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1

[Elastomeric impression materials].  

Science.gov (United States)

Elastomeric impression materials are in common use. The impression taken should be highly precise, thus, requiring specific care when manipulatingthese materials. There are 4 groups of elastomers; polysulfide, condensation silicone, addition silicone and polyether; each differ in their setting mechanism and their physical and chemical properties. This review elaborates the major properties of elastomers and its implications on their use. The impression material is inserted into the patient's mouth in a viscous state and transforms into viscoelastic state, upon withdrawal, influencing the residual deformation. The requirements are minimal residual deformation or maximal elastic recovery. As the mouth is a wet environment a major consideration is hydrophilicity. The wettability which is estimated by measuring either the contact angle of a droplet of water and the substrate post setting or the contact angle of a droplet of impression material and the wet tooth pre setting, determines the interaction of the material with both mouth fluids and gypsum. As the primary end target is to obtain a model depicting accurately the oral details, an attention to the impressions' compatibility with gypsum should also be given. Many studies were conducted to get a thorough understanding of the hydrophilic properties of each material, and the mechanism utilized, such as surfactants in hydrophilic PVS. Polyether is the only material that is truly hydrophilic; it exhibits the lowest contact angle, during and after setting. Recent studies show that during setting the Polyether hydrophilicity is increased compared to the condition after setting. Dimensional stability, a crucial property of the impression, is affected by the physical and chemical attributes of the material, such as its tear strength. Polysulfide has the highest tear strength. Tear Strength is affected by two major parameters, viscosity, a built-in property, and how fast the impression is pulled out of the mouth, the faster the impression is loaded and pulled out, the higher the tear strength is. The clinical use is dictated from the properties of each impression material, and the understanding of those enables the practitioner to minimize failures. PMID:21848031

Levartovsky, S; Folkman, M; Alter, E; Pilo, R

2011-04-01

2

Replacement of thermal column elastomeric gasket in pool type research reactors based on ageing and radiation degradation  

International Nuclear Information System (INIS)

Pool type research reactors are designed with Thermal column facilities to irradiate samples at different flux levels of thermal neutrons. The sealing of demineralised pool water between stainless steel lined pool wall and the Aluminium Thermal column plate is achieved by an elastomeric gasket. The gasket joint is subjected to pool water temperature ranging from 25degC to 45degC and radiation field of the order of 104 -106 R/hr. The gasket loses its sealing properties due to ageing and radiation degradation after a few years, leading to the leakage and loss of the pool water. Though degradation of the gasket is, generally, predictable, some amount of uncertainty always remains in the leakage rate. The paper describes the study of a few elastomers in radiation environment and replacement of the Thermal column gasket of a swimming pool type research reactor. It includes the details of features like planning and scheduling, the actual sequential execution of the job, various problems encountered and corrective measures applied, engineering and radiological safety measures adopted, development of remote tools, disassembly and reassembly procedure and finally satisfactory completion of the site job in high radiation environment with minimum time and man rem consumption. (author)

3

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

4

Long-Time Dynamic Compatibility of Elastomeric Materials with Hydrazine.  

Science.gov (United States)

The tensile property surfaces for two elastomeric materials, EPT-10 and AF-E-332, were generated in air and in liquid hydrazine environments using constant strain rate tensile tests over a range of temperatures and elongation rates. These results were use...

C. D. Coulbert, E. F. Cuddihy, R. F. Fedors

1973-01-01

5

Evaluation of elastomers as gasket materials in pneumatic and hydraulic systems  

Science.gov (United States)

In the search for superior materials from which to make gaskets for pneumatic and hydraulic systems, promising materials were selected and tested. The testing was conducted in two phases. Those materials that passed the tests of Phase 1 were tested in Phase 2, and categorized in the order of preference.

Bright, C. W.; Lockhart, B. J.

1972-01-01

6

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

7

Molecular engineering of high-performance elastomeric materials  

Science.gov (United States)

Polyurethane is a typical elastomeric material and among the most versatile materials today. It is a linear block copolymer consisting of alternating soft and hard segments with phase separation due to thermodynamic segmental incompatibility. Inspired by the hierarchical structure of spider silk, this kind of block copolymer can be synthesized with two distinct blocks that can differ in their propensity to crystallize. Either the soft or hard segments can be amorphous or semicrystalline. Recent experiments indicate that crystallizable segments lead to higher tensile strength and that systems with crystalline hard segment exhibit better stiffness, strength and mechanical toughness. Here we implement molecular dynamics simulation to investigate the influence of block architectures on mechanical properties and molecular chain movement.

Deng, Shengwei; Falk, Michael

2013-03-01

8

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

9

Irradiation cure processing of elastomeric components  

International Nuclear Information System (INIS)

A process is described for the manufacture of an article containing elastomeric components comprising the steps of, 1) compounding a layer of elastomeric material; 2) partially curing the layer of elastomeric material by exposing it to irradiation by high-speed electrons sufficient to impart an improved green strength; 3) placing the partially cured layer of elastomeric material in contact with other elastomeric components; 4) shaping the layer of elastomeric material and other elastomeric components to substantially the conformation of the desired article, and 5) curing the layer of elastomeric material and the other elastomeric components. (author)

10

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.

11

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

12

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

13

Viscoelastic properties of elastomeric materials for O-ring applications  

Science.gov (United States)

Redesign of the Space Shuttle Solid Rocket Booster necessitated re-evaluation of the material used in the field joint O-ring seals. This research project was established to determine the viscoelastic characteristics of five candidate materials. The five materials are: two fluorocarbon compounds, two nitrile compounds, and a silicon compound. The materials were tested in a uniaxial compression test to determine the characteristic relaxation functions. These tests were performed at five different temperatures. A master material curve was developed for each material from the experimental data. The results of this study are compared to tensile relaxation tests. Application of these results to the design analysis is discussed in detail.

Bower, Mark V.

1989-01-01

14

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

15

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

16

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

17

Development and evaluation of elastomeric materials for geothermal applications. Annual report, October 1977-December 1978  

Energy Technology Data Exchange (ETDEWEB)

The research involved formulation of commercially available materials and synthesis of new elastomers. Formulation studies at JPL and elsewhere produced a material having about 250-350 psi tensile strength and 30 to 80% elongation at 260/sup 0/C for at least 24 hours in simulated brine. The relationship between these laboratory test results and sealing performance in actual or simulated test conditions is not entirely clear; however, it is believed that no conventional formation or casing packer design is likely to perform well using these materials. The synthetic effort focused on high temperature block copolymers and development of curable polystyrene. Procedures were worked out for synthesizing these new materials. Initial results with heat-cured unfilled polystyrene gum at 260/sup 0/C indicated a tensile strength of about 50 psi. Cast films of the first sample of polyphenyl quinoxaline-polystyrene block copolymer, which has a graft-block structure consisting of a polystyrene chain with pendant polyphenyl quinoxaline groups, showed elastomeric behavior in the required temperature range. Its tensile strength and elongation at 260/sup 0/C were 220 to 350 psi and 18 to 36%, respectively. All of these materials also showed satisfactory hydrolytic stability. A procedure for the synthesis of a linear block copolymer of this type has been devised, and the required new intermediates have been synthesized and characterized. A description of the previous year's work is included in an appendix.

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

1979-05-15

18

The Interesting Influence of Nanosprings on the Viscoelasticity of Elastomeric Polymer Materials: Simulation and Experiment  

Science.gov (United States)

Among all carbon nano-structured materials, helical nanosprings or nanocoils have attracted particular interest. Here, carbon nanosprings are directed to adjust the viscoelasticity and reduce the resulting hysteresis loss (HL) of elastomeric polymer materials. Two kinds of nanosprings filled elastomer composites are constructed: system I is obtained by directly blending polymer chains with nanosprings, while system II is composed of the self-assembly of the tri-block structure (chain-nanospring-chain). Through coarse-grained molecular dynamics simulation, we find that the incorporation of nanosprings prominently improve the mechanical strength of the elastomer matrix, and importantly, decrease considerably the hysteresis loss. Furthermore, the spring constant of nanosprings and the interfacial chemical coupling between chains and nanosprings both play a crucial role. It is inferred that elastomer/carbon nano-structured materials with good flexibility and reversible mechanical response (nanosprings, nanocoils, nanorings and thin graphene sheet) may possess both excellent mechanical and low HL properties, which could open a new avenue to fabricate high performance automobile tires, and facilitate the large-scale industrial application of these materials.

Liu, Jun; Zhang, Liqun; Cao, Dapeng

2013-03-01

19

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

20

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

 
 
 
 
21

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

22

Application of a new composite cubic-boron nitride gasket assembly for high pressure inelastic x-ray scattering studies of carbon related materials.  

Science.gov (United States)

We have developed a new composite cubic-boron nitride (c-BN) gasket assembly for high pressure diamond anvil cell studies, and applied it to inelastic x-ray scattering (IXS) studies of carbon related materials in order to maintain a larger sample thickness and avoid the interference from the diamond anvils. The gap size between the two diamond anvils remained ~80 ?m at 48.0 GPa with this new composite c-BN gasket assembly. The sample can be located at the center of the gap, ~20 ?m away from the surface of both diamond anvils, which provides ample distance to separate the sample signal from the diamond anvils. The high pressure IXS of a solvated C(60) sample was studied up to 48 GPa, and a pressure induced bonding transition from sp(2) to sp(3) was observed at 27 GPa. PMID:21806194

Wang, Lin; Yang, Wenge; Xiao, Yuming; Liu, Bingbing; Chow, Paul; Shen, Guoyin; Mao, Wendy L; Mao, Ho-kwang

2011-07-01

23

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

24

Analytical modeling of bolted flanged joints with full face gaskets  

Energy Technology Data Exchange (ETDEWEB)

Section 8 of the ASME code covers flanges with a ring gasket located within a bolt. However, a reliable analysis of pipeline leaks relies on the ability to predict an accurate operating gasket load and flange rotation because the gasket contact stress can be deduced from gasket compression curves when these two parameters are known. A model was developed to analyze flanged joints with full face gaskets made of soft materials. This paper presented the analytical solution for full face gaskets based on the rotational flexibility of the flange, the axial flexibility of the gasket and bolt, and their interaction during load application. The remaining compression load on a full face gasket in the operating condition can also be evaluated. For comparative purposes, two different size flanges were analyzed in conjunction with different gasket materials. The suitability of the analytical approach was verified using numerical finite element analysis. It was concluded that the model provides important operating parameters based on initial bolt-up load state and pressure operating case. Future work will focus on introducing leakage as a design parameter in order to predict an appropriate assembly bolt stress level. 15 refs., 3 tabs., 8 figs.

Galai, H.; Bouzid, A.H. [Ecole de Technologie Superieure, Montreal, PQ (Canada). Dept. of Mechanical Engineering

2004-07-01

25

Studies on gasketed flange joints under bending with anisotropic Hill plasticity model for gasket  

International Nuclear Information System (INIS)

The behavior of a gasketed flange joint under bending loads has been studied by three dimensional finite element analysis (FEA) and experiments. The in-plane and bending stiffness of spiral wound gaskets are considered using anisotropic Hill plasticity material model. The variation in bolt axial force of joints under bending load predicted by the finite element analysis compares well with the experimental results. The contact stress distribution obtained have significant variation in the pattern from the previous material models and consistent with the results of Bouzid regarding flange rotation. - Highlights: ? We model gasket by Anisotropic Hill Plasticity model for joints under bending. ? We examine influence of in-plane and transverse stiffnesses. ? Proposed model shows a variation of 11 MPa in gasket stress over previous models. ? This model is suitable for joints under bending, torsional and dynamic loading.

26

Studies on gasketed flange joints under bending with anisotropic Hill plasticity model for gasket  

Energy Technology Data Exchange (ETDEWEB)

The behavior of a gasketed flange joint under bending loads has been studied by three dimensional finite element analysis (FEA) and experiments. The in-plane and bending stiffness of spiral wound gaskets are considered using anisotropic Hill plasticity material model. The variation in bolt axial force of joints under bending load predicted by the finite element analysis compares well with the experimental results. The contact stress distribution obtained have significant variation in the pattern from the previous material models and consistent with the results of Bouzid regarding flange rotation. - Highlights: > We model gasket by Anisotropic Hill Plasticity model for joints under bending. > We examine influence of in-plane and transverse stiffnesses. > Proposed model shows a variation of 11 MPa in gasket stress over previous models. > This model is suitable for joints under bending, torsional and dynamic loading.

Mathan, G. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Siva Prasad, N., E-mail: siva@iitm.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

2011-12-15

27

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

28

Service life studies and evaluation of operating experience with regard to damage of pressure vessel internals and damage caused by gaskets, lubricants and by substances used as nondestructive testing material  

International Nuclear Information System (INIS)

Project SR 451, task 4.4.1 deals with problems of aging of reactor vessel internals and other components that experienced selected damaging mechanisms e.g. stress corrosion. Operating experience has been evaluated in detail with regard to the susceptibility of the materials involved, to the fatigue and to the effects of materials used in gaskets or for lubrication and of substances used at nondestuctive testing procedures. This evaluation shows that degradations due to such effects occurred mainly at connecting elements such as screws and bolts. Degradations caused by the effect of gasket materials were confined to small diameter piping for instrumentation and control. There are various causes of degradations, they are listed and assessed. (orig.)

29

Sealing performance of various gaskets  

International Nuclear Information System (INIS)

In the high dose zone in nuclear reactors, the gaskets used for the flanges jointing different metals are subjected to the radiation damage and the repeated displacement between the flanges due to the difference of thermal expansion. But as for the gaskets withstanding both, it is the actual state that the manufacturers have little experience and result. However, in the part jointing the reflector vessel and the core vessel and in the experiment holes of the Kyoto University high neutron flux reactor (KUHFR) at the planning stage, it was calculated that the lateral deviation of about 0.6 mm arises in the gasket part at temperature difference of 43 deg C under the above condition. The prevention of the leak of primary coolant and heavy water is very important for the safety management of nuclear reactors, and it is necessary to examine beforehand on sealing method. In this study, by giving repeated displacement to gaskets, the test on sealing performance was carried out, and the results are reported. Three kinds of gaskets, that is, Balck Tight, Helicoflex and solid aluminum gasket, were selected, and the statical test and the dynamic test were carried out. The tightening load dropped largely at the initial period in all the gaskets. The Black Tight was most stable, and is suitable to the use for the KUHFR. (Kako, I.)

30

Elastomeric shutter mechanism  

Science.gov (United States)

An elastomeric shutter mechanism for opening and closing a passageway in the wall of a vessel, such as a submarine hull is presented. A single, unitary, retractable shutter member made of an elastomeric material is partially attached to the wall around a portion of a passageway. The single, unitary, retractable shutter member is moveable from a closed position when the unattached portion of the shutter member is abutting the wall around the passageway to an open position when the unattached portion of the shutter member is retracted away from the wall around the passageway. Cables are attached to the inside surface of the shutter member for retracting the shutter member and opening the passageway. Mechanical stops are positioned inside of the vessel for abutting the shutter member when retracted to the open position by the cables. On an underwater vessel such as a submarine, the shutter member is sealed in the closed position by a pressure differential between the inside surface and the outside surface of the shutter member or latched in place in the closed position. Split ribs are included on the inside surface of the shutter member to resist the expansion of the shutter member when maintained in the closed position by the pressure differential.

Curtis, Clifford M.

1995-05-01

31

A summary of laboratory testing performed to characterize and select an elastomeric O-ring material to be used in the redesigned solid rocket motors of the space transportation system  

Science.gov (United States)

An elastomeric O-ring material is used in the joints of the redesigned solid motors (RSRM's) of the National Space Transportation System (NSTS). The selection of the O-ring material used in the RSRM's was a very thorough process that included efforts by NASA's Marshall Space Flight Center and the Langley Research Center, and the Thiokol Corporation. One of the efforts performed at MSFC was an extensive in-house laboratory test regime to screen potential O-ring materials and ultimately to characterize the elastomeric material that was chosen to be used in the RSRM's. The laboratory tests performed at MSFC are summarized.

Turner, J. E.

1993-01-01

32

Evaluation of effectiveness of microwave irradiation for disinfection of silicone elastomeric impression material.  

Science.gov (United States)

Use of domestic microwave oven has been suggested as a method of disinfecting a number of dental materials used in dental practice. This study was done to analyse the effect of microwave irradiation on vinyl polysiloxane putty impression material (3M ESPE, Express™ STD) contaminated with test organisms (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans. 180 square shaped specimens of addition silicon putty material were prepared and divided into 3 groups for three test organisms. The 3 groups were subdivided into 4 subgroups (n = 15) for different exposure parameters (control group 5, 6 and 7 min exposure at 650 W. The specimens were contaminated using standard inoculums of test organism and then were irradiated using domestic microwaves. Broth cultures of the control and test group specimens were plated on selective media culture plates. Colonies formed were counted. Data analyses included Kruskal-Walli's ANOVA and Mann-Whitney's tests. Nil values shows complete elimination of C. albicans and P. aeruginosa after 5, 6 and 7 min exposure. Staphylococcus aureus showed colonies with the mean value of 7.6 × 10(3) ± 2.3 × 10(3), 4.6 × 10(3) ± 2.6 × 10(3) after 5 and 6 min respectively and nil values after 7 min exposure. 5 min exposure caused complete elimination of C. albicans and P. aeruginosa strains, while 7 min exposure eliminated S. aureus completely. PMID:24431716

Bhasin, Abhilasha; Vinod, V; Bhasin, Vinny; Mathew, Xavier; Sajjan, Suresh; Ahmed, Syed Tauqheer

2013-06-01

33

Linear dimensional changes in plaster die models using different elastomeric materials  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

34

Linear dimensional changes in plaster die models using different elastomeric materials  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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

35

Gasket-holder to put in place gaskets for connection of pipes with clamp fittings  

International Nuclear Information System (INIS)

Gasket-holder comprising 2 arms with tongues holding the gasket and fixing devices on a pipe clamp fitting and centering means. Application is made to fit circular gaskets on pipe with conic end in adverse environment

36

Decrease of reaction force of metal gaskets just after initial tightening  

International Nuclear Information System (INIS)

The decrease of reaction force of some metal gaskets inserted into the test flange at room temperature, 120 C(real cask temperature) and 200 C(accelerated condition) are measured. The reaction forces of metal gaskets in the room temperature have been almost not changed. The reaction force of 120 C and 200 C metal gaskets has decreased according to the temperature increase. After the temperature became stable, the decrease of the reaction force gradually proceeded, this decrease have been as same as previous studies. The bolts of transport and storage casks are usually tightened just after the loading of spent fuels, and then the temperature of metal gaskets at that time is almost the room temperature. The reaction forces of the metal gasket tightened at this condition would be decreased after the temperature increase due to the decay heat of spent fuels. It is confirmed that the loosening of the bolts might be happened if the tightening torque of bolts is not appropriate. It is easy to evaluate that the reaction forces of the metal gasket in storage condition according to Larson-Miller parameter or relaxation of the gasket material, but the decrease of the reaction forces of the metal gasket just after the loading is not able to evaluate by these method. It is necessary to evaluate the reaction forces according to plastic deformation property of the metal gaskets so as to fasten the gaskets safety

37

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

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

Experimental setup for the study of thermal conductivity of elastomeric material at cryogenic temperature  

Science.gov (United States)

In this work a new convenient experimental setup is made with the help of a Gifford-McMahan cryorefrigerator to study the variation of thermal conductivity with the temperature of any solid material in the range of 35-300 K. The GM refrigerator can produce a temperature down to 35 K with a refrigeration capacity of 29.20 W. The principle of this experiment is based on a guarded hotplate method. The thermal gradient along the thickness of the sample is achieved with the help of electrical heating in the range of 100-230 K. The sample has been insulated from the ambient heat inleak with the help of a vacuum of 10 -6 Torr and with a number of super insulation layers. Three samples of elastomer with different composition suitable for cryogenic appliance have been prepared in cylindrical shapes of 6.00 cm diameter and 1.2 cm thickness. The variation of thermal conductivity is studied at a mean temperature of 100, 120, 130, 150, 170, 190 and 210 K. From the experimental study it is seen that the thermal conductivity of all the samples increases with the increase of temperature and reaches a peak value in the range of 0.00165 to 0.00173 W cm -1 K -1 and then decreases, as temperature is further increased to a constant value. This is in full agreement with the published literature. The variation of peak values of thermal conductivity for different samples is found to be 1 to 6% with respect to the published data. This has ensured the reliability and accuracy of the experimental setup.

Bhowmick, T.; Pattanayak, S.

40

Fibre-optic sensors for partial discharge-generated ultrasound in elastomeric high-voltage insulation materials  

Science.gov (United States)

Recent progress in the development of ultrasonic fibre-optic sensors for detecting acoustic emission from partial discharge in elastomeric insulations is presented. These sensors are an important part of a proposed comprehensive scheme for the fibre-optic monitoring of cable accessories. After specifying the underlying design goals the improved fibre-optic sensor design is outlined. It is experimentally shown that it offers about ten-fold improvement over a previously investigated resonant cantilever-type design in terms of detection limit, making it competitive with conventional piezoelectric transducers, however with the added compatibility with strong electrical fields and electromagnetically noisy environments.

Rohwetter, P.; Habel, W.

2013-05-01

 
 
 
 
41

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

42

Corrosion quantification test for flanges with graphite-based gaskets  

Energy Technology Data Exchange (ETDEWEB)

The substitution of asbestos with nonasbestos fiber-reinforced materials in some industrial plants has caused corrosion problems in flanges and valves. A novel corrosion apparatus, the Corrosion Qualification Test, quantified corrosion and gives preliminary results of tests on flexible graphite-based gasket products.

Mameri, N.; Piron, D.L.; Bouzid, A.; Derenne, M.; Marchand, L.; Birembaut, Y.

2000-04-01

43

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

44

Reinforcement Of Elastomeric Rubber Using Carbon Fiber Laminates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 unidirec...

Sivaraman R, Roseenid Teresa A.

2013-01-01

45

Development of super elastic alloy seal gasket  

International Nuclear Information System (INIS)

In-vessel components such as blanket and divertor are activated due to 14 MeV neutrons during DT operations in ITER (International Thermonuclear Experimental Reactor), and hence they have to be maintained or replaced remotely. For the maintenance and replacement operations, a sealed cask with a double seal door is required to transport the activated in-vessel components without dispersion of the activated dust. Therefore, a seal gasket of the double seal door is required to provide seal tightness of activated dust, to allow easy handling compatible with remote operations and to withstand intense of gamma radiation. In accordance with these requirements, an application of 'Super Elastic Alloy'(SEA) to the seal gasket has been investigated. The SEA seal gasket can reduce the required fastening force while keeping reliable seal tightness, resulting in the provision of deformation flexibility comparable to rubber gasket. In addition, the SEA gasket can provide high radiation resistance comparing with rubber gasket. In this research, the SEA based on Ti-Ni alloy has been applied to the coil spring which is an elastic element of the ordinary metallic C-ring gasket. As a result, the seal performance test has shown that the required fastening force is quite low comparing to the standard metal gasket: this enables the compactness of the seal mechanism. In addition, the seal tightness can be maintained for repeatable(cyclic) operations, which is appropriate for remote operations. (author)

46

A finite strain thermo-viscoelastic constitutive model to describe the self-heating in elastomeric materials during low-cycle fatigue  

Science.gov (United States)

A thermo-visco-hyperelastic constitutive model, in accordance with the second thermodynamics principle, is formulated to describe the self-heating evolution in elastomeric materials under cyclic loading. The mechanical part of the model is based upon a Zener rheological representation in which the specific free energy potential is dependent on an added internal variable, allowing the description of the time-dependent mechanical response. The large strain mechanical behavior is described using a Langevin spring, while the continuous stress-softening under cyclic loading is taken into account by means of a network alteration kinetics. The thermo-mechanical coupling is defined by postulating the existence of a dissipation pseudo-potential, function of the viscous dilatation tensor. The proposed model is fully three-dimensional and is implemented into a finite element code. The model parameters are identified using experimental data obtained on a styrene-butadiene rubber under a given strain rate for different strain conditions. Predicted evolutions given by the model for other strain rates are found in good agreement with the experimental data.

Ovalle Rodas, C.; Zaïri, F.; Naït-Abdelaziz, M.

2014-03-01

47

Modeling the low-cycle fatigue behavior of visco-hyperelastic elastomeric materials using a new network alteration theory: Application to styrene-butadiene rubber  

Science.gov (United States)

Although several theories were more or less recently proposed to describe the Mullins effect, i.e. the stress-softening after the first load, the nonlinear equilibrium and non-equilibrium material response as well as the continuous stress-softening during fatigue loading need to be included in the analysis to propose a reliable design of rubber structures. This contribution presents for the first time a network alteration theory, based on physical interpretations of the stress-softening phenomenon, to capture the time-dependent mechanical response of elastomeric materials under fatigue loading, and this until failure. A successful physically based visco-hyperelastic model is revisited by introducing an evolution law for the physical material parameters affected by the network alteration. The general form of the model can be basically represented by two parallel networks: a nonlinear equilibrium response and a time-dependent deviation from equilibrium, in which the network parameters become functions of the damage rate (defined as the ratio of the applied cycle over the applied cycle to failure). The mechanical behavior of styrene-butadiene rubber was experimentally investigated, and the main features of the constitutive response under fatigue loading are highlighted. The experimental results demonstrate that the evolution of the normalized maximum stress only depends on the damage rate endured by the material during the fatigue loading history. The average chain length and the average chain density are then taken as functions of the damage rate in the proposed network alteration theory. The new model is found to adequately capture the important features of the observed stress-strain curves under loading-unloading for a large spectrum of strain and damage levels. The model capabilities to predict variable amplitude tests are critically discussed by comparisons with experiments.

Ayoub, G.; Zaïri, F.; Naït-Abdelaziz, M.; Gloaguen, J. M.

2011-02-01

48

Manifold gasket accommodating differential movement of fuel cell stack  

Science.gov (United States)

A gasket for use in a fuel cell system having at least one externally manifolded fuel cell stack, for sealing the manifold edge and the stack face. In accordance with the present invention, the gasket accommodates differential movement between the stack and manifold by promoting slippage at interfaces between the gasket and the dielectric and between the gasket and the stack face.

Kelley, Dana A. (New Milford, CT); Farooque, Mohammad (Danbury, CT)

2007-11-13

49

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

50

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

51

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

52

In situ evaluation of orthodontic elastomeric chains.  

Science.gov (United States)

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. PMID:23207855

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

2012-01-01

53

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 SciELO Venezuela | Language: Spanish Abstract in spanish 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

54

21 CFR 177.1210 - Closures with sealing gaskets for food containers.  

Science.gov (United States)

...natural or synthetic rubber gasket compositions. Di...copolymer resins used in...closure-sealing gasket compositions used in...natural or synthetic rubber gasket...natural or synthetic rubber gasket compositions. Polyethylene...Polyurethane resins...

2010-04-01

55

Use of soft-metal engineered surfaces to minimize galling of carbon steel bolting materials in gasketed joints at elevated temperatures  

International Nuclear Information System (INIS)

Bolting materials with soft-metal engineered surfaces applied using the PlasmaBond process retain their qualifications as pressure boundary materials. These thin, highly adherent gold or silver surfaces significantly reduce the risk of galling for joints that are heavily loaded, operate at elevated temperature, and remain stagnant for long periods. Soft-metal engineered surfaces have demonstrated in joints assembled by tensioning and the more common practice of torquing, offer improved galling resistance compared to non coated components. Field experience has shown that engineered surfaces can be used to create 'metallurgical contrast' that is more effective against galling than conventional lubricants. (author)

56

Use of soft-metal engineered surfaces to minimize galling of carbon steel bolting materials in gasketed joints at elevated temperatures  

International Nuclear Information System (INIS)

Bolting materials with soft-metal engineered surfaces applied using the PlasmaBond process retain their qualifications as pressure boundary materials. These thin, highly adherent gold or silver surfaces significantly reduce the risk of galling for joints that are heavily loaded, operate at elevated temperature, and remain stagnant for long periods. Soft-metal engineered surfaces have demonstrated in joints assembled by tensioning and the more common practice of torquing, offer improved galling resistance compared to non-coated components. Field experience has shown that engineered surfaces can be used to create 'metallurgical contrast' that is more effective against galling than conventional lubricants. (author)

57

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

58

46 CFR 56.30-35 - Gasketed mechanical couplings.  

Science.gov (United States)

...and Limitations of Piping Joints § 56.30-35 Gasketed mechanical couplings. (a) This section applied to pipe fittings that form a seal by compressing a resilient gasket onto the pipe joint primarily by threaded fasteners and...

2010-10-01

59

Liquid-Oxygen-Compatible Cement for Gaskets  

Science.gov (United States)

Fluorelastomer and metal bonded reliably by new procedure. To cure fluoroelastomer cement, metal plate/gasket assembly placed in vacuum bag evacuated to minimum vacuum of 27 inches (69 cm) of mercury. Vacuum maintained throughout heating process and until assembly returns to ambient room temperature. Used to seal gaskets and O-rings or used to splice layers of elastomer to form non-standard sized O-rings. Another possible use is to apply protective, liquid-oxygen-compatible coating to metal parts.

Elmore, N. L.; Neale, B. C.

1984-01-01

60

O-ring gasket test fixture  

Science.gov (United States)

An apparatus is presented for testing O-ring gaskets under a variety of temperature, pressure, and dynamic loading conditions. Specifically, this apparatus has the ability to simulate a dynamic loading condition where the sealing surface in contact with the O-ring moves both away from and axially along the face of the O-ring.

Turner, James Eric (inventor); Mccluney, Donald Scott (inventor)

1991-01-01

 
 
 
 
61

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

62

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.

63

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

64

Non-flammable elastomeric fiber from a fluorinated elastomer and containing an halogenated flame retardant  

Science.gov (United States)

Flame retardant elastomeric compositions are described comprised of either spandex type polyurethane having incorporated into the polymer chain halogen containing polyols, conventional spandex type polyurethanes in physical admixture with flame retardant additives, or fluoroelastomeric resins in physical admixture with flame retardant additives. Methods are described for preparing fibers of the flame retardant elastomeric materials and articles of manufacture comprised of the flame retardant clastomeric materials and non elastic materials such as polybenzimidazoles, fiberglass, nylons, etc.

Howarth, J. T.; Sheth, S. G.; Sidman, K. R.; Massucco, A. A. (inventors)

1976-01-01

65

Prospects for Materials (Plastics, Elastomers, Paints): Volume 1: Plastic Materials (Appendix 1, Plastification Systems) Prospective Matieres Plastiques - Elastomeres - Peintures. Annexe 1: Systemes de Plastification.  

Science.gov (United States)

Plastification systems were studied bibliographically and possible developments in the geometrical and mechanical design of the systems were researched. Rheology of screw in sleeve feed systems for plastic and elastomer materials is explained. Metallurgic...

C. Bord

1981-01-01

66

Gasket and snap ring installation tool  

Energy Technology Data Exchange (ETDEWEB)

This invention is comprised of a tool for installing a gasket and a snap ring including a shaft, a first plate attached to the forward end of the shaft, a second plate slidably carried by the shaft, a spring disposed about the shaft between the first and second plates, and a sleeve that is free to slide over the shaft and engage the second plate. The first plate has a loading surface with a loading groove for receiving a snap ring and a shoulder for holding a gasket. A plurality of openings are formed through the first plate, communicating with the loading groove and approximately equally spaced about the groove. A plurality of rods are attached to the second plate, each rod slidable in one of the openings. In use, the loaded tool is inserted into a hollow pipe or pipe fitting having an internal flange and an internal seating groove, such that the gasket is positioned against the flange and the ring is in the approximate plane of the seating groove. The sleeve is pushed against the second plate, sliding the second plate towards the first plate, compressing the spring and sliding the rods forwards in the openings. The rods engage the snap ring and urge the ring from the loading groove into the seating groove.

Southerland, J.M., Sr.; Barringer, C.N., Sr.

1993-08-23

67

Gasket Assembly for Sealing Mating Surfaces  

Science.gov (United States)

A pair of substantially opposed mating surfaces are joined to each other and sealed in place by means of an electrically-conductive member which is placed in proximity to the mating surfaces. The electrically-conductive member has at least one element secured thereto which is positioned to contact the mating surfaces, and which softens when the electrically-conductive member is heated by passing an electric current therethrough. The softened element conforms to the mating surfaces, and upon cooling of the softened element the mating surfaces are joined together in an effective seal. Of particular significance is an embodiment of the electrically-conductive member which is a gasket having an electrically-conductive gasket base and a pair of the elements secured to opposite sides of the gasket base. This embodiment is positioned between the opposed mating surfaces to be joined to each other. Also significant is an embodiment of the electrically-conductive member which is an electrically-conductive sleeve having an element secured to its inner surface. This embodiment surrounds cylindrical members the bases of which are the substantially opposed mating surfaces to be joined, and the element on the inner surface of the sleeve contacts the outer surfaces of the cylindrical members.

Bryant, Melvin A., III (Inventor)

2003-01-01

68

Process for spinning flame retardant elastomeric compositions. [fabricating synthetic fibers for high oxygen environments  

Science.gov (United States)

Flame retardant elastomeric compositions comprised of either spandex type polyurethane having halogen containing polyols incorporated into the polymer chain, conventional spandex type polyurethanes in physical admixture with flame retardant additives, or fluoroelastomeric resins in physical admixture with flame retardant additives were developed. Methods are described for preparing fibers of the flame retardant elastomeric materials and manufactured articles as well as nonelastic materials such as polybenzimidazoles, fiberglass, and nylons, for high oxygen environments.

Howarth, J. T.; Sheth, S.; Sidman, K. R.; Massucco, A. A. (inventors)

1978-01-01

69

Selecting appropriate dynamic model for elastomeric engine mounts to approximate experimental FRF data of them  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the capabilities of different dynamic analytical models to approximate experimentally measured FRFs of elastomeric engine mounts of a passenger car are investigated. Artificial neural networks is used in identifying the dynamic characteristics of each model. Impact hammer test is implemented to extract measured FRFs and harmonic analysis is used to get the counterpart response of the models. Here linear and orthotropic material properties are considered for elastomeric media. The frequency response functions of updated models are compared with experimentally detected ones and advantages and limitations of each model to simulate the real dynamic behaviour of elastomeric engine mounts are discussed

Jahani K.

2010-06-01

70

The manufacture of Inconel 718 alloy 'O' ring gaskets  

International Nuclear Information System (INIS)

The manufacturing process of 'O' ring gaskets of Inconel 718 alloy as well as the mechanical properties at room temperature and high temperature and the resilience of the ring gaskets are described in detail. The feasibility of the manufacturing process and the quality of products are verified based on the results of proving tests and technological appraisals. It is proved that the 'O' ring gaskets meet the design criteria of sealing and no spillage requirement under high temperature service conditions

71

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

72

Thermomechanical behavior of shape memory elastomeric composites  

Science.gov (United States)

Shape memory polymers (SMPs) can fix a temporary shape and recover their permanent shape in response to environmental stimuli such as heat, electricity, or irradiation. Most thermally activated SMPs use the macromolecular chain mobility change around the glass transition temperature ( Tg) to achieve the shape memory (SM) effects. During this process, the stiffness of the material typically changes by three orders of magnitude. Recently, a composite materials approach was developed to achieve thermally activated shape memory effect where the material exhibits elastomeric response in both the temporary and the recovered configurations. These shape memory elastomeric composites (SMECs) consist of an elastomeric matrix reinforced by a semicrystalline polymer fiber network. The matrix provides background rubber elasticity while the fiber network can transform between solid crystals and melt phases over the operative temperature range. As such it serves as a reversible "switching phase" that enables shape fixing and recovery. Shape memory elastomeric composites provide a new paradigm for the development of a wide array of active polymer composites that utilize the melt-crystal transition to achieve the shape memory effect. This potentially allows for material systems with much simpler chemistries than most shape memory polymers and thus can facilitate more rapid material development and insertion. It is therefore important to understand the thermomechanical behavior and to develop corresponding material models. In this paper, a 3D finite-deformation constitutive modeling framework was developed to describe the thermomechanical behavior of SMEC. The model is phenomenological, although inspired by micromechanical considerations of load transfer between the matrix and fiber phases of a composite system. It treats the matrix as an elastomer and the fibers as a complex solid that itself is an aggregate of melt and crystal phases that evolve from one to the other during a temperature change. As such, the composite consists of an elastomer reinforced by a soft liquid at high temperature and a stiff solid at low temperature. The model includes a kinetic description of the non-isothermal crystallization and melting of the fibers during a temperature change. As the fibers transform from melt to crystal during cooling it is assumed that new crystals are formed in an undeformed state, which requires careful tracking of the kinematics of the evolving phases which comes at a significant computational cost. In order to improve the computational efficiency, an effective phase model (EPM) is adopted to treat the evolving crystal phases as an effective medium. A suite of careful thermomechanical experiments with a SMEC was carried out to calibrate various model parameters, and then to demonstrate the ability of the model to accurately capture the shape memory behavior of the SMEC system during complex thermomechanical loading scenarios. The model also identifies the effects of microstructural design parameters such as the fiber volume fraction.

Ge, Qi; Luo, Xiaofan; Rodriguez, Erika D.; Zhang, Xiao; Mather, Patrick T.; Dunn, Martin L.; Qi, H. Jerry

2012-01-01

73

Circuit models for Sierpinski gasket antennas  

CERN Document Server

A lumped-parameter impedor-oriented and a 2-port-network-oriented circuit models for the Sierpinski gasket prefractal antenna are presented. With the former, the voltage and current patterns give a detailed understanding of the electromagnetic fields' self-similar distribution throughout the antenna geometry; on the other hand model complexity exponentially increases with the prefractal iteration order. The latter "black-box" model only controls port-oriented global parameters which are the ones commonly used in antennas' circuit models and its complexity is independent of prefractal order. The "black-box" model is also shown to converge, at fractal limit, to a reciprocal triangular network.

Arrighetti, W; Gerosa, G

2005-01-01

74

Random walks on dual Sierpinski gaskets  

Science.gov (United States)

We study an unbiased random walk on dual Sierpinski gaskets embedded in d-dimensional Euclidean spaces. We first determine the mean first-passage time (MFPT) between a particular pair of nodes based on the connection between the MFPTs and the effective resistance. Then, by using the Laplacian spectra, we evaluate analytically the global MFPT (GMFPT), i.e., MFPT between two nodes averaged over all node pairs. Concerning these two quantities, we obtain explicit solutions and show how they vary with the number of network nodes. Finally, we relate our results for the case of d = 2 to the well-known Hanoi Towers problem.

Wu, Shunqi; Zhang, Zhongzhi; Chen, Guanrong

2011-07-01

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

Engineered elastomeric proteins with dual elasticity can be controlled by a molecular regulator  

Science.gov (United States)

Elastomeric proteins are molecular springs that confer excellent mechanical properties to many biological tissues and biomaterials. Depending on the role performed by the tissue or biomaterial, elastomeric proteins can behave as molecular springs or shock absorbers. Here we combine single-molecule atomic force microscopy and protein engineering techniques to create elastomeric proteins that can switch between two distinct types of mechanical behaviour in response to the binding of a molecular regulator. The proteins are mechanically labile by design and behave as entropic springs with an elasticity that is governed by their configurational entropy. However, when a molecular regulator binds to the protein, it switches into a mechanically stable state and can act as a shock absorber. These engineered proteins effectively mimic and combine the two extreme forms of elastic behaviour found in natural elastomeric proteins, and thus represent a new type of smart nanomaterial that will find potential applications in nanomechanics and material sciences.

Cao, Yi; Li, Hongbin

2008-08-01

77

Partial-Vacuum-Gasketed Electrochemical Corrosion Cell  

Science.gov (United States)

An electrochemical cell for making corrosion measurements has been designed to prevent or reduce crevice corrosion, which is a common source of error in prior such cells. The present cell (see figure) includes an electrolyte reservoir with O-ring-edged opening at the bottom. In preparation for a test, the reservoir, while empty, is pressed down against a horizontal specimen surface to form an O-ring seal. A purge of air or other suitable gas is begun in the reservoir, and the pressure in the reservoir is regulated to maintain a partial vacuum. While maintaining the purge and partial vacuum, and without opening the interior of the reservoir to the atmosphere, the electrolyte is pumped into the reservoir. The reservoir is then slowly lifted a short distance off the specimen. The level of the partial vacuum is chosen such that the differential pressure is just sufficient to keep the electrolyte from flowing out of the reservoir through the small O-ring/specimen gap. Electrochemical measurements are then made. Because there is no gasket (and, hence, no crevice between the specimen and the gasket), crevice corrosion is unlikely to occur.

Bonifas, Andrew P.; Calle, Luz M.; Hintze, Paul E.

2006-01-01

78

Use of elastomeric elements in control of rotor instability  

Science.gov (United States)

The dynamic characteristics of elastomeric supports are discussed. Stiffness and damping characteristics for elastomers of various geometries including O-rings, buttons loaded in compression, and rectangular elements loaded in shear are presented. The effects of frequency, temperature, and amplitude are illustrated, as well as the effects of material and geometry. Empirical design methods are illustrated, and several examples are presented where elastomers have successfully controlled both synchronous and nonsynchronous vibrations.

Smalley, A. J.

1980-01-01

79

Elastomeric carbon nanotube circuits for local strain sensing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use elastomeric polydimethylsiloxane substrates to strain single-walled carbon nanotubes and modulate their electronic properties, with the aim of developing flexible materials that can sense local strain. We demonstrate micron-scale nanotube devices that can be cycled repeatedly through strains as high as 20% while providing reproducible local strain transduction by via the device resistance. We also compress individual nanotubes, and find they undergo an undulatory dist...

Maune, H.; Bockrath, M.

2006-01-01

80

Elastomeric polyurea nanocomposites  

Science.gov (United States)

The effect of multiwall carbon nanotubes (MWCNT), nano-layered silicate (nanoclay), and trisilanolphenyl-functionalized polyhedral oligomeric silsesquioxane (POSS) on the rheology and mechanical properties of an oligomeric polydiamine and the polyurea formed by its reaction with isocyanate were measured. The MWCNT and nanoclay increase the viscosity of the polydiamine and form a flocculated filler network at very low concentrations (polyurea chemistry. The tensile modulus of the cured polyurea is higher for all three additives, and using POSS significantly tougher material can be obtained, provided adjustments to the stoichiometry are made.

Casalini, R.; Roland, C. M.

2012-07-01

 
 
 
 
81

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

82

Spectral triples for the Sierpinski Gasket  

CERN Document Server

We construct a 2-parameter family of spectral triples for the Sierpinski Gasket K. We determine their associated Connes' distances in terms of suitable roots of the Euclidean metric of the plane and their dimensional spectra, and show that the pairing of the associated Fredholm module with (odd) K-theory is non-trivial. We recover the Hausdorff measure of K in terms of the residue of the functional a --> tr_omega (a |D|^{-s}) at the abscissa of convergence d, which coincides with the Hausdorff dimension of the fractal. We recover also the unique, standard Dirichlet form on K, as the residue of the functional a --> tr_omega (|[D,a]|^2 |D|^{-s}) at the abscissa of convergence delta, which we call the energy dimension. The fact that the Hausdorff dimension differs from the energy dimension reflects the fact that on K energy and volume are distributed singularly.

Cipriani, F; Isola, T; Sauvageot, J-L

2011-01-01

83

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.

84

Energy dissipation in elastomeric isolators subjected to seismic forces  

International Nuclear Information System (INIS)

In this paper, a detailed analysis is presented to elucidate thermal effects in elastomeric seismic isolators. Using the material properties of elastomers and the time history of typical seismic events, it is shown that a properly designed base structure provides effective heat transfer and limits temperature rise in the elastomer. The frequency-dependent material properties are a key factor in designing the base structure for maximum effectiveness. When thermal effects are considered, the material properties of the elastomer(s) do not change with temperature. Thus, the isolator material do not degrade during a prolonged seismic event and effectiveness is thereby optimized

85

REVIEW OF ENERGY EFFICIENCY OF REFRIGERATOR/FREEZER GASKETS  

Science.gov (United States)

The report gives results of an investigation of the significance of heat leakage through gaskets in household refrigerator/freezers, explores different design features, and suggests further study if necessary. he report gives results of an extensive literature review, interviews ...

86

Contracting Similarity Fixed Point of General Sierpinski Gasket  

Directory of Open Access Journals (Sweden)

Full Text Available The article mainly studies the contracting similarity ?xed point and the structure of the general Sierpinski gasket. Firstly, the paper analyzes the importance of contracting similarity fixed point in fractal geometry. Based on a series of definitions, the article studies the contracting similarity ?xed point. Then, the paper researches on the structure of the general Sierpinski gasket, and describes it through function. Using a new characteristic function and other techniques, the article gives two important lemmas of the general Sierpinski gasket and the complete proof. By the proved lemmas, the article gets the formula of the contracting similarity ?xed point of the Sierpinski gasket, and then proves that the aforementioned contracting similarity ?xed points form a new fractal. As application, the paper classifies the above contracting similarity ?xed points into three types and gives two examples.

Shanhui Sun

2013-12-01

87

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

88

Hybrid magnetorheological fluid elastomeric lag dampers for helicopter stability augmentation  

Science.gov (United States)

A laboratory demonstration of a hybrid magnetorheological fluid-elastomeric (MRFE) damper is investigated for adjustable or programmable lag mode damping in helicopters, so that damping requirements can be varied as a function of different flight conditions. The laboratory demonstration of this hybrid MRFE lag damper consists of a double lap shear elastomeric damper in parallel with two magnetorheological (MR) flow mode dampers. This is compared to a damper where only elastomeric materials are implemented, i.e., a double lap shear specimen. The relationship between the output force and the quasi-steady harmonic displacement input to a flow mode MR damper is exploited, where the output force can be adjusted as a function of applied magnetic field. Equivalent viscous damping is used to compare the damping characteristics of the hybrid damper to a conventional elastomeric damper under steady-state sinusoidal displacement excitation. To demonstrate feasibility, a hybrid MRFE damper test setup is designed, and single frequency (lag frequency or rotor in-plane bending frequency) and dual frequency (lag frequency and rotor frequency) tests are conducted under different magnetic fields. The hybrid MRFE damper exhibits amplitude-dependent damping behavior. However, with application of a magnetic field, the damping level is controlled to a specific damping level objective as a function of displacement amplitude. Similarly, under dual frequency conditions, damping degradation at the lag frequency, because of lag motion at the rotor frequency, can also be recovered by increasing magnetic field. A time-domain analysis is developed to study the nonlinear dynamic behavior of the hybrid MRFE damper. Using rate-dependent elasto-slides, the amplitude-dependent behavior of the hybrid MRFE damper is accurately reconstructed using both constant and current-dependent (i.e. controllable) parameters. The analysis is physically motivated and can be applied to the elastomer and MR fluid damper components separately.

Hu, Wei; Wereley, Norman M.

2008-08-01

89

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)

90

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.

91

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

Science.gov (United States)

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 CO(2) concentrations. In this study, we present a theory on how the CO(2) 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. PMID:23320654

Boesgaard, Kristine S; Mikkelsen, Teis N; Ro-Poulsen, Helge; Ibrom, Andreas

2013-01-16

92

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

93

Vibration modes of 3n-gaskets and other fractals  

International Nuclear Information System (INIS)

We rigorously study eigenvalues and eigenfunctions (vibration modes) on the class of self-similar symmetric finitely ramified fractals, which include the Sierpinski gasket and other 3n-gaskets. We consider the classical Laplacian on fractals which generalizes the usual one-dimensional second derivative, is the generator of the self-similar diffusion process, and has possible applications as the quantum Hamiltonian. We develop a theoretical matrix analysis, including analysis of singularities, which allows us to compute eigenvalues, eigenfunctions and their multiplicities exactly. We support our theoretical analysis by symbolic and numerical computations. Our analysis, in particular, allows the computation of the spectral zeta function on fractals and the limiting distribution of eigenvalues (i.e., integrated density of states). We consider such examples as the level-3 Sierpinski gasket, a fractal 3-tree, and the diamond fractal

94

The proposal and verify of new gasket of protective cover of the reactor hole  

International Nuclear Information System (INIS)

In this paper author deals with the proposal and verify of new gasket of protective cover of the reactor hole. New gaskets were tested and should be installed on reactors of the Jaslovske Bohunice NPP

95

Computer modelling of the sealing behavior of gaskets in flanged joints  

International Nuclear Information System (INIS)

A computer program is described which is designed to predict the gasket stress distribution in flanged joints. The program incorporates finite element modules for calculation of flange deflections in response to loads applied by bolts, gasket and fluid. Account is taken of non-linear gasket load-compression curves and hysteresis, and thermal deflections

96

Combination spacer and gasket provides effective static seal  

Science.gov (United States)

Closely machined steel ring having narrow sealing lands on both faces and a thin coating of a commercially available halocarbon polymer combines the functions of a spacer and static seal ring or gasket having a minimum of potential leak paths. The device is effective over a wide range of temperatures down to minus 423 deg F and at pressure up to 180 psig.

Jones, F. B.

1966-01-01

97

Elastomeric binders for electrodes. [in secondary lithium cells  

Science.gov (United States)

The poor mechanical integrity of the cathode represents an important problem which affects the performance of ambient temperature secondary lithium cells. Repeated charge of a TiS2 cathode may give rise to stresses which disturb the electrode structure and can contribute to capacity loss. An investigation indicates that the use of an inelastic binder material, such as Teflon, aggravates the problem, and can lead to electrode disruption and poor TiS2 particle-particle contact. The feasibility of a use of elastomers as TiS2 binder materials has, therefore, been explored. It was found that elastomeric binders provide an effective approach for simplifying rechargeable cathode fabrication. A pronounced improvement in the mechanical integrity of the cathode structure contributes to a prolonged cycle life.

Yen, S. P. S.; Shen, D. H.; Somoano, R. B.

1983-01-01

98

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

99

Practical Usage of Effect of Cold Weldability of Metals in Joint of Plastically Deformable Gasket and Flanges of Detachable Joint of Fuel Pipe-Line  

Science.gov (United States)

The performed investigations of the character of changing the leakage of control gas through flange connections in the process of drawing- up the bolts in to calculation moment and subsequent lowering of bolt loading to zero have shown the following. Gradual reduction of leakage through a gasket occurs in the process of increasing the tightening torque up to its complete absence. But there is no leakage through the unloaded gasket after untwisting all nuts and removal of fastening bolts from flanges. The performed analysis has shown that this effect is caused by cold weldability of the gasket with flanges; this is a result of flowing of its material into microrough holes of contact surfaces of flanges at plastic deformation with formation of strong and dense contact. Some technological methods of formation of undetachable joint have been developed for practical application of this effect. According to one of those methods, drawing- up the gasket is performed with the help of flanges preliminarily. Those bolts are substituted by less strong standard bolts for drawing- up by less moment after achievement of stress needed. Method of pressurization of the joint is more effective when technological detachable flanges and bolts are used for reduction of the gasket up to its plastic state. Those flanges and bolts are removed after drawing- up; after that standard flanges are loaded by the moment used for reception of effort only from pressure of operational medium in the pipe- line (Qoper.m.) because drawing- up of the gasket by effort (Qeff.) that provides its plastic state, is already achieved. Then we exclude the first component (Qeff.) in dependence which is known from technical literature: Qdraw. = Qeff . + Qoper .m. = qFgas. + PFpip. (1), and the final formula for calculation of the effort of drawing- up the joint (in which drawing- up the gasket with provision of cold weldability is carried out preliminarily before drawing- up the standard bolts) is expressed in such a way: Qdraw. =Fpip.(2), where q- specific pressure (stress) on the gasket which provides flowing holes of sealing surfaces at plastic deformation. q=(250-270)MPa for joints with closed sealing gate and a gasket made of copper; Fgas., Fpip.- areas of the gasket and the pipe- line; P- pressure value of medium in the pipe- line. Numeric values of effort of drawing- up which are calculated in accordance with dependence (2), for example, for locking joint, with internal diameter d1= 0.125 m sealed by the copper gasket (which operates under operational medium pressure P=2MPa), are 9.5 times less than those obtained in accordance with dependence (1). Necessary moment of drawing- up this joint is reduced in proportion to effort of drawing- up. The proposed technical solution changes the principle of designing the flange joints of fuel systems in which load- carrying elements ill not be available for provision of necessary drawing- up the gasket, and the designed structures will consist of thin flexible flanges and bolts, so there will be no relaxation of their stresses. If disassembly of such joints is needed, then one of the flanges contains some threaded holes along the perimeter for installation of technological bolts in those holes; those bolts press out the respective flange.

Danchenko, V. G.

2002-01-01

100

Properties of the energy Laplacian on Sierpinski Gasket type fractals  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we extend some results from the standard Laplacian on the Sierpinski Gasket to the energy Laplacian. We evaluate the pointwise formula for the energy Laplacian and then observe that we have the analogue of Picard's existence and uniqueness theorem also for the energy Laplacian and we approximate functions vanishing on the boundary with functions vanishing in a neighborhood of the boundary as in \\cite{str4}. Then we generalize to the level three Sierpinski Gask...

O?berg, Anders; Tsougkas, Konstantinos

2014-01-01

 
 
 
 
101

Elastomeric carbon nanotube circuits for local strain sensing  

CERN Document Server

We use elastomeric polydimethylsiloxane substrates to strain single-walled carbon nanotubes and modulate their electronic properties, with the aim of developing flexible materials that can sense local strain. We demonstrate micron-scale nanotube devices that can be cycled repeatedly through strains as high as 20% while providing reproducible local strain transduction by via the device resistance. We also compress individual nanotubes, and find they undergo an undulatory distortion with a characteristic spatial period of 100-200 nm. The observed period can be understood by the mechanical properties of nanotubes and the substrate in conjunction with continuum elasticity theory. These could potentially be used to create superlattices within individual nanotubes, enabling novel devices and applications.

Maune, H

2006-01-01

102

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.)

103

Confinement of elastomeric block copolymers via forced assembly coextrusion.  

Science.gov (United States)

Forced assembly processing provides a unique opportunity to examine the effects of confinement on block copolymers (BCPs) via conventional melt processing techniques. The microlayering process was utilized to produce novel materials with enhanced mechanical properties through selective manipulation of layer thickness. Multilayer films consisting of an elastomeric, symmetric block copolymer confined between rigid polystyrene (PS) layers were produced with layer thicknesses ranging from 100 to 600 nm. Deformation studies of the confined BCP showed an increase in ductility as the layer thickness decreased to 190 nm due to a shift in the mode of deformation from crazing to shear yielding. Postextrusion annealing was performed on the multilayer films to investigate the impact of a highly ordered morphology on the mechanical properties. The annealed multilayer films exhibited increased toughness with decreasing layer thickness and resulted in homogeneous deformation compared to the as-extruded films. Multilayer coextrusion proved to be an advantageous method for producing continuous films with tunable mechanical response. PMID:22124208

Burt, Tiffani M; Keum, Jong; Hiltner, Anne; Baer, Eric; Korley, Lashanda T J

2011-12-01

104

A Comparative Study on the Efficiency of Pigmented and non Pigmented Elastomeric Chains Using Differential Scanning Calorimetry  

Directory of Open Access Journals (Sweden)

Full Text Available Orthodontic treatment involves the use of force delivery systems such as arch wires and elastomeric chains. Their mechanical property varies among various manufacturers. It depends on their phase transformation temperature. Differential scanning calorimetry (DSC is a method of thermal analysis which is extensively employed to assess the properties of orthodontic materials. In the field of orthodontics DSC is used to assess the phase transition temperature of orthodontic arch wires, glass transition temperature of polyurethane elastomers, and to evaluate the degree of cure of dental resins. The present study highlights the clinical application of differential scanning calorimetry in evaluating the Glass transition temperature of polyurethane elastomeric chains.

Joby Paulose

2010-12-01

105

Elastomeric biodegradable polyurethane blends for soft tissue applications.  

Science.gov (United States)

Four biodegradable polyurethane blends were made from segmented polyurethanes that contain amino acid-based chain extender and diisocyanate groups. The soft segments of these parent polyurethanes were either polyethylene oxide (PEO) or polycaprolactone (PCL) diols. The blends were developed to investigate the effect of varying soft segment compositions on the overall morphological, mechanical, and degradative properties of the materials, with a view to producing a family of materials with a wide range of properties. The highly hydrophilic PEO material was incorporated to increase the blend's susceptibility to degradation, while the PCL polyurethane was selected to provide higher moduli and percent elongations (strains) than the PEO parent materials can achieve. All four blends were determined to be semi-crystalline, elastomeric materials that possess similarly shaped stress-strain curves to that of the PCL-based parent polyurethane. As the percent composition of PEO polyurethane within the blend increased, the material became weaker and less extensible. The blends demonstrated rapid initial degradation in buffer followed by significantly slower, prolonged degradation, likely corresponding to an initial loss of primarily PEO-containing polymer, followed by the slower degradation of the PCL polyurethane. All four blends were successfully formed into three-dimensional porous scaffolds utilizing solvent casting/particulate leaching methods. Since these new blends possess a range of mechanical and degradation properties and can be shaped into three-dimensional objects, these materials may hold potential for use in soft tissue engineering scaffold applications. PMID:12160300

Fromstein, J D; Woodhouse, K A

2002-01-01

106

Equations of state for ideal elastomeric gels  

Science.gov (United States)

Submerged in a solvent-containing environment and subject to applied forces, a covalent polymer network absorbs the solvent and deforms, forming an elastomeric gel. The equations of state are derived under two assumptions. First, the amount of the solvent in the gel varies when the gel changes volume, but remains constant when the gel changes shape. Second, the Helmholtz free energy of the gel is separable into the contribution due to stretching the network and that due to mixing the polymer and the solvent. We demonstrate that these equations of state fit several sets of experimental data in the literature remarkably well.

Cai, Shengqiang; Suo, Zhigang

2012-02-01

107

Accuracy and consistency of modern elastomeric pumps.  

Science.gov (United States)

Continuous peripheral nerve blockade has become a popular method of achieving postoperative analgesia for many surgical procedures. The safety and reliability of infusion pumps are dependent on their flow rate accuracy and consistency. Knowledge of pump rate profiles can help physicians determine which infusion pump is best suited for their clinical applications and specific patient population. Several studies have investigated the accuracy of portable infusion pumps. Using methodology similar to that used by Ilfeld et al, we investigated the accuracy and consistency of several current elastomeric pumps. PMID:25140510

Weisman, Robyn S; Missair, Andres; Pham, Phung; Gutierrez, Juan F; Gebhard, Ralf E

2014-01-01

108

In-situ permeation tests of elastomeric O-ring seals  

International Nuclear Information System (INIS)

A series of in-situ permeation tests are being conducted to determine permeation coefficients and breakthrough and saturation times for certain elastomeric O-rings with various gases that might be used as leak test tracers. The work is directed towards developing more effective and efficient nuclear material shipping packaging leak test procedures. The tests are in progress presently, and a formal report will be published in 1984

109

Characterisation of elastomeric latex by means of low-field NMR  

Digital Repository Infrastructure Vision for European Research (DRIVER)

[EN] The invention relates to a series of experimental methodologies based on the use of nuclear magnetic resonance (NMR), to be used in the characterisation of the most important parameters of polymeric dispersions. The invention relates to a series of experimental methods which for the first time have been applied to elastomeric latex and which can be used to obtain a complete characterisation of the solid content of the latex and the evolution of the material during the pre-vulcanisation (...

Lo?pez Valenti?n, Juan; Brasero Espada, Justo

2011-01-01

110

Tensile properties of orthodontic elastomeric chains.  

Science.gov (United States)

The purpose of this investigation was to assess the permanent elongation, tensile strength and toughness of elastomeric chains. Two types (open and closed chains, i.e. with and without an intermodular link) of three brands of elastomeric module yielding six groups were included in the study. Specimens with equal numbers of loops were measured and classified into four groups based on their ageing state: (a) as-received; (b) subjected to a 24 hour steady strain in air determined as 50 per cent of original length; (c) exposed intraorally for 24 hours; and (d) retrieved following 3 weeks of intraoral exposure. All specimens were subjected to tensile stress and their behaviour was analysed with three-way ANOVA and Tukey's multiple comparison test at alpha = 0.05 level of significance, with brand, type (open or closed chains), and treatment variables serving as discriminating variables. Modular geometry or design were found not to have significant effects on elongation, probably due to the substantial variation in chain shape, modular size, and link length among products of the same category. Similarly, no correlation was identified between specimen treatment and the tensile strength of elastomers. The toughness results were not consistent with the group rankings for tensile strength, probably because of variation in the elastic and plastic deformation of specimens upon loading. PMID:15130038

Eliades, T; Eliades, G; Silikas, N; Watts, D C

2004-04-01

111

21 CFR 177.1210 - Closures with sealing gaskets for food containers.  

Science.gov (United States)

... Type of closure-sealing gasket composition ...overall discs or annular rings from a hot melt, solution...overall discs or annular rings of vulcanized plasticized...overall discs or annular rings of polymeric or resinous-coated...50 5. Closures with sealing gaskets or...

2010-04-01

112

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

113

Rubber and alumina gaskets retain vacuum seal in high temperature EMF cell  

Science.gov (United States)

Silicone rubber gasket and an alumina gasket retain a vacuum inside a high temperature EMF cell in which higher and lower density liquid metal electrodes are separated by an intermediate density fused salt electrolyte. This innovation is in use on a sodium bismuth regenerable EMF cell in which the fused salts and metals are at about 500 deg to 600 deg C.

Hesson, J. C.

1966-01-01

114

33 CFR 183.536 - Seals and gaskets in fuel filters and strainers.  

Science.gov (United States)

...Seals and gaskets in fuel filters and strainers. 183.536 Section 183.536 ...Seals and gaskets in fuel filters and strainers. (a) [Reserved] (b) Each...each sealed joint in a fuel filter and strainer must not leak when subjected for...

2010-07-01

115

Surface effects on in-plane buckling of nanowires on elastomeric substrates  

International Nuclear Information System (INIS)

Buckling of nanowires on elastomeric substrates shows enhanced stretchability for these materials, and can foster stretchable form of nanoelectronics and nanosystems. Since surface effects can have strong influence on the mechanical behaviour of nanowires, a theoretical model is established to study the surface effects on in-plane buckling of nanowires on elastomeric substrates. The buckling wavelength, amplitude and critical buckling strain are obtained analytically in terms of surface elasticity, residual surface tension, bending and tension stiffness of the nanowire and the elastic modulus of the substrate. The results show that the buckling wavelength is only dependent on the surface elasticity, while both surface elasticity and residual surface tension can have significant effects on the buckling amplitude and critical buckling strain. (paper)

116

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

117

The characteristic of blind flanged bolted joints with full-face gaskets  

International Nuclear Information System (INIS)

In this paper, the characteristics of blind flanged bolted joints with full-face gaskets such as the contact stress distributions and the variation of axial bolt force are analyzed using axisymmetrical theory of elasticity. The effect of Young's modulus of gaskets, the gasket thickness and the bolt pitch circle diameter on the contact stress distribution are clarified by the numerical calculations. In the experiments, the contact stress distributions were measured by sensitive films when the gasket is asbestos. Variations of axial bolt force are measured using strain gages. The internal pressure is observed when the internal fluid starts to leak. The numerical results are in fairly good agreement with the experimental results. Discussions are made on the sealing performance of gaskets used in these experiments

118

Comparative study of the behaviour of conventional gasketed and compact non-gasketed flanged pipe joints under bolt up and operating conditions  

International Nuclear Information System (INIS)

Bolted flanged joints comprise an assembly of a number of important individual components, which are required to perform well together in service. The ideal requirement for a bolted flange joint is a 'zero-leak' condition. However, whilst recommended design procedures for bolted flange joints are available in international codes and standards, leakage problems are still faced by industry. These are common in both normal operating (internal pressure loading) and critical event conditions. The drive is, therefore, to find a flange joint assembly, which provides 'zero-leak condition' and requires little or no maintenance and handling. Considerable investigation in the area of optimised bolted joints has been in progress for the past 10 years comparing traditional gasketed joints and 'compact non-gasketed' joints, using both analytical and experimental approaches. In this present study, two-dimensional non-linear finite element studies have been performed for both gasketed and non-gasketed bolted flange pipe joints. Based on the stress results for the flange and the bolt and the flange rotation/displacement, compact non-gasketed flange joints are shown to be a viable and preferable alternative to the conventional gasketed flange joints. Recommendations are made for a best-fit flange model for static load conditions with 'zero-leak' sealing in a flange joint

119

Long-term compression effects on elastomeric O-ring behavior  

Science.gov (United States)

This paper discusses the results of testing performed on elastomeric seal materials that had been under compression for extended periods of time. Elastomeric seals used in the Space Shuttle redesigned solid rocket motors can experience compression times of up to six months. These seals must be capable of sealing internal motor pressure upon ignition. The tests described herein were performed in order to verify that the seals, which had experienced long-term compression could seal throughout motor operation. Testing was divided into two phases: (1) dynamic high pressure testing, and (2) resiliency testing. Dynamic testing was performed using specialized test fixtures that allowed simulation of the field joint movements during initial motor operation along with high pressure gas. Resiliency testing was performed using specialized test fixtures that also simulated field joint movements and also had the ability to measure the sealing force of the O-ring. Results from all testing indicated that the current elastomeric seals used in the redesigned solid rocket motors will seal during motor operations in the currently defined launch environments.

Clinton, R. G.; Turner, J. E.

1990-01-01

120

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

 
 
 
 
121

75 FR 47027 - In the Matter of: Certain Devices Having Elastomeric Gel and Components Thereof; Notice of...  

Science.gov (United States)

...of: Certain Devices Having Elastomeric Gel and Components Thereof; Notice of Investigation...importation of certain devices having elastomeric gel and components thereof by reason of infringement...importation of certain devices having elastomeric gel and components thereof that infringe...

2010-08-04

122

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

123

X-ray diffraction studies using diamond coated rhenium gasket to megabar pressures  

International Nuclear Information System (INIS)

X-ray diffraction studies at megabar pressures are limited by the sample thickness between the diamond anvils. High strength gaskets are desirable to improve the quality of x-ray diffraction data. We present a technique which employs a microwave plasma chemical vapor deposited diamond layer on one side of a rhenium gasket. As a test case, we show energy dispersive x-ray diffraction data on rare earth metal neodymium to 153 GPa using a synchrotron source. The increased sample thickness results in an unambiguous crystal structure determination of a monoclinic phase in neodymium above 75 GPa. [chemical vapor deposition, diamond, rhenium gasket, x-ray diffraction, neodymium

124

21 CFR 177.1210 - Closures with sealing gaskets for food containers.  

Science.gov (United States)

...CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances...only in the manufacture of polyethylene complying with item 2.1...1420 Maleic anhydride-polyethylene copolymer 5 percent...rubber gasket compositions. Polyethylene glycol 400 esters of...

2010-04-01

125

21 CFR 177.1210 - Closures with sealing gaskets for food containers.  

Science.gov (United States)

...crepe, latex, mechanical dispersions) ?-cis- 9-Octadecenyl-omega...2750-3000 0.05 percent. Polyurethane resins manufactured from...gaskets applied in aqueous dispersions to closures for containers...organisol, mechanical dispersion, or latex 50 500...

2010-04-01

126

21 CFR 177.1210 - Closures with sealing gaskets for food containers.  

Science.gov (United States)

...hydrogenated 2 percent. Chlorinated isobutylene-isoprene copolymers...predominantly straight-chain paraffin hydrocarbons averaging 20...isobutylene-isoprene and chlorinated isobutylene-isoprene copolymers...closure-sealing gaskets overcoated with wax. 2 Time and...

2010-04-01

127

46 CFR 56.25-15 - Gaskets (modifies 108.4).  

Science.gov (United States)

(c) Only metallic and suitable asbestos-free nonmetallic gaskets may be used on flat or raised face flanges if the expected normal operating pressure exceeds 720 pounds per square inch or the operating temperature exceeds -750...

2010-10-01

128

Study on long-term sealability of gaskets for spent fuel storage cask  

International Nuclear Information System (INIS)

The heating tests of the representative metal gaskets to be used for storage casks were conducted at the temperature ranging from the room temperature up to 300degC for 10,000 hours. Then the dependence of sealability and mechanical properties on time and temperature, and the long term sealability of them were examined. The results are as follows; (1) The quality, structure, and stress relaxation of gaskets affect the sealability. (2) The ratio of plastic deformation to total deformation could be expressed in terms of Larson-Miller parameter (LMP). This plastic deformation ratio expresses the relaxation property of gaskets, and the correlation between LMP and sealability was clarified. (3) The sealability of a given gasket at service temperature can be judged by the plastic deformation ratio and the relation between leakage ratio and LMP. (author)

129

21 CFR 177.1210 - Closures with sealing gaskets for food containers.  

Science.gov (United States)

...Single and Repeated Use Food Contact Surfaces ...sealing gaskets for food containers. Closures...preparing, treating, packaging, transporting, or holding food in accordance with...physical or technical effect and in...

2010-04-01

130

Development of a snubber type magnetorheological fluid elastomeric lag damper for helicopter stability augmentation  

Science.gov (United States)

Most advanced helicopter rotors are typically fitted with lag dampers, such as elastomeric or hybrid fluid-elastomeric (FE) lag dampers, which have lower parts counts, are lighter in weight, easier to maintain, and more reliable than conventional hydraulic dampers. However, the damping and stiffness properties of elastomeric and fluid elastomeric lag dampers are non-linear functions of lag/rev frequency, dynamic lag amplitude, and operating temperature. It has been shown that elastomeric damping and stiffness levels diminish markedly as amplitude of damper motion increases. Further, passive dampers tend to present severe damping losses as damper operating temperature increases either due to in-service self-heating or hot atmospheric conditions. Magnetorheological (MR) dampers have also been considered for application to helicopter rotor lag dampers to mitigate amplitude and frequency dependent damping behaviors. MR dampers present a controllable damping with little or no stiffness. Conventional MR dampers are similar in configuration to linear stroke hydraulic type dampers, which are heavier, occupy a larger space envelope, and are unidirectional. Hydraulic type dampers require dynamic seal to prevent leakage, and consequently, frequent inspections and maintenance are necessary to ensure the reliability of these dampers. Thus, to evaluate the potential of combining the simplicity and reliability of FE and smart MR technologies in augmenting helicopter lag mode stability, an adaptive magnetorheological fluid-elastomeric (MRFE) lag damper is developed in this thesis as a retrofit to an actual fluid-elastomeric (FE) lag damper. Consistent with the loading condition of a helicopter rotor system, single frequency (lag/rev) and dual frequency (lag/rev at 1/rev) sinusoidal loading were applied to the MRFE damper at varying temperature conditions. The complex modulus method was employed to linearly characterize and compare the performance of the MRFE damper with the baseline FE damper performance. Based on experimental measurements, it is shown in the research that at all test temperatures, a significant damping control range, extending beyond the baseline FE damper, can be provided by the MRFE damper with the application of varying magnetic fields. This controllable damping range can be programmed to potentially provide the required damping augmentation as a function of different flight conditions. The added benefits of employing smart MR fluids in MRFE lag dampers are to produce adequate damping at critical flight conditions while concurrently reducing periodic hub loads at other flight conditions and to compensate damping losses associated with temperature. The other main objective of the present research is to develop and formulate a comprehensive analytical model that can accurately describe the non-linear hysteretic behavior that is demonstrated by the MRFE lag damper. Thus, a hydromechanical model, which can delineate the physical flow motion of the system and accurately describe the non-linear hysteretic behavior of the MRFE damper is proposed. The hydromechanical model explored in this study is a design-based model which describes the damper system with a series of lumped hydraulic, mechanical and magnetorheological components. The model employs physical parameters such as inertia, damping, yield force and compliances that are dependent on damper geometry and material properties of components and which can potentially be approximated a priori. Further, temperature variation will mainly cause material properties to change. Once model parameters have been established, the model is shown to simulate accurately the measured hysteretic force-displacement history under single and dual frequency excitations, and varying temperatures.

Ngatu, Grum T.

131

Charge Effects on Mechanical Properties of Elastomeric Proteins  

Science.gov (United States)

Several biological molecules of nanoscale dimensions, such as elastin and resilin, are capable of performing diverse tasks with minimal energy loss. These molecules are efficient in that the ratio of energy output to energy consumed is very close to unity. This is in stark contrast to some of the best synthetic materials that have been created. For example, it is known that resilin found in dragonflies has a hysteresis loss of only 0.8% of the energy input while the best synthetic rubber made to date, polybutadiene, has a loss of roughly 20%.We simulate tensile tests of naturally occurring motifs found in resilin (a highly hydrophilic protein), as well as similar simulations found in reduced-polarity counterparts (i.e. the same motif with the charge on each individual atom set to half the natural value, the same motif with the charge on each individual atom set to zero, and a motif in which all the polar amino acids have been replaced with nonpolar amino acids). The results show a strong correlation between charge and extensibility. In order to further understand the effect of properties such as charge on the system, we will run simulations of elastomeric proteins such as resilin in different solvents.

Kappiyoor, Ravi; Balasubramanian, Ganesh; Dudek, Daniel; Puri, Ishwar

2012-02-01

132

Lee-Yang zeros and the Ising model on the Sierpinski Gasket  

CERN Document Server

We study the distribution of the complex temperature zeros for the partition function of the Ising model on a Sierpinski gasket using an exact recursive relation. Although the zeros arrange on a curve pinching the real axis at T=0 in the thermodynamic limit, their density vanishes asymptotically along the curve approaching the origin. This phenomenon explains the coincidence of the low temperature regime on the Sierpinski gasket and on the linear chain.

Burioni, R; Donetti, L

1999-01-01

133

The anisotropic quantum antiferromagnet on the Sierpinski gasket: Ground state and thermodynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate an antiferromagnetic s=1/2 quantum spin system with anisotropic spin exchange on a fractal lattice, the Sierpinski gasket. We introduce a novel approximative numerical method, the configuration selective diagonalization (CSD) and apply this method to the Sierpinski gasket with N=42. Using this and other methods we calculate ground state energies, spin gap, spin-spin correlations and specific heat data and conclude that the s=1/2 quantum antiferromagnet on the ...

Voigt, Andreas; Wenzel, Wolfgang; Richter, Johannes; Tomczak, Piotr

2004-01-01

134

Synthesis and Characterization of Elastomeric Heptablock Terpolymers Structured by Crystallization  

Energy Technology Data Exchange (ETDEWEB)

We report the synthesis and characterization of fully saturated hydrocarbon block copolymer thermoplastic elastomers with competitive mechanical properties and attractive processing features. Block copolymers containing glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were produced in a CEC-P-CEC heptablock architecture, denoted XPX, by anionic polymerization and catalytic hydrogenation. The X blocks contain equal volume fractions of C and E, totaling 40%-60% of the material overall. All the XPX polymers are disordered above the melt temperature for E (T{sub m,E} {approx_equal} 95 C) as evidenced by SAXS and dynamic mechanical spectroscopy measurements. Cooling below T{sub m,E} results in crystallization of the E blocks, which induces microphase segregation of E, C, and P into a complex morphology with a continuous rubbery domain and randomly arranged hard domains as shown by TEM. This mechanism of segregation decouples the processing temperature from the XPX molecular weight up to a limiting value. Tensile mechanical testing (simple extension and cyclic loading) demonstrates that the tensile strength (ca. 30 MPa) and strain at break (>500%) are comparable to the behavior of CPC triblock thermoplastic elastomers of similar molecular weight and glass content. However, in the CPC materials, processability is constrained by the order-disorder transition temperature, limiting the applications of these materials. Elastic recovery of the XPX materials following seven cycles of tensile deformation is correlated with the fraction of X in the heptablock copolymer, and the residual strain approaches that of CPC when the fraction of hard blocks f{sub X} {le} 0.39.

Alfonzo, C.Guillermo; Fleury, Guillaume; Chaffin, Kimberly A.; Bates, Frank S. (UMM); (Medtronic)

2010-12-07

135

Effect of storage period on the accuracy of elastomeric impressions  

Directory of Open Access Journals (Sweden)

Full Text Available 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

2007-06-01

136

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.

137

Evaluation of the durability of elastomeric easy-release coatings  

Science.gov (United States)

Novel coatings have been designed to solve problems associated with biofouling of marine structures, particularly ship hulls. The best candidates to date are multilayered coatings incorporating silicone rubber technology. These materials are efficient because they exhibit excellent release properties. However, they are very soft and tend to be more susceptible to various forms of mechanical damage. Fundamental analysis of the durability of these coatings has been done using standard laboratory tests. Simulative studies are essential to screen candidates as well as to predict the true life of the systems. The goal of this project was to develop a testing protocol for the evaluation of the durability of elastomeric easy release coatings and to implement it on selected candidate coatings. A brushing apparatus was designed and built to simulate the cleaning processes of ship hulls. Wear was measured with profilometry. The proposed methodology is valuable to study the processes of wear of the coatings, to screen various materials and to identify parameters, either functional or material, which would directly affect their durability. Two groups of candidate coatings were tested: the EXS series and the NRL series. The EXS series samples showed better wear resistance than the NRL series samples and showed no dependence on the rotational speed of the brushes. The NRL series samples showed that increasing the sliding speed resulted in a decrease in wear. An increase in the applied load resulted in increased wear for both sample series. The effect of coating thickness was also investigated and discrimination between the proposed coatings could not be established because the tips of the bristles were sharp and irregular. Scratches matching the path of the brush bristles were observed in the wear scars of both sample types under all load and speed conditions. The NRL samples also exhibited ridges perpendicular to the sliding direction similar to the abrasion pattern.

Christiaen, Anne-Claire

138

Influence of elastomeric seal plate surface chemistry on interface integrity in biofouling-prone systems: Evaluation of a hydrophobic "easy-release" silicone-epoxy coating for maintaining water seal integrity of a sliding neoprene/steel interface  

Science.gov (United States)

The scientific hypothesis of this work is that modulation of the properties of hard materials to exhibit abrasion-reducing and low-energy surfaces will extend the functional lifetimes of elastomeric seals pressed against them in abrasive underwater systems. The initial motivation of this work was to correct a problem noted in the leaking of seals at major hydropower generating facilities subject to fouling by abrasive zebra mussel shells and extensive corrosion. Similar biofouling-influenced problems can develop at seals in medical devices and appliances from regulators in anesthetic machines and SCUBA diving oxygen supply units to autoclave door seals, injection syringe gaskets, medical pumps, drug delivery components, and feeding devices, as well as in food handling equipment like pasteurizers and transfer lines. Maritime and many other heavy industrial seal interfaces could also benefit from this coating system. Little prior work has been done to elucidate the relationship of seal plate surface properties to the friction and wear of elastomeric seals during sliding contacts of these articulating materials, or to examine the secondary influence of mineralized debris within the contacting interfaces. This investigation utilized the seal materials relevant to the hydropower application---neoprene elastomer against carbon steel---with and without the application of a silicone-epoxy coating (WearlonRTM 2020.98) selected for its wear-resistance, hydrophobicity, and "easy-release" capabilities against biological fouling debris present in actual field use. Analytical techniques applied to these materials before and after wear-producing processes included comprehensive Contact Angle measurements for Critical Surface Tension (CA-CST) determination, Scanning Electron Microscopic inspections, together with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-Ray Fluorescence (XRF) measurements for determination of surface texture and inorganic composition, Multiple Attenuated Internal Reflection (MAIR-IR) and Microscopic Infrared Spectroscopy for organic surface compositional details, light microscopy for wear area quantification, and profilometry for surface roughness estimation and wear depth quantification. Pin-on-disc dynamic Coefficient of Friction (CoF) measurements provided data relevant to forecasts of seal integrity in dry, wet and biofouling-influenced sliding contact. Actual wear of neoprene seal material against uncoated and coated steel surfaces, wet and dry, was monitored after both rotary and linear cyclic wear testing, demonstrating significant reductions in elastomer wear areas and depths (and resultant volumes) when the coating was present. Coating the steel eliminated a 270% increase in neoprene surface area wear and an 11-fold increase in seal abrasive volume loss associated with underwater rusting in rotary experiments. Linear testing results confirm coating efficacy by reducing wear area in both loading regimes by about half. No coating delamination was observed, apparently due to a differential distribution of silicone and epoxy ingredients at the air-exposed vs. steel-bonded interfaces demonstrated by IR and EDS methods. Frictional testing revealed higher Coefficients of Friction (CoF) associated with the low-speed sliding of Neoprene over coated rather than uncoated steel surfaces in a wet environment, indicating better potential seal adhesion between the hydrophobic elastomer and coating than between the elastomer and intrinsically hydrophilic uncoated steel. When zebra mussel biofouling debris was present in the articulating joints, CoF was reduced as a result of a water channel path produced between the articulating surfaces by the retained biological matter. Easier release of the biofouling from the low-CST coated surfaces restored the seal integrity more rapidly with further water rinsing. Rapid sliding diminished these biofouling-related differences, but revealed a significant advantage in reducing the CoF of the elastomer-on-coating couples to less than 50% of the elastomer-on-steel coupl

Andolina, Vincent L.

139

Structural conformation of in vitro and in vivo aged orthodontic elastomeric modules.  

Science.gov (United States)

The objectives of this study were to investigate the structural characteristics of open and closed elastomeric modules in the as-received condition, and following (a) 24-hour in vitro loading determined as a 50 per cent extension relative to their original length; (b) 24-hour intra-oral exposure; (c) 3-week intra-oral exposure. Ten specimens of each type (open and closed) of the three brands of elastic chains were included in the study (total of 60). All specimens were subjected to (a) optical transmission microscopy utilizing phase contrast and polarized light modes, (b) micro MIR FT-IR spectroscopy, and (c) scanning electron microscopy and electron probe X-ray microanalysis. Stretched elastomers demonstrated a honeycomb pattern of filament detachment corresponding to strained areas. The chains possessing a well-differentiated inter-modular link presented higher strain concentration gradients located in the link. Phase contrast imaging revealed that the stress adsorption mechanism of these materials involved macromolecular chain orientation and elongation co-axially to the applied load. The specimens retrieved after 24 hours had acquired a proteinaceous film rich in alcohol groups with minimal evidence of phosphate mineralization, while the 3-week retrieved specimens presented precipitation of Ca- and P-forming calcium phosphates. The high protein content of the biofilm organized on the surface of these materials, as well as the calcification pattern found, were similar to a non-specific mechanism of film adsorption of biomaterials exposed to body fluids. The results have clinical implications for aspects of retraction control through sliding mechanics with the use of elastomeric ligatures, and the potential detrimental effects on dental and periodontal tissues such as decalcification and gingival inflammation, respectively. In addition, the experimental protocols adopted for the in vitro study of the force decay of elastomerics should be modified to include parameters pertinent to adsorption phenomena and calcification processes documented to occur in vivo. PMID:10665194

Eliades, T; Eliades, G; Watts, D C

1999-12-01

140

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

 
 
 
 
141

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; Skov, Anne Ladegaard

2011-01-01

142

Thermal stress analysis of pipe flange connections with raised-face gasket subjected to heat conduction  

International Nuclear Information System (INIS)

This paper deals with thermal stress analysis of a pipe flange connection with a raised-face gasket subjected to heat conduction. In the analysis, pipe flange, hubs of the flanges and a raised-face gasket are replaced by finite hollow cylinders. When the inner surface is subjected to heat conduction due to contained fluid and the outer surface are kept 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. Experiments are performed. The analytical results are in fairly good agreement with the experimental results concerning the variation of axial bolt force and the axial strain at the hubs of pipe flange. In the numerical calculations, the effects of the ratios of Young's modulus and the gasket thickness between the flanges and the gaskets 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

143

Mechanically tissue-like elastomeric polymers and their potential as a vehicle to deliver functional cardiomyocytes.  

Science.gov (United States)

One of the major challenges in the field of biomaterials engineering is the replication of the non-linear elasticity observed in soft tissues. In the present study, non-linearly elastic biomaterials were successfully fabricated from a chemically cross-linked elastomeric poly(glycerol sebacate) (PGS) and thermoplastic poly(L-lactic acid) (PLLA) using the core/shell electrospinning technique. The spun fibrous materials, containing a PGS core and PLLA shell, demonstrated J-shaped stress-strain curves, and having ultimate tensile strength, rupture elongation, and stiffness constants respectively comparable to muscle tissue properties. In vitro evaluations also showed that PGS/PLLA fibrous biomaterials possess excellent biocompatibility, capable of supporting human stem-cell-derived cardiomyocytes over several weeks in culture. Therefore, the core/shell electrospun elastomeric materials provide a new potential scaffold to support cells in the therapy of a wide range of soft tissues exposed to cyclic deformation, such as tendon, ligament, cardiac or smooth muscle and lung epithelium. PMID:24125905

Xu, Bing; Li, Yuan; Fang, Xiya; Thouas, George A; Cook, Wayne D; Newgreen, Donald F; Chen, Qizhi

2013-12-01

144

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  

Directory of Open Access Journals (Sweden)

Full Text Available 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, utilizando-se uma silicona de condensação. Essas réplicas foram avaliadas microscopicamente. Os resultados indicaram que, embora alguns materiais tenham apresentado comportamento superior, como o Permlastic e o Extrude, os outros materiais estudados tiveram comportamento clinicamente aceitável, desde que seus moldes sejam convenientemente manipulados, principalmente em relação ao tempo de vazamento do gessoThe purpose of this research was to make a comparative study between different systems of impression materials, such as polysulfide, condensation and addition-curing silicones, using a new non-destructive technique of evaluation, and consequently clinically applicable. After obtaining three element nickel-chromium prosthesis, three-dimensional replicas of the space between the restoration and the prepared tooth were made, using a condensation curing silicone. These replicas were microscopically evaluated. The results showed that, although some materials presented a superior behavior, as Permlastic and Extrude, other tested materials had an acceptable clinical behavior provided that their molds had been properly manipulated, specially regarding the time of cast pouring

Rossana Pereira de Almeida ANTUNES

1997-10-01

145

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  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese 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 d [...] a 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, utilizando-se uma silicona de condensação. Essas réplicas foram avaliadas microscopicamente. Os resultados indicaram que, embora alguns materiais tenham apresentado comportamento superior, como o Permlastic e o Extrude, os outros materiais estudados tiveram comportamento clinicamente aceitável, desde que seus moldes sejam convenientemente manipulados, principalmente em relação ao tempo de vazamento do gesso Abstract in english The purpose of this research was to make a comparative study between different systems of impression materials, such as polysulfide, condensation and addition-curing silicones, using a new non-destructive technique of evaluation, and consequently clinically applicable. After obtaining three element [...] nickel-chromium prosthesis, three-dimensional replicas of the space between the restoration and the prepared tooth were made, using a condensation curing silicone. These replicas were microscopically evaluated. The results showed that, although some materials presented a superior behavior, as Permlastic and Extrude, other tested materials had an acceptable clinical behavior provided that their molds had been properly manipulated, specially regarding the time of cast pouring

Rossana Pereira de Almeida, ANTUNES; Wilson, MATSUMOTO; Heitor, PANZERI.

146

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  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese 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 d [...] a 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, utilizando-se uma silicona de condensação. Essas réplicas foram avaliadas microscopicamente. Os resultados indicaram que, embora alguns materiais tenham apresentado comportamento superior, como o Permlastic e o Extrude, os outros materiais estudados tiveram comportamento clinicamente aceitável, desde que seus moldes sejam convenientemente manipulados, principalmente em relação ao tempo de vazamento do gesso Abstract in english The purpose of this research was to make a comparative study between different systems of impression materials, such as polysulfide, condensation and addition-curing silicones, using a new non-destructive technique of evaluation, and consequently clinically applicable. After obtaining three element [...] nickel-chromium prosthesis, three-dimensional replicas of the space between the restoration and the prepared tooth were made, using a condensation curing silicone. These replicas were microscopically evaluated. The results showed that, although some materials presented a superior behavior, as Permlastic and Extrude, other tested materials had an acceptable clinical behavior provided that their molds had been properly manipulated, specially regarding the time of cast pouring

Rossana Pereira de Almeida, ANTUNES; Wilson, MATSUMOTO; Heitor, PANZERI.

1997-10-01

147

10 CFR Appendix A to Part 440 - Standards for Weatherization Materials  

Science.gov (United States)

...Commercially available. Replacement windows: Aluminum frame...Testing and Materials. Replacement Doors [Standards for conformance] Replacement doors—Hinged doors...1986). Elastomeric joint sealants (normally...

2010-01-01

148

The Power Law For Buffon's Needle Landing Near the Sierpinski Gasket  

CERN Document Server

In this paper we get a power estimate from above of the probability that Buffon's needle will land within distance 3^{-n} of Sierpinski's gasket of Hausdorff dimension 1. In comparison with the case of 1/4 corner Cantor set considered in Nazarov, Peres, and the second author: we still need the technique of arXiv:0801.2942 for splitting the directions to good and bad ones, but the case of Sierpinski gasket is considerably more generic and lacks symmetry, resulting in a need for much more careful estimates of zeros of the Fourier transform of Cantor measure.

Bond, Matthew

2009-01-01

149

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

150

A 3D regression surface for the room temperature tightness gasket data reduction and bolt load design  

International Nuclear Information System (INIS)

The purpose of the present work is to propose a new approach for modelling the tightness behaviour of the gaskets used in bolted flange joints. This new approach consists of developing a mathematical model for a three-dimensional (3D) representation of the gasket tightness performance. Rather than considering a 2D graph for characterizing the complete gasket behaviour, a third axis is added to the Sg vs. Tp plot to dissociate the unloading cycles from initial gasket tightening. This leads to the definition of a surface that is represented by a simple polynomial equation that contains six coefficients that are determined by a simple regression calculation. In the first part of the paper, the new approach is tested through a database of 406 room temperature tightness (ROTT) tests performed on different gasket styles. Then, a statistical analysis of the predictions made with the new model demonstrates its ability to predict gasket leak rates much more accurately than it was previously possible with the gasket constants derived from the ROTT Draft 9 or 10 methods. It is also demonstrated that the new approach can be used to model successfully complex gasket behaviours such as the tightness hardening phenomenon. Secondly, the effect of gas pressure change on the leak rate is analysed. It turns out that at high gasket stresses, the actual scheme of the ROTT tests may not allow enough time for reaching a stabilized leak rate value because of a transitory time effete value because of a transitory time effect in the porous structure of gaskets. Then, in order to evaluate the characteristic waiting period (dwell time) before a stabilized flow rate is achieved following a change in the gas pressure level, a simple phenomenological analysis of the flow is performed

151

Effect of disinfecting solutions on accuracy of alginate and elastomeric impressions.  

Science.gov (United States)

The effect of immersion in six disinfecting solutions on the accuracy of 10 impression materials was investigated. Impressions were taken of a truncated steel cone. After setting, the impressions were either stored at room temperature for 24 h, for control, or immediately immersed in a disinfecting agent for 60 min (in one case 10 min), and after 24 h poured with gypsum. A steel ring fitting the steel cone was placed on the resulting dies, and the discrepancy between the top surface of the ring and the die was measured. From these measurements the deviation between the base diameter of the die and of the impression was calculated to express the inaccuracy. All impressions except some in Blueprint exhibited a net shrinkage, giving rise to too large die stones and incomplete seating of the steel ring. Blueprint impressions, however, occasionally swelled and resulted in too small die stones and "overseating" of the steel ring. The disinfecting solutions had no significant impact on two impression materials. For the remaining eight materials the accuracy was decreased, increased, or unaffected by the immersion. Generally, the accuracy of the alginates investigated were more affected by the disinfecting solutions than were the elastomeric impression materials. The accuracy of the three alginates was drastically impaired by immersion in 70% ethanol, whereas the remaining five disinfecting solutions had a smaller, though sometimes statistically significant, effect on the accuracy. For the elastomeric materials only a few specific combinations of impression material and disinfecting solution reduced the accuracy.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2515589

Peutzfeldt, A; Asmussen, E

1989-10-01

152

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)

153

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

154

Detection of polystyrene sphere translocations using resizable elastomeric nanopores  

CERN Document Server

Resizable elastomeric nanopores have been used to measure pulses of ionic current caused by carboxylated polystyrene spheres of diameter 200 nm and 800 nm. The nanopores represent a novel technology which enables nanoscale resizing of a pore by macroscopic actuation of an elastomeric membrane. Three different pores were employed with variable applied strain, transmembrane potential, particle concentration and sphere radius. Theory describing current pulse magnitude has been extended to conical pore geometry. A consistent method for interpretation of data close to the noise threshold has been introduced, and experimental data has been used to compare several methods for efficient, non-destructive calculation of pore dimensions. The most effective models emphasize the absolute pulse size, which is predominantly determined by the opening radius at the narrowest part of the roughly conical pores, rather than the profile along the entire pore length. Experiments were carried out in a regime for which both electro-...

Willmott, Geoff R

2010-01-01

155

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

156

Pigment effect on the long term elasticity of elastomeric ligatures  

Directory of Open Access Journals (Sweden)

Full Text Available 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 an 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

2012-06-01

157

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)

158

49 CFR 173.40 - General packaging requirements for toxic materials packaged in cylinders.  

Science.gov (United States)

...plug and inert gasketing material. (4) The materials of construction for the cylinder, valves...combination offered for transportation containing a Division 2...1 Hazard Zone A or B material must conform to the...

2010-10-01

159

Manikin-based performance evaluation of elastomeric respirators against combustion particles.  

Science.gov (United States)

This study investigated the effects of faceseal leakage, breathing flow, and combustion material on the overall (non-size-selective) penetration of combustion particles into P-100 half and full facepiece elastomeric respirators used by firefighters. Respirators were tested on a breathing manikin exposed to aerosols produced by combustion of three materials (wood, paper, and plastic) in a room-size exposure chamber. Testing was performed using a single constant flow (inspiratory flow rate = 30 L/min) and three cyclic flows (mean inspiratory flow rates = 30, 85, and 135 L/min). Four sealing conditions (unsealed, nose-only sealed, nose and chin sealed, and fully sealed) were examined to evaluate the respirator faceseal leakage. Total aerosol concentration was measured inside (C(in)) and outside (C(out)) the respirator using a condensation particle counter. The total penetration through the respirator was determined as a ratio of the two (P = C(in) / C(out)). Faceseal leakage, breathing flow type and rate, and combustion material were all significant factors affecting the performance of the half mask and full facepiece respirators. The efficiency of P-100 respirator filters met the NIOSH certification criteria (penetration ?0.03%); it was not significantly influenced by the challenge aerosol and flow type, which supports the current NIOSH testing procedure using a single challenge aerosol and a constant airflow. However, contrary to the NIOSH total inward leakage (TIL) test protocol assuming that the result is independent on the type of the tested aerosol, this study revealed that the challenge aerosol significantly affects the particle penetration through unsealed and partially sealed half mask respirators. Increasing leak size increased total particle penetration. The findings point to some limitations of the existing TIL test in predicting protection levels offered by half mask elastomeric respirators. PMID:23442086

He, Xinjian; Yermakov, Michael; Reponen, Tiina; McKay, Roy T; James, Kelley; Grinshpun, Sergey A

2013-01-01

160

75 FR 64742 - In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of...  

Science.gov (United States)

...337-TA-732] In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of Commission Determination Not...States after importation of certain devices having elastomeric gel and components thereof by reason of infringement of certain...

2010-10-20

 
 
 
 
161

76 FR 13434 - In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of a...  

Science.gov (United States)

...337-TA-732] In the Matter of Certain Devices Having Elastomeric Gel and Components Thereof; Notice of a Commission Determination...States after importation of certain devices having elastomeric gel and components thereof by reason of infringement of certain...

2011-03-11

162

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

163

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

164

Elastomer degradation sensor using a piezoelectric material  

Science.gov (United States)

A method and apparatus for monitoring the degradation of elastomeric materials is provided. Piezoelectric oscillators are placed in contact with the elastomeric material so that a forced harmonic oscillator with damping is formed. The piezoelectric material is connected to an oscillator circuit,. A parameter such as the resonant frequency, amplitude or Q value of the oscillating system is related to the elasticity of the elastomeric material. Degradation of the elastomeric material causes changes in its elasticity which, in turn, causes the resonant frequency, amplitude or Q of the oscillator to change. These changes are monitored with a peak height monitor, frequency counter, Q-meter, spectrum analyzer, or other measurement circuit. Elasticity of elastomers can be monitored in situ, using miniaturized sensors.

Olness, Dolores U. (Livermore, CA); Hirschfeld, deceased, Tomas B. (late of Livermore, CA)

1990-01-01

165

PRELIMINARY REPORT: EFFECTS OF IRRADIATION AND THERMAL EXPOSURE ON ELASTOMERIC SEALS FOR CASK TRANSPORTATION AND STORAGE  

Energy Technology Data Exchange (ETDEWEB)

A testing and analysis approach to predict the sealing behavior of elastomeric seal materials in dry storage casks and evaluate their ability to maintain a seal under thermal and radiation exposure conditions of extended storage and beyond was developed, and initial tests have been conducted. The initial tests evaluate the aging response of EPDM elastomer O-ring seals. The thermal and radiation exposure conditions of the CASTOR® V/21 casks were selected for testing as this cask design is of interest due to its widespread use, and close proximity of the seals to the fuel compared to other cask designs leading to a relatively high temperature and dose under storage conditions. A novel test fixture was developed to enable compression stress relaxation measurements for the seal material at the thermal and radiation exposure conditions. A loss of compression stress of 90% is suggested as the threshold at which sealing ability of an elastomeric seal would be lost. Previous studies have shown this value to be conservative to actual leakage failure for most aging conditions. These initial results indicate that the seal would be expected to retain sealing ability throughout extended storage at the cask design conditions, though longer exposure times are needed to validate this assumption. The high constant dose rate used in the testing is not prototypic of the decreasingly low dose rate that would occur under extended storage. The primary degradation mechanism of oxidation of polymeric compounds is highly dependent on temperature and time of exposure, and with radiation expected to exacerbate the oxidation.

Verst, C.; Skidmore, E.; Daugherty, W.

2014-05-30

166

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)

167

Flexible Connection Elastomeric Rubber as a Pounding Resisting Element between Two Adjacent Building  

Directory of Open Access Journals (Sweden)

Full Text Available Flexible Connection Elastomeric Rubber as a Pounding Resisting Element between Two Adjacent Buildings To solve pounding problem of two adjacent buildings, structural designer usually employs a dilatation between the structures or make the two structures as a monolith structure. Other alternative is by using an elastomeric rubber as a pounding resisting element between the two structures. Effectiveness in applying elastomeric rubber component as flexible connection of two adjacent structures is the main focus of this paper. Various simulations such as structure models, earthquake excitations and openings in gap element are studied. Observation of maximum structural responses will be performed for structure model with elastomeric rubber in comparison with (1 monolith structure model and (2 structure model with rigid element (steel element. Simulation results show that application of elastomeric rubbercomponent to prevent structures from pounding problem provides advantages especially in reducing internal forces in the shorter building. However, it slightly increases displacement of both structures.

James Jatmiko Oetomo

2011-11-01

168

Buckling dynamics of a solvent-stimulated stretched elastomeric sheet  

Science.gov (United States)

When stretched uniaxially, a thin elastic sheet may exhibit buckling. The occurrence of buckling depends on the geometrical properties of the sheet and the magnitude of the applied strain. Here we show that an elastomeric sheet initially stable under uniaxial stretching can destabilize when exposed to a solvent that swells the elastomer. We demonstrate experimentally and computationally that the features of the buckling pattern depend on the magnitude of stretching, and this observation offers a new way for controlling the shape of a swollen homogeneous thin sheet.

Lucantonio, Alessandro; Roché, Matthieu; Nardinocchi, Paola; Stone, Howard A.

169

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

170

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

171

GASKET-2, Thermal Neutron Scattering Law for Moderators, Harmonic Vibrations and Gaseous  

International Nuclear Information System (INIS)

1 - Description of problem or function: GASKET calculates the thermal neutron scattering law, s(alpha,beta), for a large class of moderators. Provision has been made in GASKET for the following dynamical modes of the scatterer - (1) free translation (gas), (2) diffusive or Brownian motion, (3) harmonic isotropic vibrations with continuous frequency spectrum, (4) harmonic anisotropic vibrations with continuous frequency spectrum (as applied for instance to graphite), (5) harmonic isotropic vibrations with discrete frequency spectrum. 2 - Method of solution: Neutron scattering kernels are obtained from the scattering law using the relation sigma(e0 to e,?) = (?b/4?)*?(e/e0)*exp(-?/2)* where e0 and e are, respectively, initial and final neutron energies, theta is the cosine of the neutron scattering angle in the laboratory, and alpha and beta respectively, dimensionless momentum and energy transfers. GASKET calculates s at points of a 2-dimensional alpha,beta mesh. Numerical methods are used to evaluate Fourier transforms of s. For very large values of alpha and beta an option is included to use Wick's short collision approximation for s. 3 - Restrictions on the complexity of the problem: Maxima of - 100 points in distributed frequency spectrum; 100 points in anisotropic part of the frequency spectrum; 2 discrete oscillators if w sub 1 does not equal zero, otherwise 20; 20 phonon terms calculated for each delta line

172

Cavitation in elastomeric solids: I—A defect-growth theory  

Science.gov (United States)

It is by now well established that loading conditions with sufficiently large triaxialities can induce the sudden appearance of internal cavities within elastomeric (and other soft) solids. The occurrence of such instabilities, commonly referred to as cavitation, can be attributed to the growth of pre-existing defects into finite sizes. This paper introduces a new theory to study the phenomenon of cavitation in soft solids that: (i) allows to consider general 3D loading conditions with arbitrary triaxiality, (ii) applies to large (including compressible and anisotropic) classes of nonlinear elastic solids, and (iii) incorporates direct information on the initial shape, spatial distribution, and mechanical properties of the underlying defects at which cavitation can initiate. The basic idea is to first cast cavitation in elastomeric solids as a homogenization problem of nonlinear elastic materials containing random distributions of zero-volume cavities, or defects. This problem is then addressed by means of a novel iterated homogenization procedure, which allows to construct solutions for a specific, yet fairly general, class of defects. These include solutions for the change in size of the defects as a function of the applied loading conditions, from which the onset of cavitation — corresponding to the event when the initially infinitesimal defects suddenly grown into finite sizes — can be readily determined. In spite of the generality of the proposed approach, the relevant calculations amount to solving tractable Hamilton-Jacobi equations, in which the initial size of the defects plays the role of "time" and the applied load plays the role of "space". When specialized to the case of hydrostatic loading conditions, isotropic solids, and defects that are vacuous and isotropically distributed, the proposed theory recovers the classical result of Ball (1982) for radially symmetric cavitation. The nature and implications of this remarkable connection are discussed in detail.

Lopez-Pamies, Oscar; Idiart, Martín I.; Nakamura, Toshio

2011-08-01

173

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)

174

Strain-induced phase transformation under compression in a diamond anvil cell: Simulations of a sample and gasket  

Science.gov (United States)

Combined high pressure phase transformations (PTs) and plastic flow in a sample within a gasket compressed in diamond anvil cell (DAC) are studied for the first time using finite element method. The key point is that phase transformations are modelled as strain-induced, which involves a completely different kinetic description than for traditional pressure-induced PTs. The model takes into account, contact sliding with Coulomb and plastic friction at the boundaries between the sample, gasket, and anvil. A comprehensive computational study of the effects of the kinetic parameter, ratio of the yield strengths of high and low-pressure phases and the gasket, sample radius, and initial thickness on the PTs and plastic flow is performed. A new sliding mechanism at the contact line between the sample, gasket, and anvil called extrusion-based pseudoslip is revealed, which plays an important part in producing high pressure. Strain-controlled kinetics explains why experimentally determined phase transformation pressure and kinetics (concentration of high pressure phase vs. pressure) differ for different geometries and properties of the gasket and the sample: they provide different plastic strain, which was not measured. Utilization of the gasket changes radial plastic flow toward the center of a sample, which leads to high quasi-homogeneous pressure for some geometries. For transformation to a stronger high pressure phase, plastic strain and concentration of a high-pressure phase are also quasi-homogeneous. This allowed us to suggest a method of determining strain-controlled kinetics from experimentation, which is not possible for weaker and equal-strength high-pressure phases and cases without a gasket. Some experimental phenomena are reproduced and interpreted. Developed methods and obtained results represent essential progress toward the understanding of PTs under compression in the DAC. This will allow one optimal design of experiments and conditions for synthesis of new high pressure phases.

Feng, Biao; Levitas, Valery I.; Ma, Yanzhang

2014-04-01

175

From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials.  

Science.gov (United States)

In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters adjusted to match the macro-level mechanical test data. Fiber model validation was performed at the microscopic level by individual fiber mechanical tests using AFM. Results demonstrated very good agreement to the experimental data, and revealed the formation of extended preferential fiber orientations spanning the entire model space. We speculate that these emergent structures may be responsible for the tissue-like macroscale behaviors observed in electrospun scaffolds. To conclude, the modeling approach has implications for (1) gaining insight on the intricate relationship between fabrication variables, structure, and mechanics to manufacture more functional devices/materials, (2) elucidating the effects of cell or particulate inclusions on global construct mechanics, and (3) fabricating better performing tissue surrogates that could recapitulate native tissue mechanics. PMID:25128869

D'Amore, Antonio; Amoroso, Nicholas; Gottardi, Riccardo; Hobson, Christopher; Carruthers, Christopher; Watkins, Simon; Wagner, William R; Sacks, Michael S

2014-11-01

176

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

177

Microsphere-assisted fabrication of high aspect-ratio elastomeric micropillars and waveguides  

Science.gov (United States)

High aspect-ratio micropillars are in strong demand for microtechnology, but their realization remains a difficult challenge, especially when attempted with soft materials. Here we present a direct drawing-based technique for fabricating micropillars with poly(dimethylsiloxane). Despite the material’s extreme softness, our technique enables routine realization of micropillars exceeding 2,000??m in height and 100 in aspect-ratio. It also supports in situ integration of microspheres at the tips of the micropillars. As a validation of the new structure’s utility, we configure it into airflow sensors, in which the micropillars and microspheres function as flexible upright waveguides and self-aligned reflectors, respectively. High-level bending of the micropillar under an airflow and its optical read-out enables mm?s-1 scale-sensing resolution. This new scheme, which uniquely integrates high aspect-ratio elastomeric micropillars and microspheres self-aligned to them, could widen the scope of soft material-based microdevice technology.

Paek, Jungwook; Kim, Jaeyoun

2014-02-01

178

Composite bimetallic gasket and compact mechanical anvil retainer for magnetic measurements in a diamond-anvil cell to 30 GPa  

Science.gov (United States)

A composite gasket was designed for diamond-anvil cells where the load was supported mainly by the inner part made of NiCrAl with a diameter slightly larger than the culet of the anvil. A BeCu girdle encased the NiCrAl washer and prevented it from fracturing. The thickness of the gasket was about 30?m at a pressure of 30GPa applied with a pair of diamond anvils having 500 and 550?m culets. The magnetic contribution of the composite gasket to the background signal was almost the same as that of a BeCu gasket having the same size. The diamond anvils were fixed to the pistons with four miniature screws through small BeCu rings that were press fitted to the circumference of the diamond anvils. The performance of this composite gasket together with the anvil retainer was illustrated by the measurements of the temperature dependence of the dc magnetic susceptibility of Cs2CuF4 under various pressures up to 26GPa using a superconducting quantum interference device vibrating coil magnetometer.

Ishizuka, Mamoru

2005-12-01

179

Shape-Memory Polymers Based on Fatty Acid-Filled Elastomeric Ionomers  

Science.gov (United States)

Shape memory polymers (SMPs) have applications as medical devices, actuators, sensors, artificial muscles, switches, smart textiles, and self-deployable structures. All previous design of SMPs has involved synthesizing new polymers or modifying existing polymers. This paper describes a new type of SMP based on blends of an elastomeric ionomer and low molar mass fatty acids or their salts (FAS). Shape memory elastomers were prepared from mixtures of a sulfonated EPDM ionomer and various amounts of a FAS (e.g., zinc stearate, zinc oleate, and various aliphalic acids). Nanophase separation of the metal sulfonate groups provided the ``permanent'' crosslinks, while sub-microscopic crystals of the low molecular weight FAS provided a physical crosslink needed for the temporary shape. The material was deformed above the melting point of the FAS and the new shape was fixed by cooling the material while under stress to below the melting point of the FAS. Polar interactions between the ionomer and the FAS stabilized the dispersion of the FAS in the polymer and provided the continuity between the phases that allowed the crystals of the FAS to provide a second network of physical crosslinks. The temporary shape was erased and the material returned to the primary shape by heating above the melting point of the FAS.

Izzo, Elise; Weiss, Robert

2009-03-01

180

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 | Language: 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.

 
 
 
 
181

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

182

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

183

Tests on a 1,75 m O.D. bolted flange assembly with spiral-wound gaskets  

International Nuclear Information System (INIS)

Paper reports on a test program involving leakage behaviour of a double gasketed 1.75 m (O.D.) bolted flange assembly subjected to hydrostatic pressure at room temperature. Fabrication of a heat exchanger for a CANDU-NPP was temporarily stopped so that the channel-cover-tubesheet assembly could be used for the tests. Special instrumentation was developed to measure bolt stress, inner and outer flange displacements, flange to tubesheet metal contact stress and intergasket leakage. The results of two of several flange-face configurations tested are reported. Main conclusions follow: - Very high gasket seating stresses are necessary for adequate sealing. - Flange movement alters contact pressure on inner and outer gaskets. Simple flange face modifications adequatly compensates for this and provides leak-tight joint. (orig.)

184

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

185

A NOVEL DESIGN OF MULTIBAND SQUARE PATCH ANTENNA EMBEDED WITH GASKET FRACTAL SLOT FOR WLAN & WIMAX COMMUNICATION  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A compact multiband patch antenna embedded with gasket fractal slots is proposed in this paper. The structure consists of square patch element with modified gasket slots on both radiating edge side. The antenna is fed by 50? co-planar waveguide (CPW) to make the structure purely planar. The investigation took place ranges between 1-7.5 GHz using CST MWS electromagnetic simulator. There are 3 resonant frequencies appeared at 2.45GHz, 3.6GHz & 5.6 GHz. From the return loss plot it is seen the ...

Panda, Asit K.; Panda, Amit K.

2012-01-01

186

Elastomeric Angled Microflaps with Reversible Adhesion for Transfer-Printing Semiconductor Membranes onto Dry Surfaces.  

Science.gov (United States)

Recent research for unconventional types of electronics has revealed that it is necessary to transfer-print high-performance microelectronic devices onto diverse surfaces, including flexible or stretchable surfaces, to relieve mechanical constraints associated with conventional rigid electronics. Picking up and placing ultrathin microdevices without damage are critical procedures for the successful manufacture of various types of unconventional electronics. This paper introduces elastomeric angled microflaps that have reversible adhesion; i.e., they generate higher adhesion for picking up and low adhesion for printing because of their structural shapes and viscoelastic material properties. The microstructured stamp, fabricated in relatively simple ways, enables simultaneous transfer-printing of multiple silicon membranes that have irregular shapes in sizes ranging from micrometer to millimeter scales. Mechanical characterizations by experiment reveal optimal parameters for picking up and placing ultrathin membranes on a programmable custom-built microstage. Further refinement of the structures and materials should be useful for many applications requiring the microassembly of multiple semiconductor membranes in diverse shapes and sizes on dry surfaces without the aid of liquid adhesives. PMID:25330816

Yoo, Byungsuk; Cho, Sungbum; Seo, Seungwan; Lee, Jongho

2014-11-12

187

Cryo Atomic Force Microscopy: A New Way to Investigate Elastomeric Samples  

International Nuclear Information System (INIS)

Full text: The sectioning of samples at low temperatures down to -190oC is known as cryoultramicrotomy. Combined with an atomic force microscope (AFM) operating at the same temperature this is a new method that offers great possibilities to investigate soft materials, e.g. polymers. We are encouraged to share the results of AFM measurements, done at room temperature and under cryo conditions, to point out new opportunities in material characterization. One crucial influence on the quality of measurements is sample preparation by ultramicrotomy. Since we use elastomers, ultramicrotomy has to be operated under cryo conditions due to the fact that soft polymers usually have a glass transition temperature significantly below 00C and most elastomers and their composites can only be sectioned at temperatures 10 to 20 degrees lower than their glass transition temperature. By comparing block faces after sectioning, done at room temperature and under cryo conditions it is easy to see how the quality of the surfaces and therefore the AFM image quality is improved. Preparation of a sample with the ultramicrotome and measuring the bulk surface right after, both under cryo conditions, lead to new observations. Measuring at room temperature would imply heating up of the sample and therefore changes in the internal structure. It is now the first time that we are able to observe polymers in the cryo state and prevent the samples from changes between sectioning and measuring. We would like to discuss these results by looking at experiments done using different elastomeric polymer blends. (author)

188

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

189

Fabrication and characterization of heparin-grafted poly-L-lactic acid-chitosan core-shell nanofibers scaffold for vascular gasket.  

Science.gov (United States)

Electrospun nanofibers were widely studied to be applied as potential materials for tissue engineering. A new technology to make poly-l-lactic acid/chitosan core/shell nanofibers from heterologous solution by coaxial electrospinning technique was designed for vascular gasket. Chitosan surface was cross-linked by genipin and modified by heparin. Different ratios of PLA/CS in heterologous solution were studied to optimize the surface morphology of fibers. Clean core-shell structures formed with a PLA/CS ratio at 1:3. Superior biocompatibility and mechanical properties were obtained by optimizing the core-shell structure morphology and surface cross-linking of chitosan. UE7T-13 cells grew well on the core-shell structure fibers as indicated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) results and scanning electron microscopy (SEM) images. Compared with the pure PLA fiber meshes and commercial vascular patch, PLA/CS core-shell fibers had better mechanical strength. The elastic modulus was as high as 117.18 MPa, even though the yield stress of the fibers was lower than that of the commercial vascular patch. Attachment of red blood cell on the fibers was evaluated by blood anticoagulation experiments and in vitro blood flow experiments. The activated partial thromboplastin time (APTT) and prothrombin time (PT) value from PLA/CS nanofibers were significantly longer than that of pure PLA fibers. SEM images indicated there were hardly any red blood cells attached to the fibers with chitosan coating and heparin modification. This type of fiber mesh could potentially be used as vascular gasket. PMID:23586670

Wang, Ting; Ji, Xuyuan; Jin, Lin; Feng, Zhangqi; Wu, Jinghang; Zheng, Jie; Wang, Hongyin; Xu, Zhe-Wu; Guo, Lingling; He, Nongyue

2013-05-01

190

24 CFR Appendix A to Part 200 - Standards Incorporated by Reference in the Minimum Property Standards for Housing (HUD Handbook...  

Science.gov (United States)

...Standard Specification for Elastomeric Cellular Preformed Gasket...Standard Specification for Dense Elastomeric Compression Seal Gaskets...Fundamentals—1989. ASHRAE Cooling and Heating Load Calculation Manual...Association of Plumbing-Heating-Cooling Contractors, P.O. Box...

2010-04-01

191

Measurement of liquid compressibility in a gasketed diamond anvil cell by a modified piston-displacement method  

International Nuclear Information System (INIS)

The compressibility of liquids was measured in a gasketed diamond anvil cell using a modified piston displacement method. A pair of metal markers was fixed on the diamonds. The gasket thickness at different pressures was measured by monitoring the distance change between the markers using a micrometer microscope. The area of the gasket hole was measured by means of microphotography. Then the product of the average area and thickness of the gasket hole determined the sample volume. Using this method the compressibility of a 4:1 v/v methanol-ethanol liquid mixture at hydrostatic pressures up to 8 GPa was obtained and it was found that the liquid volume at 8 GPa decreases to 51.5% of the initial volume. By the least-squares method, the experimental data were fitted to the Tait equation and obtained values of C=0.4055, B=0.5436 GPa. The relative error is estimated to be about 1.7%. This simple and convenient method could significantly extend the pressure range of liquid compressibility measurements

192

Comparison of canine retraction by in vivo method using four brands of elastomeric power chain  

Science.gov (United States)

Objective: To investigate the amount of space closure by movement of canines into the extraction spaces using four brands of elastomeric power chains (EPCs) by intraoral application with pre-adjusted appliance for 6 weeks. Materials and Methods: The sample size calculation was based on the studies of Boester and Johnston and also with repeated measures analysis of variance (ANOVA) continuous data for force degradation, standard deviation of 24.9 g, and also from a pilot study, which totaled to around 17 patients with a mean age of 20 ± 2 years and receiving fixed orthodontic treatment that required retraction of canines into the premolar extraction spaces in all four dental arch quadrants. Four brands of EPCs, namely the Ormco, 3M Unitek, Rocky Mountain, and Highland, which were closed-link with five loops delivering less than or equal to 250 g were used. The rates of canine retraction were measured between the attachment points on the canine bracket hook and first molar hook using a Mitutoyo Digital Vernier Caliper at the time of first application, after 3 weeks of use, and at the end of 6 weeks of use, and were subjected to statistical calculations. Results: The distances recorded from canine retraction were similar with slight differences noticed in the four brands of EPCs. However, no statistically significant difference was observed in relation to the EPCs. Conclusion: Although all brands of the EPCs produced space closure of canines, it was observed that not much of a significant difference existed among the products tested.

Kanuru, Ravi Krishna; Azaneen, Mustafa; Narayana, Veera; Kolasani, Balaram; Indukuri, Ravikishore Reddy; Babu, P Firoz

2014-01-01

193

High-performance supercapacitors, actuators and elastomeric composites based on CNT assemblies  

Science.gov (United States)

A number of materials ranging from carbon nanotube (CNT) yarns, sheets and CNT-based composites to shape memory alloys (SMA) have been explored for the application in the area of energy conversion and storage. Highly porous sheets comprised of Single Walled Carbon Nanotubes and doped polypyrrole (SWNT-PPy) were found to possess remarkably high specific capacitance of about 131 F/g; CNT-elastomeric polymer composites exhibited electrical conductivity of about 0.5 S/cm and can be stretched by 1400%. We found that if powered electrically, the isometric stress generated by the CNT-based actuators could be as large as 12 MPa. This approaches the stress generation capability of commercial ferroelectrics and is significantly larger than that of natural muscles. We also report several types of artificial muscles that convert the chemical energy of high--energy-density fuels to mechanical energy. Because of more than 30 times higher energy density obtainable for fuels like methanol, compared to that for the most advanced batteries, the major expected benefits are dramatic increase in energy conversion efficiency, work capacity, power performance.

Kozlov, Mikhail; Oh, Jiyoung; Shin, Minkyoon; Robles, Raquel; Lima, M. Árcio; Baughman, Ray

2009-03-01

194

Effects of spontaneous surface buckling on the diffraction performance of an Au-coated elastomeric grating  

Science.gov (United States)

Stretchable silicone gratings show promise as dynamic beam scanners but are usually limited to transmission applications because of the low reflectivity of the material. We modify an elastomeric replicated grating for use in reflection geometries by adding a 100 nm surface layer of Au. Diffraction efficiency in the sample increases by a factor of 50. Scanning of the first-order diffraction is performed by stretching the grating in one direction, with ? ? = 2.34° for normal incidence at a maximum applied strain of 7.6%. Distortion of the deflected beam is minimal. Buckles on the Au surface perpendicular to the grating grooves spontaneously appear in response to compressive stress resulting from elongation. Diffraction efficiency decreases with increasing strain. This is attributed to reflectivity loss and secondary diffraction from the buckling structures. The initial efficiency and its variation with strain are dependent on the specific area of the grating being used. We are able to describe the observed behavior of efficiency vs. strain in terms of an inverse relationship between efficiency and compressive stress.

Guerrero, Raphael A.; Barretto, Jerry T.; Uy, Jerwin L. V.; Culaba, Ivan B.; Chan, Benjamin O.

2007-02-01

195

Microfluidic molding of photonic microparticles with engraved elastomeric membranes.  

Science.gov (United States)

A microfluidic approach to prepare photonic microparticles by repeated molding of photocurable colloidal suspension is reported. An elastomeric membrane with negative relieves which vertically separates two microfluidic channels is integrated; bottom channel is used for suspension flow, whereas water-filled top channel is used for pneumatic actuation of the membrane. Upon pressurization of the top channel, membrane is deformed to confine the suspension into its negative relieves, which is then polymerized by UV irradiation, making microparticles with mold shape. The microparticles are released from the mold by relieving the pneumatic pressure and flows through the bottom channel. This one cycle of molding, polymerization, and release can be repeatedly performed in microfluidic device of which pneumatic valves are actuated in a programmed manner. The microparticles exhibit structural colors when the suspension contains high concentration of silica nanoparticles; the nanoparticles form regular arrays and the microparticles reflect specific wavelength of light as a photonic crystals. The silica nanoparticles can be selectively removed to make pronounced structural colors. In addition, the microparticles can be further functionalized by embedding magnetic particles in the matrix of the microparticles, enabling the remote control of rotational motion of microparticles. PMID:24947445

Sim, Jae Young; Choi, Jae-Hoon; Lim, Jong-Min; Cho, Soojeong; Kim, Shin-Hyun; Yang, Seung-Man

2014-10-15

196

Identification of dynamic stiffness matrices of elastomeric joints using direct and inverse methods  

Science.gov (United States)

New experiments are designed to permit direct comparison between direct and inverse identification methods of the dynamic stiffness matrices of elastomeric joints, including non-diagonal terms. The joints are constructed with combinations of inclined elastomeric cylinders to control non-diagonal terms in the stiffness matrix. The inverse experiment consists of an elastic metal beam end-supported by elastomeric joints coupling the in-plane transverse and longitudinal beam motion. A prior method is extended to identify the joint dynamic stiffness matrices of dimension 3 from limited modal measurements of the beam. The dynamic stiffness and loss factors of the elastomeric cylinders are directly measured in a commercial elastomer test machine in shear, compression, and inclined configurations and a coordinate transformation is used to estimate the kinematic non-diagonal stiffness terms. Agreement is found for both dynamic stiffness and loss factors between the direct and inverse methods at small displacements. Further, the identified joint properties are employed in a model that successfully predicts the modal parameters and accelerance spectra of the inverse experiment. This article provides valuable insight on the difficulties encountered when comparing system and elastomeric component test results.

Noll, Scott; Dreyer, Jason T.; Singh, Rajendra

2013-08-01

197

Nanosecond response ''gasket-type'' magnetic loop current monitor for relativistic electron beam current measurements.  

Science.gov (United States)

A fast response magnetic loop current monitor has been developed to measure relativistic electron beam return currents. The monitor has a rise time of about a nanosecond and a high degree of symmetry with moderate sensitivity, variable from about 1 to 10 V/kA. This simple monitor, with a thickness of 0.254 mm or less, is thin enough to be placed between segments of return current path in the diode or drift tube regions, is insensitive to flashover, beam and plasma bombardment, and radiation effects, and measures net current, thus offering some advantages over conventional magnetic probes, since the main components are outside of the vacuum region. Design criteria, an equivalent circuit analysis, and typical calibration waveforms are presented. Experimental current measurements for a pinched electron beam diode configuration using both conventional magnetic probes and ''gasket-type''current monitors with the FX-75 relativistic electron beam accelerator are presented. PMID:18699476

Copeland, R L; Adamski, J L; Doggett, W O; Morrow, D L; Bennett, W H

1979-02-01

198

Structural evaluation of Marman V-band coupling and flange with conoseal gasket  

Science.gov (United States)

Results are described of a development test program directed at evaluating the structural capabilities of the Marman V-band coupling and flange with conoseal gasket. The intended end use was for the 75K NERVA flight engine propellant lines. Of major importance in the structural evaluation was the ability to predict stresses throughout the assembly for a variety of loading conditions. Computer finite element analysis was used to predict these stresses but, for the subject configuration, large uncertainties were introduced in modeling the complex geometry and boundary conditions. The purpose of the structural tests was to obtain actual stresses and deflections for correlation with, and updating of the finite element model. Results of the incomplete test program are inconclusive with respect to determining suitability for use on the NERVA engine.

Oates, J. H.

1972-01-01

199

Nanosecond response ''gasket-type'' magnetic loop current monitor for relativistic electron beam current measurements  

International Nuclear Information System (INIS)

A fast response magnetic loop current monitor has been developed to measure relativistic electron beam return currents. The monitor has a rise time of about a nanosecond and a high degree of symmetry with moderate sensitivity, variable from about 1 to 10 V/kA. This simple monitor, with a thickness of 0.254 mm or less, is thin enough to be placed between segments of return current path in the diode or drift tube regions, is insensitive to flashover, beam and plasma bombardment, and radiation effects, and measures net current, thus offering some advantages over conventional magnetic probes, since the main components are outside of the vacuum region. Design criteria, an equivalent circuit analysis, and typical calibration waveforms are presented. Experimental current measurements for a pinched electron beam diode configuration using both conventional magnetic probes and ''gasket-type''current monitors with the FX-75 relativistic electron beam accelerator are presented

200

Modified Sierpinski Gasket Patch Antenna for UMTS and 2.4/5.2 WLAN  

Directory of Open Access Journals (Sweden)

Full Text Available A modified Sierpinski Gasket fractal antenna for multiband application is proposed in this paper. The modified ground plane and the microstrip feed are used to obtain the wider bandwidth at the resonance frequency. The antenna is designed and printed on two layers FR-4 substrate (?r=4.4 and h=1.6 mm to cover the UMTS and 2.4/5.2 WLAN. The radiation pattern of the proposed antenna is similar to an omnidirectional. The proposed antenna has maximum gain of 1.88, 1.6, 4.31 dB at 2, 2.4, 5.2 GHz, respectively The properties of the antenna such as return losses, radiation pattern, input resistance and gain are determined via numerical CST Microwave Studio 2010 software.

Y. E. Ali

2013-05-01

 
 
 
 
201

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

202

Paper-supported elastomeric opal films for enhanced and reversible solvatochromic response  

Science.gov (United States)

Paper-supported solvent-responsive elastomeric opal films based on hard-soft core-interlayer-shell spheres featuring remarkably distinct iridescent reflection colors were investigated. By using extrusion and compression molding, elastomeric opal films could be obtained, which were incorporated into a porous paper sheet to build robust composites. Swelling of the opal paper composites caused by various solvents was accompanied with a tremendous photonic band gap shift of the reflection colors. The combination of the extraordinary optical properties of the elastomeric opal films used with the remarkable features of highly porous paper can be the basis for a whole family of polymer-based soft sensors featuring a fascinating optical, fast and reversible response.

Schäfer, Christian G.; Biesalski, Markus; Hellmann, Goetz P.; Rehahn, Matthias; Gallei, Markus

2013-01-01

203

Thermally tailored gradient topography surface on elastomeric thin films.  

Science.gov (United States)

We report a simple method for creating a nanopatterned surface with continuous variation in feature height on an elastomeric thin film. The technique is based on imprinting the surface of a film of thermo-curable elastomer (Sylgard 184), which has continuous variation in cross-linking density introduced by means of differential heating. This results in variation of viscoelasticity across the length of the surface and the film exhibits differential partial relaxation after imprinting with a flexible stamp and subjecting it to an externally applied stress for a transient duration. An intrinsic perfect negative replica of the stamp pattern is initially created over the entire film surface as long as the external force remains active. After the external force is withdrawn, there is partial relaxation of the applied stresses, which is manifested as reduction in amplitude of the imprinted features. Due to the spatial viscoelasticity gradient, the extent of stress relaxation induced feature height reduction varies across the length of the film (L), resulting in a surface with a gradient topography with progressively varying feature heights (hF). The steepness of the gradient can be controlled by varying the temperature gradient as well as the duration of precuring of the film prior to imprinting. The method has also been utilized for fabricating wettability gradient surfaces using a high aspect ratio biomimetic stamp. The use of a flexible stamp allows the technique to be extended for creating a gradient topography on nonplanar surfaces as well. We also show that the gradient surfaces with regular structures can be used in combinatorial studies related to pattern directed dewetting. PMID:24697617

Roy, Sudeshna; Bhandaru, Nandini; Das, Ritopa; Harikrishnan, G; Mukherjee, Rabibrata

2014-05-14

204

Locally auxetic behavior of elastomeric polypropylene on the 100 nm length scale.  

Science.gov (United States)

We observe unexpected locally auxetic behavior in elastomeric polypropylene, a semicrystalline polymer with a natural microstructure and a low degree of crystallinity. Our series of scanning force microscopy images show the nanomechanical deformation processes that occur upon stretching a thin film of elastomeric polypropylene. Upon uniaxial stretching, the angle between epitaxially grown lamella branches remains constant and the lamellae elongate, resulting in locally auxetic behavior (negative Poisson's ratio) on the 100-nanometer scale. This mechanism causing auxetic behavior, which was previously proposed on the basis of geometric arguments, appears to be an intrinsic property of certain semicrystalline polymers. PMID:21495686

Franke, Mechthild; Magerle, Robert

2011-06-28

205

A NOVEL DESIGN OF MULTIBAND SQUARE PATCH ANTENNA EMBEDED WITH GASKET FRACTAL SLOT FOR WLAN & WIMAX COMMUNICATION  

Directory of Open Access Journals (Sweden)

Full Text Available A compact multiband patch antenna embedded with gasket fractal slots is proposed in this paper. The structure consists of square patch element with modified gasket slots on both radiating edge side. The antenna is fed by 50? co-planar waveguide (CPW to make the structure purely planar. The investigation took place ranges between 1-7.5 GHz using CST MWS electromagnetic simulator. There are 3 resonant frequencies appeared at 2.45GHz, 3.6GHz & 5.6 GHz. From the return loss plot it is seen the antenna achieved the IEEE Bluetooth / WLAN (2.4-2.484 GHz, WiMAX (3.4-3.69 GHz & WIFI (5.1-5.825 GHz frequency band with -10 dB return loss and also nearly omni-directional radiation patterns achieved. The peak realized antenna gain is around 5dB in all distinct bands.

Asit K. Panda

2012-03-01

206

Compositional GC-FID analysis of the additives to PVC, focusing on the gaskets of lids for glass jars.  

Science.gov (United States)

A gas chromatographic (FID) method is described which aims at the quantitative compositional analysis of the additives in plasticized PVC, particularly the plastisols used as gaskets for lids of glass jars. An extract of the PVC is analysed directly as well as after transesterification to ethyl esters. Transesterification enables the analysis of epoxidized soya bean and linseed oil (ESBO and ELO) as well as polyadipates. For most other additives, the shifts in the chromatogram resulting from transesterification is used to confirm the identifications made by direct analysis. In the gaskets of 69 lids from the European market used for packaging oily foods, a broad variety of plastisol compositions was found, many or possibly all of which do not comply with legal requirements. In 62% of these lids, ESBO was the principal plasticizer, whereas in 25% a phthalate had been used. PMID:16356892

Biedermann-Brem, Sandra; Biedermann, Maurus; Fiselier, Katell; Grob, Koni

2005-12-01

207

Experimental and numerical study of damage initiation mechanism in elastomeric composites  

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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

208

Encyclopedia of polymer science and engineering, Vol. 11: Photographic applications to polyesters, elastomeric  

Energy Technology Data Exchange (ETDEWEB)

The contents of this book are: Photographic Applications; Photocrosslinking; Phthaloccyanine Polymers; Pipe; Plant Design; Plasma Polymerizaton; Plastic; Plasticizers; Plastics; Identification; Plastics, Processing; Polyacetals; Poly(alkylidene sulfides); Polyalkylidenes; Polyamides; Polyamides, Aromatic; Polyamides, Fibers; Polyamides, Plastics; Polyamides from Fatty Acids; Polyamides; Polyaminotriazoles; Polyampholtyes; Polyanhydrides; Poly(arylene sulfides); Polybenzimidazoles; Polybenzothiazoles; Polybenzoxazinones; Polybithiazoles; Polycarbonates; Polyelectrolytes; Polyesters, Polyesters, Aromatic; Polyesters, Containers; and Polyesters, Elastomeric.

Mark, H.F.; Bikales, N.; Overberger, C.G.; Menges, G.

1987-01-01

209

Migration of epoxidized soya bean oil from plasticized PVC gaskets into baby food.  

Science.gov (United States)

Expoxidized soya bean oil (ESBO) is used as a plasticizer in PVC gaskets in lids for glass jars used for packaging of ready-cooked baby food. The migration of ESBO from the lids has been determined in 81 samples of different dishes of baby food, including purées of beef, pork, fish, poultry, berries and vegetables. The level of ESBO in baby food has been determined using a gas chromatography/mass spectrometry (GC/MS) analytical procedure with a detection limit of 1.5 mg/kg. Residues of ESBO were found in all dishes except in blueberries. The levels ranged from < 1.5 to 50.8 mg/kg, with a mean of 11.9 mg/kg and a median of 7.8 mg/kg in food with detectable levels. Expoxidized fatty acids may also occur naturally in food. Baby food which had never been in contact with the lids was therefore analysed and no detectable levels of diepoxidized C18-methylester, which was used for the determination of ESBO, were found. That demonstrates that the presented levels of ESBO in the baby food are only due to migration from the lids and not of natural origin. PMID:9602927

Hammarling, L; Gustavsson, H; Svensson, K; Karlsson, S; Oskarsson, A

1998-01-01

210

Study of the hydro-mechanical behaviour of expanded graphite gaskets  

International Nuclear Information System (INIS)

The poro-mechanical behaviour models developed by O. Coussy permit to consider various phenomena observed experimentally: thermo-hydro-mechanical couplings, plasticity, etc. The aim of this study is to implement the simplest poro-mechanical model (i.e. the isotropic linear poro-elastic model) to model the gasket hydro-mechanical behaviour. First, isotropic poro-elastic characteristics of expanded graphite have been estimated from these tests conducted at Departement Mecanique et Technologie des Composants (MTC) and data from literature. Then, analytical solutions of the tightness tests developed at the MTC Department have been carried out. These calculations provide a first estimation of porosity variations during a tightness tests with metal/metal contact or in elastic recovery, and during a 'hot thermal transient'. Thickness controlled numerical calculations have proved the analytical calculations relevance. With regard to simulation of tests with metal/metal contact or 'hot thermal transient', stress controlled numerical calculations have pointed out: - a greater vertical displacement on the inner side of the graphite ring and - a z dependence of the radial displacement and thus a porous differential variation between the upper and lower faces of the ring. (author)

211

Molecular Genetic Approaches to Biomolecular Materials.  

Science.gov (United States)

We are using protein engineering to produce biomolecular materials that mimic or extend the properties of materials found in nature. Our current focus is on bacterial S layers and the elastomeric protein abductin. For the most part, these studies are in a...

H. Bayley

2000-01-01

212

Potts model on infinitely ramified Sierpinski-gasket-type fractals and algebraic order at antiferromagnetic phases  

Science.gov (United States)

We propose families of infinitely ramified fractals, which we call the m-sheet Sierpinski gasket with side b [(mSG)b], on which the q-state Potts model can be exactly solvable through a real-space renormalization-group (RSRG) technique for which there are phase transitions at finite temperatures for m>1. We also propose, within a cell-to-cell RSRG scheme, a criterion for a suitable choice of cells in the study of antiferromagnetic (AF) classical spin models defined on (or approximated by) multirooted hierarchical lattices, and apply it for the AF Potts model on some (mSG)b fractals. Concerning the Ising model on the (mSG)2 family, we obtain the exact para (P)-ferromagnetic (F) critical temperature as a function of m and verify that, for m=1 and 2, there is no AF order (not even at zero temperature). We calculated the exact P-F and possibly exact P-AF critical frontiers and the corresponding correlation-length critical exponents for q=2-, 3-, and 4-state Potts model on the (mSG)4. The AF q=2 and 4 cases have highly degenerate ground states and each one presents, above a certain critical fractal dimension Dcf(q,m), an unusual low-temperature phase whose attractor occurs at a non-null temperature. For q=2 and Df(2,m)>=5.1, we prove that the correlations have a power-law decay with distance along this entire phase.

de Menezes, Fortunato S.; de Magalhães, Aglaé C. N.

1992-11-01

213

A simple scanning spectrometer based on a stretchable elastomeric reflective grating  

International Nuclear Information System (INIS)

We report a scanning optical spectrometer based on the use of a stretchable elastomeric reflective grating. The grating is obtained by supersonic cluster beam implantation of silver nanoparticles on polydimethylsiloxane previously grooved by molding to create a replica of a commercial digital versatile disk grating. The use of a stretchable grating allows the spectrometer spanning the whole optical wavelength range by solely extending the diffraction element by more than 100% of its original dimensions. The stretchable reflective optical grating shows excellent performances and stability upon thousands of stretching cycles. The use of this elastomeric element makes the optical layout and the mechanics of the spectrometer extremely simple and advantageous for those applications where spectral resolution is not a major requirement. As a proof of principle, we present the absorption spectrum of Rhodamine B in solution obtained by our spectrometer and compared to commercial instruments

214

Stability of Nafcillin Sodium Solutions in the Accufuser® Elastomeric Infusion Device  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this study was to investigate the stabilities of two kinds of solutions of nafcillin sodium (2.5 mg/mL) in 0.9% sodium chloride solution (NS, normal saline) and in injectable 5% dextrose water (D5W) in the intravenous elastomeric infusion device (Accufuser®) based on recommended solutions and storage periods. The injectable nafcillin solutions (NS- and D5W-nafcillin) in the Accufuser® device we...

Min-A Kang; Ju-Seop Kang

2013-01-01

215

Pneumatically-driven elastomeric devices for a programmable lab on a chip and applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This dissertation presents two programmable lab-on-a-chip (PLoC) systems based on pneumatically-driven elastomeric devices for continuous-flow microfluidics and optoelectrowetting (OEW) for digital microfluidics, respectively. The successful development of the systems drastically reduces cost, simplifies fabrications, and provides a general-purpose platform for multi-biochemical assays. The novelties of this research are (i) a complete PDMS-based PLoC system integrating all microfluidic compo...

Chuang, Han-sheng

2010-01-01

216

Investigation of the recycling of tires to elastomeric requirements by techniques of thermal compression  

Science.gov (United States)

In this work is investigated the recycling of tires to elastomeric requirements by thermal compression. The production of recycled products is carried out starting from the powder, of elastomeric nature, coming from the grinding of used tires denominated GTR (Ground Tire Rubber) of different grain size, although the fundamental objective is the recycling of powder of 0,2mm grain size. The process of forming used for obtaining the recycled product is thermal compression, due to its simplicity and low cost. The composition of the powder has been analyzed and also the influence, on the elastomeric characteristics of the recycled product, of different parameters: Grain size, compact pressure, temperature, time, thickness of the recycled product and combination of sizes. At last we give an hypothesis that justifies the mechanism that gives cohesion to the powder GTR and allows their recycling. We also have carried out an analysis of the investigation lines, at the present, on the recycling of tires in general and an economic study of the viability of the recycled product in front of present products in the market, agglomerated with polyurethane, that have their application in using it in different types of floors.

Nadal Gisbert, Antonio V.

217

Elasto-Plastic FEM Stress Analysis and Mechanical Characteristics of Pipe Flange Connections with Non-Asbestos Gaskets under Internal Pressure  

Science.gov (United States)

The effects of the nominal diameter of pipe flange connections with non-asbestos spiral wound gaskets(SWG) under internal pressure on the mechanical characteristics such as the contact gasket stress distribution which governs the sealing performance, the load factor and the hub stress of the connections were evaluated. The stresses in the connections with the nominal diameters from 3” to 24” under internal pressure are analyzed using the elasto-plastic(EP) FEM analysis taking account the hysteresis and non-linearity of deformation behavior of the non-asbestos SWG. As a result, it is found that the variations in the contact gasket stress distributions are substantial due to the flange rotation in the connections with the larger nominal diameter. Leakage tests were conducted to measure the axial bolt forces (the load factor) and the hub stress. The results obtained from the EP-FEM analyses are fairly consistent with the experimental results concerning the variation in the axial bolt forces (the load factor) and the hub stress. Using the obtained contact gasket stress distributions and the fundamental relationship between the amount of leakage and the contact gasket stress, the amount of the leakage of the connections is estimated. It is observed that the sealing performance of the connections with larger nominal diameter is worse than that of the connection with smaller nominal diameter because of the flange rotation. The estimated results are in a fairly good agreement with the measured results. The difference in the hub stress between the EP-FEM and ASME code is demonstrated and the differences in the load factor and the sealing performance of the connections are shown between the asbestos and non-asbestos gaskets.

Takagi, Yoshio; Omiya, Yuya; Kobayashi, Takashi; Sawa, Toshiyuki

218

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 microm in diameter and approximately 50 microm 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 degrees 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 degrees 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 degrees 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 microm, a pressure of 76 MPa at 500 degrees C was maintained for 2 h with no change in the original fluid density. PMID:19045909

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

2008-11-01

219

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

220

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

 
 
 
 
221

Quantitative Evaluation of Dental Biofilm Accumulation in Elastomeric Ligatures in Relation to the Amount of Time Within the Oral Cavity  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: The aim of this study was to evaluate the amount of dental biofilm accumulation in the elastomeric ligatures of orthodontic patients, and compare the volume of biofilm on these ligatures after one, two, three and four weeks of use. Method: Twenty patients with permanent dentition were selected from the Clinic of Orthodontics of the UFJF. No specific instructions regarding oral hygiene were given to these patients. After prophilaxis, only the four second premolars of each patient in the sample received the same type of elastomeric ligatures. All ligatures were individually stored in a Petri plaque, prepared and numbered. Each plaque received one ligature and was weighed in an analytic scale up to two hours before its insertion into the oral cavity. The elastomeric ligatures were removed from the second premolars after one, two, three and four weeks respectively. The ANOVA and the Student's “t” test were applied (P< 0.05. Results: The results showed a weekly and progressive increase in weight of the elastomeric ligatures, being the second week the least relevant. It could be verified that the difference between the initial and final weights was statistically significant. Conclusion: The elastomeric ligatures can accumulate a considerable amount of dental biofilm which tends to increase with time.

Hélida Neiva CAMPOS

2006-04-01

222

Stiffness and damping of elastomeric O-ring bearing mounts  

Science.gov (United States)

A test rig to measure the dynamic stiffness and damping of elastomer O rings was described. Test results for stiffness and loss coefficient in the frequency range from 50 Hz to 1000 Hz are presented. Results are given for three different materials, for five temperatures, for three amplitudes, for five values of squeeze for three values of stretch for three values of cross-section diameter and for three values of groove width. All test data points were plotted. In addition, trend summary plots were presented which compare the effect of material, temperature, amplitude, squeeze, stretch, cross-section diameter, and groove width. O ring deflections under a static load for different material were presented; and effective static stiffness values were compared with dynamic values.

Smalley, A. J.

1977-01-01

223

Elastomeric impression as a diagnostic method of cavitation in proximal dentin caries in primary molars  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The purpose of this study was to validate the elastomeric impression after temporary tooth separation as a method of cavitation detection in proximal caries lesions in primary molars with outer half dentin radiolucency. Fifty-one children (4-10 years old), presenting radiolucency in the outer half o [...] f the dentin at the proximal surfaces of primary molars and proximal anatomic contact with the adjacent tooth (without restoration/cavitated caries lesion) were enrolled in the study. Temporary tooth separation was performed with an orthodontic rubber ring placed around the contact point during 2-3 days. Thereafter, impression of the proximal surfaces was made. The elastomeric impressions were classified as "non-cavitated" or "cavitated" surfaces. Visual inspection after tooth separation was considered as the gold standard. Examiner reliability of visual inspection after tooth separation was determined (kappa 0.92). Impression examination was repeated every 5 participants to evaluate the reproducibility of the method. The frequency of cavitated lesions was 65%, and 67% of those were inactive. Sensitivity, specificity, positive and negative predictive values were 0.88% (95%CI 0.73-0.95), 0.89% (95%CI 0.67-0.97), 0.94% (95%CI 0.79-0.98) and 0.80% (95%CI 0.58-0.92), respectively. Impression examination showed total agreement regarding cavitation. The evaluation of elastomeric impression after tooth separation is a useful clinical resource in cavitation detection for clinicians and researchers when visual inspection is doubtful.

Adriela Azevedo Souza, Mariath; Ana Eliza Lemes, Bressani; Fernando Borba de, Araujo.

2007-12-01

224

Generation of the additional fluorescence radiation in the elastomeric shields used in computer tomography (CT)  

International Nuclear Information System (INIS)

Two commercially available (EP, Z) and eight new elastomeric composites (M1-M4, G1-G4, of thickness ?1 mm) containing mixtures of differing proportions of heavy metal additives (Bi, W, Gd and Sb) have been synthesised and examined as protective shields. The intensity of the X-ray fluorescence radiation generated in the typical elastomeric shields for CT, containing Bi and other heavy metal additives influence on the practical shielding properties. A method for assessing the radiation shielding properties of elastomeric composites used in CT examination procedures via X-ray spectrometry has been proposed. To measure the radiation reduction ability of the protective shields, the dose reduction factor (DRF) has been determined. The lead equivalents for the examined composites were within the ranges of 0.046-0.128 and 0.048-0.130 mm for 122.1 and 136.5 keV photons, respectively. The proposed method, unlike to the common approach, includes a dose contribution from the induced X-ray fluorescence radiation of the heavy metal elements in the protective shields. The results clearly indicate that among the examined compositions, the highest values DRF have been achieved with preparations containing Bi+W, Bi+W+Gd and Bi+W+Sb mixtures with gradually decreasing content of heavy metal additives in the following order: Bi, W, Gd and Sb. The respective values of DRF obtained for the investigated composites were 21, 28 and 27 % dose reduction for a 1 mm thick shield and 39 and ?50for a 1 mm thick shield and 39 and ?50 % for a 2 mm thick layer (M1-M4). (author)

225

Optical manipulation of shape-morphing elastomeric liquid crystal microparticles doped with gold nanocrystals  

Science.gov (United States)

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, Yaoran; Evans, Julian S.; Lee, Taewoo; Senyuk, Bohdan; Keller, Patrick; He, Sailing; Smalyukh, Ivan I.

2012-06-01

226

46 CFR 53.05-3 - Materials (modifies HG-401.2).  

Science.gov (United States)

Materials for valves must be in accordance with HG-401.2 of section IV of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1) except that nonmetallic materials may be used only for gaskets and packing. [USCG-2003-16630, 73 FR 65164, Oct. 31,...

2010-10-01

227

Radiation resistance of elastomers; Vieillissement des elastomeres sous irradiation  

Energy Technology Data Exchange (ETDEWEB)

The COMOR group is a network of laboratories from both the CEA and the CNRS. This network is particularly involved in fundamental and applied studies on the ageing of polymers under irradiation. COMOR has studied the ageing of EPDM (ethylene-propylene-diene-monomer) because this elastomer is often used in nuclear environment (in cable coating for instance). In this study, we have prepared materials with different formulations and we have characterised their use-condition properties (dielectric and mechanical) before and after {gamma} irradiation. The dielectric measurements are well adapted to study the oxidation and the crosslinking phenomena which appear during the irradiation ageing. We have shown that after a short time, the oxidation is limited by the diffusion of oxygen. A phenolic antioxidant is not able to protect the polymer against the oxidation. However, we used a concentration typical of a purely thermal stabilisation case (0,1%). On the other hand, a diamine type additive with a concentration of 1% showed efficient stabilisation. The mechanical properties of the regular EPDM are strongly affected by the irradiation but there is little difference with regard to radiation resistance between both types of raw materials. Nevertheless, the NORDEL IP 3725 stabilised with the amine has better initial mechanical properties whereas the NORDEL 2722 offers higher strength above 300 kGy. Our results emphasize the stake of a proper stabilisation of polymers with respect to ionising radiation. (authors)

Hourquebie, P.; Bigarre, J.; Forveille, J.L.; Raby, J. [CEA Centre d' Etudes du Ripault, Laboratoire Materiaux Organiques et Dielectriques, DMAT/SCMF/LOD, 37 - Tours (France); Lazare, L. [CEA Centre d' Etudes du Ripault, Lab. de Physico-Chimie, DXPL/SMEP/LPC, 37 - Tours (France)

2002-07-01

228

Power turbine dynamics - An evaluation of a shear-mounted elastomeric damper  

Science.gov (United States)

As an alternative to the more conventional squeeze-film bearing damper designs, a Viton-70 shear-mounted, elastomeric damper was built and tested in a T-55 power turbine high-speed balancing rig. This application demonstrated, for the first time, the feasibility of using elastomers as the primary rotor damping source in production turbine engine hardware. The shear-mounted damper design was selected because of its compatibility with actual gas turbine engine radial space constraints, its accommodation of both the radial and axial thrust loads present in gas turbine engines, and its capability of controlled axial preload. Test results showed that the Viton-70 elastomeric damper operated successfully and provided excellent control of both synchronous and nonsynchronous vibrations through all phases of testing to the maximum rotor speed of 1676 rad/s (16,000 rpm). Excellent correlation between the predicted and experienced critical speeds, mode shapes, and log decrements for the power turbine rotor and elastomer damper assembly was also achieved.

Zorzi, E. S.; Walton, J.; Cunningham, R.

1983-01-01

229

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

230

Hemocompatibility evaluation of small elastomeric hollow fiber membranes as vascular substitutes.  

Science.gov (United States)

One of the main challenges for clinical implementation of small diameter vascular grafts (SDVGs) is their limited hemocompatibility. Important design specifications for such grafts include features that minimize the long-term risks of restenosis, fouling, and thrombus formation. In our lab, we have developed elastomeric hollow fiber membranes (HFMs), using a phase inversion method, as candidates for SDVGs. Here, we present our results for in vitro hemocompatibility testing of our HFM under flow and static conditions. Our results showed that the polymer-based HFMs do not damage the integrity of human red blood cells (RBCs) as shown by their low hemolytic extent (less than 2%). When analyzed for blood cell lysis using lactate dehydrogenase (LDH) activity as an indicator, no significant differences were observed between blood exposed to our HFMs and uncoagulated blood. Analysis of protein adsorption showed a low concentration of proteins deposited on the surfaces of HFM after 24?h. Platelet adhesion profiles using human platelet-rich plasma (PRP) showed that a low level of platelets adhered to the HFMs after 24?h, indicating minimal thrombotic potential. Under the majority of conditions, no significant differences were observed between medical-grade polymers and our HFMs. Eventual optimization of hemocompatible elastomeric HFM vessel grafts could lead to improved tissue vascularization as well as vascularized, tissue-engineered scaffolds for organ repair. PMID:24913612

Mercado-Pagán, Ángel E; Ker, Dai Fei Elmer; Yang, Yunzhi

2014-10-01

231

Frictional resistance of orthodontic wires tied with 3 types of elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The aims of this study were to determine and compare frictional resistance obtained by low-friction and conventional elastomeric ligatures in the presence of artificial saliva, and observe whether this variable changed after 21 days. Super Slick® low-friction elastomeric ligatures and conventional l [...] igatures of the brands TP conventional® and Unitek® were placed on standard edgewise maxillary central incisor metal brackets, slot .022" × .028" tying rectangular orthodontic wires .018" × .025". Three experimental groups were arranged according to the type of ligature and a control group in which no wires were used. The friction values obtained between the bracket/wire/ligature set were measured using a Universal Test Machine at a speed of 20 mm/minute, at two experimental time intervals: T0 - immediately after specimen fabrication; and T1 - 21 days after fabrication and immersion in artificial saliva at 37 ºC. Conventional Unitek ligatures and the low-friction ligature (Super Slick) showed the lowest friction values at T0. After 21 days (T1), however, conventional Unitek ligatures presented the lowest value. All groups assessed from T0 to T1 showed a numerical reduction in friction values, suggesting that time, heat and humidity may cause elastic degradation, however this was not verified statistically (P > 0.05).

Amanda Carneiro da, Cunha; Mariana, Marquezan; Amanda Osório Ayres de, Freitas; Lincoln Issamu, Nojima.

2011-12-01

232

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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

233

Frictional resistance of orthodontic wires tied with 3 types of elastomeric ligatures  

Directory of Open Access Journals (Sweden)

Full Text Available The aims of this study were to determine and compare frictional resistance obtained by low-friction and conventional elastomeric ligatures in the presence of artificial saliva, and observe whether this variable changed after 21 days. Super Slick® low-friction elastomeric ligatures and conventional ligatures of the brands TP conventional® and Unitek® were placed on standard edgewise maxillary central incisor metal brackets, slot .022" × .028" tying rectangular orthodontic wires .018" × .025". Three experimental groups were arranged according to the type of ligature and a control group in which no wires were used. The friction values obtained between the bracket/wire/ligature set were measured using a Universal Test Machine at a speed of 20 mm/minute, at two experimental time intervals: T0 - immediately after specimen fabrication; and T1 - 21 days after fabrication and immersion in artificial saliva at 37 ºC. Conventional Unitek ligatures and the low-friction ligature (Super Slick showed the lowest friction values at T0. After 21 days (T1, however, conventional Unitek ligatures presented the lowest value. All groups assessed from T0 to T1 showed a numerical reduction in friction values, suggesting that time, heat and humidity may cause elastic degradation, however this was not verified statistically (P > 0.05.

Amanda Carneiro da Cunha

2011-12-01

234

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

235

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

236

Transient dynamic mechanical properties of resilin-based elastomeric hydrogels.  

Science.gov (United States)

The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young's modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels. PMID:24809044

Li, Linqing; Kiick, Kristi L

2014-01-01

237

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

238

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

239

Development of a low-cost, modified resin transfer molding process using elastomeric tooling and automated preform fabrication  

Science.gov (United States)

This paper describes the design and process development of low-cost structural parts made by a modified resin transfer molding process. Innovative application of elastomeric tooling to increase laminate fiber volume and automated forming of fiber preforms are discussed, as applied to fabrication of a representative section of a cruise missile fuselage.

Doane, William J.; Hall, Ronald G.

1992-01-01

240

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

Science.gov (United States)

...maximum stress thus calculated and the factor of 4.25 shall not exceed the...arrangements shall ensure that the tightness can be maintained in any sea conditions. For this purpose tests for tightness shall be required at the...

2010-10-01

 
 
 
 
241

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

Science.gov (United States)

...these loads. Mild steel plating forming the tops of covers shall be not less in thickness than one percent of the spacing of stiffeners or 0.24 inches if that be greater. The provisions of § 42.15-25(b)(4) are applicable for vessels of not...

2010-10-01

242

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

243

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.

244

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

245

Elastomeric Capture Microparticles (ECmuPs) and Their use with Acoustophoresis to Perform Affinity Capture Assays  

Science.gov (United States)

This dissertation describes the development of elastomeric capture microparticles (ECmicroPs) and their use with acoustophoresis to perform affinity capture assays. EC?Ps that function as negative acoustic contrast particles were developed by crosslinking emulsion-based droplets composed of commercially available silicone precursors followed by functionalization with avidin/biotin reagents. The size distribution of the EC?Ps was very broad or narrow depending on the emulsion system that was used during the synthesis process. Elastomeric particles exhibited a very broad size distribution when a bulk-emulsion process was used; however, when microfluidic systems were utilized, their size distribution became comparatively narrow. The functionalization of elastomeric particles was accomplished by the non-specific adsorption of avidin protein followed by bovine serum albumin (BSA) blocking and bio-specific adsorption of a biotinylated-capture antibody. Polydisperse EC?Ps were functionalized to bind prostate specific antigen (PSA) or IgG-phycoerythrin (PE) in aqueous media (buffer, plasma, blood); whereas monodisperse EC?Ps were functionalized to bind a high density lipoprotein in the aqueous media. Polydisperse EC?Ps functionalized to bind PSA in a physiological buffer (PBS pH 7.4) demonstrated nanomolar detection using flow cytometry analysis; whereas EC?Ps functionalized to bind IgG-PE demonstrated picomolar detection in 10% porcine plasma. EC?Ps have a specific density of ~1.03 and are more compressible than their surrounding aqueous media; which allowed the EC?Ps to exhibit negative acoustic contrast properties under an ultrasonic acoustic standing wave field. The negative acoustic contrast property of EC?Ps was advantageously utilized in an IgG-PE assay conducted in 0.1% whole porcine blood. The ligand-bound EC?Ps suspended in the diluted blood sample were flowed through an acoustofluidic device where the application of an ultrasonic acoustic standing wave field focused the ligand-bound EC?Ps to pressure antinodes and the positive acoustic contrast blood cells to the central pressure node of the microchannel. As a result of laminar flow, focused ligand-bound EC?Ps and blood cells were flowed into properly aligned outlet channels at the downstream trifurcation, where they where collected separately off-chip. The cell-free fraction containing ligand-bound EC?Ps was analyzed using flow cytometry; where the detection of IgG-PE was in the picomolar range. This approach has potential applications in the development of rapid assays that detect the presence of low concentrations of biomarkers in a number of biological sample types.

Cushing, Kevin Wallace

246

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

247

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

248

Mechanically tunable three-dimensional elastomeric network/air structures via interference lithography.  

Science.gov (United States)

We show how to employ an interference lithographic template (ILT) as a facile mold for fabricating three-dimensional bicontinuous PDMS (poly(dimethylsiloxane)) elastomeric structures and demonstrate the use of such a structure as a mechanically tunable PDMS/air phononic crystal. A positive photoresist was used to make the ILT, and after infiltration with PDMS, the resist was removed in a water-based basic solution which avoided PDMS swelling or pattern collapse occurring during the ILT removal process. Since the period of the structure is approximately 1 microm, the density of states of gigahertz phonons are altered by the phononic PDMS/air crystal. Brillouin light scattering (BLS) was employed to measure phononic modes of the structure as a function of mechanical strain. The results demonstrate that the phononic band diagram of such structures can be tuned mechanically. PMID:16608275

Jang, Ji-Hyun; Ullal, Chaitanya K; Gorishnyy, Taras; Tsukruk, Vladimir V; Thomas, Edwin L

2006-04-01

249

Dynamic characterization of a soft elastomeric capacitor for structural health monitoring applications  

Science.gov (United States)

A novel thin film sensor consisting of a soft elastomeric capacitor (SEC) for meso-scale monitoring has been developed by the authors. Each SEC transduces surface strain into a measurable change in capacitance. In previous work, the authors have shown that the performance of the SEC compares well with conventional resistive strain gauges, providing a resolution of 25 ?? using an inexpensive off-the-shelf data acquisition system for capacitance measurements. Here, we further the understanding of the thin film sensor by characterizing its dynamic behavior. The SEC is subjected to dynamic loads in bending mode. The study of Fourier and wavelet transforms indicates that the sensor can be used to identify dynamic inputs. Overall results demonstrate the promising capabilities of the thin film sensor at dynamic monitoring of civil structures.

Saleem, Hussam; Laflamme, Simon; Ubertini, Filippo

2014-03-01

250

Elastomeric 2D grating and hemispherical optofluidic chamber for multifunctional fluidic sensing.  

Science.gov (United States)

We present an optofluidic sensor based on an elastomeric two-dimensional (2D) grating integrated inside a hemispherical fluid chamber. A 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-based electromagnetic method. For the 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 the glucose concentration can be monitored when mixed in a different concentrated phosphate-buffered saline 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 a monitor of biofluid, such as blood in hemodialysis. PMID:24323007

Xu, Zhida; Wang, Xinhao; Han, Kevin; Li, Shuo; Liu, G Logan

2013-12-01

251

Experimental and analytical qualification of elastomeric seals in nuclear power stations  

International Nuclear Information System (INIS)

During refueling of the pressurized water reactor type of nuclear power stations, the cavity surrounding the top of the reactor is filled with water to maintain acceptable levels of radiation while fuel is being transferred from the reactor. A generic illustration of this type of seal is shown which was a commonly used pneumatic seal. This particular seal has continued to receive some attention since I ampersand E Bulletin 84-03 was issued. While most plants addressed this issue at some time in the past, some plants continue to address concerns about other types of seals located in the plant. At the time of the I ampersand E Bulletin 84-03, other elastomeric-type seals were examined at meetings such as those held under the auspices of the Institute of Nuclear Power Operations. This paper addresses the testing performed on the seal used in refueling as well as the analytical method employed to accomplish the same purpose

252

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

253

Mechanics of nanowire buckling on elastomeric substrates with consideration of surface stress effects  

Science.gov (United States)

In this paper, the surface stress effects are considered in the analysis of nanowire buckling on elastomeric substrates. Theoretical solutions of the buckling wavenumber, amplitude, and the critical strain for the out-of-surface buckling are derived firstly. After that, the influences of the surface properties, size, bulk modulus, and the shape of the cross section of the nanowire on the out-of-surface and in-surface buckling behavior are systematically discussed. Our study indicates that the buckling mode of the nanowire can be greatly influenced by the surface effects. For nanowires with small cross section sizes and low bulk modulus, the buckling mode may be varied by tuning the surface properties. Based on the energy criterion, we explicitly determine the range of the parameters where the two buckling modes take place.

Gao, Fei; Cheng, Qian; Luo, Jun

2014-11-01

254

Free Out-Of Vibrations of a Rotating Beam with Non-Linear Elastomeric Constraints  

Science.gov (United States)

Free out-of-plane vibration of a rotating beam with a non-linear, elastomeric constraint has been investigated. The elastomer is modelled as a parallel combination of spring and damper elements. The stiffness and damping parameters are evaluated by using the previous experimental data. The linear analysis is performed by two techniques, one based on a power series expansion and the other based on the Rayleigh-Ritz principle. The results are found to be in excellent agreement. In the non-linear analysis, a numerical-perturbation technique is applied to determine the frequency-amplitude relationship. A parametric study revealing the influence of the non-linear constraint is presented.

Pohit, G.; Mallik, A. K.; Venkatesan, C.

1999-02-01

255

21 CFR 177.1210 - Closures with sealing gaskets for food containers.  

Science.gov (United States)

...American Society for Testing and Materials (ASTM) method D 1646-81, “Standard Test Method for Rubber—Viscosity and Vulcanization Characteristics (Mooney Viscometer),” which is incorporated by reference in accordance with 5 U.S.C....

2010-04-01

256

A rheology model of soft elastomeric capacitor for Weigh-In-Motion application  

Science.gov (United States)

As a result of fast growing industry, there is an increase in traffic congestion and deterioration of transportation inventory. Real-time traffic characterisation could be used to amoliorate the efficiency of our transportation system. Weigh-In-Motion (WIM) systems offer the advantages of vehicle classification, speed measurement, in addition to weight measurement while vehicles are moving. In this thesis, state-of-the-art WIM systems are discussed and limitations of current technologies are identified. A Soft Elastomeric Capacitor (SEC) that works as a large scale surface strain gauge is introduced to address the limitations in existing techniques and investigated for its applicability as a WIM sensor. Though the novel SEC has potential advantages, the relationship axial strain-to-stress needs to be modeled to enable its utilization as a WIM sensor. A Zener model is selected and modified by the addition of a slider to characterize the polymer behavior. An overstress approach is used to study the resultant stress-strain response owing to its simplicity and computational benefits. Since the overstress approach is data-driven, an experimental testing scheme is used to identify the model parameters. The tests comprise three types of applied strain loading: multi step relaxation, simple relaxation and cyclic compression. Specimens with varying stiffness are employed for these tests. Numerical simulations for the cyclic compression loading are presented to assess the model performance. The model is found to be capable of reproducing the experimental data with an absolute maximum error value of 0.085 MPa for slow loading rate tests and 0.175 MPa for high loading rate tests. Comparative studies are completed to investigate the impact of patch stiffness on the mechanical behavior of the soft elastomeric capacitor patches. It is observed that as stiffness decreases, the nonlinearity in stress-strain response increases

Kollipara, Venkata Dharmateja

257

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

258

The use of dual material seals for packaging  

International Nuclear Information System (INIS)

The use of dual material seals, metal and elastomeric for a transportation package, provides a viable option for packages requiring high temperature seal capability. Allowing the seal area to go to higher temperatures then allowed for all elastomeric seal reduce the necessity of providing thermal protection during a postulated accident condition fire. It also increases the options for impact limiting features that do not also mitigate the affects of accident thermal events. Typically, high temperature seals require the use of metal O-rings. Only one seal (typically identified as the containment seal) needs to survive the hypothetical accident conditions, including the high temperatures that may occur during the prescribed hypothetical thermal event. However, to expedite the assembly leakage rate testing of radioactive material packages, a dual O-ring seal arrangement is often used to allow creation of a relatively small volume test cavity between the seals. For any package that is being used on a frequent basis, the total cost of seals can be significantly reduced by using an elastomeric seal as the secondary seal. The elastomeric seal is not the containment boundary seal and does not need to survive the high temperature condition. To get the dual material O-ring seals to seat properly, a different approach has to be taken than with closure of a radioactive material package that does not use metallic O-ring(s). A metal O-ring requires an application of a seating force while the elastomeric package requires a certain percentage of deformation. This is further complicated when the seating force is developed using a multi-bolt closure. Because of the nature of multi-bolt closures, elastic interaction prevents the equal application of force. This paper develops the methods involved in properly closing and establishing containment when using dual material seals with a multi-bolt closure. These methods were demonstrated in two production casks requiring testing leak rates of 10-7 standard cc/sec

259

Evaluation of the susceptibility to pigmentation of orthodontic esthetic elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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.

260

Evaluation of the susceptibility to pigmentation of orthodontic esthetic elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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

 
 
 
 
261

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

262

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

263

The Redistribution of Load in Bolted Gasketed Joints Subjected to Steady State Thermal Loading  

International Nuclear Information System (INIS)

Pressure vessel joints operating at high temperature are often very difficult to seal. The existing flange design methods do not address thermal effects other than the variation of flange material mechanical properties with temperature. It is possible to include the effects of temperature loading in joint analysis, however, presently very few guidelines exist for this type of analysis. This paper outlines the theoretical analysis used for the determination of the steady state operating temperature and the induced loads in flange joints. It details the theoretical equations necessary to predict the temperature and the redistribution of load due to the thermal expansion of the joint components for the case of a pair flange and the case of a flange with a blind-cover. The results from the theoretical models are verified by comparison to finite element results. (authors)

264

The Implementation of a Visco-hyperelastic Numerical Material Model for Simulating the Behaviour of Polymer Foam Materials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Polyurethane foam has been in use for some time in wheelchair seating systems as it offers good pressure relieving capabilities in most cases. However, little characterisation work has gone into seating foam materials by comparison with conventional elastomeric materials. Accurate material models could allow better prediction of foam in-service behaviour, which could potentially improve seating design practises. The objective of this work was to develop an approach for the validation of hyper...

Briody, Conor; Duignan, Barry; Jerrams, Stephen; Tiernan, John

2012-01-01

265

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

266

Non-linear analysis of a closure manway using spiral wound gasket with metal-metal contact and a new geometry approach  

International Nuclear Information System (INIS)

The results of a PWR pressurizer closure manway analysis are presented. The manway geometry is slightly different from the conventional solution with the goal to reduce the bending stresses in the bolts when the system is pressurized. So the salt stresses value will also be reduced. The viability of the proposed solution will be confirmed by: verification of the stresses in the bolts connecting the blind flange to the nozzle by ASME III, subsection NB and level of the tightness reached in the spiral wound (type SG) gasket based in the criteria defined in the references. (author)

267

Rapid micropatterning of cell lines and human pluripotent stem cells on elastomeric membranes.  

Science.gov (United States)

Tissue function during development and in regenerative medicine completely relies on correct cell organization and patterning at micro and macro scales. We describe a rapid method for patterning mammalian cells including human embryonic stem cells (HESCs) and induced pluripotent stem cells (iPSCs) on elastomeric membranes such that micron-scale control of cell position can be achieved over centimeter-length scales. Our method employs surface engineering of hydrophobic polydimethylsiloxane (PDMS) membranes by plasma polymerization of allylamine. Deposition of plasma polymerized allylamine (ppAAm) using our methods may be spatially restricted using a micro-stencil leaving faithful hydrophilic ppAAm patterns. We employed airbrushing to create aerosols which deposit extracellular matrix (ECM) proteins (such as fibronectin and Matrigel™) onto the same patterned ppAAm rich regions. Cell patterns were created with a variety of well characterized cell lines (e.g., NIH-3T3, C2C12, HL1, BJ6, HESC line HUES7, and HiPSC line IPS2). Individual and multiple cell line patterning were also achieved. Patterning remains faithful for several days and cells are viable and proliferate. To demonstrate the utility of our technique we have patterned cells in a variety of configurations. The ability to rapidly pattern cells at high resolution over macro scales should aid future tissue engineering efforts for regenerative medicine applications and in creating in vitro stem cell niches. PMID:22511037

Paik, Isha; Scurr, David J; Morris, Bryan; Hall, Graham; Denning, Chris; Alexander, Morgan R; Shakesheff, Kevin M; Dixon, James E

2012-10-01

268

An investigation on low-velocity impact response of elastomeric & crushable foams  

Science.gov (United States)

The mechanical behavior of elastomeric foam, in particular, Ethylene Propylene Diene Methyle (EPDM) and crushable foams, in particular, Expanded Poly-Propylene (EPP) and Poly Urthane Rigid (PUR), under low-velocity impact are studied experimentally and numerically. At first, these foams were loaded under quasi-static loading in compression. In order to study the dependence of their behavior on strain rate, the loadings were performed in two rates, 3 mm/min and 100 mm/min. The low-velocity impact tests were applied using a drop hammer testing machine. The drop heights of projectile in all tests were 0.5 and 1 m. The thickness effect of specimens on absorption of energy and parameters such as, contact force and displacement of specimens are discussed. Then, the dynamic factors of force and energy for three types of foam are investigated. Since, EPP showed an insensitive property to the thickness of specimen in the impact tests, it is possible to define dynamic factors for different thickness of this type of foam. Finally, all test results are compared with numerical results through implementation of ABAQUS finite element package. Good agreements between numerical results and experimental data show the capability of numerical modeling to fulfill the experimental investigation.

Sadighi, Mojtaba; Salami, Sattar Jedari

2012-12-01

269

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. PMID:25376886

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

2014-01-01

270

Relationship Between Structure and Dynamic Mechanical Properties of a Carbon Nanofiber Reinforced Elastomeric Nanocomposite  

International Nuclear Information System (INIS)

The tensile and dynamic mechanical properties of a nanocomposite, containing modified carbon nanofibers (MCNFs) homogenously dispersed in an elastomeric ethylene/propylene (EP) copolymer semicrystalline matrix (84.3 wt% P), have been correlated with the structure development. These properties were characterized by in situ synchrotron X-ray diffraction during stretching, dynamic mechanical analysis and X-ray analysis techniques over a wide temperature range. Upon sequential drawing, the tensile strength of the nanocomposite film was notably higher than that of the unfilled polymer even though both samples exhibited a similar amount of crystal fraction and the same degree of crystal orientation, revealing the effect of nanofiller reinforcement in the semicrystalline matrix. The mechanical spectra of the 10 wt% MCNF filled samples in both stretched and non-stretched states showed broadening of the elastic modulus at high temperatures, where the corresponding crystallinity index also decreased. It is conceivable that a significant fraction of chain orientation is induced in the vicinity of the nanofillers during stretching, and these stretched chains with reduced mobility significantly enhance the thermal mechanical properties

271

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

272

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

273

Materials  

...de Interests: biomaterials; porous materials; scaffolds; tissue engineering; bioactive glasses; composite materials; waste recycling; carbon nanotubes; electrophoretic deposition; vascularization; bioceramics; biofabrication; bioactive coatings; drug delivery Contribution: Special Issue: Tissue Engineering Scaffolds Special Issue: Biodegradability of Materials in Biomedical Applications 2011 In other journals: Special Issue: Biodegradability of Materials in Biomedical Applications 2011 PD Dr. Dominik Brühwiler Zurich University of Applied Sciences (ZHAW), Institute of Chemistry and Biological Chemistry, Einsiedlerstrasse 31, CH-8820 Wädenswil, Switzerland Tel. +41 58 934 ...

274

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.

275

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

International Nuclear Information System (INIS)

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 (? 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

276

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

277

Summary of experimental tests of elastomeric seismic isolation bearings for use in nuclear reactor plants  

International Nuclear Information System (INIS)

This paper describes an experimental test program for isolator bearings which was developed to help establish the viability of using laminated elastomer bearings for base isolation of nuclear reactor plants. The goal of the test program is to determine the performance characteristics of laminated seismic isolation bearings under a wide range of loadings. Tests were performed on scale-size laminated seismic isolators both within the design shear strain range to determine the response of the bearing under expected earthquake loading conditions, and beyond the design range to determine failure modes and to establish safety margins. Three types of bearings, each produced from a different manufacturer, have been tested: (1) high shape factor-high damping-high shear modulus bearings; (2) medium shape factor-high damping-high shear modulus bearings; and (3) medium shape factor-high damping-low shear modulus bearings. All of these tests described in this report were performed at the Earthquake Engineering Research Center at the University of California, Berkeley, with technical assistance from ANL. The tests performed on the three types of bearings have confirmed the high performance characteristics of the high damping-high and low shear modulus elastomeric bearings. The bearings have shown that they are capable of having extremely large shear strains before failure occurs. The most common failure mechanism was the debonding of the top steel plate from the isolators. This failure mechanism can be virtually eliminated by improved manufacturing quality control. The most important result of the failure test of the isolators is the fact that bearings can sustain large horizontal displacement, several times larger than the design value, with failure. Their performance in moderate and strong earthquakes will be far superior to conventional structures

278

Synthesis, characterization, and paclitaxel release from a biodegradable, elastomeric, poly(ester urethane)urea bearing phosphorylcholine groups for reduced thrombogenicity.  

Science.gov (United States)

Biodegradable polymers with high elasticity, low thrombogenicity, and drug loading capacity continue to be pursued for vascular engineering applications, including vascular grafts and stents. A biodegradable elastomeric polyurethane was designed as a candidate material for use as a drug-eluting stent coating, such that it was nonthrombogenic and could provide antiproliferative drug release to inhibit smooth muscle cell proliferation. A phosphorylcholine containing poly(ester urethane) urea (PEUU-PC) was synthesized by grafting aminated phosphorylcholine onto backbone carboxyl groups of a polyurethane (PEUU-COOH) synthesized from a soft segment blend of polycaprolactone and dimethylolpropionic acid, a hard segment of diisocyanatobutane and a putrescine chain extender. Poly(ester urethane) urea (PEUU) from a soft segment of polycaprolactone alone was employed as a control material. All of the synthesized polyurethanes showed high distensibility (>600%) and tensile strengths in the 20-35 MPa range. PEUU-PC experienced greater degradation than PEUU or PEUU-COOH in either a saline or lipase enzyme solution. PEUU-PC also exhibited markedly inhibited ovine blood platelet deposition compared with PEUU-COOH and PEUU. Paclitaxel loaded in all of the polymers during solvent casting continued to release for 5 d after a burst release in a 10% ethanol/PBS solution, which was utilized to increase the solubility of the releasate. Rat smooth muscle cell proliferation was significantly inhibited in 1 wk cell culture when releasate from the paclitaxel-loaded films was present. Based on these results, the synthesized PEUU-PC has promising functionality for use as a nonthrombogenic, drug eluting coating on metallic vascular stents and grafts. PMID:23035885

Hong, Yi; Ye, Sang-Ho; Pelinescu, Anca L; Wagner, William R

2012-11-12

279

Summary of experimental tests of elastomeric seismic isolation bearings for use in nuclear reactor plants  

International Nuclear Information System (INIS)

This paper describes an experimental test program for isolator bearings which was developed to help establish the viability of using laminated elastomer bearings for base isolation of nuclear reactor plants. The goal of the test program is to determine the performance characteristics of laminated seismic isolation bearings under a wide range of loadings. Tests were performed on scale-size laminated seismic isolators both within the design shear strain range to determine the response of the bearing under expected earthquake loading conditions, and beyond the design range to determine failure modes and to establish safety margins. The test program was funded by the U.S. Department of Energy (DOE) and the National Science Foundation (NSF). Three types of bearings, each procured from a different manufacturer, have been tested: (1) high shape factor-high damping-high shear modulus bearings; (2) medium shape factor-high damping-high shear modulus bearings; and (3) medium shape factor-high damping-low shear modulus bearings. These bearings were designed by ANL and made according to ANL specifications. All of these tests described in this report were performed at the Earthquake Engineering Research Center (EERC) at the University of California, Berkeley, with technical assistance from ANL. In addition, tests were performed by ETEC on two of the type (1) bearings cited above. Those tests will be reported by others at this workshop. The tests performed on the three types of bearings have confirmed the high performance characteristics of the high damping-high and low shear modulus elastomeric bearings. The bearings have shown that they are capable of having extremely large shear strains before failure occurs. The most common failure mechanism was the debonding of the top steel plate from the isolators. This failure mechanism can be virtually eliminated by improved manufacturing quality control. The most important result of the failure test of the isolators is the fact that bearings can sustain large horizontal displacement, several times larger than the design value, without failure. The results of these test programs should give the designer confidence that base isolated structures can be designed and built with more than adequate safety margins. Their performance in moderate and strong earthquakes will be far superior to conventional structures. (author)

280

Stability of Nafcillin Sodium Solutions in the Accufuser® Elastomeric Infusion Device  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to investigate the stabilities of two kinds of solutions of nafcillin sodium (2.5 mg/mL in 0.9% sodium chloride solution (NS, normal saline and in injectable 5% dextrose water (D5W in the intravenous elastomeric infusion device (Accufuser® based on recommended solutions and storage periods. The injectable nafcillin solutions (NS- and D5W-nafcillin in the Accufuser® device were stored and evaluated at controlled temperatures (room temperature, RT, 5? ± 2? and cold temperature, CT, 4? ± 2? during 6 weeks. Effects of the periods of storage (from 0 to 6 weeks and the temperatures of storage (RT and CT on the physicochemical appearances and concentrations of active compounds were determined. The visual clarity, pH, and concentrations of nafcillin sodium were determined by stability-indicating high-performance liquid chromatography (HPLC-ultraviolet (UV detection. The results showed that in NS and D5W solutions, the amount of nafcillin slightly changed and remained 92.66% and 97.30% of their initial amounts at CT during 6 weeks, respectively. On the other hand, in NS and D5W solutions at RT, the amount significantly decreased with time and reached 27.66% and 31.97% of their initial amounts during 4 weeks, respectively. Slight decrement of pH was observed in CT storage while significant change was observed in the RT storage. Moreover, in CT, no significant changes in physical appearances and colors of the solutions were observed during the study. However, the solutions changed into yellowish color and some particles were detected in both kinds of nafcillin solutions (NS and D5W after 1.5 weeks in RT conditions. To sum up, under CT two kinds of nafcillin sodium solutions (NS and D5W were stable with time in Accufuser® without any significant physical changes and retained almost all of the initial concentrations up to 6 weeks. However, the solutions were not stable in RT storage. We suggest that nafcillin sodium solutions in an Accufuser® should be preferentially diluted in NS and D5W while storing in CT condition.

Min-A Kang

2013-01-01

 
 
 
 
281

Buffon needle lands in $\\epsilon$-neighborhood of a 1-Dimensional Sierpinski Gasket with probability at most $|\\log\\epsilon |^{-c}$  

CERN Document Server

In recent years, relatively sharp quantitative results in the spirit of the Besicovitch projection theorem have been obtained for self-similar sets by studying the $L^p$ norms of the "projection multiplicity" functions, $f_\\theta$, where $f_\\theta(x)$ is the number of connected components of the partial fractal set that orthogonally project in the $\\theta$ direction to cover $x$. In \\cite{NPV}, it was shown that $n$-th partial 4-corner Cantor set with self-similar scaling factor 1/4 decays in Favard length at least as fast as $\\frac{C}{n^p}$, for $p0$. A few observations were needed to adapt the approach of \\cite{NPV} to the gasket: we sketch them here. We also formulate a result about all self-similar sets of dimension 1.

Bond, Matt

2009-01-01

282

Epoxidized soy bean oil migrating from the gaskets of lids into food packed in glass jars. Analysis by on-line liquid chromatography-gas chromatography.  

Science.gov (United States)

The migration of epoxidized soy bean oil (ESBO) from the gasket in the lids of glass jars into foods, particularly those rich in edible oil, often far exceeds the legal limit (60 mg/kg). ESBO was determined through a methyl ester isomer of diepoxy linoleic acid. Transesterification occurred directly in the homogenized food. From the extracted methyl esters, the diepoxy components were isolated by normal-phase LC and transferred on-line to gas chromatography with flame ionization detection using the on-column interface in the concurrent solvent evaporation mode. The method involves verification elements to ensure the reliability of the results for every sample analyzed. The detection limit is 2-5 mg/kg, depending on the food. Uncertainty of the procedure is below 10%. PMID:16035364

Fankhauser-Noti, Anja; Fiselier, Katell; Biedermann-Brem, Sandra; Grob, Koni

2005-08-01

283

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

284

The effect of 810-nm low-level laser therapy on pain caused by orthodontic elastomeric separators.  

Science.gov (United States)

The purpose of this study was to assess the effect of 810-nm (DMC Equipamentos, Sao Carlos, Brazil) continuous wave low-level laser therapy (LLLT) on the pain caused by orthodontic elastomeric separators. Thirty-seven orthodontic patients (12 male and 25 female, aged 11-32 years, mean age?=?24.97 years) participated in the study, including 20 subjects aged 18 years or more, and 17 under 18 years of age. Four elastomeric separators (Dentarum, Springen, Germany) were placed for the first permanent molars (distal and mesial), either for maxillary (22 patients) or mandibular (15 patients) arches; one quadrant was randomly selected and used as a placebo group (received no laser irradiation). After separator placement for each quadrant, patients received 10 doses (2 J/cm(2), 100 mW, 20 s) of laser irradiation on the buccal side (at the cervical third of the roots), for distal and mesial of the second premolars and first permanent molars, as well as distal of second permanent molars (five doses). The same procedure was repeated for the lingual or palatal side (five doses). After 24 h, patients returned to the clinic and received another 10 doses of laser irradiation on the same quadrant. Postseparation pain level recorded on a 10-cm visual analog scale for both jaws immediately (hour?0), and after 6, 24, 30 h, as well as on days?3, 4, 5, 6, and 7. Significant differences in the pain perception (PP) were found between the laser and placebo groups at 6, 24, 30 h, and day?3 of the experiment (P?laser (chi-square?=?173.407, P?=?0.000) and placebo (chi-square?=?184.712, P?=?0.000) groups. In both groups, pain was highest at 6 and 30 h after placing elastomeric separators. No gender differences were observed in both groups. More pain was recorded in the mandible (P?laser group) and 30 h (both groups) after starting the experiment. The PP was significantly higher (P?laser group only] of the experiment. The 810-nm continuous wave LLLT significantly reduced the PP in the first 3 days after orthodontic separation. However, the mean postseparation PP in both groups was low and wide ranges of PP scores were observed. PMID:23334785

Eslamian, Ladan; Borzabadi-Farahani, Ali; Hassanzadeh-Azhiri, Aidin; Badiee, Mohammad R; Fekrazad, Reza

2014-03-01

285

Materials and mechanics for stretchable electronics.  

Science.gov (United States)

Recent advances in mechanics and materials provide routes to integrated circuits that can offer the electrical properties of conventional, rigid wafer-based technologies but with the ability to be stretched, compressed, twisted, bent, and deformed into arbitrary shapes. Inorganic and organic electronic materials in microstructured and nanostructured forms, intimately integrated with elastomeric substrates, offer particularly attractive characteristics, with realistic pathways to sophisticated embodiments. Here, we review these strategies and describe applications of them in systems ranging from electronic eyeball cameras to deformable light-emitting displays. We conclude with some perspectives on routes to commercialization, new device opportunities, and remaining challenges for research. PMID:20339064

Rogers, John A; Someya, Takao; Huang, Yonggang

2010-03-26

286

NASA Materials Research for Extreme Conditions  

Science.gov (United States)

This Technical Memorandum briefly covers various innovations in materials science and development throughout the course of the American Space program. It details each innovation s discovery and development, explains its significance, and describes the applications of this material either in the time period discovered or today. Topics of research include silazane polymers, solvent-resistant elastomeric polymers (polyurethanes and polyisocyanurates), siloxanes, the Space Shuttle thermal protection system, phenolic-impregnated carbon ablator, and carbon nanotubes. Significance of these developments includes the Space Shuttle, Apollo programs, and the Constellation program.

Sharpe, R. J.; Wright, M. D.

2009-01-01

287

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)

288

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

289

Avaliação in vitro da força liberada por elásticos em cadeia / In vitro evaluation of force delivered by elastomeric chains  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: avaliar in vitro e comparar a redução de intensidade das forças liberadas por três grupos de elásticos em cadeia, com diferentes configurações, de um mesmo fabricante, medidas em intervalos de tempo preestabelecidos. MÉTODOS: os segmentos de elásticos em cadeia foram alongados e mantidos a [...] tivados durante o experimento com o auxílio de um dispositivo desenvolvido especialmente para esse fim e para possibilitar a leitura das forças. A avaliação da degradação da força foi realizada medindo-se a intensidade da força ao longo do tempo, e calculando-se o percentual de força perdida em relação à força inicial, em cada intervalo de tempo e para cada amostra testada. RESULTADOS E CONCLUSÕES: os dados coletados foram submetidos a análises estatísticas e os resultados demonstraram que, nos momentos seguintes ao inicial, a intensidade da força variou, dentro dos grupos e entre os grupos, nos diferentes momentos. A leitura dos valores das forças remanescentes em cada momento, comparada à referência da força inicial, resultou em valores diferentes, com significância estatística, em todas as comparações efetuadas dentro de cada grupo de elásticos (curto, médio, longo). Após a análise dos resultados das comparações entre os grupos de elásticos em cadeia, conclui-se que, apesar de verificados alguns resultados estatisticamente significativos para a comparação das magnitudes das forças liberadas em cada momento, essas diferenças parecem não ter expressão clínica, demonstrando que, aparentemente, o espaçamento entre os elos não representa uma característica clinicamente significativa na degradação da força ao longo do tempo. Abstract in english OBJECTIVE: To evaluate and compare, in vitro, the decrease in the forces delivered in three groups of elastomeric chains, produced by the same manufacturer, according to the distance between links (short, medium, long). METHODS: The segments of elastomeric chains were stretched and kept activated du [...] ring the trial using a device developed especially for this purpose, which also allowed force readings. Force degradation was evaluated by measuring force along time and calculating the percentage of force decrease from initial force at each time interval and for each specimen under test. RESULTS AND CONCLUSIONS: Data were statistically analyzed and results showed that at the different time points after initial readings, force intensity varied within and between groups. Readings of remaining forces at each time moment compared with the initial reference force revealed statistically significant differences in all the comparisons in each group of elastics (short, medium, long). Although the comparisons between forces delivered at each time point revealed statistically significant differences, these differences do not seem to have a clinical significance. The space between links does not seem to be a clinically significant characteristic in force degradation along time.

Andréa Fonseca Jardim da, Motta; Adriana de Alcantara, Cury-Saramago; Lincoln Issamu, Nojima.

2011-12-01

290

Materials for vacuum seals and dielectric breaks in near term and commercial reactor designs  

International Nuclear Information System (INIS)

Evaluations have been made of currently available sealing materials and concepts and their potential applicability to fusion reactor devices. The environments imposed on seals for fusion reactors are more severe than most applications. Elastomeric, metal, and welded seals were evaluated. Elastomeric materials are not effective for use at radiation dose levels greater than 108 rads; the best are polyurethane or ehtylene propylene. Welded seals and metal seals offer the advantage of realiability once a seal is made but lack the case of use inherent in elastomer seals. The sealing of a fusion reactor vacuum chamber is a non-trivial matter and will require R and D on a multitude of design options. (orig.)

291

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 their further application in more complex biological investigations, and the versatility of PBW in lab-on-a-chip development.

292

Defined 2-D microtissues on soft elastomeric silicone rubber using lift-off epoxy-membranes for biomechanical analyses.  

Science.gov (United States)

Surface patterning with complex molecules has become a valuable tool in cell biology and biotechnology, as it enables one to control cell shape and function in culture. However, this technique for micro-contact printing is normally performed on rigid substrates, e.g. Petri dishes or glass. Despite the fact that these substrates can easily be patterned they are artificially stiff environments for cells affecting their morphology and function. Those artifacts can be avoided on tissue elasticity resembling substrates, leading to a nature like cell morphology and behavior. However, reproducible patterning of very soft elastomeric substrates is challenging. Here, we describe a simple and highly accurate method through cavities of lift-off membranes for protein patterning of silicone rubber substrates in an elasticity range down to 1.5 kPa without altering their mechanical properties. Membranes are made of epoxy resin with feature sizes that can be chosen almost arbitrarily including widths down to 5 ?m and aspect ratios of 100 and more. Different feature shapes were used to actively manipulate cell adhesion, cell morphology and the actin cytoskeleton on soft substrates. Manipulation of cytoskeletal organization furthermore allowed the comparison of myofibril alignment and cellular forces of cardiac myocytes. These data could show that cell forces are largely unaffected upon active disordering of overall myofibril alignment on a single cell level while aligned multicellular systems generate cell forces in an additive manner. PMID:24623394

Hampe, Nico; Jonas, Thorsten; Wolters, Benjamin; Hersch, Nils; Hoffmann, Bernd; Merkel, Rudolf

2014-04-14

293

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

294

Pulse-driven magnetostatic micro-actuator array based on ultrasoft elastomeric membranes for active surface applications  

Science.gov (United States)

An array of pulse-driven magnetostatic micro-actuators with 2 mm pitch is proposed for highly deformable active surfaces. A wide range of applications can benefit from such devices, from droplet manipulation and active flow control to tactile display, for which this device was initially designed. This design ensures robustness, ease of fabrication and mass production compatibility. The device is composed of an array of 4 × 4 highly resistant elastomeric membranes achieved using microfabrication techniques. The magnetostatic actuation system is based on the interaction between a miniature coil and a SmCo micro-magnet. This mechanism was optimized by the finite-element method, leading to the introduction of different ferromagnetic circuits. Mechanical characterizations were achieved by laser interferometry. The micro-actuators can be used either in continuous mode or in pulse mode, allowing wide bandwidth, from dc to 1.5 kHz, and vibration amplitudes up to 150 ?m for instantaneous forces of 30 mN. The device has good actuation homogeneity with ±20% amplitude variations between its actuators; low crosstalk (<5%) was also demonstrated. Finally, an improved actuation design benefiting from electroplated NiFe thin films is proposed and characterized, increasing performances (forces and displacements) by 50%.

Streque, J.; Talbi, A.; Pernod, P.; Preobrazhensky, V.

2012-09-01

295

To boost elastomer vulcanization through ionization; Pousser la vulcanisation des elastomeres par ionisation  

Energy Technology Data Exchange (ETDEWEB)

The beta and gamma irradiation of elastomers makes easier the handling of the reticulation process in room temperature conditions and in adequate depth inside the material. The irradiation generates free radicals along the polymer chains, these radicals by combining form new chemical bonds (reticulation reaction). The irradiation of an elastomer is featured by the formation of covalent carbon-carbon type bonds while sulfur vulcanization leads to chain bridging based on sulfur-sulfur bonds. The reticulation process entails a rise of the ramification rate of the polymer. These modifications confer to the irradiated material a higher dimensional stability in high temperature conditions and in aggressive environment that may lead, in certain conditions to no need for the usual extra coating. The gamma irradiation facilities of the Ionisos company allow the treatment of molded plastic materials directly in their packaging and in bulk quantity. (A.C.)

Rouif, S. [Ionisos, 01 - Dagneux (France); Noireaux, P. [Centre de Transfert de Technologies du Mans (CTTM), 72 - Le Mans (France)

2006-07-01

296

Flow-Enhanced Crystallization and Morphology Development of Blends of Isotactic Polypropylene and Elastomeric Polyolefins  

Science.gov (United States)

Studies on flow-induced crystallization and morphology were conducted on impact polyolefin materials by in situ rheo-optical measurements and ex situ microscopic observations. An homologous series of materials consisting of an isotactic polypropylene base resin (PP), that resin with nucleant added (PPN), and the nucleated resin with elastomer blended as a minor component (PPNB) was examined. All materials were subjected to a short shear pulse, after which enhanced crystallization kinetics was observed. The influence on crystallization and structure of the heterogeneous nucleant on these samples was studied for different shear wall stresses and shearing times. Their effect decreased at higher shear stresses, which suggests that at such conditions the amount of homogeneous flow-induced nuclei dominates. Also, the role of melt rheology was investigated by shearing samples near the nominal melting point and allowing to relax before cooling to crystallization.

Fernandez-Ballester, Lucia; Thurman, Derek W.; Korfield, Julia A.

2002-03-01

297

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

298

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

Science.gov (United States)

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. PMID:21849722

Baudis, Stefan; Nehl, Franziska; Ligon, S Clark; Nigisch, Anneliese; Bergmeister, Helga; Bernhard, David; Stampfl, Jürgen; Liska, Robert

2011-10-01

299

Die bleibende Deformation nach Elongation elastomerer Silikon-Abformmaterialien vom Typ 3  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Einführung: Das Ziel der vorliegenden Studie bestand darin, die klinisch relevanten Einflussfaktoren auf die bleibende Deformation nach Elongation (Dehnung) von Silikon-Abformmaterialien vom Typ 3 auch bei Dehnraten unter 50% zu untersuchen. Material und Methode: Es wurden vier Abformmaterialien aus der Gruppe der A-Silikone (a. Aquasil Ultra LV, b. Express 2 Light Body Standard, c. Flexitime Correct Flow und d. Honigum-Light) und ein C-Silikon (e. Xantopren Comfort Light) untersucht. Na...

Taraba, Meike

2013-01-01

300

An elastomeric patch electrospun from a blended solution of dermal extracellular matrix and biodegradable polyurethane for rat abdominal wall repair.  

Science.gov (United States)

A biodegradable elastomeric scaffold was created by electrospinning a mixed solution of poly(ester urethane)urea (PEUU) and porcine dermal extracellular matrix (dECM) digest, with PEUU included to provide elasticity, flexibility, and mechanical support and dECM used to enhance bioactivity and biocompatibility. Micrographs and differential scanning calorimetry demonstrated partial miscibility between PEUU and dECM. With greater dECM content, scaffolds were found to possess lower breaking strains and suture retention strength, although initial modulus was greater with higher dECM concentrations. The hybrid scaffolds containing 0% to 50% dECM had tensile strengths of 5 to 7 MPa, breaking strains of 138% to 611%, initial moduli of 3 to 11 Mpa, and suture retention strengths of 35 to 59 MPa. When hydrated, scaffolds were found to contract markedly with 50% dECM content. When used in a rat full-thickness abdominal wall replacement model, no herniation, infection, or tissue adhesion was observed after 4 and 8 weeks with a scaffold containing 25% dECM or a control 100% PEUU scaffold. Scaffolds incorporating dECM were significantly thicker at the time of explant, with greater numbers of associated smooth muscle actin-positive staining cells than in the control, but minimal cellular infiltration and remodeling of the scaffold were detected regardless of dECM addition. The processing of dECM and PEUU from a mixed solution thus provided a scaffold with evidence of better bioactivity and with mechanical properties not achievable with digested dECM alone. PMID:21933017

Hong, Yi; Takanari, Keisuke; Amoroso, Nicholas J; Hashizume, Ryotaro; Brennan-Pierce, Ellen P; Freund, John M; Badylak, Stephen F; Wagner, William R

2012-02-01

 
 
 
 
301

Structure and Mechanical Behavior of Elastomeric Multiblock Terpolymers Containing Glassy, Rubbery, and Semicrystalline Blocks  

Energy Technology Data Exchange (ETDEWEB)

Multiblock copolymers containing glassy poly(cyclohexylethylene) (C), rubbery poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were synthesized by sequential anionic polymerization of styrene, isoprene, and butadiene followed by catalytic hydrogenation. The resulting CECPCEC (denoted XPX) and CECP (XP) multiblock copolymers each contain 50 vol % of P and equal amounts of C and E. These materials have been studied by dynamic mechanical spectroscopy (DMS), transmission electron microscopy (TEM), small- and wide-angle X-ray scattering (SAXS and WAXS), differential scanning calorimetry (DSC), and tensile deformation to characterize the morphology, phase behavior, and mechanical properties. Microphase separation in these compounds is induced by crystallization of E and/or chemical incompatibility between the three blocks, leading to a new type of morphology which contains continuous region of P and continuous region of microphase-separated X, resulting in mechanically resilient materials. High molecular weight block copolymers microphase separate with two different length scales associated with segregation between C and E and X and P. These structural features produce a nonclassical scaling relationship for the C-E domain spacing, d {approx} N{sup 0.31}, where N is the degree of polymerization of CEC portion. The role of semicrystalline E domains during uniaxial deformation has been exposed with WAXS experiments, which support a two-step mechanism involving recoverable and nonrecoverable deformation to different extents. Strain hardening is observed in double-anchored XPX, but not in single-anchored XP, at large tensile strains.

Zuo, Feng; Alfonzo, C. Guillermo; Bates, Frank S. (UMM)

2012-11-14

302

Microstructural Organization of Elastomeric Polyurethanes with Siloxane-Containing Soft Segments  

Science.gov (United States)

In the present study, we investigate the microstructure of two series of segmented polyurethanes (PUs) containing siloxane-based soft segments and the same hard segments, the latter synthesized from diphenylmethane diisocyanate and butanediol. The first series is synthesized using a hydroxy-terminated polydimethylsiloxane macrodiol and varying hard segment contents. The second series are derived from an oligomeric diol containing both siloxane and aliphatic carbonate species. Hard domain morphologies were characterized using tapping mode atomic force microscopy and quantitative analysis of hard/soft segment demixing was conducted using small-angle X-ray scattering. The phase transitions of all materials were investigated using DSC and dynamic mechanical analysis, and hydrogen bonding by FTIR spectroscopy.

Choi, Taeyi; Weklser, Jadwiga; Padsalgikar, Ajay; Runt, James

2011-03-01

303

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

304

Surface modification of elastomeric stamps for microcontact printing of polar inks.  

Science.gov (United States)

Chemical modification of the surface of a stamp used for microcontact printing (microCP) is interesting for controling the surface properties, such as the hydrophilicity. To print polar inks, plasma polymerization of allylamine (PPAA) was employed to render the surface of poly(dimethylsiloxane) (PDMS), polyolefin plastomers (POP), and Kraton elatomeric stamps hydrophilic for long periods of time. A thin PPAA film of about 5 nm was deposited on the stamps, which increased the hydrophilicity, and which remained stable for at least several months. These surface-modified stamps were used to transfer polar inks by microCP. The employed microCP schemes are as follows: (a) a second generation of dendritic ink having eight dialkyl sulfide end groups to fabricate patterns on gold substrates by positive microCP, (b) fluorescent guest molecules on beta-cyclodextrin (beta-CD) printboards on glass employing host-guest recognition, and (c) Lucifer Yellow ethylenediamine resulting in covalent patterning on an aldehyde-terminated glass surface. All experiments resulted in an excellent performance of all three PPAA-coated stamp materials to transfer the polar inks from the stamp surface to gold and glass substrates by microCP, even from aqueous solutions. PMID:17480107

Sadhu, Veera Bhadraiah; Perl, Andras; Péter, Maria; Rozkiewicz, Dorota I; Engbers, Gerard; Ravoo, Bart Jan; Reinhoudt, David N; Huskens, Jurriaan

2007-06-01

305

Analgesia invasiva domiciliaria en el manejo del dolor postoperatorio en cirugía mayor ambulatoria mediante bombas elastoméricas intravenosas / Home invasive analgesia in the management of postoperative pain alter outpatient major surgery using intravenous elastomeric pumps  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Introducción: el dolor postoperatorio moderado-severo sigue siendo un problema en cirugía ambulatoria, ya que provoca problemas de flujo de pacientes, retrasando el alta de los pacientes, siendo uno de los principales motivos de reingreso en los hospitales, y por tanto un importante indicador de cal [...] idad de estas Unidades. El empleo de técnicas analgésicas invasivas domiciliarias, en todos sus regímenes, puede controlar el dolor postoperatorio en estas intervenciones y permitir incluirlas en los programas de cirugía ambulatoria. Objetivos: el objetivo de nuestro estudio es valorar la viabilidad y la seguridad de la utilización de bombas de perfusión continua elastoméricas para la administración de analgesia endovenosa continua domiciliaria, a la vez que valorar la eficacia analgésica y el grado de satisfacción de los pacientes intervenidos en régimen ambulatorio. Material y métodos: estudio retrospectivo de 463 pacientes. Una vez intervenidos bajo estrategia de analgesia multimodal, se les coloca dos tipos diferentes de bombas elastoméricas endovenosas (elastómero de dexketoprofeno o de metamizol). La intensidad del dolor, para evaluar la necesidad de analgesia de rescate, se cuantifica con la escala visual analógica o con la escala verbal simple. En el domicilio (24 horas tras la cirugía), la Unidad de Atención Domiciliaria revisa los efectos secundarios, alteraciones del sueño, intensidad del dolor, necesidad de analgesia de rescate y grado de satisfacción. Resultados: un 69% de los pacientes presentaron dolor de carácter leve o ausencia de dolor tras la intervención y únicamente 16 de los 463 pacientes presentaron dolor de carácter severo. El 27% de los pacientes necesitaron analgesia de rescate y un 9% de los pacientes presentaron efectos secundarios atribuibles a los fármacos analgésicos (4% vómitos, 2% mareos, 2,5% somnolencia y 0,5% insomnio). Ningún paciente tuvo que ser reingresado después del alta. Un 83% de los pacientes mostró un alto grado de satisfacción, un 16% de los pacientes satisfacción moderada y un 0,2% poca satisfacción. Conclusión: nuestro estudio demuestra la viabilidad y seguridad de la utilización de infusores elastoméricos endovenosos como método de analgesia postoperatoria, que permiten controlar los casos de dolor moderado a severo en procedimientos aplicados a la cirugía ambulatoria. Sin embargo se necesitan más estudios comparativos con técnicas analgésicas convencionales, así como con diferentes regímenes de infusión. Abstract in english Introduction: moderate to severe postoperative pain is still a problem in outpatient surgery, since it causes patient flow problems and delays the discharge of patients, being one of the major causes of re-hospitalization and hence a relevant quality indicator of these Units. The use of home invasiv [...] e analgesic techniques, in all their regimes, can be effective for the management of postoperative pain in these surgical procedures and allow them to be included in outpatient surgery programs. Objectives: the aim of our study was to determine the feasibility and safety of the use of elastomeric continuous perfusion pumps for the administration of home continuous endovenous analgesia, as well as to assess analgesic effectiveness and degree of satisfaction of patients undergoing outpatient surgerys. Material and methods: we conducted a simple retrospective study in 463 patients. After the surgical procedure was performed under multimodal analgesia, two differents elastomeric endovenous pumps (dexketoprofeno pump or metamizol pump) were used. Pain intensity by means of a visual analog scale and a plain oral scale, the need for supplemental analgesics. At home (24 hours after the surgical operation), the Home Care Unit checked side effects, sleep disorders, pain intensity, need of rescue analgesia and degree of satisfaction. Results: 69% of the patients report absence or slight pain 24 h after the surgical operation, just 16 out of 463

R., Rodríguez de la Torre; E., Medina Madrid; M. L., Dávila Arias; A., Pérez García; A., Torres López; E., Cuéllar Obispo.

2011-06-01

306

Analgesia invasiva domiciliaria en el manejo del dolor postoperatorio en cirugía mayor ambulatoria mediante bombas elastoméricas intravenosas Home invasive analgesia in the management of postoperative pain alter outpatient major surgery using intravenous elastomeric pumps  

Directory of Open Access Journals (Sweden)

Full Text Available Introducción: el dolor postoperatorio moderado-severo sigue siendo un problema en cirugía ambulatoria, ya que provoca problemas de flujo de pacientes, retrasando el alta de los pacientes, siendo uno de los principales motivos de reingreso en los hospitales, y por tanto un importante indicador de calidad de estas Unidades. El empleo de técnicas analgésicas invasivas domiciliarias, en todos sus regímenes, puede controlar el dolor postoperatorio en estas intervenciones y permitir incluirlas en los programas de cirugía ambulatoria. Objetivos: el objetivo de nuestro estudio es valorar la viabilidad y la seguridad de la utilización de bombas de perfusión continua elastoméricas para la administración de analgesia endovenosa continua domiciliaria, a la vez que valorar la eficacia analgésica y el grado de satisfacción de los pacientes intervenidos en régimen ambulatorio. Material y métodos: estudio retrospectivo de 463 pacientes. Una vez intervenidos bajo estrategia de analgesia multimodal, se les coloca dos tipos diferentes de bombas elastoméricas endovenosas (elastómero de dexketoprofeno o de metamizol. La intensidad del dolor, para evaluar la necesidad de analgesia de rescate, se cuantifica con la escala visual analógica o con la escala verbal simple. En el domicilio (24 horas tras la cirugía, la Unidad de Atención Domiciliaria revisa los efectos secundarios, alteraciones del sueño, intensidad del dolor, necesidad de analgesia de rescate y grado de satisfacción. Resultados: un 69% de los pacientes presentaron dolor de carácter leve o ausencia de dolor tras la intervención y únicamente 16 de los 463 pacientes presentaron dolor de carácter severo. El 27% de los pacientes necesitaron analgesia de rescate y un 9% de los pacientes presentaron efectos secundarios atribuibles a los fármacos analgésicos (4% vómitos, 2% mareos, 2,5% somnolencia y 0,5% insomnio. Ningún paciente tuvo que ser reingresado después del alta. Un 83% de los pacientes mostró un alto grado de satisfacción, un 16% de los pacientes satisfacción moderada y un 0,2% poca satisfacción. Conclusión: nuestro estudio demuestra la viabilidad y seguridad de la utilización de infusores elastoméricos endovenosos como método de analgesia postoperatoria, que permiten controlar los casos de dolor moderado a severo en procedimientos aplicados a la cirugía ambulatoria. Sin embargo se necesitan más estudios comparativos con técnicas analgésicas convencionales, así como con diferentes regímenes de infusión.Introduction: moderate to severe postoperative pain is still a problem in outpatient surgery, since it causes patient flow problems and delays the discharge of patients, being one of the major causes of re-hospitalization and hence a relevant quality indicator of these Units. The use of home invasive analgesic techniques, in all their regimes, can be effective for the management of postoperative pain in these surgical procedures and allow them to be included in outpatient surgery programs. Objectives: the aim of our study was to determine the feasibility and safety of the use of elastomeric continuous perfusion pumps for the administration of home continuous endovenous analgesia, as well as to assess analgesic effectiveness and degree of satisfaction of patients undergoing outpatient surgerys. Material and methods: we conducted a simple retrospective study in 463 patients. After the surgical procedure was performed under multimodal analgesia, two differents elastomeric endovenous pumps (dexketoprofeno pump or metamizol pump were used. Pain intensity by means of a visual analog scale and a plain oral scale, the need for supplemental analgesics. At home (24 hours after the surgical operation, the Home Care Unit checked side effects, sleep disorders, pain intensity, need of rescue analgesia and degree of satisfaction. Results: 69% of the patients report absence or slight pain 24 h after the surgical operation, just 16 out of 463 patients of the study had severe pain. The 27% of patients required rescue therapy and the 9

R. Rodríguez de la Torre

2011-06-01

307

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)

308

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)

309

The effect of configuration on strength, durability, and handle of Kevlar fabric-based materials  

Science.gov (United States)

Five Kevlar based laminates and three Kevlar based coated materials were designed, hand made, and tested against comparative conventional Dacron based materials for strength, peel, tear, puncture, creases, and handle. Emphasis was placed on evaluating geometric orientation of constituents, use of elastomeric film in place of high modulus films, and the use of flying thread loom bias reinforcement of Kevlar yarns. Whereas, the performance of the Kevlar laminates was severely degraded by crease effects, significant gains in overall performance factors were shown for the coated Kevlar materials.

Reuter, L. L.; Munson, J. B.

1977-01-01

310

Active materials by four-dimension printing  

Science.gov (United States)

We advance a paradigm of printed active composite materials realized by directly printing glassy shape memory polymer fibers in an elastomeric matrix. We imbue the active composites with intelligence via a programmed lamina and laminate architecture and a subsequent thermomechanical training process. The initial configuration is created by three-dimension (3D) printing, and then the programmed action of the shape memory fibers creates time dependence of the configuration—the four-dimension (4D) aspect. We design and print laminates in thin plate form that can be thermomechanically programmed to assume complex three-dimensional configurations including bent, coiled, and twisted strips, folded shapes, and complex contoured shapes with nonuniform, spatially varying curvature. The original flat plate shape can be recovered by heating the material again. We also show how the printed active composites can be directly integrated with other printed functionalities to create devices; here we demonstrate this by creating a structure that can assemble itself.

Ge, Qi; Qi, H. Jerry; Dunn, Martin L.

2013-09-01

311

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

312

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

313

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

314

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

International Nuclear Information System (INIS)

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.

315

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

Energy Technology Data Exchange (ETDEWEB)

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. [Core Systems, 1050 Kifer Road Sunnyvale, CA 94086 (United States); FI Silicon, 1050 Kifer Road Sunnyvale, CA 94086 (United States); Core Systems, 1050 Kifer Road Sunnyvale, CA 94086 (United States)

2012-11-06

316

Modular glovebox connector and associated good practices for control of radioactive and chemically toxic materials.  

Science.gov (United States)

Design and associated good practices are described for a modular glovebox connector to improve control of radioactive and chemically toxic materials. The connector consists of an anodized aluminum circular port with a mating spacer, gaskets, and retaining rings for joining two parallel ends of commercially available or custom-manufactured glovebox enclosures. Use of the connector allows multiple gloveboxes to be quickly assembled or reconfigured in functional units. Connector dimensions can be scaled to meet operational requirements for access between gloveboxes. Options for construction materials are discussed, along with recommendations for installation of the connector in new or retrofitted systems. Associated good practices include application of surface coatings and caulking, use of disposable glovebags, and proper selection and protection of gasket and glove materials. Use of the connector at an inhalation toxicology research facility has reduced the time and expense required to reconfigure equipment for changing operational requirements, the dispersion of contamination during reconfigurations, and the need for decommissioning and disposal of contaminated enclosures. PMID:9883950

Hoover, M D; Mewhinney, C J; Newton, G J

1999-01-01

317

Modular glovebox connector and associated good practices for control of radioactive and chemically toxic materials  

International Nuclear Information System (INIS)

Design and associated good practices are described for a modular glovebox connector to improve control of radioactive and chemically toxic materials. The connector consists of an anodized aluminum circular port with a mating spacer, gaskets, and retaining rings for joining two parallel ends of commercially available or custom-manufactured glovebox enclosures. Use of the connector allows multiple gloveboxes to be quickly assembled or reconfigured in functional units. Connector dimensions can be scaled to meet operational requirements for access between gloveboxes. Options for construction materials are discussed, along with recommendations for installation of the connector in new or retrofitted systems. Associated good practices include application of surface coatings and caulking, use of disposable glovebags, and proper selection and protection of gasket and glove materials. Use of the connector at an inhalation toxicology research facility has reduced the time and expense required to reconfigure equipment for changing operational requirements, the dispersion of contamination during reconfigurations, and the need for decommissioning and disposal of contaminated enclosures

318

Silicone working actively as automobile materials. Jidosha zairyo to shite katsuyakusuru silicone  

Energy Technology Data Exchange (ETDEWEB)

This paper describes characteristics and applications of silicone products as an automotive material. An elastomer system in silicone products is used as a silicone adhesive and sealant for cylinder head covers, oil pans, and radiators. A gasket seal of the formed-in-place gasket type using liquid silicone rubber produced in robot-based process has realized a large cost reduction as a result of reduced number of parts, weight reduction, and improved sealability. Silicone rubber is used as an engine crank shaft rear sealing material because of its superior heat resistance. Hoses are the application for silicone rubber to utilize its cold and hot heat resistance from {minus} 60 {degree}C to 250{degree}C, waterproofness, and resistance to oil and coolant. Non-elastomer-based silicone is used as silicone grease and oil for cam shaft, starter motor, and viscous clutch in four-wheel drive cars. Amount of silicone rubber is sharply increasing recently for coating air bags. 3 refs., 1 fig., 2 tabs.

Momii, K. (Shinetsu Chemical Co. Ltd., Tokyo (Japan))

1992-06-18

319

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

320

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

 
 
 
 
321

Comparison of Raman spectroscopy vs. high performance liquid chromatography for quality control of complex therapeutic objects: model of elastomeric portable pumps filled with a fluorouracil solution.  

Science.gov (United States)

This study compares the performance of a reference method of HPLC to Raman spectroscopy (RS) for the analytical quality control (AQC) of complex therapeutic objects. We assessed a model consisting of a widely used anticancer drug, i.e., 5-fluorouracil, which was compounded in a complex medical device, i.e., an elastomeric portable infusion pump. In view of the main objective, the two methods provided excellent results for the analytical validation key criteria, i.e., trueness, precision and accuracy, ranging from 7.5 to 50mg/mL and in either isotonic sodium or 5% dextrose. The Spearman and Kendall correlation tests (p-valueoptimization, combining matrix and packaging responses. In this new application, we demonstrate at least eight benefits of RS: (a) operator safety, (b) elimination of disposables, (c) elimination of analysis waste, which contributes to the protection of the environment, (d) a fast analytical response of less than 2min, (e) the ability to identify the solubilizing phase, (f) reduction of the risk of errors because no intrusion or dilution are needed, (g) negligible maintenance costs and (h) a reduction in the budget dedicated to technician training. Overall, we indicate the potential of non-intrusive AQC performed by RS, especially when the analysis is not possible using the usual techniques, and the technique's high potential as a contributor to the safety of medication. PMID:24463044

Bourget, Philippe; Amin, Alexandre; Vidal, Fabrice; Merlette, Christophe; Lagarce, Frédéric

2014-03-01

322

24 CFR 3280.604 - Materials.  

Science.gov (United States)

...Vinyl Chloride) (PVC) Plastic Piping Systems—ASTM D2564-91a. Specification for Neoprene Rubber Gaskets for HUB and Spigot Cast Iron Soil Pipe and Fittings—CISPI-HSN-85. Plumbing System Components for Manufactured Homes and Recreational...

2010-04-01

323

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

324

Micromechanics and constitutive models for soft active materials with phase evolution  

Science.gov (United States)

Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.

Wang, Binglian

325

Accuracy of three interocclusal recording materials used to mount a working cast.  

Science.gov (United States)

When remaining occlusal contacts of a dental posterior quadrant have been prepared to receive complete or partial coverage restorations, it is necessary to use an interocclusal recording material to approximate the casts for laboratory mounting procedures. Inaccuracy in working cast approximation leads to occlusal discrepancies in the fabricated restorations that require correction by the dentist at the time of insertion. Traditionally waxes, impression compounds, plasters, and zinc oxide-eugenol pastes have been used intraorally to record maxillomandibular relationships. Elastomeric materials have also been advocated. Manufacturers of thermoplastic resins have recently suggested that these materials may be used with ease and accuracy for interocclusal records. This investigation measured and compared the accuracies of a thermoplastic resin, an acrylic resin, and a vinyl polysiloxane interocclusal recording material. A measuring method was developed in which a computerized axiograph was used to record positional errors in three planes, next to the posterior teeth, with the interocclusal recording materials listed. PMID:8164168

Breeding, L C; Dixon, D L; Kinderknecht, K E

1994-03-01

326

Physics-Based Simulation and Experiment on Blast Protection of Infill Walls and Sandwich Composites Using New Generation of Nano Particle Reinforced Materials  

Science.gov (United States)

A critical issue for the development of nanotechnology is our ability to understand, model, and simulate the behavior of small structures and to make the connection between nano structure properties and their macroscopic functions. Material modeling and simulation helps to understand the process, to set the objectives that could guide laboratory efforts, and to control material structures, properties, and processes at physical implementation. These capabilities are vital to engineering design at the component and systems level. In this research, experimental-computational-analytical program was employed to investigate the performance of the new generation of polymeric nano-composite materials, like nano-particle reinforced elastomeric materials (NPREM), for the protection of masonry structures against blast loads. New design tools for using these kinds of materials to protect Infill Walls (e.g. masonry walls) against blast loading were established. These tools were also extended to cover other type of panels like sandwich composites. This investigation revealed that polymeric nano composite materials are strain rate sensitive and have large amount of voids distributed randomly inside the materials. Results from blast experiments showed increase in ultimate flexural resistance achieved by both unreinforced and nano reinforced polyurea retrofit systems applied to infill masonry walls. It was also observed that a thin elastomeric coating on the interior face of the walls could be effective at minimizing the fragmentation resulting from blast. More conclusions are provided with recommended future research.

Irshidat, Mohammad

327

Effect of temperature and gap opening rate on the resiliency of candidate solid rocket booster O-ring materials  

Science.gov (United States)

In the redesign of the Space Shuttle solid rocket motor following the Challenger accident, the field and nozzle-to-case joints were designed to minimize gap opening caused by internal motor pressurization during ignition. The O-ring seals and glands for these joints were designed both to accommodate structural deflections and to promote pressure assisted sealing. The resiliency behavior of several candidate O-ring materials was evaluated for the effects of temperature and gap opening rates. The performance of three of the elastomeric materials was tested under the specific redesign gap opening requirement. Dynamic flexure conditions unique to launch produce low frequency vibrations in the gap opening. The effect of these vibrations on the ability of the O-ring to maintain contact with the sealing surface was addressed. The resiliency of the O-ring materials was found to be extremely sensitive to variations in temperature and gap opening rate. The top three elastomeric materials tracked the simulated solid rocket booster (SRB) field joint deflection at 75 and 120 F. The external tank/SRB attach strut load vibrations had a negligible effect on the ability of the O-ring to track the simulated SRB field joint deflection.

Lach, Cynthia L.

1992-01-01

328

Novel nanocomposite technologies for dynamic monitoring of structures: a comparison between cement-based embeddable and soft elastomeric surface sensors  

Science.gov (United States)

The authors have recently developed two novel solutions for strain sensing using nanocomposite materials. While they both aim at providing cost-effective solutions for the monitoring of local information on large-scale structures, the technologies are different in their applications and physical principles. One sensor is made of a cementitious material, which could make it suitable for embedding within the core of concrete structures prior to casting, and is a resistor, consisting of a carbon nanotube cement-based transducer. The other sensor can be used to create an external sensing skin and is a capacitor, consisting of a flexible conducting elastomer fabricated from a nanocomposite mix, and deployable in a network setup to cover large structural surfaces. In this paper, we advance the understanding of nanocomposite sensing technologies by investigating the potential of both novel sensors for the dynamic monitoring of civil structures. First, an in-depth dynamic characterization of the sensors using a uniaxial test machine is conducted. Second, their performance at dynamic monitoring of a full-scale concrete beam is assessed, and compared against off-the-shelf accelerometers. Experimental results show that both novel technologies compare well against mature sensors at vibration-based structural health monitoring, showing the promise of nanocomposite technologies for the monitoring of large-scale structural systems.

Ubertini, Filippo; Laflamme, Simon; Ceylan, Halil; Materazzi, Annibale Luigi; Cerni, Gianluca; Saleem, Hussam; D'Alessandro, Antonella; Corradini, Alessandro

2014-04-01

329

Correlation of electrical reactor cable failure with materials degradation  

International Nuclear Information System (INIS)

Complete circuit failure (shortout) of electrical cables typically used in nuclear power plant containments is investigated. Failure modes are correlated with the mechanical deterioration of the elastomeric cable materials. It is found that for normal reactor operation, electrical cables are reliable and safe over very long periods. During high temperature excursions, however, cables pulled across corners under high stress may short out due to conductor creep. Severe cracking will occur in short times during high temperatures (>1500C) and in times of the order of years at elevated temperatures (1000C to 1400C). A theoretical treatment of stress distribution responsible for creep and for cracking by J.E. Reaugh of Science Applications, Inc. is contained in the Appendix. 29 refs., 32 figs

330

Correlation of electrical reactor cable failure with materials degradation  

Energy Technology Data Exchange (ETDEWEB)

Complete circuit failure (shortout) of electrical cables typically used in nuclear power plant containments is investigated. Failure modes are correlated with the mechanical deterioration of the elastomeric cable materials. It is found that for normal reactor operation, electrical cables are reliable and safe over very long periods. During high temperature excursions, however, cables pulled across corners under high stress may short out due to conductor creep. Severe cracking will occur in short times during high temperatures (>150/sup 0/C) and in times of the order of years at elevated temperatures (100/sup 0/C to 140/sup 0/C). A theoretical treatment of stress distribution responsible for creep and for cracking by J.E. Reaugh of Science Applications, Inc. is contained in the Appendix. 29 refs., 32 figs.

Stuetzer, O.M.

1986-03-01

331

Open-access dielectric elastomer material database  

Science.gov (United States)

Dielectric Elastomer Transducers (DETs) are deformable capacitors that can be used as sensors, actuators and generators. The design of effective and optimized DETs requires the knowledge of a set of relevant properties of the employed Dielectric Elastomer (DE) material, which make it possible to accurately predict their electromechanical dynamic behavior. In this context, an open-access database for DE materials has been created with the aim of providing the practicing engineer with the essential information for the design and optimization of new kinds of DET. Among the electrical properties, dielectric susceptibility, dielectric strength and conductivity are considered along with their dependence on mechanical strain. As regards mechanical behavior, experimental stress-strain curves are provided to predict hyperelasticity, plasticity, viscosity, Mullins effect and mechanical rupture. Properties of commercial elastomeric membranes have been entered in the database and made available to the research community. This paper describes the instrumentations, experimental setups and procedures that have been employed for the characterization of the considered DE materials. To provide an example, the experimental data acquired for a commercially available natural rubber membrane (OPPO Band Red 8012) are presented.

Vertechy, R.; Fontana, M.; Stiubianu, G.; Cazacu, M.

2014-03-01

332

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

333

Lateral-crack-free, buckled, inkjet-printed silver electrodes on highly pre-stretched elastomeric substrates  

International Nuclear Information System (INIS)

We report the formation of lateral-crack-free silver electrodes on highly pre-stretched poly(dimethylsiloxane) (PDMS) substrates using the inkjet-printing method followed by an annealing process under the pre-stretched state. Due to Poisson's effect, cracks are easily obtained in the direction lateral to the pre-stretching and releasing directions when the highly pre-stretched substrate is released after the electrode formation. In our method, however, Poisson's effect is suppressed significantly from the PDMS thermal expansion perpendicular to the pre-stretched direction during the annealing process. In order to prevent the formation of a lateral crack, the annealing temperature needs to be optimized for each pre-stretching condition. We modelled their relationship using Poisson's ratios and thermal expansion coefficients of the substrate and silver materials. Our measurement results showed consistent result with the simulation. The resistance of the fabricated silver electrodes negligibly changes under up to 17% strain and even after 1000 time stretching cycle tests. (paper)

334

Engineered bi-histidine metal chelation sites map the structure of the mechanical unfolding transition state of an elastomeric protein domain GB1.  

Science.gov (United States)

Determining the structure of the transition state is critical for elucidating the mechanism behind how proteins fold and unfold. Due to its high free energy, however, the transition state generally cannot be trapped and studied directly using traditional structural biology methods. Thus, characterizing the structure of the transition state that occurs as proteins fold and unfold remains a major challenge. Here, we report a novel (to our knowledge) method that uses engineered bi-histidine (bi-His) metal-binding sites to directly map the structure of the mechanical unfolding transition state of proteins. This method is adapted from the traditional ?-value analysis, which uses engineered bi-His metal chelation sites to probe chemical (un)folding transition-state structure. The ?(M2+)(U)-value is defined as ??G(‡-N)/??G(U-N), which is the energetic effects of metal chelation by the bi-His site on the unfolding energy barrier (?G(‡-N)) relative to its thermodynamic stability (?G(U-N)) and can be used to obtain information about the transition state in the mutational site. As a proof of principle, we used the small protein GB1 as a model system and set out to map its mechanical unfolding transition-state structure. Using single-molecule atomic force microscopy and spectrofluorimetry, we directly quantified the effect of divalent metal ion binding on the mechanical unfolding free energy and thermodynamic stability of GB1, which allowed us to quantify ?(M2+)(U)-values for different sites in GB1. Our results enabled us to map the structure of the mechanical unfolding transition state of GB1. Within GB1's mechanical unfolding transition state, the interface between force-bearing ?-strands 1 and 4 is largely disrupted, and the first ?-hairpin is partially disordered while the second ?-hairpin and the ?-helix remain structured. Our results demonstrate the unique application of ?-value analysis in elucidating the structure of the transition state that occurs during the mechanical unfolding process, offering a potentially powerful new method for investigating the design of novel elastomeric proteins. PMID:22947942

Shen, Tao; Cao, Yi; Zhuang, Shulin; Li, Hongbin

2012-08-22

335

Performance characteristics of O-ring seals for radioactive material packages when subjected to extreme temperatures  

International Nuclear Information System (INIS)

Performance requirements for radioactive material (RAM) packages are specified in Title 10, Code of Federal Regulations, Part 71 (10CFR71). Seals that provide the containment system interface between the packaging body and closure must function in both high and low temperature environments which are characteristic of the hypothetical fire accident and the -40F (233 K)1 normal transport condition, respectively. A research and testing program has been initiated at Sandia National Laboratories to examine the performance of elastomeric O-ring seal materials commonly used in RAM packages during the temperature extremes. Performance characteristics including permeation times, static compression set, and leakage rate versus temperature and time are being examined using helium or neon as the tracer gas. The results of this study can be used as an aid to package designers when selecting O-ring seal materials for specific applications

336

An in vitro study of the bond strength of five adhesives used for vinyl polysiloxane impression materials and tray materials.  

Science.gov (United States)

Although stock trays often provide mechanical retention for elastomeric impression materials, manufacturers typically recommend the use of an adhesive, whether a stock or custom tray is used. The mention of the bond strength on the adhesive packaging is not available, therefore the clinician has no idea whatsoever of the ideal adhesive. The aim of this study was to evaluate the bond strength of three vinyl polysiloxane (VPS) materials, one with a poly(methyl methacrylate) autopolymerizing (PMMA) specimen and another with a light-polymerizing tray material (VLC), using the adhesive recommended by the manufacturer of the impression material, and two universal adhesives. A total of ninety specimens (15 × 15 × 20 mm) were used, 45 specimens were made in PMMA and rest 45 was made in VLC. Five paint-on adhesives (Coltene, Caulk, 3M, universal Zhermack and universal GC) were applied. Three impression materials, Affinis, Reprosil, and 3M, were mixed and injected into a perforated poly vinyl chloride cylinder. Tray specimens were positioned against the open cylinder end in contact with the VPS material. Tensile strength tests were conducted until adhesive separation failure. Mean values and standard errors of the adhesive strength were recorded in MPa for each material combination. GC paint-on universal adhesive provided significantly higher adhesive strength values. PMID:24604999

Kumar, Surender; Gandhi, Udey Vir; Banerjee, Saurav

2014-03-01

337

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

338

Accuracy of stone casts obtained by different impression materials  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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

339

Accuracy of stone casts obtained by different impression materials  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

340

"Material" mechanics of materials  

Directory of Open Access Journals (Sweden)

Full Text Available The paper outlines recent developments and prospects in the application of the continuum mechanics expressed intrinsically on the material manifold itself. This includes applications to materially inhomogeneous materials physical effects which, in this vision, manifest themselves as quasi-in homogeneities, and the notion of thermo dynamical driving force of the dissipative progress of singular point sets on the material manifold with special emphasis on fracture, shock waves and phase-transition fronts. .

Maugin Gérard A.

2002-01-01

 
 
 
 
341

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

342

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

343

Sealing Materials for Use in Vacuum at High Temperatures  

Science.gov (United States)

Sealing materials that can be applied and left in place in vacuum over a wide range of temperatures (especially temperatures of a few thousand degrees Celsius) have been conceived and investigated for potential utility in repairing thermal-protection tiles on the space shuttles in orbit before returning to Earth. These materials are also adaptable to numerous terrestrial applications that involve vacuum processing and/or repair of structures that must withstand high temperatures. These materials can be formulated to have mechanical handling characteristics ranging from almost freely flowing liquid-like consistency through paste-like consistency to stiff puttylike consistency, and to retain these characteristics in vacuum until heated to high curing temperatures. A sealing material of this type can be formulated to be used in any of several different ways for example, to be impregnated into a high-temperature-fabric patch, impregnated into a high-temperature-fabric gasket for sealing a patch, applied under a patch, or applied alone in the manner of putty or wallboard compound. The sealing material must be formulated to be compatible with, and adhere to, the structural material(s) to be repaired. In general, the material consists of a vacuum-compatible liquid containing one or more dissolved compound(s) and/or mixed with suspended solid particles. Depending on the intended application, the liquid can be chosen to be of a compound that can remain in place in vacuum for a time long enough to be useful, and/or to evaporate or decompose in a controlled way to leave a useful solid residue behind. The evaporation rate is determined by proper choice of vapor pressure, application of heat, and/or application of ultraviolet light or other optical radiation. The liquid chosen for the original space shuttle application is a commercial silicone vacuum-pump oil.

Pettit, Donald R.; Camarda, Charles J.; Lee Vaughn, Wallace

2012-01-01

344

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 SciELO Mexico | Language: Spanish Abstract in spanish 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

345

Evaluation of Ion Exchange Materials in K Basin Floor Sludge and Potential Solvents for PCB Extraction from Ion Exchange Materials  

International Nuclear Information System (INIS)

Approximately 73 m3 of heterogeneous solid material, ''sludge,'' (upper bound estimate, Packer 1997) have accumulated at the bottom of the K Basins in the 100 K Area of the Hanford Site. This sludge is a mixture of spent fuel element corrosion products, ion exchange materials (organic and inorganic), graphite-based gasket materials, iron and aluminum metal corrosion products, sand, and debris (Makenas et al. 1996, 1997). In addition, small amounts of polychlorinated biphenyls (PCBs) have been found. These small amounts are significant from a regulatory standpoint. Ultimately, it is planned to transfer the K Basins sludge to the Hanford double shell tanks (DSTs). Chemical pretreatment is required to address criticality issues and the destruction or removal of PCBs before the K Basin sludge can be transferred to the DSTs. Eleven technologies have been evaluated (Papp 1997) as potential pretreatment methods. Based on the evaluations and engineering studies and limited testing, Fluor Daniel Hanford recommended solvent washing of the K Basin sludge, followed by nitric acid dissolution and, potentially, peroxide addition (FDH 1997). The solvent washing (extraction) and peroxide addition would be used to facilitate PCB removal and destruction. Following solvent extraction, the PCBs could be distilled and concentrated for disposal as a low-level waste. The purpose of the work reported here was to continue investigating solvent extraction, first by better identifying the ion exchange materials in the actual sludge samples and then evaluating various solvents for removing the PCBs or possibly dissolving the resins. This report documents some of the process knowledge on ion exchange materials used and spilled in the K Basins and describes the materials identified from wet sieving KE Basin floor and canister sludge and the results of other analyses. Several photographs are included to compare materials and illustrate material behavior. A summary of previous tests on solvent extraction of PCB surrogates from simulant K Basin sludge is also given

346

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

347

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

348

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

349

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 SciELO Brazil | Language: Portuguese Abstract in portuguese 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

350

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 SciELO Brazil | Language: Portuguese Abstract in portuguese 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.

351

46 CFR 69.117 - Spaces exempt from inclusion in gross tonnage.  

Science.gov (United States)

...caulking, or gaskets of any material are not used. (5) An interior...caulking, or gaskets of any material are not used. (6) An interior...caulking, or gaskets of any material are not used. (7...screen or temporarily closed by canvas secured at the top and...

2010-10-01

352

24 CFR 3280.604 - Materials.  

Science.gov (United States)

...for Polybutylene (PB) Plastic Hot- and Cold-Water...ASTM D3309-92a. Plastic Piping Components and...Gaskets for Cast Iron Soil Pipe and Fittings—ASTM...Vinyl Chloride) (PVC) Plastic Piping Systems—ASTM...and Spigot Cast Iron Soil Pipe and...

2010-04-01

353

78 FR 42929 - Foreign-Trade Zone (FTZ) 41-Milwaukee, Wisconsin, Notification of Proposed Production Activity...  

Science.gov (United States)

...packaging materials, plastic packing, plastic bags, plastic trim pieces and switch covers, rubber spacers, plastic items, rubber gaskets, gaskets...screens, roof/wall caps, screws, fasteners, stainless steel screws, nuts,...

2013-07-18

354

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

355

Compatibility of refrigerants and lubricants with elastomers  

Energy Technology Data Exchange (ETDEWEB)

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. 97% of the swell measurements have been made to date. The other 3% of the measurements are contingent on the availability of additional quantities of R-32. Swell behavior in the 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.

1992-10-01

356

Compatibility of refrigerants and lubricants with elastomers. Quarterly report, 1 July 1992--30 September 1992  

Energy Technology Data Exchange (ETDEWEB)

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. 97% of the swell measurements have been made to date. The other 3% of the measurements are contingent on the availability of additional quantities of R-32. Swell behavior in the 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.

1992-10-01

357

COMPRESSIVE AND SHEAR ANALYSIS OF RUBBER BLOCK UNDER LARGE STRAIN  

Directory of Open Access Journals (Sweden)

Full Text Available The Elastomeric materials have found use in a wide range of applications, including hoses, tires, gaskets, seals, vibration isolators, bearings and dock fenders. The analysis of rubber blocks for its compression and shear behavior has been carried out using the imaging techniques. The dynamic stressing and its associated change in shape of the rubber blocks during large compression are very limited as their measurements were difficult. A newly developed Machine Vision based image processing test has been effectively used to study the deformation characteristics of the rubber blocks under large strains. An extended analysis on the rubber blocks has been carried out to understand the compression and deformation behavior in static and dynamic condition and the nonlinear behavior were also characterized. The rubber blocks of distinguished geometries have shown diverse change in shape and nonlinear deformation behavior under compression/shear loading.

K. Sridharan

2013-01-01

358

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

359

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

360

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.

 
 
 
 
361

Determination of the mixed-mode fracture energy of elastomeric structural adhesives: evaluation of debonding buckling in fibre-metal hybrid laminates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fibre–metal hybrid laminates combine layers of metal with laminates made of composites – polymeric matrix reinforced with glass-fibre woven fabric. Interface behaviour plays a fundamental role in the overall properties of the hybrid material, especially in the failure mode by debonding buckling of the outermost metal layer. A proper measurement of adhesive fracture energy is required so as to avoid this early failure mechanism during bending. Tapered double cantilever beam test and dissim...

Sua?rez Bermejo, Juan Carlos; Lopez Martin, Francisco; Miguel Alonso, Santiago; Pinilla Cea, Maria Paz; Herreros Sierra, Miguel Angel

2009-01-01

362

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 nos 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.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

2012-01-01

363

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.

364

Refrigeration engineering: Creep behaviour of elastomeric insulation materials. Physical fundamentals of moisture-intake by vapour diffusion; Kaeltetechnik: Langzeitverhalten von elastomeren Daemmstoffen. Physikalische Grundlagen der Feuchtigkeits-Aufnahme durch Dampfdiffusion  

Energy Technology Data Exchange (ETDEWEB)

The most important tasks for a refrigeration insulation are the avoidance of dew water and the minimization of energy losses during the complete operation period of the device. During this time for dimensioning of insulation it must be taken into account that energy losses due to moisture influx can increase drastically. A more reliable insulation system, presented here, has to protect against inadmissible soaking. (GL)

Stoerkmann, M.

2006-04-28

365

Compliant layer bearings in artificial joints. Part 2: simulator and fatigue testing to assess the durability of the interface between an elastomeric layer and a rigid substrate.  

Science.gov (United States)

Artificial joints have been much improved since their introduction but they still have a limited lifetime. In an attempt to increase their life by improving the lubrication acting within these prostheses, compliant layered polyurethane (PU) joints have been devised. These joints mimic the natural synovial joint more closely by promoting fluid film lubrication. In this study, tests were performed on compliant layer joints to determine their ability to function under a range of conditions. Both static and dynamic compression tests were undertaken on compliant artificial hip joints of two different radial clearances. Friction tests were also performed before and after static loading. In addition to this, knee wear tests were conducted to determine the suitability of a compliant layer in these applications. In the knee tests, variations in experimental testing conditions were investigated using both active and passive rotation and severe malalignment of the tibial inserts. The static compression tests together with the friction studies suggest that a small radial clearance is likely to result in 'grabbing' contact between the head and cup. The larger radial clearance (0.33 microm) did not exhibit these problems. The importance of the design of the compliant layer joints was highlighted with delamination occurring on the lateral bearings during the knee wear studies. The bearings with a layer 2 mm thick performed better than the bearings with a layer 3 mm thick. Tests conducted on flat PU bearings resulted in no delamination; therefore, it was concluded that the layer separation was caused by design issues rather than by material issues. It was found that, with careful material choice, consideration of design, and effective manufacturing techniques, the compliant layer joint functioned well and demonstrated durability of the union between the hard and soft layers. These results give encouragement for the suitability of these joints for clinical use. PMID:19239063

Jones, E; Scholes, S C; Burgess, I C; Ash, H E; Unsworth, A

2009-01-01

366

Composite materials  

International Nuclear Information System (INIS)

A superconductor composite is described comprising at least one longitudinally extending superconductor filament or bundle of sub-filaments, each filament or bundle of sub-filaments being surrounded by and in good electrical contact with a matrix material, the matrix material comprising a plurality of longitudinally extending cells of a metal of high electrical conductivity surrounded by a material of lower electrical conductivity. The high electrical conductivity material surrounding the superconducting filament or bundle of sub-filaments is interrupted by a radially extending wall of the material of the lower electrical conductivity, the arrangement being such that at least two superconductor filaments or sub-filaments are circumferentially circumscribed by a single annulus of the material of high electrical conductivity. The annulus is electrically interrupted by a radially extending wall of the material of low electrical conductivity

367

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 SciELO Colombia | Language: Spanish Abstract in spanish 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.

368

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 SciELO Colombia | Language: Spanish Abstract in spanish 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

369

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

370

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 SciELO Brazil | Language: Portuguese Abstract in portuguese 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 co