  

DEFF Research Database (Denmark)

The invention relates to novel monodisperse or polydisperse compounds, in general named DNO (diamino acid Nalpha-substituted oligopeptides), preferably low molecular weight polypeptides, e.g., based on ornithine, lysine, diaminobutyric acid, diaminopropionic acid, aminoethylglycine or other amino acids or peptides having azobenzenes or other physicially functional groups, e.g., photoresponsive groups, as side chains. These compounds may be synthesized using solid phase peptide synthesis techniques. Materials, e.g., thin films, comprising such compounds may be used for optical storage of information (holographic data storage), nonlinear optics (NLO), as photoconductors, photonic band-gap materials, electrically conducting materials, electroluminescent materials, piezo-electric materials, pyroelectric materials, magnetic materials, ferromagnetic materials, ferroelectric materials, photorefractive materials, or materials in which light-induced conformational changes can be produced. Optical anisotropy may reversibly be generated with polarized laser light whereby a hologram is formed. First order diffraction efficiencies of up to around 80% have been obtained.

Berg, Rolf Henrik Technical University of Denmark,

393

Nonlinear and electrooptic materials: nonlinear materials laboratory  

International Nuclear Information System (INIS)

This year the program launched a new project in nonlinear materials. Its purpose is to identify materials whose properties (non-linear and otherwise) permit reduced cost and improved laser performance. The program's primary focus is on harmonic generation and electrooptic switching for fusion lasers; the secondary focus is on high-average-power lasers. Their scientific aim is to lay a solid basis for optimizing nonlinear materials for high-power-level applications

394

Forensic Evidence : Materializing Bodies, Materializing Crimes  

OpenAIRE

Based on an ethnographic study of fingerprint and DNA evidence practices in the Swedish judicial system, this article analyses the materialization of forensic evidence. It argues that forensic evidence, while popularly understood as firmly rooted in materiality, is inseparably technoscientific and cultural. Its roots in the material world are entangled threads of matter, technoscience and culture that produce particular bodily constellations within and together with a particular sociocultural...

Kruse, Corinna

2010-01-01

395

Art as material culture  

OpenAIRE

With questions concerning the physical basis and the material substructure of works of art as topic, the article surveys a number of related problem areas. These include the objecthood of art, art products as physical remnants, the situatedness and reproduction of art, materials expertise and the iconology of materials. The untenability of materialism features implicitly as an underlying theme.

Den Berg, Dirk Johannes

2001-01-01

396

Insulation Materials Investigation  

Science.gov (United States)

Students test the insulation properties of different materials by timing how long it takes ice cubes to melt in the presence of various insulating materials. Students learn about the role that thermal insulation materials can play in reducing heat transfer by conduction, convection and radiation, as well as the design and implementation of insulating materials in construction and engineering.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

397

Materials for microenvironment construction  

International Nuclear Information System (INIS)

This paper describes the key contamination control considerations in selecting polymeric materials for use in the construction of microenvironments. Some of the test methods available to evaluate materials for microenvironment use are summarized. Data on selected materials is presented for illustrative purposes. This paper is intended to aid in the process of evaluation and selection of materials for microenvironments, not to prescribe specific materials for use in microenvironments

398

Neutron absorber materials  

International Nuclear Information System (INIS)

Subcommittee C26.03 on Neutron Absorber Materials was formed early in the history of C-26 on Nuclear Fuel Cycle. It was recognized that control materials were an essential part of the reactor system and it was therefore logical to consider appropriate standards for these materials and the related burnable poisons. Standards for control materials, burnable poisons, insulator materials, moderators, and spent fuels are discussed

399

Composite Materials Handbook  

Science.gov (United States)

From the US Army Research Laboratory, Materials Sciences Corporation, and University of Delaware Center for