WorldWideScience
 
 
1

Degradation of elastomeric gasket materials in PEM fuel cells  

International Nuclear Information System (INIS)

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

2007-02-15

2

Fluorinated elastomeric materials  

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-02-13

3

Fluorinated elastomeric materials  

Energy Technology Data Exchange (ETDEWEB)

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

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

1986-11-04

4

Non-asbestos gasket materials for sealing internal combustion engines  

Energy Technology Data Exchange (ETDEWEB)

At the moment, the replacement of asbestos in gasket materials is not required by law. Nevertheless, Elring Dichtungswerke GmbH presents now 3 non-asbestos gasket materials which in many cases can be used in exchange for existing asbestos gaskets. On presenting the new products, the problems in manufacturing and developing of these new gasket materials are described.

Kuenzel, H.T.

1985-03-01

5

Comparison of elastomeric impression materials' thixotropic behavior.  

UK PubMed Central (United Kingdom)

The improved flow characteristics of new elastomeric impression materials are significant factors in the selection ofsuitableproductsfor clinical applications. The aim of this study was to assess the thixotropic behavior and compare the flow characteristics of seven different elastomeric impression materials using a shark fin test. One polyvinylsiloxane showed the highest shark fin height values, while the newly formed vinylsiloxanether material exhibited no significant differences when compared with two polyvinylsiloxanes. One of the five polyvinylosiloxanes presented significantly lower shark fin values than all other materials. It was concluded that flow characteristics for most of the tested materials are acceptable.

Tolidis K; Tortopidist D; Gerasimou P; Theocharidou A; Boutsiouki C

2013-06-01

6

Hydrogen isotope permeation in elastomeric materials  

International Nuclear Information System (INIS)

[en] 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

1975-09-30

7

Effect of ozonated water sanitization on gasket materials used in fluid food processing.  

UK PubMed Central (United Kingdom)

Standard-molded, one piece O-ring food processing plant gaskets (1.5 in or 36.1 mm diameter) made of seven different substances (Buna N, white Buna N, EPDM (ethylene propylene diene monomer), polyethylene, silicone rubber, PTFE (polytetrafluoroethylene or Teflon) and steam-resistant Viton) were treated with chlorine sanitizer or ozonated water. After treatment, only very slight differences were noted visually between control and treated gaskets. Measurements indicated that ozone treatment affected the tensile strength of EPDM and Viton, but not significantly more than chlorine treatment. The tensile strengths of other gasket materials were not significantly affected by ozone treatment. The elasticity of ozone-treated PTFE gaskets was significantly different from chlorine-treated PTFE gaskets. Other gasket materials were not significantly affected by ozone treatment.

Greene AK; Vergano PJ; Few BK; Serafini JC

1994-01-01

8

Diffusion welding of magnetic materials through porous gaskets made of rolled strips  

International Nuclear Information System (INIS)

[en] Results are presented of studying peculiarities of producing rolled porous gaskets from nickel strips and formation of magnetic material joints by diffusion welding through such gaskets. The optimum mode of pyrolysis (573 K, 9 K/min) ensuring reduction of formate nickel with specific surface 16-18 m2/g is established. 60-80 ?m thick strips with 50-60% porosity prepared at the 190 mm/min rolling rate are recommended as porous nickel gaskets. Optimum working parameters are determined for diffusion welding of magnetic-soft materials with magnetic-hard ones through porous nickel gaskets ensuring the formation of precise joints with preservation of initial physico-mechanical properties without development of volumetric plastic strains

1984-01-01

9

Diffusion welding of magnetic materials through porous gaskets made of rolled strips  

Energy Technology Data Exchange (ETDEWEB)

Results are presented of studying peculiarities of producing rolled porous gaskets from nickel strips and formation of magnetic material joints by diffusion welding through such gaskets. The optimum mode of pyrolysis (573 K, 9 K/min) ensuring reduction of formate nickel with specific surface 16-18 m/sup 2//g is established. 60-80 ..mu..m thick strips with 50-60% porosity prepared at the 190 mm/min rolling rate are recommended as porous nickel gaskets. Optimum working parameters are determined for diffusion welding of magnetic-soft materials with magnetic-hard ones through porous nickel gaskets ensuring the formation of precise joints with preservation of initial physico-mechanical properties without development of volumetric plastic strains.

Karakozov, Eh.S.; Panaetov, V.G.; Tarlavskij, V.Eh.; Lyushinskij, A.V. (Moskovskij Vechernij Metallurgicheskij Inst. (USSR))

1984-10-01

10

Review of radiation resistance for plastic and elastomeric leave materials  

Energy Technology Data Exchange (ETDEWEB)

A review of the radiation resistance for plastic and elastomeric materials is given in the form of tables in which literature data are listed. After introductory remarks, the factors which can influence the radiation effects and the consideration of these factors in the tables are explained. Particular attention is given to the variation of the radiation resistance with dose rate for irradiation in air.

Wuendrich, K. (Bundesanstalt fuer Materialpruefung, Berlin (Germany, F.R.))

1984-01-01

11

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

International Nuclear Information System (INIS)

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

2004-01-01

12

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

International Nuclear Information System (INIS)

[en] Elastomeric seals are a frequently favoured method of sealing radioactive material transport (RMT) packages. The sealing technology has been proven for many years in a wide range of industrial applications. The requirements of the RMT package applications, however, are significantly different from those commonly found in other industries. This guide outlines the regulatory performance requirements placed on an RMT package sealing system by the IAEA transport regulations TS-R-1 (1996) and then summarises the material, environment and geometry characteristics of elastomeric seals relevant to RMT applications. Tables list typical material properties for a range of elastomeric materials commonly used in RMT packages. (author)

2002-01-01

13

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-07-01

14

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

2000-01-01

15

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

Energy Technology Data Exchange (ETDEWEB)

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

BRONOWSKI,DAVID R.

2000-06-01

16

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

17

Linear dimensional stability of elastomeric impression materials over time.  

UK PubMed Central (United Kingdom)

The purpose of this study was to evaluate the linear dimensional stability of different elastomeric impression materials over time. A metal mold was designed with its custom trays, which were made of thermoplastic sheets (Sabilex sheets 0.125 mm thick). Three impressions were taken of it with each of the following: the polyvinylsiloxane Examix-GC-(AdEx), Aquasil-Dentsply-(AdAq) and Panasil-Kettenbach-(AdPa), and the polydimethylsiloxane Densell-Dental Medrano-(CoDe), Speedex-Coltene-(CoSp) and Lastic-Kettenbach-(CoLa). All impressions were taken with putty and light-body materials using a one-step technique. Standardized digital photographs were taken at different time intervals (0, 15, 30, 60, 120 minutes; 24 hours; 7 and 14 days), using an "ad-hoc" device, and analyzed using software (Image Tool) by measuring the distance between lines previously made at the top of the mold. The results were analyzed by ANOVA for repeated measures. The initial and final values for mean and SD were: AdEx: 1.32 (0.01) and 1.31 (0.00); AdAq: 1.32 (0.00) and 1.32 (0.00), AdPa: 1.327 (0.006) and 1.31 (0.00); CoDe: 1.32 (0.00) and 1.32 (0.01); CoSp: 1.327 (0.006) and 1.31 (0.00), CoLa: 1.327 (0.006) and 1.303 (0.006). Statistical evaluation showed that both material and time have significant effects. Conclusion: Under the conditions in this study we conclude that time would significantly affect the lineal dimensional stability of elastomeric impression materials.

Garrofé AB; Ferrari BA; Picca M; Kaplan AE

2011-01-01

18

Working time of elastomeric impression materials: relevance of rheological tests.  

UK PubMed Central (United Kingdom)

PURPOSE: To study possible relationships between rheological parameters of elastomeric impression materials and their dimensional accuracy at different stages during setting within the manufacturers' recommended working time. METHODS: Four chemically different impression material-types were tested. Impressions were taken of a master cone at 30-second intervals after mixing and up to 30 seconds beyond the recommended working time. Impression accuracy (deltad) was determined as the dimensional deviation of stone dies from the master cone. The phase angle delta(t) and storage modulus G'(t) were measured and the working time determined according to ISO 4823. Three operators assessed the latest point in time for uncompromised impression taking. Correlation analysis was performed using Spearman's Rho (P = 0.05). RESULTS: For most materials investigated, deltad(t) was constant within the manufacturers' recommended working time whereas delta(t) and G'(t) changed significantly. There was no correlation (P > 0.05) between deltad(t) versus delta(t) and G'(t), respectively. When determined according to ISO 4823, working time was longer than operator-assessed working time for all materials investigated.

Balkenhol M; Kanehira M; Finger WJ; Wöstmann B

2007-12-01

19

Recent developments in PVRC gasket testing  

Energy Technology Data Exchange (ETDEWEB)

For the past 15--20 years, a major research program aimed at solving the problem of leakage of gasketed flanged joints has been undertaken by the Pressure Vessel Research Council (PVRC). This program has resulted in greatly enhanced understanding of the leakage phenomena of a flanged joint and improvements of the ASME Code design procedures. The PVRC bolted flanged program has been organized into six areas: (1) implement PVRC gasket constants and test procedure development; (2) issue a flange design guidelines report considering items such as modeling, tightness, transients, relaxation, etc.; (3) flange rating parameters for standard flanges; (4) design parameters for ASME joints; (5) gasket testing for temperature behavior data and test method developments; and (6) flanged joint assembly and interaction effects. This paper presents an update of the recent developments in the area of gasket testing; specifically, testing on flexible graphite gaskets, elastomeric sheet gaskets, and fugitive emissions gasket characteristics with various types of fluids are described.

Hsu, K.H. [Babcock and Wilcox, Barberton, OH (United States); Payne, J.R. [JPAC Inc., Long Valley, NJ (United States); Derenne, M. [Ecole Polytechnique, Montreal, Quebec (Canada)

1996-12-01

20

Summary of geothermal elastomeric materials (GEM) technology transfer  

Energy Technology Data Exchange (ETDEWEB)

High temperature elastomer technology which significantly advances the state-of-the-art was developed by L'Garde under DOE sponsorship. DOE exercised foresight and sponsored direct transferal of this technology to industry. Consequently, the technology can be readily purchased today from three commercial sources in the form of finished elastomeric parts. This paper provides a summary and conclusion of this effort which transcended important technology from a report gathering dust to three ready sources of elastomeric parts providing the benefits of Y267 EPDM technology.

Hirasuna, Alan R.

1982-10-08

 
 
 
 
21

Carriage of oral flora on irreversible hydrocolloid and elastomeric impression materials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study assessed the carriage and persistence of oral flora on irreversible hydrocolloid and elastomeric impression materials. In the first part of the study, a single isolate each of Streptococcus mutans, Escherichia coli, Staphylococcus aureus, and Candida albicans were inoculated onto each of ...

Samaranayake, LP; Hunjan, M; Jennings, KJ

22

Orthopaedic gasket  

UK PubMed Central (United Kingdom)

The utility model relates to an orthopaedic gasket, in particular to a gasket used for curing the ligament avulsion at the joint part of a bone and other diseases. The orthopaedic gasket is characterized in that a central hole is formed on the disc-shaped main body and at least one tooth-shaped small column is arranged on the back side of the main body. Six tooth-shaped small columns are evenly distributed on the back side of the main body. A spherical concave cambered surface is arranged on the frontal surface of the main body. The tooth-shaped small columns on the back side of the main body are embedded at the tail end of the ligament and fixed on the bone with a hollow nail in a matched manner for curing the ligament avulsion. The gasket can be obliquely used by being matched with the hollow nail. The orthopaedic gasket solves the problems of infirm fixation between the ligament and the bone, ligament necrotizing at the tail end of the ligament, and the like, which easily occur clinically, and is particularly suitable for the bones with osteoporosis.

ZHIXIONG LIN

23

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

24

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.

2012-01-01

25

Surface detail reproduction with new elastomeric dental impression materials.  

UK PubMed Central (United Kingdom)

OBJECTIVES: To compare the surface detail reproduction ability of 2 polyethers, 1 polyether-polyvinyl siloxane (PVS) hybrid, and 1 polyvinyl siloxane reference impression material when impressions of prepared dentin are made, and to determine the wettability of the nonset and set impression materials. METHOD AND MATERIALS: Impressions from air-dried or wet dentin surfaces were made with the light-bodied impression materials P2 Polyether (P2L), Impregum Garant L DuoSoft (IMP), the hybrid-type Fusion/Senn Light (SEN), and the PVS Flexitime Correct Flow (FLE). Roughness (Rz, Ra) was determined on 5 dentin specimens and 5 impressions (dry or wet) for each material. Data were analyzed using ANOVA and Duncan's test (a <.05). Wettability with water of nonset and set impression materials was recorded with an optical contact-angle measuring device. The set materials' wettability was determined on dry surfaces and after rinsing with water. RESULTS: Differential dentin surface reproduction with IMP, SEN, and FLE was between -2 and +2 Microm (Rz), and -0.2 and +0.2 Microm (Ra). Curing of P2L on dentin was inhibited. The contact angle of nonset IMP was less than 45 degrees, and initial angles for nonset SEN, FLE, and P2L were greater than 90 degrees. Early contact angles on rinsed FLE, P2L, and SEN were greater than 90 degrees. Angles on set IMP were consistently between initial 75 degrees and final 55 degrees. CONCLUSION: IMP, SEN, and FLE reproduce prepared dentin accurately, whereas P2L does not cure on dry or wet dentin. All materials have a reasonable potential of wetting moist surfaces.

Kanehira M; Finger WJ; Komatsu M

2007-06-01

26

ANTIMICROBIAL ELASTOMERIC PRODUCTS  

UK PubMed Central (United Kingdom)

This invention relates to elastomeric products having an antimicrobial coating. The antimicrobial coating is comprised of iodinated resin particles incorporated in a polymer. The coatings are prepared by forming a coating mixture of polymer and iodinated resin particles in water. The coating is then applied to the elastomeric material through a dipping or spraying procedure. A thixotrope may be added to increase the uniformity of the polymer coating over the surface of the elastomeric product. The antimicrobial coatings may be applied to a variety of different elastomeric products including gloves and catheters and are capable providing a high level of protection against microbes and other contaminants.

MESSIER PIERRE J; OHAYON DAVID; TRUSCOTT WAVA; LITTLETON KERMIT

27

Elastomeric Diaper Fastening Tab  

UK PubMed Central (United Kingdom)

A diaper fastening system including at least one elastomeric connection tab disposed at a side portion of the diaper. The connection tab has a body portion of stitch-bonded construction including an elastomeric expansion zone. The elastomeric expansion zone includes an inelastic stitching substrate of fibrous material with a plurality of accordion pleats and a zigzag network of elastomeric yarns disposed in underlying relation to the pleats. The zigzag network is adapted to apply contracting forces to the stitching substrate in the length dimension of the connection tab.

WILDEMAN MARTIN; SEARS LORI SHANNON

28

Working times of elastomeric impression materials determined by dimensional accuracy.  

Science.gov (United States)

The working times of five poly(vinyl siloxane) impression materials were estimated by evaluating the dimensional accuracy of stone dies of impressions of a standard model made at successive time intervals. The stainless steel standard model was represented by two abutments having known distances between landmarks in three dimensions. Three dimensions in the x-, y-, and z-axes of the stone dies were measured with a traveling microscope. A time interval was rejected as being within the working time if the percentage change of the resultant dies, in any dimension, was statistically different from those measured from stone dies from previous time intervals. The absolute dimensions of those dies from the rejected time interval also must have exceeded all those from previous time intervals. Results showed that the working times estimated with this method generally were about 30 seconds longer than those recommended by the manufacturers. PMID:8639243

Tan, E; Chai, J; Wozniak, W T

29

Working times of elastomeric impression materials determined by dimensional accuracy.  

UK PubMed Central (United Kingdom)

The working times of five poly(vinyl siloxane) impression materials were estimated by evaluating the dimensional accuracy of stone dies of impressions of a standard model made at successive time intervals. The stainless steel standard model was represented by two abutments having known distances between landmarks in three dimensions. Three dimensions in the x-, y-, and z-axes of the stone dies were measured with a traveling microscope. A time interval was rejected as being within the working time if the percentage change of the resultant dies, in any dimension, was statistically different from those measured from stone dies from previous time intervals. The absolute dimensions of those dies from the rejected time interval also must have exceeded all those from previous time intervals. Results showed that the working times estimated with this method generally were about 30 seconds longer than those recommended by the manufacturers.

Tan E; Chai J; Wozniak WT

1996-03-01

30

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

2004-01-01

31

Surface detail reproduction of elastomeric impression materials related to rheological properties.  

UK PubMed Central (United Kingdom)

OBJECTIVES: The purpose of this work was to discern, for elastomeric impression materials, the important rheological properties and importance of hydrophilicity for detail reproduction. METHODS: Viscosity, modulus and tan delta were measured using a controlled-stress rheometer in cone/plate configuration. The flow of the materials, immediately after mixing and at the manufacturer's stated working time, was measured using a shark fin test and the interaction with moist surfaces was determined by taking impressions from two different sized grooves in moist gypsum casts. RESULTS: Tan delta was found to be the parameter most indicative of the accuracy of the impression and the flow of the material. Impregum samples, a polyether material, exhibited the highest initial tan delta (7.4), the largest shark fins at both time periods and the most accurate impressions from both grooves. Aquasil, a polyvinylsiloxane material, had similar initial tan delta values (6.9) and impressions taken on the deep groove with this material closely matched the groove. The other two polyvinylsiloxane materials (Affinis and Flexitime) had significantly lower initial tan delta values (3.1 and 2.9, respectively), exhibited much smaller shark fins and a worse ability to accurately reproduce the deep groove. SIGNIFICANCE: For large features, it is clear that the higher the initial tan delta of the impression material the better the ability to replicate larger features. However, with smaller features the relative hydrophobicity of the material becomes an important factor, with more hydrophilic materials better able to reproduce fine detail.

German MJ; Carrick TE; McCabe JF

2008-07-01

32

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1994-01-01

33

Mechanical properties of 3 hydrophilic addition silicone and polyether elastomeric impression materials.  

UK PubMed Central (United Kingdom)

STATEMENT OF PROBLEM: New "hydrophilic" elastomeric impression materials have been introduced with the goals of reducing marginal voids and distortion in the impressions and improving the quality of gypsum dies, but there are insufficient data on the mechanical properties of these materials. PURPOSE: Mechanical properties, including elastic recovery, strain in compression, tear energy, and tensile strength of 3 hydrophilic impression materials with low and high consistencies were compared. MATERIAL AND METHODS: Two addition silicone impression brands (Imprint II, 3M ESPE; Flexitime, Heraeus Kulzer) and a polyether brand (Impregum, 3M ESPE) were studied. Two consistencies of each material (light-body and heavy-body) were investigated. Elastic recovery (%) and strain in compression (%) were tested according to ISO 4823; tear energy (J/m2) and tensile strength (MPa) were tested following Webber and Ryge's method and ASTM D412 (Test Method A), respectively. Five specimens were made for each group for a total of 24 groups and 120 specimens. Results were analyzed by 2-way analysis of variance, and Fisher's protected least significance difference intervals were calculated (alpha=.05). Correlation analysis was used to evaluate the relationships among properties. RESULTS: P values were smaller than .0001 for material, consistency, and interaction for strain in compression, tear energy, and tensile strength. For elastic recovery, P values were smaller than .0001 for material and the interaction between material and consistency, but equal to .4150 for consistency. Strain in compression correlated with other mechanical properties (P<.05), but tensile strength and tear resistance were not correlated. CONCLUSIONS: In general, new "soft" polyether impression materials had higher strain in compression and lower tensile strength compared to new "hydrophilic" addition silicone materials. Heavy-body materials had higher tear properties and tensile strength than light-body materials. Strain in compression was correlated with elastic recovery, tear energy, and tensile strength. Tear resistance and tensile strength were not correlated.

Lu H; Nguyen B; Powers JM

2004-08-01

34

Linear dimensional changes in plaster die models using different elastomeric materials  

Scientific Electronic Library Online (English)

Full Text Available 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 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 ab (more) utment 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

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

2010-09-01

35

METAL-DETECTABLE ELASTOMERIC MATERIAL FOR PISTON SEALS AND THE LIKE  

UK PubMed Central (United Kingdom)

An elastomeric material for articles such as dynamic seals (20) and the like is rendered detectable by conventional metal detectors (18) through the incorporation of particles of a metallic alloy (22). Preferably, the resulting impregnated material contains at least 0.25 % and no more than 50 % by volume of the alloy, with 2 % by volume being the most favored. In one embodiment, the alloy contains 11.0 % to 22.0 % by weight of Iron, 70.0 % to 90.0 % by weight of Nickel, and 0.0 % to 7.0 % by weight of Molybdenum. In another embodiment, the alloy contains 14.0 % to 19.0 % by weight of Iron, 80.0 % to 83.0 % by weight of Nickel, and 1.0 % to 3.0 % by weight of Molybdenum, and in the most preferred embodiment, the alloy contains about 15.43 % by weight of Iron, about 82.39 % by weight of Nickel, and about 2.17 % by weight of Molybdenum.

LICATA Michael P.

36

Metal-detectable elastomeric material for piston seals and the like  

UK PubMed Central (United Kingdom)

An elastomeric material for articles such as dynamic seals and the like is rendered detectable by conventional metal detectors through the incorporation of particles of a metallic alloy. Preferably, the resulting impregnated material contains at least 0.25% and no more than about 50% by volume of the alloy, with 2% by volume being the most favored. In one embodiment, the alloy contains 11.0% to 22.0 % by weight of Iron, 70.0% to 90.0% by weight of Nickel, and 0.0% to 7.0% by weight of Molybdenum. In another embodiment, the alloy contains 14.0% to 19.0% by weight of Iron, 80.0% to 83.0% by weight of Nickel, and 1.0% to 3.0% by weight of Molybdenum, and in the most preferred embodiment, the alloy contains about 15.43% by weight of Iron, about 82.39% by weight of Nickel, and about 2.17% by weight of Molybdenum.

LICATA MICHAEL P

37

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

Energy Technology Data Exchange (ETDEWEB)

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 {approx}80 {micro}m at 48.0 GPa with this new composite c-BN gasket assembly. The sample can be located at the center of the gap, {approx}20 {micro}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{sub 60} sample was studied up to 48 GPa, and a pressure induced bonding transition from sp{sup 2} to sp{sup 3} was observed at 27 GPa.

Wang, Lin; Yang, Wenge; Xiao, Yuming; Liu, Bingbing; Chow, Paul; Shen, Guoyin; Mao, Wendy L.; Mao, Ho-kwang (Jilin); (Stanford); (CIW)

2011-09-15

38

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

UK PubMed Central (United Kingdom)

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.

Wang L; Yang W; Xiao Y; Liu B; Chow P; Shen G; Mao WL; Mao HK

2011-07-01

39

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; Karina Yumi Murata; Accácio Lins do Valle; Janaina Salomon Ghizoni; Fábio Kenji Shiratori

2010-01-01

40

Serpentine metal gasket  

Energy Technology Data Exchange (ETDEWEB)

A metallic seal or gasket for use in the joining of cryogenic fluid conduits, the seal or gasket having a generally planar and serpentine periphery defining a central aperture. According to a preferred embodiment, the periphery has at least two opposing elongated serpentine sides and two opposing arcuate ends joining the opposing elongated serpentine sides and is of a hexagonal cross-section.

Rothgeb, Timothy Moore (Norfolk, VA); Reece, Charles Edwin (Yorktown, VA)

2009-06-02

 
 
 
 
41

Fiber gasket and method of making same  

Energy Technology Data Exchange (ETDEWEB)

A gasket (1) is made by repetitively spirally winding a fiber (3) back on itself in a closed path. The gasket (1) so made has a multi-layer spiral winding (1) formed in a loop (5). The fiber (3) can be wound at a constant wrap rate to form a gasket with a uniform cross-section around the loop. Alternatively, the wrap rate can be varied, increased to increase cross-sectional bulk, and decreased to reduce cross-section bulk around the loop (5). Also, the spiral winding (7) can be applied over a core (13) of either strands of the fiber (3) or a dissimilar material providing a desired property such as resiliency, stiffness or others. For high temperature applications, a ceramic fiber (3) can be used. The gasket (1) can have any of various geometric configurations with or without a core (13).

Bruck, Gerald Joseph (Murrysville, PA); Alvin, Mary Anne (Pittsburgh, PA); Smeltzer, Eugene E. (Export, PA)

2003-01-01

42

Experience with gasket testing according to new DIN standards  

Energy Technology Data Exchange (ETDEWEB)

In 1995 new DIN standards were published containing gasket factor definitions, gasket testing procedures and requirements as a basis for technical delivery conditions. The gasket factors in DIN 28090 are consistent with those in the design rules for bolted flanged connections laid down in DIN EN 1591. Both standards together are an advanced and reliable tool for strength analysis and tightness assessment for bolted flanged connections. The new DIN standards contain new features in detail: gasket factors are related to tightness classes allowing tightness classification of flanged joints; time and temperature effects are regarded by means of high temperature longterm aging leakage tests; and gasket material degradation due to chemical attack is covered by means of chemical resistance tests. Verification of gasket testing according to the new DIN standards by means of tests on real flanged joints is under way.

Kockelmann, H. [Univ. of Stuttgart (Germany). Staatliche Materialpruefungsanstalt; Bartonicek, J. [Gemeinschaftskernkraftwerk Neckar GmbH, Neckarwestheim (Germany); Hirschvogel, A. [SGL Technik GmbH, Meitingen (Germany)

1996-12-01

43

Selection of elastomeric materials for compliant-layered total hip arthroplasty.  

UK PubMed Central (United Kingdom)

A selection procedure has been developed to identify suitable commercial materials for use in compliant-layer artificial hip joints. Mechanical requirements, notably hardness and strength, as well as biocompatibility, constituted the specification for the compliant layer. Applying these constraints, candidate materials were identified in a broad range of polymeric material classes. Detailed sourcing and literature searching helped to identify materials appropriate to the application, with suitable mechanical and physical properties, as well as a history of successful clinical use. Some likely materials were identified but were prohibited from further consideration by limited commercial availability. Physical and mechanical characterization together with literature data were used to determine the relative ranking of the candidate materials and through a weighted materials property selection procedure the materials of choice were identified. The linear segmented aromatic polyurethanes, Tecothane 1085 and Estane 5714F1, emerged as the preferred materials.

Quigley FP; Buggy M; Birkinshaw C

2002-01-01

44

Flexible all-metal gaskets halt heat exchanger leakage  

Energy Technology Data Exchange (ETDEWEB)

The Oyster Creek site of Texas Operations, Dow Chemical Company in Freeport, TX, was concerned about the potential fire hazard of hydrogen and hot hydrocarbon vapors leaking past the sealing gaskets of two process heat exchangers in the phenol acetone unit. Intermittent process upsets and periodic shutdown of operations for routine maintenance subjected the conventionally gasketed surfaces of the ANSI B16.5 raised face flanges to severe thermal cycling. To prevent leakage of flammable materials to the atmosphere, it was necessary to retighten the bolts on the heat exchanger heads. Eventually, the units had to be shut down two or three times a year to replace the gaskets. About two years ago, the conventional composite metal gaskets were replaced with flexible all-metal gaskets specially designed for lead-tight sealing under extreme operating conditions. The gasket's basic design is two metal linings formed around a helically wound spring to provide an elastic core. Each coil operates independently during radial compression to maintain pressure contact between the surfaces and to provide optimum spring-back in case of slight flange separation. The gasket linings, in a wide selection of ductile metals and alloys, will plastically deform and fill any faults or voids in the surface to be sealed. The flexible all-metal gaskets prevent leakage of the flammable gases and vapors from the heat exchangers during both normal and severe thermal cyclic conditions, and are now changed out only during annual shutdown for inspection and maintenance. The higher cost of the gaskets is partially offset by the lower frequency of changeout and labor cost, but the biggest payout is elimination of the potential fire hazard.

Gambrell, M.; Stadig, W.P.

1985-11-01

45

Effect of storage time on the viscoelastic properties of elastomeric impression materials.  

UK PubMed Central (United Kingdom)

PURPOSE: The aim of this study was to evaluate creep and viscoelastic properties of dental impression materials after different storage times. METHODS: Six commercially available impression materials (one polyether and five silicones) were tested after being stored for 30 min to 2 weeks under both static and dynamic testing. Shear and Young's moduli, dynamic viscosity, loss tangent and other viscoelastic parameters were calculated. Four of the materials were tested 1 h after setting under creep for three hours and recovery was recorder for 50 h. RESULTS: The tested materials showed differences among them, while storage time had significant influence on their properties. Young's modulus E ranged from 1.81 to 12.99 MPa with the polyether material being the stiffest. All of the materials showed linear viscoelastic behavior exhibiting permanent deformation after 50h of creep recovery. CONCLUSION: As storage time affects the materials' properties, pouring time should be limited in the first 48 h after impression.

Papadogiannis D; Lakes R; Palaghias G; Papadogiannis Y

2012-01-01

46

Influence of prolonged setting time on permanent deformation of elastomeric impression materials.  

UK PubMed Central (United Kingdom)

STATEMENT OF PROBLEM: Upon removal, tear forces occur in various areas of an impression. As a result, thin sulcus details may be permanently deformed, affecting the impression's accuracy. PURPOSE: The purpose of this study was to investigate the effect of the chemistry and prolonged setting time on the permanent deformation of light-body impression materials after stretching. MATERIAL AND METHODS: A dumbbell-shaped mold (2 mm x 4 mm x 75 mm) was used to prepare specimens (n=20) of 6 different impression materials (Affinis Light Body, Aquasil Ultra XLV, Express 2 Light Body Flow Quick, Flexitime Correct Flow, P2 Polyether Light, and Impregum Garant L DuoSoft). After water storage (35 degrees C), either for the manufacturer's suggested setting time or for 5 minutes, specimens were stretched by 80% using a universal testing machine at a crosshead speed of 200 mm/min. The permanent deformation (Deltal (%)) was determined after 2 hours of storage in ambient conditions. A 2-way ANOVA followed by a Games-Howell test was used to analyze the influence of material and storage time (alpha=.05). RESULTS: Polyether materials showed a significantly higher permanent deformation (Deltal>4% to 5%) than vinyl polysiloxane materials (P<.05). Extending the manufacturer's suggested setting time resulted in clinically relevant improvements in elastic recovery for products with a polyether backbone only. CONCLUSIONS: Increasing the setting time might be necessary for impression materials with a polyether backbone to improve elastic recovery.

Balkenhol M; Haunschild S; Erbe C; Wöstmann B

2010-05-01

47

[Measuring the accuracy of various elastomeric impression materials using a CNC coordinate measuring device (Part 1)  

UK PubMed Central (United Kingdom)

This study compares the accuracy of 23 impression materials. With each material seven impressions of a stainless steel master die were taken under standardized conditions. Characteristical dimensions of the master die and of the stone dies as well were determined by means of a CNC coordinate measuring device. Differences in prepared tooth heights ranged between -36 and +19 microns. The occlusal distances between prepared teeth were 2 to 54 microns greater on the stone dies than on the master die. Diameters differed by -89 to +52 microns. The two phase impressions tended to result in stone dies of reduced size, whereas single phase and double mix impression techniques produced larger stone dies than the master die.

Wichmann M; Borchers L; Limmroth E

1990-08-01

48

[Measuring the accuracy of various elastomeric impression materials using a CNC coordinate measuring device (Part 1)].  

Science.gov (United States)

This study compares the accuracy of 23 impression materials. With each material seven impressions of a stainless steel master die were taken under standardized conditions. Characteristical dimensions of the master die and of the stone dies as well were determined by means of a CNC coordinate measuring device. Differences in prepared tooth heights ranged between -36 and +19 microns. The occlusal distances between prepared teeth were 2 to 54 microns greater on the stone dies than on the master die. Diameters differed by -89 to +52 microns. The two phase impressions tended to result in stone dies of reduced size, whereas single phase and double mix impression techniques produced larger stone dies than the master die. PMID:2269183

Wichmann, M; Borchers, L; Limmroth, E

1990-08-01

49

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-07-01

50

Elastomerically impregnated ePTFE to enhance stretch and recovery properties for vascular grafts and coverings  

UK PubMed Central (United Kingdom)

An elastomerically recoverable PTFE material is provided including a longitudinally compressed fibrils of ePTFE material penetrated by elastomeric material within the pores defining the elastomeric matrix. The elastomeric matrix and the compressed fibris cooperatively expand and recover without plastic deformation of the ePTFE material. The material may be used for various prosthesis, such as a vascular a prosthesis like a patch, a graft and an implantable tubular stent. Further, a method of producing the elastomerically recoverable PTFE material is provided herein.

SOWINSKI KRZYSZTOF; RAKOS RONALD

51

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

52

Prediction of fluid behavior in elastomeric seals  

Energy Technology Data Exchange (ETDEWEB)

Fluids sealed under pressure dissolve in the surface of elastomeric seals and then proceed to diffuse into the interior. In the case of gases, a subsequent decompression of the sealed fluid can result in dissolved gas coming out of solution in the interior of the elastomeric material and causing structural damage, explosive decompression. As part of a broader program of work concerned with seal life prediction, software has been developed for the prediction of elastomer/fluid interactions. This computer model is briefly described and examples of results are presented for a variety of operating conditions, seal materials, seal types, and fluids.

Ho, E.; Flitney, R.K.; Nau, B.S. [British Hydromechanics Research Group Ltd., Cranfield (United Kingdom). Fluid Sealing Technology

1993-12-31

53

46 CFR 56.30-35 - Gasketed mechanical couplings.  

Science.gov (United States)

...2012-10-01 false Gasketed mechanical couplings. 56.30-35...SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES...56.30-35 Gasketed mechanical couplings. ...Inspection. (b) Gasketed mechanical couplings may be used...

2012-10-01

54

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.

Federica Boraldi; Chiara Coppi; Sergio Bortolini; Ugo Consolo; Roberta Tiozzo

2009-01-01

55

Thermoforming film or plate useful for producing an orthodontic splint or a mouth guard splint and dental thermoforming technique, comprises silicone blocks and organic blocks of a polymer material, preferably elastomeric silicone copolymer  

UK PubMed Central (United Kingdom)

Thermoforming film or plate comprises silicone blocks and organic blocks of a polymer material, preferably of the type Geniomer(RTM: Thermoplastic Elastomeric Silicone Copolymer). An independent claim is also included for producing a double-layer thermoforming film or plate comprising (a) surface activation of the hard layer, preferably by corona treatment or plasma treatment and (b) laminating the flexible layer and the surface activated hard layer in a hot press

SCHEU CHRISTIAN; PAUL TOBIAS

56

Development of super elastic alloy seal gasket  

Energy Technology Data Exchange (ETDEWEB)

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)

Taguchi, Kou; Tada, Eisuke [Department of Fusion Engineering Resesarch(Tokai Site), Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan)

1999-11-01

57

Gaskets of teflon-bonded EPDM halt leakage from acid lines - low sealing force design eliminates flange distress  

Energy Technology Data Exchange (ETDEWEB)

The W.R. Grace Chemical Division plant in Lake Charles, LA had to stop producing catalysts for the oil refining industry whenever a piping system for 98% sulfuric acid developed a leak. Gaskets of a nonasbestos material were being used between the flanges of the steel pipe lined with TFE or polypropylene. The flange bolts were kept tight, but the gaskets usually failed to maintain a leaktight seal with the acid at 60 psi for more than a few weeks or months. The acid lines had to be drained before the faulty gasket could be replaced, and production downtime would range from one to three hours. In July 1986, the plant decided to try a chemical resistant gasket of Teflon molded and bonded to a core of Shore A 65-66 durometer EPDM rubber in the acid lines. The resilient gasket also has patented double convex rings on both faces for optimum sealing with only one-eighth the bolt tightening torque commonly required with flat-faced gaskets. The low sealing force requirement prolongs the life of the gasket, eliminates plastic cold flow at the flange of lined steel pipe, and avoids stresses that can damage thermoplastic and fiberglass piping systems. The gasket has a temperature range of {minus}4 to 210{degree}F and is available in 1/2 through 12 inch sizes that conform to ANSI B16.1 flange dimensions. Alternative gasket materials are Kynar PVDF-bonded EPDM and EPDM without a fluoropolymer laminate. The Teflon-bonded EPDM gaskets eliminated unscheduled catalyst production downtime due to leakage from the sulfuric acid piping system. The plant maintains an inventory of the low torque gasket, but has never had to replace any that have been in service since July 1986.

Walker, I.S.; Gaines, A.

1987-11-01

58

Elastomeric energy recovery system  

Energy Technology Data Exchange (ETDEWEB)

An energy recovery system for a machine, and particularly an automotive vehicle, includes an energy storage device which selectively receives energy from the prime mover for storage via a predetermined path and delivers stored energy to the prime mover load via the same path. In the preferred embodiment the energy storage device is an elastomeric tube which is disposed for rotational movement about a shaft and secured at the ends to respective end members. Braking units permit selective braking and releasing of the end members relative to fixed supports. A set of planet gears are controlled by the brake actuation to drive a sun gear or be driven by a ring gear to effect energy inflow and outflow, respectively, from the elastomeric tube. The storage device is permitted to store energy or release its stored energy as a function of vehicle control and operational parameters.

Gill, J.D.

1984-10-30

59

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

60

Development of New Metallic Gasket and its Optimum Design for Leakage Performance  

Science.gov (United States)

This paper introduces a new all-metal gasket that incorporates strategically located circumferential annular lips that form seal lines with the flanges. This gasket, named Super Seal Gasket, by virtue of its special shape, makes use of the material's spring effect, resulting in sealing performance. This change in approach, from the traditional one based on material development to one of mechanical design, brings with it the need for optimization of the different design parameters for leakage performance. We were able to develop an optimization methodology for this new product using the Taguchi method. As a test case, a 25A sized industrial gasket was optimized using this methodology. In FEM analysis, contact stress and deformation information was used to quantify leaking. Helium leak testing reveals considerable improvement in the sealing performance, hence verifying the applicability of the methodology developed. This work has proved that material development is not the only approach towards the development of new, more effective gaskets and novel gaskets, such as the one introduced in this study, have a useful part to play in the sealing of flanged joints.

Saeed, Hasan Aftab; Izumi, Satoshi; Sakai, Shinsuke; Haruyama, Shigeyuki; Nagawa, Masato; Noda, Hideki

 
 
 
 
61

Manifold gasket accommodating differential movement of fuel cell stack  

Energy Technology Data Exchange (ETDEWEB)

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

62

Double-grooved gasket for galvanic cells  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a galvanic cell having an anode, an electrolyte and a cathode assembled in a sealed cell housing, the housing comprising, (a) a first cover member having at least one dependent skirt; (b) a second cover member having at least one dependent skirt; (c) an electrically non-conductive gasket having a central opening, an upper surface with a groove disposed in the upper surface, and an inner wall inward of the upper and lower surface grooves defining the central opening. The dependent skirt of the first cover member is positioned in the groove in the lower surface of the gasket. The dependent skirt of the second cover member is positioned in the groove in the upper surface of the gasket and, the inner wall of the gasket contacts interior portions of both of the cover members and having a height equal to the distance between the cover members in the interior of the cell housing.

Vourlis, H.

1986-11-18

63

Method for making an elastomeric member with end pieces  

Energy Technology Data Exchange (ETDEWEB)

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

64

Porous elastomeric infills  

UK PubMed Central (United Kingdom)

A method of forming a porous elastomeric composition for use as an infill for installation at the base of trees and signs comprises the steps of encapsulating recycled styrene butadiene rubber (SBR) with pigmented polyurethane to form coloured SBR granules, mixing the coloured SBR granules with a polyurethane based moisture curing prepolymer to form an uncured porous polymeric composition. The composition, when used, is applied as the uncured porous polymeric composition to the base of a tree or sign, tamped until its uppermost surface is level with a surrounding area and allowed the to cure. For preference, the pigment is iron oxide.

BOWERS FRANK

65

Investigation of extrusion failures of PTFE-based gaskets in chemical plant service  

Energy Technology Data Exchange (ETDEWEB)

PTFE-based gaskets in chemical plant service typically fail in an extrusion mode, sometimes referred to as blowout. Test work previously published by Monsanto indicated that correctly installed PTFE-based gaskets have pressure performance far exceeding system pressure ratings. These results have since been confirmed by extensive testing at the Montreal based Ecole Polytechnique Tightness Testing and Research Laboratory (TTRL), funded by a consortium of gasket users and manufacturers. With the knowledge that properly installed gaskets can withstand system pressures in excess of 1,000 psig [6,894 kPa], failures at two chemical plants were re-examined. This analysis indicates that extrusion type failures can be caused by excessive internal pressures, associated with sections of pipe having an external source of heat coincident with a blocked flow condition. This results in high system pressures which explain the extrusion type failures observed. The paper discusses details of individual failures and examines methods to prevent them. Other causes for extrusion failures are reviewed, with a recommendation that stronger gasket materials not be utilized to correct problems until it is verified that excessive pressure build-up is not the problem. Also summarized are the requirements for proper installation to achieve the potential blowout resistance found in these gaskets.

Winter, J.R. [Eastman Chemical Co., Kingsport, TN (United States); Keywood, S.S. [Monsanto Co.--The Chemical Group, Pensacola, FL (United States)

1996-12-01

66

Qualitative and quantitative three-dimensional accuracy of a single tooth captured by elastomeric impression materials: an in vitro study.  

UK PubMed Central (United Kingdom)

STATEMENT OF PROBLEM: The accuracy of impressions has been described in 1 or 2 dimensions, whereas it is most desirable to evaluate the accuracy of impressions spatially, in 3 dimensions. PURPOSE: The purpose of this study was to demonstrate the accuracy and reproducibility of a 3-dimensional (3-D) approach to assessing impression preciseness and to quantitatively comparing the occlusal correctness of gypsum dies made with different impression materials. MATERIAL AND METHODS: By using an aluminum replica of a maxillary molar, single-step dual viscosity impressions were made with 1 polyether/vinyl polysiloxane hybrid material (Identium), 1 vinyl polysiloxane (Panasil), and 1 polyether (Impregum) (n=5). Corresponding dies were made of Type IV gypsum and were optically digitized and aligned to the virtual reference of the aluminum tooth. Accuracy was analyzed by computing mean quadratic deviations between the virtual reference and the gypsum dies, while deviations of the dies among one another determined the reproducibility of the method. The virtual reference was adapted to create 15 occlusal contact points. The percentage of contact points deviating within a ±10 µm tolerance limit (PDP(10) = Percentage of Deviating Points within ±10 µm Tolerance) was set as the index for assessing occlusal accuracy. Visual results for the difference from the reference tooth were displayed with colors, whereas mean deviation values as well as mean PDP(10) differences were analyzed with a 1-way ANOVA and Scheffé post hoc comparisons (?=.05). RESULTS: Objective characterization of accuracy showed smooth axial surfaces to be undersized, whereas occlusal surfaces were accurate or enlarged when compared to the original tooth. The accuracy of the gypsum replicas ranged between 3 and 6 µm, while reproducibility results varied from 2 to 4 µm. Mean (SD) PDP(10)-values were: Panasil 91% (±11), Identium 77% (±4) and Impregum 29% (±3). One-way ANOVA detected significant differences among the subjected impression materials (P<.001). CONCLUSIONS: The accuracy and reproducibility of impressions were determined by 3-D analysis. Results were presented as color images and the newly developed PDP(10)-index was successfully used to quantify spatial dimensions for complex occlusal anatomy. Impression materials with high PDP(10)-values were shown to reproduce occlusal dimensions the most accurately.

Schaefer O; Schmidt M; Goebel R; Kuepper H

2012-09-01

67

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

68

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

2010-01-01

69

Properties and degradation of the gasket component of a proton exchange membrane fuel cell--a review.  

UK PubMed Central (United Kingdom)

Proton exchange membrane (PEM) fuel cell stack requires gaskets and seals in each cell to keep the reactant gases within their respective regions. Gasket performance is integral to the successful long-term operation of a fuel cell stack. This review focuses on properties, performance and degradation mechanisms of the different polymer gasket materials used in PEM fuel cell under normal operating conditions. The different degradation mechanisms and their corresponding representative mitigation strategies are also presented here. Summary of various properties of elastomers and their advantages and disadvantages in fuel cell'environment are presented. By considering the level of chemical degradation, mechanical properties and cost effectiveness, it can be proposed that EPDM is one of the best choices for gasket material in PEM fuel cell. Finally, the challenges that remain in using rubber component as in PEM fuel cell, as well as the prospects for exploiting them in the future are discussed.

Basuli U; Jose J; Lee RH; Yoo YH; Jeong KU; Ahn JH; Nah C

2012-10-01

70

A cubic boron nitride gasket for diamond-anvil experiments.  

Science.gov (United States)

To maximize the thickness of the sample chamber in high-pressure experiments, we have conducted tests and have developed techniques relevant to the cubic boron nitride (c-BN) gasket for diamond-anvil cells. The c-BN gasket provides a sample chamber several times thicker than conventional metal gaskets. We have developed methods to prepare the gasket and to fill the chamber with the sample. By using the c-BN gasket, we have successfully measured x-ray diffraction patterns of SiO2 glass, a low-Z noncrystalline sample, up to 100 GPa. PMID:18513075

Funamori, Nobumasa; Sato, Tomoko

2008-05-01

71

A cubic boron nitride gasket for diamond-anvil experiments.  

UK PubMed Central (United Kingdom)

To maximize the thickness of the sample chamber in high-pressure experiments, we have conducted tests and have developed techniques relevant to the cubic boron nitride (c-BN) gasket for diamond-anvil cells. The c-BN gasket provides a sample chamber several times thicker than conventional metal gaskets. We have developed methods to prepare the gasket and to fill the chamber with the sample. By using the c-BN gasket, we have successfully measured x-ray diffraction patterns of SiO2 glass, a low-Z noncrystalline sample, up to 100 GPa.

Funamori N; Sato T

2008-05-01

72

Development of high energy radiation resistant elastomeric composites  

International Nuclear Information System (INIS)

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

1992-01-01

73

Adhesive, elastomeric gel impregnating composition  

Energy Technology Data Exchange (ETDEWEB)

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

74

Recent buckling experiences with spiral wound flexible graphite filled gaskets  

Energy Technology Data Exchange (ETDEWEB)

Given the long and successful history of spiral wound asbestos filled gaskets as widely used in petrochemical plants and refineries, the evolution to flexible graphite filled spiral wound gaskets was expected to be relatively straightforward. For the most part, the transition to flexible graphite has occurred with relatively good success consistent with its improved sealing performance. However, recent experiences reported with buckling type instability problems of flexible graphite filled spiral wound gaskets warrants another look at the industry practices covering this type of gasket. The paper presents findings from 2 different but related instability problems involving spiral would flexible graphite filled gaskets. The first involved Class 1500 and 2500 spiral wound gaskets fitted with inner retaining rings which suffered severe inward buckling with initial boltup. The second experience pertains to Class 600 and lower gaskets supplied without inner retaining rings. Gaskets supplied in both cases complied fully with ASME B16.20 requirements, which highlights possible inadequacies in this standard for spiral wound gaskets. Efforts have been initiated to work with manufacturers in their assessment of fundamental design considerations and with appropriate Code committees to address apparent deficiencies discovered with the industry standards for this type of gasket.

Mueller, R.T. [Exxon Research and Engineering Co., Florham Park, NJ (United States)

1996-12-01

75

Flexible ceramic gasket for SOFC generator  

Science.gov (United States)

A solid oxide fuel cell generator (10) contains stacks of hollow axially elongated fuel cells (36) having an open top end (37), an oxidant inlet plenum (52), a feed fuel plenum (11), a combustion chamber (94) for combusting reacted oxidant/spent fuel; and, optionally, a fuel recirculation chamber (106) below the combustion chamber (94), where the fuel recirculation chamber (94) is in part defined by semi-porous fuel cell positioning gasket (108), all within an outer generator enclosure (8), wherein the fuel cell gasket (108) has a laminate structure comprising at least a compliant fibrous mat support layer and a strong, yet flexible woven layer, which may contain catalytic particles facing the combustion chamber, where the catalyst, if used, is effective to further oxidize exhaust fuel and protect the open top end (37) of the fuel cells.

Zafred, Paolo (Murrysville, PA); Prevish, Thomas (Trafford, PA)

2009-02-03

76

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

2013-01-01

77

Electropolishing of aluminum gasket for linear accelerator  

Energy Technology Data Exchange (ETDEWEB)

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

Tajiri, Keisuke; Kabeya, Zensaburo [Mitsubishi Heavy Industries Ltd., Nagoya, Aichi (Japan). Nagoya Aerospace Systems Works

1997-06-01

78

Electropolishing of aluminum gasket for linear accelerator  

International Nuclear Information System (INIS)

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

1997-01-01

79

Elastomeric Launch System for Submarines.  

Science.gov (United States)

An apparatus for providing a pressurized liquid to a launch tube for launching projectiles into a liquid medium. The device comprises an elastomeric bladder disposed inside a cylindrical bypass tube. The forward end of the bypass tube is open to the liqui...

P. E. Moody

1994-01-01

80

Magnet coil electrical gaskets of high compliance and ampacity  

International Nuclear Information System (INIS)

[en] 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 ?8,000 kG each). For that reason the authors subdivided them into a series of manageable subcoils that they will subsequently bolt together. Electrical terminals attached to the subcoils conductors are rigidly embedded and precisely located during vacuum impregnation. However; they anticipate some misalignment and nonuniform gaping to occur between terminals at assembly. They have elected to use electrical gaskets of high 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

1996-01-01

 
 
 
 
81

Magnet coil electrical gaskets of high compliance and ampacity  

International Nuclear Information System (INIS)

[en] 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

1995-01-01

82

Thermocross-Linked Elastomeric Opal Films.  

UK PubMed Central (United Kingdom)

An efficient and convenient thermal cross-linking protocol in elastomeric opal films leading to fully reversible and stretch-tuneable optical materials is reported. In this study, functional monodisperse core-shell particles were arranged in a face-centred cubic (fcc) lattice structure by a melt-flow process. A problem up to now was that uncross-linked films could not be drawn fully reversibly and hence lost their optical and mechanical performance. After thermal cross-linking reaction, the obtained films can be drawn like rubbers and the colour of their Bragg reflection changes due to controlled lattice deform¬ation which makes the cross-linked films mechano¬chromic sensors. Different techniques were developed for the cross-linking of the films a posteriori, after their pre¬paration in the melt flow process. A photocross-linking approach was reported earlier. This study now deals with a very efficient thermocross-linking approach based on the chemistry of hydroxyl- and isocyanate-functionalities that form urethane bridges. The focus of the present work is the mechanism and efficiency of this cross-linking process for elastomeric opal films with excellent mechanical and optical properties.

Schäfer CG; Viel B; Hellmann GP; Rehahn M; Gallei M

2013-10-01

83

Fluid sealing of static gasketed joints  

International Nuclear Information System (INIS)

This book brings together the points of view of searchers, gaskets and pressure vessels manufacturers and users concerning fluid sealing problems. The tightness parameter is now considered as a failure criterion and, thus, some aspects concerning the conceiving and building of pressure vessels and apparatuses (and more particularly the bolted assemblies with gaskets), were questioned in order to improve their safety and reliability. New calculation methods, including the tightness parameter are now proposed to standardization authorities. The preoccupations concerning the environmental protection have led the legislative authorities to fix admissible levels of leakage for different industrial components, in particular for petrochemical uses. Strict regulations were enforced in the USA (Clean Air Act) and in Germany (TA Luft). Four papers out of 39 presented in this book of proceedings deal with the control and prevention of leakage in petrochemical refineries, gas production plants and storage systems, and were selected for ETDE. Four other papers dealing with leakage problems in nuclear facilities and high energy physics instruments were selected for INIS. (J.S.)

1996-01-01

84

Multigeneration buckling on model elastomeric surfaces  

Science.gov (United States)

We describe a simple method for generating topographically corrugated elastomeric surfaces comprising multidimensional cascades of buckles. The buckled surfaces are generated by stretching films (about 0.5 mm) of silicone elastomers, exposing their surfaces to prolonged ultraviolet/ozone (UVO) treatment and releasing the initial strain imposed on the samples. A combination of microscopy probes including optical, scanning probe (profilometry and atomic force microscopy) techniques is utilized to study the topography of the buckled surfaces. Our results reveal the presence of at least 5 generation of buckles; the buckle periodicity ranges from several nanometers to tens of micrometers. A simple model is invoked that explains the mechanism of the buckle formation. Using this model a scaling relation between the buckle amplitude, periodicity and the strain is developed. We also show how these buckles surfaces can be used in material assembly and surface chemical patterning.

Efimenko, Kirill; Genzer, Jan; Rackaitis, Mindaugas; Manias, Evangelos; Mahadevan, L.

2004-03-01

85

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

86

A comparative evaluation of disinfection effect of exposures to ultra-violet light and direct current glow discharge on Candida Albicans colonies coated over elastomeric impression material: An in vitro study.  

UK PubMed Central (United Kingdom)

AIM: The aim of our study is to compare the efficacy of ultra-violet light (U-V light) and direct current glow discharge in disinfecting Candida Albicans coated elastomeric impression material. MATERIALS AND METHODS: Two hundred and forty samples of addition silicone material in the form of circular discs measuring (diameter-30 mm, thickness-3 mm) were prepared. Samples were divided into four groups namely A, B, C, D, with each group containing 60 samples. All samples in each group were sub grouped as follows for exposure time 15, 30, 60, 90, 120 and 180 s respectively. Group A samples were exposed to U-V light with 8 watts. Group B samples were exposed to U-V light with 16 watts. Group C samples were exposed to U-V light with 24 watts. Group D samples were exposed to direct current glow discharge. After exposure, the impression material was swabbed on sabourauds dextrose agar (SDA) plates and incubated at 37°C for 48 h. The total number of colonies indicating the number of C. Albicans that survived the direct current glow discharge and U-V light treatment was then determined using a microscope. RESULTS AND CONCLUSION: Group A samples exhibited proportionate decrease in the number of colonies with each greater time of exposure. Group B samples exhibited proportionate decrease in the number of colonies with each greater time of exposure. Group C samples exhibited total absence of C. Albicans colonies at 90 s exposure. In Group D samples there was a proportionate decrease in number of C. Albicans colonies with exposure to direct current glow discharge for more seconds. Hence, this study reveals that exposure to U-V light drastically reduced the C. Albicans colonies compared with exposure to direct current glow discharge. It was observed that with greater wattage of U-V light tube in U-V light unit chamber, greater decrease in colony count was observed in lesser time of exposure.

Anand V

2013-06-01

87

Sierpinski Gasket As A Martin Boundary  

UK PubMed Central (United Kingdom)

We show that a Sierpi'nski gasket in N dimension is homeomorphic to the minimalMartin boundary of some Markov chain which is not irreducible and does not have thebounded range structure.x1 IntroductionThe boundary theory for Markov chains originates in the work of Doob [Do] and hasrecently found new interest in random walks on trees and abstract hyperbolic graphs(see Woess [Wo], Gromov[Gr]). The most important boundary from a probabilistic andpotential theoretic viewpoint is the Martin boundary which describes all positive harmonicand superharmonic functions by integrals on the boundary (see [Dy]). In many cases, thisalso leads to a solution of the associated Dirichlet problem. It is therefore a naturalquestion to identify the Martin boundary. In this note we make a contribution to thisidentification problem.The existing proofs of such an identification theorem follow a certain pattern. First oneassigns a topological boundary to the paths of the chain and then proves tha...

Gasket As A Martin Boundary; Manfred Denker; Hiroshi Sato

88

Conductive elastomeric composites  

International Nuclear Information System (INIS)

Conductive elastic materials are formed by distributing conductive particles within an elastic polymer. We consider a novel composite based on dendritic nickel particles that exhibit remarkably strong negative piezoresistivity with an increase in conductivity of up to 10 orders of magnitude with strains of the order of 0.2. A vital factor for the conductivity of conductive elastomers is the concentration of conductive fillers and many aspects can be understood in terms of percolation theory. In this system the concentration of particles within the composite does not change with strain, yet due to the shape of the particles, the concentration of electrical contacts between the particles does change. We have developed a new model based on the concentration of contact sites, rather than particles which enables us to successfully model this remarkable strain-dependence of conductivity.

2009-08-01

89

Sealability of API R, RX, and BX ring gaskets  

Energy Technology Data Exchange (ETDEWEB)

This report presents work done to determine the sealability limits of API R, RX, and BX gaskets. The work included finite element modeling and full scale testing. The research teaches that bolt stresses of 15 to 30 ksi are necessary to seat the gaskets. If these seating loads are not achieved, the gaskets will likely leak at design pressure, particularly for gas service. If the flanges are properly madeup, the sealability limits in API Bulletins 6AF and 6AF2 are too conservative and can be eliminated for non cyclic service.

Fowler, J.R. [Stress Engineering Services, Inc., Houston, TX (United States)

1995-12-31

90

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 ...

91

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.

1996-01-01

92

Statistical study of static gasket conductance  

International Nuclear Information System (INIS)

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

2005-01-01

93

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.

2009-11-09

94

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

International Nuclear Information System (INIS)

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

1000-01-00

95

Gasket-holder to put in place gaskets for connection of pipes with clamp fittings. Porte-joint utilisable pour placer des joints a des raccordements de tuyaux a collier de serrage  

Energy Technology Data Exchange (ETDEWEB)

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.

Fiori, R.

1989-09-08

96

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

97

Galvanic cell having a saturated fluorocarbon plasma-treated sealing gasket  

Energy Technology Data Exchange (ETDEWEB)

Galvanic cells employing compressible gaskets having at least a portion of the sealing areas of such gaskets coated with plasma deposited fluorine atoms demonstrate increased resistance to electrolyte leakage.

Yasuda, H.; van Lier, J. A.

1985-02-26

98

Blends of thermoplastic and elastomeric matrices with liquid crystalline polymers  

Energy Technology Data Exchange (ETDEWEB)

Liquid crystalline polymers (LCPs) present a unique balance of properties and, when added to thermoplastic (TP) or elastomeric (EL) matrices, can impart to the relevant blends specific properties that can be utilized for specific applications. As regards TP/LCP blends, the proclivity of LCPs to form fibrous structures and their low melt viscositiy allowed to obtain blends reinforced and easier to process than the pure TPs: particularly, depending on the LCP-TP structures and on the processing parameters, materials with improved processability, high modulus, enhanced impact strength and creeping resistance were obtained. As regards EL/LCP blends, that based on fluoroelastomers were in depth investigated and offered outstanding properties.

Roggero, A.; Pedretti, U.; La Mantia, F.P. [Eniricerche, Milanese (Italy)

1995-12-01

99

Elastomeric chain force decay in artificial saliva: an in vitro study.  

UK PubMed Central (United Kingdom)

INTRODUCTION: The main objective of this study was to reexamine the mechanical properties of elastomeric chains after stretching in various artificial saliva solutions and in air. MATERIALS AND METHODS: Five brands of elastomeric chain manufactured by different companies were selected. For each brand, four types were tested in different artificial media. A dismountable test kit was used to stretch the chains up to various initial force levels. They were then immersed in pre-prepared solutions, with control samples exposed to air only. Residual force was measured at multiple time points using a hand-held dynamometer. RESULTS AND DISCUSSION: The force delivered by the elastomeric chains decayed rapidly and differently over time. This decay varied depending on multiple factors, discussed here.

Halimi A; Azeroual MF; Doukkali A; El Mabrouk K; Zaoui F

2013-03-01

100

Recombinant exon-encoded resilins for elastomeric biomaterials.  

UK PubMed Central (United Kingdom)

Resilin is an elastomeric protein found in specialized regions of the cuticle of most insects, providing outstanding material properties including high resilience and fatigue lifetime for insect flight and jumping needs. Two exons (1 and 3) from the resilin gene in Drosophila melanogaster were cloned and the encoded proteins expressed as soluble products in Escherichia coli. A heat and salt precipitation method was used for efficient purification of the recombinant proteins. The proteins were solution cast from water and formed into rubber-like biomaterials via horseradish peroxidase-mediated cross-linking. Comparative studies of the two proteins expressed from the two different exons were investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Circular Dichrosim (CD) for structural features. Little structural organization was found, suggesting structural order was not induced by the enzyme-mediated di-tyrosine cross-links. Atomic Force Microscopy (AFM) was used to study the elastomeric properties of the uncross-linked and cross-linked proteins. The protein from exon 1 exhibited 90% resilience in comparison to 63% for the protein from exon 3, and therefore may be the more critical domain for functional materials to mimic native resilin. Further, the cross-linking of the recombinant exon 1 via the citrate-modified photo-Fenton reaction was explored as an alternative di-tyrosine mediated polymerization method and resulted in both highly elastic and adhesive materials. The citrate-modified photo-Fenton system may be suitable for in vivo applications of resilin biomaterials.

Qin G; Rivkin A; Lapidot S; Hu X; Preis I; Arinus SB; Dgany O; Shoseyov O; Kaplan DL

2011-12-01

 
 
 
 
101

Hydrostatic low-range pressure applications of the Paris–Edinburgh cell utilizing polymer gaskets for diffuse X-ray scattering measurements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The use of a polymeric (Torlon or polyamide–imide) gasket material in a Paris–Edinburgh pressure cell for in situ high-pressure X-ray scattering measurements is demonstrated. The quality of the data obtained in this way is suitable for Bragg and pair distribution function analysis.

Chapman, Karena W.; Chupas, Peter J.; Kurtz, Charles A.; Locke, Darren R.; Parise, John B.; Hriljac, Joseph A.

102

Testing the influence of various conditions on the migration of epoxidised soybean oil from polyvinylchloride gaskets.  

UK PubMed Central (United Kingdom)

Epoxidised soybean oil (ESBO) is widely used as a plasticiser and stabiliser mainly in food contact materials on the base of polyvinylchloride (PVC), especially in the gaskets of jar lids. PVC gaskets containing 10-37% of ESBO were prepared by the baking of PVC plastisols at various process temperatures (180-240°C) in the laboratory. ESBO migration into olive oil and 3% acetic acid was studied at various temperatures (4°C, 25°C, 40°C and 60°C) during a storage time up to 12 months. ESBO released into food simulants was transmethylated, derivatised and analysed by gas chromatography-mass spectrometry (GC/MS). The effect of food processing, i.e. pasteurisation (80°C and 100°C) and sterilisation (125°C) on ESBO migration was also evaluated. The results were critically assessed with respect to the test conditions of specific migration in accordance with the current European Union legislation (Regulation (EU) No. 10/2011). The levels of ESBO migration found confirmed that the test conditions (i.e. 40°C or 60°C, 10 days) representing contact in the worst foreseeable use scenario seem to be insufficient for the simulation of ESBO migration during long-term storage and thus do not provide satisfactory objective results.

Hanušová K; Rajchl A; Votavová L; Dobiáš J; Steiner I

2013-11-01

103

Testing the influence of various conditions on the migration of epoxidised soybean oil from polyvinylchloride gaskets.  

UK PubMed Central (United Kingdom)

Epoxidised soybean oil (ESBO) is widely used as a plasticiser and stabiliser mainly in food contact materials on the base of polyvinylchloride (PVC), especially in the gaskets of jar lids. PVC gaskets containing 10-37% of ESBO were prepared by the baking of PVC plastisols at various process temperatures (180-240°C) in the laboratory. ESBO migration into olive oil and 3% acetic acid was studied at various temperatures (4°C, 25°C, 40°C and 60°C) during a storage time up to 12 months. ESBO released into food simulants was transmethylated, derivatised and analysed by gas chromatography-mass spectrometry (GC/MS). The effect of food processing, i.e. pasteurisation (80°C and 100°C) and sterilisation (125°C) on ESBO migration was also evaluated. The results were critically assessed with respect to the test conditions of specific migration in accordance with the current European Union legislation (Regulation (EU) No. 10/2011). The levels of ESBO migration found confirmed that the test conditions (i.e. 40°C or 60°C, 10 days) representing contact in the worst foreseeable use scenario seem to be insufficient for the simulation of ESBO migration during long-term storage and thus do not provide satisfactory objective results.

Hanušová K; Rajchl A; Votavová L; Dobiáš J; Steiner I

2013-08-01

104

Elastomeric Recombinant Protein-based Biomaterials.  

UK PubMed Central (United Kingdom)

Elastomeric protein-based biomaterials, produced from elastin derivatives, are widely investigated as promising tissue engineering scaffolds due to their remarkable properties including substantial extensibility, long-term stability, self-assembly, high resilience upon stretching, low energy loss, and excellent biological activity. These elastomers are processed from different sources of soluble elastin such as animal-derived soluble elastin, recombinant human tropoelastin, and elastin-like polypeptides into various forms including three dimensional (3D) porous hydrogels, elastomeric films, and fibrous electrospun scaffolds. Elastin-based biomaterials have shown great potential for the engineering of elastic tissues such as skin, lung and vasculature. In this review, the synthesis and properties of various elastin-based elastomers with their applications in tissue engineering are described.

Annabi N; Mithieux SM; Camci-Unal G; Dokmeci MR; Weiss AS; Khademhosseini A

2013-08-01

105

Anisotropic random walks and asymptotically one-dimensional diffusion on abc-gaskets  

Science.gov (United States)

Asymptotically one-dimensional diffusion processes are studied on the class of fractals called abc-gaskets. The class is a set of certain variants of the Sierpi?ski gasket containing infinitely many fractals without any nondegenerate fixed point of renoramalization maps. While the "standard" method of constructing diffusions on the Sierpi?ski gasket and on nested fractals relies on the existence of a nondegenerate fixed point and hence it is not applicable to all abc-gaskets, the asymptotically one-dimensional diffusion is constructed on any abc-gasket by means of an unstable degenerate fixed point. To this end, the generating functions for numbers of steps of anisotropic random walks on the abc-gaskets are analyzed, along the line of the authors' previous studies. In addition, a general stategy of handling random walk sequences with more than one parameter for the construction of asymptotically one-dimensional diffusion is proposed.

Hattori, Tetsuya; Watanabe, Hiroshi

1997-07-01

106

Experiences with new European standards for calculation of flanged joints including necessary gasket factors  

Energy Technology Data Exchange (ETDEWEB)

The correct function of a flanged joint in a given construction (flanges, bolts) and with given loads (pressure, temperature, additional forces) depends on the following: (1) choice of the gasket for the operation environment; (2) determination of the gasket stress for assembly conditions; and (3) gasket stress in operation, i.e., the conditions when leakage has to be minimized. For the correct choice of a gasket it is necessary to have gasket factors available, as given by DIN 28090 (Sept. 95) together with the test procedures. These gasket factors determine the tightening characteristics as well as the deformation capability of the gaskets. Furthermore, these gasket factors must be available for use in calculations. On the basis of calculations a stress analysis (i.e. a limitation of the stresses in flanges and bolts) must be possible as well as the determination of the bolt forces for the assembly state and of the gasket stress for operating conditions. This is one of the goals of the standard pr DIN EN 1591. The paper first introduces the actual European standards. Calculations are reviewed using test data from special test rigs and from real flanged joints. The calculations were made according to DIN 2505 (initial German standard for flanged joints) and pr DIN EN 1591. Additionally, 2D and 3D Finite Element analysis calculations were performed.

Bartonicek, J. [GKN Gemeinschaftskernkraftwerk Neckar, Neckarwestheim (Germany); Kockelmann, H. [Univ. Stuttgart (Germany). MPA Staatliche Materialpruefungsanstalt; Schoeckle, F. [AMTEC Advanced Measurements, Leinfelden (Germany)

1996-12-01

107

Elastomeric polymer light-emitting devices and displays  

Science.gov (United States)

The emergence of devices that combine elasticity with electronic or optoelectronic properties offers exciting new opportunities for applications, but brings significant materials challenges. Here, we report the fabrication of an elastomeric polymer light-emitting device (EPLED) using a simple, all-solution-based process. The EPLED features a pair of transparent composite electrodes comprising a thin percolation network of silver nanowires inlaid in the surface layer. The resulting EPLED, which exhibits rubbery elasticity at room temperature, is collapsible, and can emit light when exposed to strains as large as 120%. It can also survive repeated continuous stretching cycles, and small stretching is shown to significantly enhance its light-emitting efficiency. The fabrication process is scalable and was readily adapted for the demonstration of a simple passive matrix monochrome display featuring a 5 × 5 pixel array.

Liang, Jiajie; Li, Lu; Niu, Xiaofan; Yu, Zhibin; Pei, Qibing

2013-10-01

108

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.).

1993-01-01

109

Stretchable ferroelectric nanoribbons with wavy configurations on elastomeric substrates.  

UK PubMed Central (United Kingdom)

Applications of ferroelectric ceramics, ranging from components for sensors, memory devices, microelectromechanical systems, and energy convertors, all involve planar and rigid layouts. The brittle nature of such materials and their high-temperature processing requirements limit applications to devices that involve only very small mechanical deformations and narrow classes of substrates. Here, we report a strategy for integrating nanoribbons of one of the most widely used ferroelectric ceramics, lead zirconate titanate, in "wavy" geometries, on soft, elastomeric supports to achieve reversible, linear elastic responses to large strain deformations (i.e., stretchable properties), without any loss in ferroelectric or piezoelectric properties. Theoretical and computational analysis of the mechanics account for these characteristics and also show that the amplitudes of the waves can be continuously tuned with an applied electric field, to achieve a vertical (normal) displacement range that is near 1000 times larger than is possible in conventional planar layouts. The results suggest new design and application possibilities in piezoelectric devices.

Feng X; Yang BD; Liu Y; Wang Y; Dagdeviren C; Liu Z; Carlson A; Li J; Huang Y; Rogers JA

2011-04-01

110

The effects of varying alcohol concentrations commonly found in mouth rinses on the force decay of elastomeric chain.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To test the effect of alcohol on force decay of elastomeric chains in vitro in order to determine if increasing alcohol concentrations results in an increased amount of elastomeric chain force decay. MATERIALS AND METHODS: A prospective laboratory study was completed to test the effect of alcohol exposure on orthodontic elastomeric chain. A total of 450 specimens were divided into five test groups. Two test groups were each exposed to different alcohol concentrations (14% and 26.9%) and the other two test groups were exposed to different commercially available mouth rinses (C?pacol -14% alcohol and Listerine - 26.9% alcohol) for 60 seconds twice a day. The control group followed all of the same procedures but was only exposed to deionized (DI) water. Force measurements were taken at six time points (initial, 1 day, 7 days, 14 days, 21 days, and 28 days). RESULTS: There were no significant differences among groups at the initial time point (P ?=? .52). Statistically significant effects of time on force decay were seen in all groups. All test groups showed significantly more force decay than the control group. Only a few statistically significant differences were observed when comparing force decay among the test groups. CONCLUSIONS: Alcohol causes an increase in force decay of elastomeric chain over time. A concentration dependence of alcohol on force decay of elastomeric chain was not observed.

Larrabee TM; Liu SS; Torres-Gorena A; Soto-Rojas A; Eckert GJ; Stewart KT

2012-09-01

111

Process for preparing elastomeric ep(d)m copolymers  

UK PubMed Central (United Kingdom)

Process for preparing elastomeric copolymers of ethylene-propylene (EPM) type and elastomeric terpolymers of ethylene-propylene-diene (EPDM) type with a propylene content comprised within the range of from 15 to 75%, carried out in the presence of metallocenes of formula (I)

BANZI VIVIANO; GILA LILIANA; SANTI ROBERTO; BIAGINI PAOLO; BORSOTTI GIAMPIETRO

112

Investigations of different types of gaskets for ILC cavity flanges  

International Nuclear Information System (INIS)

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

2009-01-01

113

Multifractals of Normalized First Passage Time in Sierpinski Gasket  

CERN Multimedia

The multifractal behavior of the normalized first passage time is investigated on the two dimensional Sierpinski gasket with both absorbing and reflecting barriers. The normalized first passage time for Sinai model and the logistic model to arrive at the absorbing barrier after starting from an arbitrary site, especially obtained by the calculation via the Monte Carlo simulation, is discussed numerically. The generalized dimension and the spectrum are also estimated from the distribution of the normalized first passage time, and compared with the results on the finitely square lattice.

Kim, K; Kong, Y S; Kim, Kyungsik

1998-01-01

114

High-throughput generation of micropatterns of dye-containing capsules embedded in transparent elastomeric monoliths by inkjet printing.  

UK PubMed Central (United Kingdom)

We report the high-throughput fabrication of transparent elastomeric monoliths containing customized micropatterns of microcapsules, which might be used as highly flexible identity tags, sensor elements, and photochromic, photonic, or phononic systems. High-throughput replication molding of microsphere monolayers used as sacrificial primary templates via negative secondary replicas and positive tertiary replicas yielded elastomeric specimens containing dense hexagonal arrays of open spherical microcavities. In a subsequent inkjet printing step, some of the open-spherical microcavities were filled with functional materials such as dyes. The subsequent addition of an elastomeric cover layer led to encapsulation of the dyes trapped in the printed microcavities, while empty microcavities were filled with elastomer and vanished.

Rengarajan GT; Walder L; Gorb SN; Steinhart M

2012-03-01

115

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; Rhea Mini Jayan

2010-01-01

116

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; Abdel-Hakim Bouzid

2013-01-01

117

Windows based computer program for gasket determination based on two different calculation procedures  

Energy Technology Data Exchange (ETDEWEB)

The windows based computer program for gasket calculation was presented. C++ computer language was used. On the basis of experimental results and data sets available in the literature and calculated with the help of FSA and PVRC method, the assembly parameters were determined. The result is DONIT TESNITI Diskette, a smart tool to select gaskets on the basis of service conditions and tightness requirements.

Bernard, F. [Univ. of Ljubljana (Slovenia). Faculty of Maritime Studies and Transport; Borovnicar, I. [Technical Service, Medvode (Slovenia); Ghirlanda, M. [Guarco Industria Srl, La Spezia (Italy)

1996-12-01

118

Force-Degradation Pattern of Six Different Orthodontic Elastomeric Chains  

Directory of Open Access Journals (Sweden)

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

AH Mirhashemi; A Safarshahroudi; A Sodagar; M Atai

2012-01-01

119

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

Energy Technology Data Exchange (ETDEWEB)

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.

Sawa, Toshiyuki [Yamanashi Univ., Kofu, Yamanashi (Japan). Dept. of Mechanical Engineering

1996-12-01

120

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-01

 
 
 
 
121

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)

2013-03-27

122

Restrictions of Harmonic Functions on the Sierpinski Gasket to Segments  

CERN Multimedia

The restrictions of a harmonic function on the Sierpinski Gasket (SG) to the segments in SG have been of some interest. We show that the sufficient conditions for the monotonicity of these restrictions given by Dalrymple, Strichartz and Vinson are also necessary. We then prove that the normal derivative of a harmonic function on SG on the junction points of the contour of a triangle in SG is always nonzero with at most a single exception. We finally give an explicit derivative computation for the restriction of a harmonic function on SG to segments at specific points of the segments: The derivative is zero at points dividing the segment in ratio 1:3. This shows that the restriction of a harmonic function to a segment of SG has the following curious property: The restriction has infinite derivatives on a dense set of the segment (at junction points) and vanishing derivatives on another dense set.

Demir, B; Koçak, S; Ureyen, M

2003-01-01

123

Flow-Through Elastomeric Launch System for Submarines.  

Science.gov (United States)

An apparatus for providing a pressurized liquid to a launch tube for launching projectiles into a liquid medium. The device comprises an elastomeric bladder disposed inside a cylindrical bypass tube. The bypass tube is hollow with a sealing ring disposed ...

R. Waclawik S. D. Boyd

1994-01-01

124

Metal layer cylinder-head gaskets with coined stoppers; Metalllagen-Zylinderkopfdichtungen mit gepraegten Stoppern  

Energy Technology Data Exchange (ETDEWEB)

With the development of coined stoppers, ElringKlinger has launched the third generation of Metaloflex metal layer cylinder-head gaskets on the market. In addition to meander and honeycomb stoppers, the newly introduced segment stopper now provides the optimum solution for every installation thickness and application. This system is not only more efficient economically but also offers further crucial advantages for modern engine designs: The available bolt load is utilized more efficiently thanks to the consistent topographic design of the gasket. This enables the component deformation in the cylinder head and block to be reduced further while additionally increasing the sealing potential of the gasket despite increasingly critical basic conditions. (orig.)

Diez, A. [ElringKlinger AG (Germany)

2006-12-15

125

FEM analysis of ultra-flex gasket for ILC cavity flanges  

International Nuclear Information System (INIS)

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

2010-01-01

126

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

International Nuclear Information System (INIS)

[en] 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

1989-01-01

127

Material morphology and electrical resistivity differences in EPDM rubbers.  

Energy Technology Data Exchange (ETDEWEB)

Electrical resistance anomalies noted in EPDM gaskets have been attributed to zinc-enriched surface sublayers, about 10-{micro}m thick, in the sulfur cured rubber material. Gasket over-compression provided the necessary connector pin contact and was also found to cause surprising morphological changes on the gasket surfaces. These included distributions of zinc oxide whiskers in high pressure gasket areas and cone-shaped features rich in zinc, oxygen, and sulfur primarily in low pressure protruding gasket areas. Such whiskers and cones were only found on the pin side of the gaskets in contact with a molded plastic surface and not on the back side in contact with an aluminum surface. The mechanisms by which such features are formed have not yet been defined.

Yang, Nancy Y. C.; Domeier, Linda A.

2008-03-01

128

Do mouthwashes with and without bleaching agents degrade the force of elastomeric chains?  

UK PubMed Central (United Kingdom)

OBJECTIVE: To evaluate, in vitro, the effect of mouthwashes with and without bleaching agents on the force of elastomeric chains. MATERIALS AND METHODS: A total of 108 elastomeric chain specimens was divided into six groups (n = 18 in each group). Two test groups were exposed to two types of commonly used mouthwashes (Plax and Listerine), and two groups were exposed to mouthwashes containing bleaching agent (Plax Whitening and Listerine Whitening). Immersion in the solutions was performed twice a day for 60 seconds. One group of control specimens remained immersed in artificial saliva throughout the entire experimental period, and the other control specimens were exposed to distilled water. Force measurements were performed at six time intervals (initial, 1 day, 7 days, 14 days, 21 days, and 28 days). RESULTS: No statistically significant differences were found between the groups in the initial period (P > .05). Statistically significant differences were found between the control group and the Plax, Plax Whitening, and Listerine groups at the time intervals of 7, 14, and 21 days. In the initial period, the force was statistically significantly higher than it was in any of the other experimental periods (P < .05). The control group with distilled water and the test group with Plax Whitening maintained the most force during the experimental period. CONCLUSION: The presence of bleaching agent has no influence on the force degradation of elastomeric chains.

Pithon MM; Rodrigues AC; Sousa EL; Santos LP; Soares Ndos S

2013-07-01

129

The Effect of Prestretching on Force Degradation of Synthetic Elastomeric Chains  

Directory of Open Access Journals (Sweden)

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

Fattahi HR.; Poursayah A.

2011-01-01

130

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

Science.gov (United States)

...closure-sealing gasket composition) Arachidy-l-behenyl amide (C20 -C22 fatty acid amides) 5 percent. Azodicarbonamide 1. 2 percent. 2. 5 percent; for use only in the manufacture of polyethylene complying with item 2.1...

2009-04-01

131

Development of UHV compatible machined diamond profile gaskets for INDUS-2  

Science.gov (United States)

Ultra High Vacuum (UHV) compatible demountable joints are needed in Indus-2 (2.5 GeV, 300mA) electron storage ring for connecting Al-alloy vacuum chambers (homogeneous joints) as well as Al-alloy vacuum chambers to well proven stainless steel components like beam diagnostic components and RF-shielded bellow assemblies (heterogeneous joints). Bakeable & reliable diamond profile Al-alloy gaskets have been developed for Helium leak rate less than 2×10-10 Std. CC/sec, which eliminated the need of any Al to SS transition pieces onto the Aluminium vacuum chambers. Salient features of these gaskets are: high reliability, low cost, reduced flange thickness, self alignment, ease in installation, less torque requirement, formability to non-circular shape & ultra cleanliness. These diamond profile gaskets were machined from extruded Al-alloy 6061-T5 pipes using specially developed high-speed steel formed cutting tools. Thermal cyclic tests were carried to check the reliability of these gaskets. No leaks were found even after several bakeouts at 150°C. Non-circular metallic gaskets like the one used in UHV gate valve bonnet seal can also be manufactured using specially developed formed toolings. This paper describes basic design philosophy, manufacturing process and testing details of these gaskets.

Yadav, D. P.; Shiroman, R.; Shukla, S. K.; Kotaiah, S.

2008-05-01

132

Development of UHV compatible machined diamond profile gaskets for INDUS-2  

Energy Technology Data Exchange (ETDEWEB)

Ultra High Vacuum (UHV) compatible demountable joints are needed in Indus-2 (2.5 GeV, 300mA) electron storage ring for connecting Al-alloy vacuum chambers (homogeneous joints) as well as Al-alloy vacuum chambers to well proven stainless steel components like beam diagnostic components and RF-shielded bellow assemblies (heterogeneous joints). Bakeable and reliable diamond profile Al-alloy gaskets have been developed for Helium leak rate less than 2x10{sup -10} Std. CC/sec, which eliminated the need of any Al to SS transition pieces onto the Aluminium vacuum chambers. Salient features of these gaskets are: high reliability, low cost, reduced flange thickness, self alignment, ease in installation, less torque requirement, formability to non-circular shape and ultra cleanliness. These diamond profile gaskets were machined from extruded Al-alloy 6061-T5 pipes using specially developed high-speed steel formed cutting tools. Thermal cyclic tests were carried to check the reliability of these gaskets. No leaks were found even after several bakeouts at 150 deg. C. Non-circular metallic gaskets like the one used in UHV gate valve bonnet seal can also be manufactured using specially developed formed toolings. This paper describes basic design philosophy, manufacturing process and testing details of these gaskets.

Yadav, D P; Shiroman, R; Shukla, S K; Kotaiah, S [Ultra High Vacuum Section, Accelerator Programme, RRCAT, Indore-452013 (India)], E-mail: dpyadav@cat.ernet.in

2008-05-01

133

Impact of graphite gasket/duplex stainless steel couples on crevice chemistry and likelihood of crevice attack in seawater  

Energy Technology Data Exchange (ETDEWEB)

Electrochemical polarization measurements have been made on a graphite laminate gasket and a super-duplex stainless steel (DSS) in deaerated IM NaCl solution over a range of pH. The open circuit potential of the graphite is significantly more noble than that of the duplex stainless steel and the kinetics of the hydrogen ion reduction are greater at potentials more positive than about 0.0 V SCE. The data were used as input to a model of crevice chemistry and predictions made for potentials up to +0.4 V SCE. For crevices of parallel plates of DSS-DSS and DSS-Plastic, the usual acidic conditions were predicted but for a DSS-Graphite combination the pH was predicted to be alkaline. The latter is a consequence of the enhanced kinetics for cathodic reduction of hydrogen ions and water on the graphite which, when contained within the crevice, act to elevate the pH. The predictions suggest that coupling to graphite, contained within the crevice, may act to prevent crevice corrosion initiation in contrast to the usual perception of behavior when coupling to more noble materials. In practice, there have been significant crevice corrosion failures of a super-duplex stainless steel associated with graphite gaskets. However, in all cases, the failures were in chlorinated systems for which the corrosion potentials are particularly high and beyond the range for which a benefit from graphite could be anticipated.

Turnbull, A. [National Physical Lab., Teddington (United Kingdom). Centre for Materials Measurement and Technology

1998-12-31

134

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.

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; Leonardo Fernandes da Cunha; Ana Raquel Benetti

2007-01-01

136

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

137

Introduction of patents. Seal structure for preventing exfoliation of liquid gasket; Tokkyo shokai. Ekitai gasket no hakuri wo boshisuru seal kozo  

Energy Technology Data Exchange (ETDEWEB)

Introduced herein is a Nissan Motors' patent that produces good results. It is a seal structure for preventing exfoliation of liquid gasket, filed on January 29 1987. This invention is to be applied to the section at which an oil pan is attached to an engine, characterized by connecting the periphery around the lower ends of a cylinder block and front cover to the oil pan flange, and the cylinder block to front cover via a liquid gasket, and also by forming a cavity, to be filled with the liquid gasket, at the lower end of the front cover by chamfering the edge. The cavity, located between the front cover and cylinder block, keeps their corners separated from each other to some extent, even when temperature increases to thermally expand the front cover more than the cylinder block, moving the lower face of the former downward. This prevents formation of a large difference in level which may cause the liquid gasket to separate from the lower face of the cylinder block, thereby keeping these members sealed for extended periods. (NEDO)

NONE

1999-06-01

138

Dimensional stability and detail reproduction of irreversible hydrocolloid and elastomeric impressions disinfected by immersion.  

UK PubMed Central (United Kingdom)

STATEMENT OF PROBLEM: Because irreversible hydrocolloid impressions imbibe blood and saliva, immersion rather than spray disinfection may be more effective. Polyether has been shown to be dimensionally sensitive to immersion disinfection. PURPOSE: The aim of this study was to determine whether irreversible hydrocolloid and polyether impressions could be disinfected by immersion without sacrificing accuracy and surface quality. MATERIAL AND METHODS: Impressions were made of a master mandibular arch containing a crown preparation. Changes between the master and working casts were assessed. Irreversible hydrocolloids (Jeltrate; Palgaflex), a polyether (Impregum F), and an addition silicone (President) were used. Disinfectants were an iodophor (Biocide), a glyoxal glutaraldehyde (Impresept de), and a phenol glutaraldehyde (Sporicidin). The control was without disinfection. Casts were formed in Type IV gypsum. The roughness of working dies was also recorded and an analysis of variance was used for statistical evaluation. Results. Casts from disinfected irreversible hydrocolloid and elastomeric impressions maintained accuracy for anteroposterior and cross arch dimensions where differences from the master was less than 0.1%. Buccolingual and mesiodistal dimensions of working dies (disinfected and control) were 6 to 8 microm larger than the master for addition silicones and 11 to 16 pm for polyethers. The occlusogingival dimension of dies for control and disinfected polyether was 9 pm longer than the master compared with -3 microm for addition silicone. The range of mean surface roughness of working dies made from irreversible hydrocolloids was 1.4 to 1.7 microm and ranged from 0.5 to 0.7 microm for elastomeric impressions. Conclusion. Immersion disinfection of Jeltrate material with iodophor and Palgaflex material with glyoxal glutaraldehyde produced casts and dies as accurate as the control. Control and disinfected elastomeric impression produced dies as clinically accurate and smooth as the master. Disinfection of irreversible hydrocolloid impressions with the glyoxal and phenol glutaraldehyde produced a surface smoother than controls.

Johnson GH; Chellis KD; Gordon GE; Lepe X

1998-04-01

139

Diseño de un proceso de separación de los componentes de residuos metaloplásticos de la fabricación de juntas para estanqueidad en la empresa FRACO S. A./ Designing a Process for Separating Leftover Metoplastic Materials in the Production of Engine Gaskets at FRACO S.A./ Desenho de um processo de separação dos componentes de resíduos metaloplásticos da fabricação de juntas de estanqueidade na empresa FRACO S. A.  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese O presente artigo apresenta os resultados da primeira etapa do Projeto de recuperação contingente no marco de cooperação universidade-empresaestado, financiado por Colciencias e executado pela Universidade de Boyaca e a Fabrica Colombiana de Peças Automotoras (FRACO S. A.), que consiste em buscar alternativas de reaproveitamento para os materiais metaloplásticos, sobra do processo de elaboração de juntas de estanqueidade para motor. Nesta fase da pesquisa foi estu (more) dada a forma de separar os materiais que conformam esses materiais para duas referências do produto denominados FracoPlay e FracoPack. O estudo recorreu um árduo trabalho de laboratório, guiado por um estrito desenho estadístico, no qual foram provados dois agentes de separação em diferentes condições de concentração e temperatura. Os resultados obtidos são exitosos e permitem iniciar a etapa de elaboração de novos materiais a partir dos separados. Abstract in spanish El presente artículo presenta los resultados de la primera etapa del Proyecto de recuperación contingente en el marco de cooperación universidad-empresa-Estado, financiado por Colciencias y ejecutado por la Universidad de Boyacá y la Fábrica Colombiana de Repuestos Automotores (FRACO S. A.), que consiste en buscar alternativas de reaprovechamiento para los materiales metaloplásticos sobrantes del proceso de elaboración de juntas de estanqueidad para motor. En esta (more) fase de la investigación se estudió la forma de separar los materiales que conforman estos materiales para dos referencias de producto denominados FracoPlay y FracoPack. Se recurrió a un arduo trabajo de laboratorio, guiado por un estricto diseño estadístico, en el que se probaron dos agentes de separación a diferentes condiciones de concentración y temperatura. Los resultados obtenidos son exitosos y permiten iniciar la etapa de elaboración de nuevos materiales a partir de los separados. Abstract in english This article shows the results of the first stage of the project Contingent Recovery under a University-Company-State Cooperation framework, sponsored by Colciencias and carried out by the University of Boyacá and the Colombian Factory for Auto Parts (FRACO S.A). This project seeks alternatives for re-usage of leftover metoplastic materials from the process of producing gaskets for engines. This phase of research deals with the manner of separating the components that fo (more) rm these materials, with reference to two of the products called FracoPlay and FracoPack. Extensive lab work was involved, guided by a well-planned statistical design in which the separation agents were tested at different conditions of concentration and temperature. The results obtained are satisfactory and allow the beginning of the development stage of new materials from the separated ones.

Suescún, Óscar Buitrago; Zambrano Gómez, Víctor; Zambrano Arroyo, Daniel

2008-12-01

140

New elastomeric silicone based networks applicable as electroactive systems  

DEFF Research Database (Denmark)

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

Bejenariu, Anca Gabriela; Boll, Mads

2011-01-01

 
 
 
 
141

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

International Nuclear Information System (INIS)

[en] 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

1996-01-01

142

The method for decrease of helium gas leak with double O-ring rubber gasket  

Energy Technology Data Exchange (ETDEWEB)

Nuclear components are required to be highly airtight. To get satisfactory airtightness, helium leak detection had been used. However helium gas atom is smaller than other gas atom except hydrogen and so has very high permeability. Therefore, leak of helium gas atom from O-ring rubber gasket was detected by helium leak detector in airtight test. It is very difficult to distinguish permeation from leakage. To solve the problem, we made double O-ring rubber gasket and tested its ability of decreasing permeation, examined its effect. As a result of the test and the examination, we found the gap between outer ring and inner ring of double O-ring rubber gasket was very important for decrease permeation helium gas. (author)

Ohba, Toshihiro; Kikuchi, Taiji; Taka, Isamu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment] [and others

2001-10-01

143

Voltage-controlled surface wrinkling of elastomeric coatings.  

UK PubMed Central (United Kingdom)

Wrinkling of elastomeric coatings by an electric field is reported. The associated changes in the coating's optical properties yield switchable mirrors and windows. The field Ec needed to induce wrinkling is a factor of 4.4 lower than the theoretically predicted value, which is attributed to space-charge injection.

van den Ende D; Kamminga JD; Boersma A; Andritsch T; Steeneken PG

2013-07-01

144

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

145

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

Energy Technology Data Exchange (ETDEWEB)

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 S{sub g} 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 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.

Jolly, Pascal [Departement de Genie Mecanique, Ecole Polytechnique, P.O. Box 6079, Station ' Centre Ville' , Montreal, QC, H3C 3A7 (Canada)], E-mail: pascal-jolly@wanadoo.fr; Marchand, Luc [Departement de Genie Mecanique, Ecole Polytechnique, P.O. Box 6079, Station ' Centre Ville' , Montreal, QC, H3C 3A7 (Canada)], E-mail: luc.marchand@polymtl.ca

2008-07-15

146

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 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

2008-01-01

147

Impact of graphite gasket/duplex stainless steel couples on crevice chemistry and the likelihood of crevice attack in seawater  

Energy Technology Data Exchange (ETDEWEB)

Crevice corrosion in seawater usually is assumed to be induced by attainment of a critical solution chemistry. Electrochemical polarization measurements were made on a graphite laminate gasket and a super-duplex stainless steel (DSS) in deaerated 1M sodium chloride (NaCl) solution over a range of pH. The open-circuit potential of the graphite was significantly more noble than that of the DSS, and the kinetics of the hydrogen ion reduction were greater at potentials more positive than {approximately} 0.0 V{sub SCE}. Data were used as input to a model of crevice chemistry, and predictions were made for potentials up to 0.4 V{sub SCE}. For crevices of parallel plates of DSS-DSS and DSS-plastic, the usual acidic conditions were predicted. However, for a DSS-graphite combination, there was no significant decrease in pH. The latter was a consequence of the enhanced kinetics for cathodic reduction of hydrogen ions and water on the graphite which, when confined within the crevice, opposed the fall in pH associated with the metal-ion hydrolysis process. The predictions suggested that coupling to graphite, contained within the crevice, may act to prevent crevice corrosion initiation in contrast to the usual perception of behavior when coupling to more noble materials. In practice, there have been significant crevice corrosion failures of DSS associated with graphite gaskets. However, in all cases, the failures were in chlorinated systems for which corrosion potentials are particularly high and beyond the range for which a benefit from graphite could be anticipated.

Turnbull, A. [National Physical Lab., Middlesex (United Kingdom). Centre for Materials Measurement and Technology

1999-02-01

148

In vitro evaluation of force degradation of elastomeric chains used in orthodontics.  

UK PubMed Central (United Kingdom)

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. CONCLUSIONS: 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.

Weissheimer A; Locks A; de Menezes LM; Borgatto AF; Derech CD

2013-01-01

149

Self-interacting self-avoiding walks on the Sierpinski gasket  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Exact recurrence relations for generating functions for self-interacting self-avoiding random walks on a Sierpinski gasket lattice are given. Their analysis reveals that the mean end-to-end separation of N-step walks varies as N? with ? = In (2)/ln {(7 - 5)/2}, regardless of the (finite) strength of...

Klein, D.J.; Seitz, W.A.

150

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

Directory of Open Access Journals (Sweden)

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

Osmolovsky D. S.

2011-01-01

151

Water and steam tightness tests of expanded graphite static gaskets for nuclear power plant steam generators  

International Nuclear Information System (INIS)

We first recalled the information which can be acquired regarding the mechanical behaviour and the tightness of spiral wound gaskets (with asbestos and with expanded graphite) and gaskets made of pure expanded graphite. Tests have been carried out under an hydraulic press at ambient temperature and up to 350 deg C, using helium (up to 200 bar) and a mass spectrometer. We briefly explained why the results achieved are not sufficient to evaluate the gasket leak rate when a liquid is used. Other tests are consequently necessary. We give a short description of the plant used to carry out tests with steam and water up to 350 deg C and 200 bar and to measure a leak rate which may vary from 10-8 g/s to 10-3 g/s and more. The procedure selected will first be indicated as well as the results obtained when using and expanded graphite gasket (ring inserted between two stainless steal rings) at various temperatures under a pressure (steam and then, water) ranging from 1 to 200 bar. (authors). 17 figs., 14 refs

1992-01-01

152

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

Energy Technology Data Exchange (ETDEWEB)

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)

Wataru, Masumi; Shirai, Koji; Saegusa, Toshiari; Ito, Chihiro; Takeda, Hirofumi; Namba, Kousuke [Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko-shi, Chiba-ken 270-1194 (Japan)

2009-06-15

153

Silicone absorption of elastomeric closures--an accelerated study.  

Science.gov (United States)

There is a trend in the parenteral industry to move from the use of elastomeric closures which are washed, siliconized, dried and sterilized in-house at the pharmaceutical manufacturers' site to pre-prepared closures purchased from the closure supplier. This preparation can consist of washing to reduce particle-load and bioburden, siliconization, placement in ready-to-sterilize bags and may eventually extend to sterilization by steam autoclave or gamma irradiation. Since silicone oil lubrication is critical to the processability/machinability of closures, research was designed to investigate this phenomenon in closures prepared using the Westar RS (Ready-to-Sterilize) process. This paper presents the data gathered in a study of the characteristic of silicone absorption into elastomeric closures under accelerated conditions. Variables such as silicone viscosity, rubber formulation, effect of sterilization and others are considered. PMID:9542410

Degrazio, F L; Hlobik, T; Vaughan, S

154

Silicone absorption of elastomeric closures--an accelerated study.  

UK PubMed Central (United Kingdom)

There is a trend in the parenteral industry to move from the use of elastomeric closures which are washed, siliconized, dried and sterilized in-house at the pharmaceutical manufacturers' site to pre-prepared closures purchased from the closure supplier. This preparation can consist of washing to reduce particle-load and bioburden, siliconization, placement in ready-to-sterilize bags and may eventually extend to sterilization by steam autoclave or gamma irradiation. Since silicone oil lubrication is critical to the processability/machinability of closures, research was designed to investigate this phenomenon in closures prepared using the Westar RS (Ready-to-Sterilize) process. This paper presents the data gathered in a study of the characteristic of silicone absorption into elastomeric closures under accelerated conditions. Variables such as silicone viscosity, rubber formulation, effect of sterilization and others are considered.

Degrazio FL; Hlobik T; Vaughan S

1998-01-01

155

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

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; Fabrício Mezzomo Collares; Vicente Castelo Branco Leitune; Susana Maria Werner Samuel; Carmen Beatriz Borges Fortes

2012-01-01

157

Pigment effect on the long term elasticity of elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available 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 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 (more) , 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.

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

2012-06-01

158

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

UK PubMed Central (United Kingdom)

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.

He X; Yermakov M; Reponen T; McKay RT; James K; Grinshpun SA

2013-01-01

159

Silicon micro-masonry using elastomeric stamps for three-dimensional microfabrication  

Science.gov (United States)

We present a micromanufacturing method for constructing microsystems, which we term ‘micro-masonry’ based on individual manipulation, influenced by strategies for deterministic materials assembly using advanced forms of transfer printing. Analogous to masonry in construction sites, micro-masonry consists of the preparation, manipulation, and binding of microscale units to assemble microcomponents and microsystems. In this paper, for the purpose of demonstration, we used microtipped elastomeric stamps as manipulators and built three dimensional silicon microstructures. Silicon units of varied shapes were fabricated in a suspended format on donors, retrieved, delivered, and placed on a target location on a receiver using microtipped stamps. Annealing of the assembled silicon units permanently bound them and completed the micro-masonry procedure.

Keum, Hohyun; Carlson, Andrew; Ning, Hailong; Mihi, Agustin; Eisenhaure, Jeffrey D.; Braun, Paul V.; Rogers, John A.; Kim, Seok

2012-05-01

160

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

 
 
 
 
161

Elastomer degradation sensor using a piezoelectric material  

Energy Technology Data Exchange (ETDEWEB)

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

162

Accuracy of elastomeric impressions disinfected by immersion.  

Science.gov (United States)

This study evaluates the accuracy and surface quality of stone dies made from impressions that had been placed in disinfectants. Results indicated that selection of the type of impression material is more important than selection of the disinfectant. Addition silicone and polysulfide impressions were disinfected without a loss in accuracy, whereas polyether impressions were adversely affected. The surface quality of dies was acceptable with disinfection and one disinfectant contributed to an improvement in surface quality compared with the control. PMID:3132494

Johnson, G H; Drennon, D G; Powell, G L

1988-04-01

163

Accuracy of elastomeric impressions disinfected by immersion.  

UK PubMed Central (United Kingdom)

This study evaluates the accuracy and surface quality of stone dies made from impressions that had been placed in disinfectants. Results indicated that selection of the type of impression material is more important than selection of the disinfectant. Addition silicone and polysulfide impressions were disinfected without a loss in accuracy, whereas polyether impressions were adversely affected. The surface quality of dies was acceptable with disinfection and one disinfectant contributed to an improvement in surface quality compared with the control.

Johnson GH; Drennon DG; Powell GL

1988-04-01

164

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.

Yuskar Lase; James Jatmiko Oetomo

2011-01-01

165

Elastic buckling of AlN ribbons on elastomeric substrate  

International Nuclear Information System (INIS)

[en] For optoelectronic applications requiring unconventional substrates, use of flexible forms of semiconductors may be inevitable. We have fabricated a flexible form of single crystalline AlN ribbons with periodic and wavelike structures on an elastomeric substrate. Single crystalline AlN films were grown on Si (111) substrate using high vacuum unbalanced magnetron sputtering. Crystallinity of the AlN films was confirmed with x-ray diffraction and pole figure. The AlN ribbons were transferred to a prestrained (3.1%) elastomeric substrate and the resulting ''wavy'' ribbons on the substrate were flexible up to 30% strain without any crack formation on the surface. As the film thickness changed from 300 to 900 nm, the periods of the waves varied from 95 to 277 ?m, which were within a 10% error of the calculated values. When we applied more than 30% strain, mechanical instability, such as the failure of AlN ribbons due to the cracks on the surface and the merged ribbons, was observed

2009-03-02

166

Elastomeric microparticles for acoustic mediated bioseparations  

Science.gov (United States)

Background Acoustophoresis has been utilized successfully in applications including cell trapping, focusing, and purification. One current limitation of acoustophoresis for cell sorting is the reliance on the inherent physical properties of cells (e.g., compressibility, density) instead of selecting cells based upon biologically relevant surface-presenting antigens. Introducing an acoustophoretic cell sorting approach that allows biochemical specificity may overcome this limitation, thus advancing the value of acoustophoresis approaches for both the basic research and clinical fields. Results The results presented herein demonstrate the ability for negative acoustic contrast particles (NACPs) to specifically capture and transport positive acoustic contrast particles (PACPs) to the antinode of an ultrasound standing wave. Emulsification and post curing of pre-polymers, either polydimethylsiloxane (PDMS) or polyvinylmethylsiloxane (PVMS), within aqueous surfactant solution results in the formation of stable NACPs that focus onto pressure antinodes. We used either photochemical reactions with biotin-tetrafluorophenyl azide (biotin-TFPA) or end-functionalization of Pluronic F108 surfactant to biofunctionalize NACPs. These biotinylated NACPs bind specifically to streptavidin polystyrene microparticles (as cell surrogates) and transport them to the pressure antinode within an acoustofluidic chip. Conclusion To the best of our knowledge, this is the first demonstration of using NACPs as carriers for transport of PACPs in an ultrasound standing wave. By using different silicones (i.e., PDMS, PVMS) and curing chemistries, we demonstrate versatility of silicone materials for NACPs and advance the understanding of useful approaches for preparing NACPs. This bioseparation scheme holds potential for applications requiring rapid, continuous separations such as sorting and analysis of cells and biomolecules.

2013-01-01

167

Elastomeric microparticles for acoustic mediated bioseparations.  

UK PubMed Central (United Kingdom)

BACKGROUND: Acoustophoresis has been utilized successfully in applications including cell trapping, focusing, and purification. One current limitation of acoustophoresis for cell sorting is the reliance on the inherent physical properties of cells (e.g., compressibility, density) instead of selecting cells based upon biologically relevant surface-presenting antigens. Introducing an acoustophoretic cell sorting approach that allows biochemical specificity may overcome this limitation, thus advancing the value of acoustophoresis approaches for both the basic research and clinical fields. RESULTS: The results presented herein demonstrate the ability for negative acoustic contrast particles (NACPs) to specifically capture and transport positive acoustic contrast particles (PACPs) to the antinode of an ultrasound standing wave. Emulsification and post curing of pre-polymers, either polydimethylsiloxane (PDMS) or polyvinylmethylsiloxane (PVMS), within aqueous surfactant solution results in the formation of stable NACPs that focus onto pressure antinodes. We used either photochemical reactions with biotin-tetrafluorophenyl azide (biotin-TFPA) or end-functionalization of Pluronic F108 surfactant to biofunctionalize NACPs. These biotinylated NACPs bind specifically to streptavidin polystyrene microparticles (as cell surrogates) and transport them to the pressure antinode within an acoustofluidic chip. CONCLUSION: To the best of our knowledge, this is the first demonstration of using NACPs as carriers for transport of PACPs in an ultrasound standing wave. By using different silicones (i.e., PDMS, PVMS) and curing chemistries, we demonstrate versatility of silicone materials for NACPs and advance the understanding of useful approaches for preparing NACPs. This bioseparation scheme holds potential for applications requiring rapid, continuous separations such as sorting and analysis of cells and biomolecules.

Johnson LM; Gao L; Shields IV CW; Smith M; Efimenko K; Cushing K; Genzer J; López GP

2013-01-01

168

Storage containers for radioactive material  

Energy Technology Data Exchange (ETDEWEB)

A radioactive material storage system for use in the laboratory having a flat base plate with a groove in one surface thereof and a hollow pedestal extending perpendicularly away from the other surface thereof, a sealing gasket in the groove, a cover having a filter therein and an outwardly extending flange which fits over the plate, the groove and the gasket, and a clamp for maintaining the cover and the plate sealed together, whereby the plate and the cover and the clamp cooperate to provide a storage area for radioactive material readily accessible for use or

Groh, Edward F. (Naperville, IL); Cassidy, Dale A. (Valparaiso, IN); Dates, Leon R. (Elmwood Park, IL)

1981-01-01

169

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

Directory of Open Access Journals (Sweden)

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

P.PRABHU; R.RANJITH KUMAR; S.YOGAPRIYA; R.RAJALAKSHMI; N.AHAMEDU NISHA

2013-01-01

170

Response of elastomeric packaging components to a corrosive simulant mixed waste  

International Nuclear Information System (INIS)

[en] 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

1997-10-02

171

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 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.

2007-01-01

172

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

Energy Technology Data Exchange (ETDEWEB)

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 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.

Krementz, D

2007-11-27

173

Optimal elastomeric scaffold leaflet shape for pulmonary heart valve leaflet replacement.  

Science.gov (United States)

Surgical replacement of the pulmonary valve (PV) is a common treatment option for congenital pulmonary valve defects. Engineered tissue approaches to develop novel PV replacements are intrinsically complex, and will require methodical approaches for their development. Single leaflet replacement utilizing an ovine model is an attractive approach in that candidate materials can be evaluated under valve level stresses in blood contact without the confounding effects of a particular valve design. In the present study an approach for optimal leaflet shape design based on finite element (FE) simulation of a mechanically anisotropic, elastomeric scaffold for PV replacement is presented. The scaffold was modeled as an orthotropic hyperelastic material using a generalized Fung-type constitutive model. The optimal shape of the fully loaded PV replacement leaflet was systematically determined by minimizing the difference between the deformed shape obtained from FE simulation and an ex-vivo microCT scan of a native ovine PV leaflet. Effects of material anisotropy, dimensional changes of PV root, and fiber orientation on the resulting leaflet deformation were investigated. In-situ validation demonstrated that the approach could guide the design of the leaflet shape for PV replacement surgery. PMID:23294966

Fan, Rong; Bayoumi, Ahmed S; Chen, Peter; Hobson, Christopher M; Wagner, William R; Mayer, John E; Sacks, Michael S

2013-01-05

174

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

2013-04-29

175

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

UK PubMed Central (United Kingdom)

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.

Wang T; Ji X; Jin L; Feng Z; Wu J; Zheng J; Wang H; Xu ZW; Guo L; He N

2013-05-01

176

Coined stoppers. A significant advance with metaloflex cylinder-head gaskets; Gepraegte Stopper. Wichtiger Entwicklungsschritt bei Metaloflex-Metallagen Zylinderkopfdichtungen  

Energy Technology Data Exchange (ETDEWEB)

New coining technologies give engine manufacturers a variety of new possibilities of controlling the distribution of force in the sealing gap. Here's why: multi-layer metal cylinder-head gaskets with coined meander or honey comb stoppers offer not only high cost-efficiency but other decisive advantages, as well. (orig.)

Baur, M.; Diez, A.

2004-09-01

177

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

Scientific Electronic Library Online (English)

Full Text Available 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 (more) 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 (more) 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.

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

2013-02-01

178

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

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

179

Impact-Induced Glass Transition in Elastomeric Coatings  

Science.gov (United States)

When an elastomer layer is applied to the front surface of steel, the resistance to penetration by hard projectiles increases significantly. It is not obvious why a soft polymer should affect this property of metals, and most rubbers do not. However, we have found that a few are very effective; the requirement is that the polymer undergo a viscoelastic phase transition upon impact. This means that the frequency of its segmental dynamics correspond to the impact frequency. The latter is estimated as the ratio of the projectile velocity to the coating thickness, and is on the order of 10^5 s-1 for the experiments herein. Our data and a non-linear dynamics finite-element analysis offer support for this resonance condition as a primary mechanism underlying the penetration-resistance of elastomer-coated metal substrates. The impact-induced phase transition causes large energy absorption, decreasing the kinetic energy of the impacting projectile. However, this energy absorption only accounts for about half the enhanced stopping power of the elastomer/steel bilayer. An additional mechanism is lateral spreading of the impact force, resulting from the transient hardening of the elastomeric during its transition to the glassy state -- the modulus of the rubber increases 1000-fold over a time period of microseconds. The penetration-resistance is a very nonlinear function of the coating thickness. Moreover, tests on various metals show that hardness is the principal substrate parameter controlling the contribution of the coating.

Roland, C. M.

2013-03-01

180

Dynamic analysis of fiber-reinforced elastomeric isolation structures  

International Nuclear Information System (INIS)

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

2009-01-01

 
 
 
 
181

Elastomeric negative acoustic contrast particles for affinity capture assays.  

UK PubMed Central (United Kingdom)

This report describes the development of elastomeric capture microparticles (EC?Ps) and their use with acoustophoretic separation to perform microparticle assays via flow cytometry.We have developed simple methods to form EC?Ps by cross-linking droplets of common commercially available silicone precursors in suspension followed by surface functionalization with biomolecular recognition reagents. The EC?Ps are compressible particles that exhibit negative acoustic contrast in ultrasound when suspended in aqueous media, blood serum, or diluted blood. In this study, these particles have been functionalized with antibodies to bind prostate specific antigen and immunoglobulin (IgG). Specific separation of the EC?Ps from blood cells is achieved by flowing them through a microfluidic acoustophoretic device that uses an ultrasonic standing wave to align the blood cells, which exhibit positive acoustic contrast, at a node in the acoustic pressure distribution while aligning the negative acoustic contrast EC?Ps at the antinodes. Laminar flow of the separated particles to downstream collection ports allows for collection of the separated negative contrast (EC?Ps) and positive contrast particles (cells). Separated EC?Ps were analyzed via flow cytometry to demonstrate nanomolar detection for prostate specific antigen in aqueous buffer and picomolar detection for IgG in plasma and diluted blood samples. 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 KW; Piyasena ME; Carroll NJ; Maestas GC; López BA; Edwards BS; Graves SW; López GP

2013-02-01

182

Tunable SERS using gold nanoaggregates on an elastomeric substrate.  

Science.gov (United States)

We report on the self-assembly of colloidal gold nanoparticles on a stretchable, elastomeric membrane, and the use of this membrane as a base substrate for far-field confocal Raman measurements. Surface-enhanced Raman scattering (SERS) enhancement for such a substrate was estimated as 10(6) to 10(7). Atomic force microscopy has been used to study the changes in nanoparticle topography when the membrane is stretched. The homogeneous strain defined by average relative motion of nanoparticles is approximately half the macroscopically-applied biaxial strain. The SERS intensity was maximized when the membrane was at rest (i.e. without stretch), and reduced as stretching was increased. Our measurements are consistent with theoretical and numerical SERS enhancements for the interstitial gap between two spheres. The data indicate that the resting gap between the spheres is 11 nm or 16 nm, using two theoretical models. This work represents progress towards particularly facile sample fabrication and in situ tuning techniques for SERS. PMID:23958839

Hossain, M Kamal; Willmott, Geoff R; Etchegoin, Pablo G; Blaikie, Richard J; Tallon, Jeffery L

2013-08-20

183

Tunable SERS using gold nanoaggregates on an elastomeric substrate.  

UK PubMed Central (United Kingdom)

We report on the self-assembly of colloidal gold nanoparticles on a stretchable, elastomeric membrane, and the use of this membrane as a base substrate for far-field confocal Raman measurements. Surface-enhanced Raman scattering (SERS) enhancement for such a substrate was estimated as 10(6) to 10(7). Atomic force microscopy has been used to study the changes in nanoparticle topography when the membrane is stretched. The homogeneous strain defined by average relative motion of nanoparticles is approximately half the macroscopically-applied biaxial strain. The SERS intensity was maximized when the membrane was at rest (i.e. without stretch), and reduced as stretching was increased. Our measurements are consistent with theoretical and numerical SERS enhancements for the interstitial gap between two spheres. The data indicate that the resting gap between the spheres is 11 nm or 16 nm, using two theoretical models. This work represents progress towards particularly facile sample fabrication and in situ tuning techniques for SERS.

Hossain MK; Willmott GR; Etchegoin PG; Blaikie RJ; Tallon JL

2013-10-01

184

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 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

2003-01-01

185

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Elastomeric proteins have evolved independently multiple times through evolution. Produced as monomers, they self-assemble into polymeric structures that impart properties of stretch and recoil. They are composed of an alternating domain architecture of elastomeric domains interspersed with cross-li...

Song, Hongyan; Parkinson, John

186

Tunable optical gratings based on buckled nanoscale thin films on transparent elastomeric substrates  

Science.gov (United States)

This letter reports a tunable optical grating based on buckled thin film with periodic sinusoidal patterns on a transparent elastomeric substrate. Submicron scale sinusoidal gratings have been fabricated with nanometer thick Gold/Palladium film coated on 30% pretensioned polydimethylsiloxane substrates. Due to competition between the soft elastomeric substrates and relatively stiff films, periodic wavy profiles are created upon releasing the pretension. The buckling profiles can be easily tuned by mechanically stretching or compressing. Optical transmittance diffraction testing has been conducted, and 85 nm peak wavelength shifts of the first order diffraction have been achieved by stretching the grating up to 30% of its original length.

Yu, Cunjiang; O'Brien, Kevin; Zhang, Yong-Hang; Yu, Hongbin; Jiang, Hanqing

2010-01-01

187

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.

Amit K. Panda; Asit K. Panda

2012-01-01

188

New MLS Technology for multi-layer steel cylinder head gaskets; Die neue Technologie fuer Mehrlagen-Stahl-Zylinderkopfdichtungen  

Energy Technology Data Exchange (ETDEWEB)

A breakthrough innovation during the development of the Multi-Layer Steel Cylinder Head Gasket (MLS-CHG) was to separate the gasket into supporting components and elastic components in order to distribute the highly variable load conditions that occur during engine operation in accordance with the load-bearing capabilities of the gasket design elements. The Victor Reinz MLS-CHG (RETALL {sup trademark}) embodies this concept in an excellent manner. With the so-called 'wave stopper', an element that allows extremely flexible design was developed in order to achieve secure sealing in modern internal combustion engines. (orig.) [German] Es war bereits eine durchschlagende Innovation, bei der Entwicklung der Mehr-Lagen-Stahl-Zylinderkopfdichtung (MLS-ZKD) den elastischen vom stuetzenden Teil zu trennen und damit die stark wechselnden Bedingungen waehrend des Motorbetriebs entsprechend den Belastbarkeiten der Konstruktionselemente der Dichtung zu verteilen. Die Victor Reinz MLS-ZKD (RETALL {sup circledR}) verkoerpert dieses Konzept in hervorragender Weise. Mit dem sogenannten 'Wellenstopper' wurde ein aeusserst flexibel auslegbares Element zur sicheren Abdichtung moderner Verbrennungsmotoren entwickelt. (orig.)

Ludwig, J.; Weiss, A.; Unseld, G.; Rebien, H.; Sailer, A. [Victor Reinz Dichtungs GmbH, Neu-Ulm (Germany)

2001-10-01

189

Expansive-graphite-sandwiched spiral-wound stainless steel gasket applied to manhole sealing joints of nuclear equipment  

International Nuclear Information System (INIS)

The test results of domestic expansive-graphite-sandwiched spiral-wound stainless steel gaskets which were mounted on a manhole of steel vessel model with 1 : 1 scale are summarized. After testing mechanical properties in the cold state, the tests were carried out on a large hot-state experimental rig. Conditions were selected in accordance with actual operating conditions of nuclear primary equipment or more severe. The tightness of sealing, stud tension, and variations of angular displacement and gap between manhole cover and base were examined under conditions equivalent to the duration of reactor start-up (temperature and pressure up), normal operation and shut-down (temperature down). The simulation of changes of tightness, adjacent stud tensions and total tension that caused by one stud broken has been completed. The effect of impurity of sulphur contained in gaskets on water quality in the circuit was studied. The reliability of domestic gaskets applied to manhole sealing joints in nuclear equipment is also discussed

1991-01-01

190

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).

1997-01-01

191

Soft elastomeric nanopillar stamps for enhancing absorption in organic thin-film solar cells.  

Science.gov (United States)

An elastomeric poly(dimethylsiloxane) (PDMS) block engraved with periodically arrayed nanopillars serves as a transferable light-trapping stamp for encapsulated organic thin-film solar cells. Diffracted light rays from the stamp interfere with one another and self-focus onto the active layer of the solar cell, generating enhanced absorption, as indicated in the current density-voltage measurements. PMID:23047618

Hyun, Jerome K; Ahn, Changui; Kang, Hyunbum; Kim, Hyeong Jun; Park, Junyong; Kim, Ki-Hyun; Ahn, Chi Won; Kim, Bumjoon J; Jeon, Seokwoo

2012-10-09

192

Evaporation-induced self-alignment and transfer of semiconductor nanowires by wrinkled elastomeric templates.  

UK PubMed Central (United Kingdom)

The evaporation-induced self-alignment of semiconductor nanowires is achieved using wrinkled elastomeric templates. The wrinkled templates, which have a surface topography that can be tuned via changes in the mechanical strain, are used as both a template to align the nanowires and as a stamp to transfer the aligned nanowires to target substrates.

Lee SG; Kim H; Choi HH; Bong H; Park YD; Lee WH; Cho K

2013-04-01

193

Soft elastomeric nanopillar stamps for enhancing absorption in organic thin-film solar cells.  

UK PubMed Central (United Kingdom)

An elastomeric poly(dimethylsiloxane) (PDMS) block engraved with periodically arrayed nanopillars serves as a transferable light-trapping stamp for encapsulated organic thin-film solar cells. Diffracted light rays from the stamp interfere with one another and self-focus onto the active layer of the solar cell, generating enhanced absorption, as indicated in the current density-voltage measurements.

Hyun JK; Ahn C; Kang H; Kim HJ; Park J; Kim KH; Ahn CW; Kim BJ; Jeon S

2013-02-01

194

Periodontal and microbiologic evaluation of 2 methods of archwire ligation: ligature wires and elastomeric rings.  

UK PubMed Central (United Kingdom)

INTRODUCTION: Prophylactic programs to prevent dental biofilm accumulation must be implemented to minimize the risk for periodontal diseases in orthodontic patients. Therefore, we assessed the possible periodontal and microbiologic changes resulting from the use of 2 methods of orthodontic archwire ligation: elastomeric rings and steel ligatures. METHODS: The following parameters were measured: plaque index, gingival bleeding index, probing depth, and biofilm samples from the maxillary second premolars and the mandibular lateral incisors were evaluated in 14 subjects without clinical signs of gingival inflammation before orthodontic appliance placement and after 6 months of treatment. Each orthodontic arch was fixed with elastomeric rings on 1 side of the midline, and steel ligatures were used on the opposite side. Polymerase chain reaction analysis was used to detect Porphyromonas gingivalis, Tannerella forsythia, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and P nigrescens. RESULTS: The elastomeric rings were associated with a higher score for plaque index and bleeding than steel ligatures, as well as many positive sites of T forsythia and P nigrescens (P <0.05). CONCLUSIONS: Elastomeric rings favored these 2 periodontopathogens and harmed gingival conditions.

Alves de Souza R; Borges de Araújo Magnani MB; Nouer DF; Oliveira da Silva C; Klein MI; Sallum EA; Gonçalves RB

2008-10-01

195

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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-Ampic...

Min A Kang; Ju-Seop Kang

196

Territory covered by N random walkers on fractal media: the Sierpinski gasket and the percolation aggregate.  

UK PubMed Central (United Kingdom)

We address the problem of evaluating the number S(N)(t) of distinct sites visited up to time t by N noninteracting random walkers all starting from the same origin in fractal media. For a wide class of fractals (of which the percolation cluster at criticality and the Sierpinski gasket are typical examples) we propose, for large N and after the short-time compact regime, an asymptotic series for S(N)(t) analogous to that found for Euclidean media: S(N)(t) approximately S(N)(t)(1-Delta). Here S(N)(t) is the number of sites (volume) inside a hypersphere of radius L[ln(N)/c]1/v where L is the root-mean-square chemical displacement of a single random walker, and v and c determine how fast 1-Gamma(t)(l) (the probability that a given site at chemical distance l from the origin is visited by a single random walker by time t) decays for large values of l/L: 1-Gamma(t)(l) approximately exp[-c(l/L)(v)]. For the fractals considered in this paper, v=d(l)w/((d(l)w)-1), d(l)w being the chemical-diffusion exponent. The corrective term Delta is expressed as a series in ln(-n)(N)ln(m) ln(N) (with n> or =1 and 0< or =m< or =n), which is given explicitly up to n=2. This corrective term contributes substantially to the final value of S(N)(t) even for relatively large values of N.

Acedo L; Yuste SB

2001-01-01

197

Elastomers for Geothermal Casing-Packer Seals: Four elastomeric systems for casing-packer seals performed satisfactorily at geothermal conditions.  

Science.gov (United States)

This citation summarizes a one-page announcement of technology available for utilization. A report describes the development of elastomeric compounds for casing-packer seals that will withstand a 260C geothermal environment. A preliminary study had determ...

1982-01-01

198

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

UK PubMed Central (United Kingdom)

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.

Chou IM; Bassett WA; Anderson AJ; Mayanovic RA; Shang L

2008-11-01

199

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-05-17

200

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

Science.gov (United States)

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

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

2010-06-01

 
 
 
 
201

Roll to plate printed stretchable silver electrode using single walled carbon nanotube on elastomeric substrate.  

UK PubMed Central (United Kingdom)

Stretchable electronics may open new applications in display, sensors and actuators. To attain the stretchable electronics, the ink formulation should be compatible with elastomeric substrates. Here, we present the formulation of silver nanoparticles and single walled carbon nanotubes (SWNTs) for printing stretchable silver electrodes on the elastomeric substrates. Highly conductive stretchable electrodes can be printed directly on the poly(styrene-b-butadiene-b-styrene) (PSBS) substrates by roll to plate (R2P) gravure printer. During the stretching test, R2P printed silver based stretchable electrodes show the high conductivity of 1000 S cm(-1) at 0.27 wt% of SWNT loading. Furthermore, the resistance of the printed silver electrode was not changed up to 15% of tensile strain.

Jung M; Noh J; Kim J; Kim D; Cho G

2013-08-01

202

3D structural patterns in scalable, elastomeric scaffolds guide engineered tissue architecture.  

Science.gov (United States)

Microfabricated elastomeric scaffolds with 3D structural patterns are created by semiautomated layer-by-layer assembly of planar polymer sheets with through-pores. The mesoscale interconnected pore architectures governed by the relative alignment of layers are shown to direct cell and muscle-like fiber orientation in both skeletal and cardiac muscle, enabling scale up of tissue constructs towards clinically relevant dimensions. PMID:23765688

Kolewe, Martin E; Park, Hyoungshin; Gray, Caprice; Ye, Xiaofeng; Langer, Robert; Freed, Lisa E

2013-06-14

203

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 of 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

2007-01-01

204

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

UK PubMed Central (United Kingdom)

This study investigated the cytotoxicity exists between latex and non-latex Orthodontic elastomeric ligatures. Six elastomeric ligatures (1 latex, 2 latex-free and 3 polyurethane) from different manufacturers were divided into 6 groups of 15 elastics each: A (Latex-free, American Orthodontics), M (Polyurethane, Morelli), G (Polyurethane,GAC International), Te (Polyurethane, Tecnident), TP (Natural latex,TP Orthodontics) and U (Latex-free,3M Unitek). The cytotoxicity assay was performed using cell cultures (L929 mouse fibroblast cell line), which were subjected to the cell viability test with neutral red ("dye-uptake") at 1, 2, 3, 7 and 28 days. Data were analyzed statistically by ANOVA and Tukey's test (?=0.05). No statistically significant differences (p>0.05) were observed between Groups M and Te in all experimental periods, except at 2 days. No significant differences (p>0.05) in cell viability were found either among Groups A, G, TP and U or between Groups M and Te at 24 h or among Groups CC, A, G, TP and U at 2 and 28 days. It may be concluded that latex-free elastomeric ligatures from American Orthodontics and Unitek trademarks induced less cell lysis compared to latex and polyurethane ligatures.

Santos RL; Pithon MM; Martins FO; Romanos MT; Ruellas AC

2010-01-01

205

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; J. Stabik

2007-01-01

206

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english The introduction of epoxy groups into the main chain of elastomers has emerged as a promising alternative, considering the monitoring of polymer-filler interaction leading to changes in the properties of vulcanizates. The epoxidation reaction (in situ) was chosen to modify elastomers, such as polybutadiene (BR) and copolymer of styrene-butadiene-rubber (SBR), because it is a simple, easily controlled reaction, even considering the small epoxidation degree. The modificatio (more) n 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.

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

2006-06-01

207

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; Marly M. Jacobi; Dimitrios Samios; Robert H. Schuster

2006-01-01

208

Baseline and Lifetime Assessments for DC745U Elastomeric Components  

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-12-20

209

Semicarbazide is a minor thermal decomposition product of azodicarbonamide used in the gaskets of certain food jars.  

Science.gov (United States)

Evidence is presented for the first time showing that semicarbazide (SEM) is a minor thermal decomposition product of the blowing agent azodicarbonamide (ADC). A novel direct analytical method based on liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) has been developed to determine SEM in foamed polyvinyl chloride (PVC) seals of metal lids, as well as in commercially available ADC. The direct LC-MS/MS method for gaskets entails extraction of the gaskets in hot water, addition of ((15)N(2)(13)C)-SEM as internal standard, and injection of an aliquot directly into the LC-MS system, achieving good sensitivity (S/N = 348 for 2 ng injected on-column) and monitoring three characteristic mass transitions (m/z 76-->31; 76 -->44; 76-->59). Semicarbazide can be detected in thermally treated ADC, reaching up to 0.93 mmol mol(-1) at 220 degrees C, as determined by the direct LC-MS/MS method. This new method is also compared to the classical derivatization method using 2-nitrobenzaldehyde (2-NBA) that is routinely employed to determine SEM as an indicator of the usage of the antimicrobial drug nitrofurazone, the use of which is not authorized in the European Union (EU). Both methods revealed proportional results, with approx. 3-fold higher levels recorded by the direct SEM approach, probably due to differences in the extraction procedures used. A limited survey of plastic seals from used press twist and twist-off metal lids on food jars (non-foamed and foamed) revealed levels of SEM ranging from 2 to 8689 microg kg(-1)(average = 1593 microg kg(-1), n= 57 determinations). PMID:14978533

Stadler, Richard H; Mottier, Pascal; Guy, Philippe; Gremaud, Eric; Varga, Natalia; Lalljie, Sam; Whitaker, Richard; Kintscher, Jurgen; Dudler, Vincent; Read, Wendy A; Castle, Laurence

2004-01-20

210

Semicarbazide is a minor thermal decomposition product of azodicarbonamide used in the gaskets of certain food jars.  

UK PubMed Central (United Kingdom)

Evidence is presented for the first time showing that semicarbazide (SEM) is a minor thermal decomposition product of the blowing agent azodicarbonamide (ADC). A novel direct analytical method based on liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) has been developed to determine SEM in foamed polyvinyl chloride (PVC) seals of metal lids, as well as in commercially available ADC. The direct LC-MS/MS method for gaskets entails extraction of the gaskets in hot water, addition of ((15)N(2)(13)C)-SEM as internal standard, and injection of an aliquot directly into the LC-MS system, achieving good sensitivity (S/N = 348 for 2 ng injected on-column) and monitoring three characteristic mass transitions (m/z 76-->31; 76 -->44; 76-->59). Semicarbazide can be detected in thermally treated ADC, reaching up to 0.93 mmol mol(-1) at 220 degrees C, as determined by the direct LC-MS/MS method. This new method is also compared to the classical derivatization method using 2-nitrobenzaldehyde (2-NBA) that is routinely employed to determine SEM as an indicator of the usage of the antimicrobial drug nitrofurazone, the use of which is not authorized in the European Union (EU). Both methods revealed proportional results, with approx. 3-fold higher levels recorded by the direct SEM approach, probably due to differences in the extraction procedures used. A limited survey of plastic seals from used press twist and twist-off metal lids on food jars (non-foamed and foamed) revealed levels of SEM ranging from 2 to 8689 microg kg(-1)(average = 1593 microg kg(-1), n= 57 determinations).

Stadler RH; Mottier P; Guy P; Gremaud E; Varga N; Lalljie S; Whitaker R; Kintscher J; Dudler V; Read WA; Castle L

2004-03-01

211

Compliant layer bearings in artificial joints. Part 1: the effects of different manufacturing techniques on the interface strength between an elastomeric layer and a rigid substrate.  

UK PubMed Central (United Kingdom)

The premise that elastomeric materials could be used as one or more of the articulating components in both hip and knee prostheses was postulated first by Unsworth and co-workers. It was thought that such materials might have the capacity to mimic natural joint behaviour more closely than the more rigid bearing surfaces commonly in use. A more natural joint function in artificial joints should promote better tribology, with full fluid-film lubrication being the goal. Early tests showed that this objective could potentially be achieved with a judicious choice of materials and carefully controlled manufacturing techniques. This paper (Part 1 of a two-part series) describes and explains the techniques used to verify the material selection as well as to determine the most appropriate manufacturing procedure to obtain a strong and robust interface between the support and bearing material of the prosthesis. Two polycarbonate urethane (PU) materials with different hardness values (Corethane 80A and Corethane 75D) gave sufficient interfacial strength when moulded under optimum conditions. Corethane 80A was used as the soft bearing material while Corethane 75D provided the rigid backing component. Peel tests revealed strong interface bonds, varying with processing conditions between 350 and 862 N. Fourier transform infrared spectroscopy and micro-thermal analysis showed that a fusion bond over 30 microm thick formed at the interface. The results of the range of tests and analyses, which have been used in this study, have provided sufficient evidence to validate the process used to manufacture these components.

Burgess IC; Jones E; Scholes SC; Unsworth A

2008-08-01

212

A micromachined elastomeric tip array for contact printing with variable dot size and density  

Science.gov (United States)

We report a flexible and versatile microcontact printing process using a micromachined elastomeric PDMS (poly-dimethylsiloxane) stamp with two-dimensional arrays of pyramidal tips. The PDMS stamp was molded from a bulk-etched single-crystalline silicon master. By changing the contact pressure, arrayed dot patterns with different dot sizes (from submicron to a few microns) were obtained controllably with one single PDMS stamp. Variable density of dot patterns was also achieved in a 'step-print' manner by conducting multiple printing on a transitional stage. This technique is expected to be useful in many nano- and biotechnology applications, including single cell and neuron studies.

Hong, Jung Moo; Ozkeskin, Fatih M.; Zou, Jun

2008-01-01

213

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-06-11

214

Fabrication and characterization of PDMS microlenses based on elastomeric molding technology.  

Science.gov (United States)

Elastomeric molding technology is adopted to fabricate polydimethilsiloxane (PDMS)-based solid microlenses, as they can have different focal lengths and achieve different lens types (such as concave and convex) using the same mold structure. The only parameter that needs to be controlled is the pressure applied during the molding process. These PDMS lenses can also be transformed from the original spherical ones into microlenses having elliptic surface profiles simply by stretching their substrates in one direction. This provides the process with additional tunability of astigmatism. PMID:19881625

Yu, Hongbin; Zhou, Guangya; Chau, Fook Siong; Lee, Feiwen

2009-11-01

215

Fabrication and characterization of PDMS microlenses based on elastomeric molding technology.  

UK PubMed Central (United Kingdom)

Elastomeric molding technology is adopted to fabricate polydimethilsiloxane (PDMS)-based solid microlenses, as they can have different focal lengths and achieve different lens types (such as concave and convex) using the same mold structure. The only parameter that needs to be controlled is the pressure applied during the molding process. These PDMS lenses can also be transformed from the original spherical ones into microlenses having elliptic surface profiles simply by stretching their substrates in one direction. This provides the process with additional tunability of astigmatism.

Yu H; Zhou G; Chau FS; Lee F

2009-11-01

216

Effect of material bulk and undercuts on the accuracy of impression materials.  

UK PubMed Central (United Kingdom)

A truncated cone-shaped chromium steel die was used to determine the influence of the bulk of elastomeric impression material and size of undercut on the dimension of stone dies. It was found that both conditions affect the accuracy of stone dies. The possible clinical implications of the inaccuracies were discussed.

de Araujo PA; Jorgensen KD

1985-12-01

217

Effect of material bulk and undercuts on the accuracy of impression materials.  

Science.gov (United States)

A truncated cone-shaped chromium steel die was used to determine the influence of the bulk of elastomeric impression material and size of undercut on the dimension of stone dies. It was found that both conditions affect the accuracy of stone dies. The possible clinical implications of the inaccuracies were discussed. PMID:3908659

de Araujo, P A; Jorgensen, K D

1985-12-01

218

Biodegradabilite et proprietes energetiques d'elastomeres azotures  

Science.gov (United States)

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

Lavoie, Jonathan

219

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

UK PubMed Central (United Kingdom)

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).

Cunha AC; Marquezan M; Freitas AO; Nojima LI

2011-11-01

220

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; Mariana Marquezan; Amanda Osório Ayres de Freitas; Lincoln Issamu Nojima

2011-01-01

 
 
 
 
221

Multi-stimuli-responsive elastomeric opal films: processing, optics, and applications  

Science.gov (United States)

A new strategy to build large-scale solvent-responsive elastomeric opal films that are candidates for a wide range of optical sensor applications is reported. Hard-soft core-interlayer-shell (CIS) beads were used to prepare paper-supported elastomeric opal films with remarkably distinct iridescent reflection colors. Extrusion and compression molding of the CIS beads directly on the top of a highly porous paper sheet followed by UV cross-linking led to polymer-paper composite films with a high tensile strength and an outstanding solvent resistivity. Due to the high porosity of the paper sheets used, these composites could be easily swollen by various solvents. The swelling changed the crystalline lattice of the opals which provoked a tremendous photonic band gap shift and also enhanced the brilliance of these colors. After deswelling, the original opal structure was totally restored which means that the shift of the photonic band gap was completely reversible. This approach can become the basis for a whole family of polymer-based soft sensors with a fascinating optical response.

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

2013-09-01

222

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.

Simon Petrov?i?; David Koren; Vojko Kilar

2009-01-01

223

Testing and operational behaviour of elastomeres which are used as sealing materials in engine building  

Energy Technology Data Exchange (ETDEWEB)

The simultaneous advance of lubricant and elastomer technology is cited as being coincidental with the occurence of elastomer failures as measured by laboratory tests. By means of engine manufacturers' laboratory test procedures, changes in lubricant composition are demonstrated to influence elastomer performance. The significance of these results is discussed in terms of the composition of the lubricant. This data is contrasted with the importance of field experience and the effect of aged oils.

Broadwell, H.E.; Clark, C.A.; Fuhrmann, J.

1982-09-01

224

Geothermal Elastomeric Materials Technology Application (GEM-TA) Program. Final report, August 1981-August 1983  

Energy Technology Data Exchange (ETDEWEB)

In 1979, L'Garde, Inc. completed the development of several geothermal elastomer compounds. Major advances in the state of the art were achieved with successes at extreme conditions such as temperatures up to and exeeeding 320/sup 0/C (608/sup 0/F), pressures up to and exceeding 138 MPa (20,000 psi), and fluids ranging from brines to hydrocarbons. Because various geothermal projects had many elastomers problems and their solutions were critical to the project success, the DOE sponsored this effort to help provide the advantages of the earlier developed technology described above. The technology applications supported are as follows: pump lineshaft bearings; seals for Freon 114, synthetic hydrocarbon, and brine service; electrically insulative seals for logging tools; seals for nitrate salt explosive and steam service; and cementing wiper plugs. In addition there were minor efforts to further disseminate information associated with the elastomer development and case history experiences.

Hirasuna, A.R.; Davis, D.L.; Friese, G.J.; Trailer, J.W.

1984-08-01

225

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

226

Scientific approach to the development filled elastomeric materials applied in aviation ???????????????? ?????????????????? ???????????? ????????? ???????????? ??????? ??????????????? ??????????????? ??????????? ????????? ???????????? ???????  

Directory of Open Access Journals (Sweden)

Full Text Available  The results of latex structure investigation by means of optical microscopy had been presented of  low dilution by water. The micelles obtained have not close packed structure. Statistical polyisopren macromolecules balls of natural latex had been studied by UF-spectroscopy of high dilution. ???????? ?????????? ???????????? ????????? ??????? ?????????? ???????????? ??? ????????? ??????????? ?????. ???????? ???????, ??????? ????? ????????? ????????. ??????????? ?????????????? ?????? ???????????? ???????????? ???????????? ??????? ??? ??????? ?????????? (103) ???????????????? ??????????????. ????????? ?????????? ?????????? ????????? ??????? ???????? ???????????? ??? ?????? ??????????? ?????. ???????? ??????, ?? ????? ???????? ????????. ?????????? ??????????? ?????? ???????????? ???????????? ???????????? ??????? ??? ???????? ??????????? (103) ???????????????? ??????????????.

?.?. ????????????; ?.?. ??????; ?.?. ?????????

2005-01-01

227

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 whic...

Joby Paulose; Rhea Mini Jayan

228

Determination of polyadipates migrating from lid gaskets of glass jars. Hydrolysis to adipic acid and measurement by LC-MS/MS.  

Science.gov (United States)

Polyadipate plasticizers can be present in the polyvinylchloride (PVC) gaskets used to seal the lids of glass jars. As the gaskets can come into direct contact with the foodstuffs inside the jar, the potential exists for polyadipate migration into the food. The procedure and performance characteristics of a test method for the analysis of polyadipates in food simulants (3% aqueous acetic acid and 10% aqueous ethanol) and the volatile test media used in substitute fat tests (isooctane and 95% aqueous ethanol) are described. The PVC gaskets were exposed to the food simulants or their substitutes under standard test conditions. Studies were initially carried out using direct measurement of the polyadipate oligomers by liquid chromatography with time-of-flight mass spectrometric detection (LC-TOF-MS) but this was not practical due to the number of peaks detected. Instead, the migrating polyadipates were hydrolysed to adipic acid and measured by liquid chromatography with tandem mass spectrometric detection (LC-MS/MS). The amount of polyadipate that this measurement of adipic acid represents was then calculated. Method performance was assessed by analysis of gaskets from two types of jar lids by single-laboratory validation. Linearity, sensitivity, repeatability, intermediate reproducibility and recovery were determined to be suitable for checking compliance with the 30 mg/kg specific migration limits for polyesters of 1,2-propane diol and/or 1,3- and/or 1,4-butanediol and/or polypropylene-glycol with adipic acid, which may be end-capped with acetic acid or fatty acids C(12)-C(18) or n-octanol and/or n-decanol. The method was found to be much quicker than previous methods involving extraction, clean-up, hydrolysis, esterification, derivatisation and GC measurement, consequently saving time and money. PMID:20730648

Driffield, M; Bradley, E L; Harmer, N; Castle, L; Klump, S; Mottier, P

2010-10-01

229

Determination of polyadipates migrating from lid gaskets of glass jars. Hydrolysis to adipic acid and measurement by LC-MS/MS.  

UK PubMed Central (United Kingdom)

Polyadipate plasticizers can be present in the polyvinylchloride (PVC) gaskets used to seal the lids of glass jars. As the gaskets can come into direct contact with the foodstuffs inside the jar, the potential exists for polyadipate migration into the food. The procedure and performance characteristics of a test method for the analysis of polyadipates in food simulants (3% aqueous acetic acid and 10% aqueous ethanol) and the volatile test media used in substitute fat tests (isooctane and 95% aqueous ethanol) are described. The PVC gaskets were exposed to the food simulants or their substitutes under standard test conditions. Studies were initially carried out using direct measurement of the polyadipate oligomers by liquid chromatography with time-of-flight mass spectrometric detection (LC-TOF-MS) but this was not practical due to the number of peaks detected. Instead, the migrating polyadipates were hydrolysed to adipic acid and measured by liquid chromatography with tandem mass spectrometric detection (LC-MS/MS). The amount of polyadipate that this measurement of adipic acid represents was then calculated. Method performance was assessed by analysis of gaskets from two types of jar lids by single-laboratory validation. Linearity, sensitivity, repeatability, intermediate reproducibility and recovery were determined to be suitable for checking compliance with the 30 mg/kg specific migration limits for polyesters of 1,2-propane diol and/or 1,3- and/or 1,4-butanediol and/or polypropylene-glycol with adipic acid, which may be end-capped with acetic acid or fatty acids C(12)-C(18) or n-octanol and/or n-decanol. The method was found to be much quicker than previous methods involving extraction, clean-up, hydrolysis, esterification, derivatisation and GC measurement, consequently saving time and money.

Driffield M; Bradley EL; Harmer N; Castle L; Klump S; Mottier P

2010-10-01

230

Valve stem seals and cylinder head gaskets for minimal exhaust gas emissions and oil consumption; Ventilschaft- und Zylinderkopfdichtungen fuer minimale Abgasemissionen und Oelverbrauch  

Energy Technology Data Exchange (ETDEWEB)

It is a well known fact that ash from engine oil additives causes modern particulate filters in diesel cars to become clogged. Since the particulate filter is widely accepted throughout Europe, minimizing oil consumption has become a focal point in engine development. Above all, valve stem seals and cylinder head gaskets offer here the potential to keep exhaust gas emissions and oil consumption to a bare minimum. This article of Freudenberg Schwingungs- und Dichtungstechnik presents new sealing solutions. (orig.)

Pepin, F. [Freudenberg Dichtungs- und Schwingungstechnik GmbH und Co KG, Weinheim (Germany). Lead Center Zylinderkopfdichtungen

2007-04-15

231

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

Scientific Electronic Library Online (English)

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

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

2010-01-01

232

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.

2004-01-01

233

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

International Nuclear Information System (INIS)

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

1000-01-00

234

Fully reversible shape transition of soft spheres in elastomeric polymer opal films.  

UK PubMed Central (United Kingdom)

Core-interlayer-shell (CIS) beads featuring noncross-linked hard cores were used to prepare large and well-defined elastomeric opal films with remarkably distinct iridescent reflection colors. The matrix of the opal films was cross-linked by UV-irradiation after compression molding of the CIS beads mixed with a bifunctional monomer. Stress-induced deformation of the embedded PS cores lead to hexagonally arranged spheroid oblates with an aspect ratio of 2.5. Optical characterization shows that bead deformation provokes a tremendous photonic band gap shift of about 160 nm. Fully reversible shape transition from the spheroid oblates back to the spherical beads and hence full recovery of the original photonic band gap can be achieved.

Schäfer CG; Smolin DA; Hellmann GP; Gallei M

2013-09-01

235

Transition to an elastomeric infusion pump in home care: an evidence-based approach.  

Science.gov (United States)

A fatal overdose of a chemotherapeutic agent delivered to a patient via an electronic infusion device served as a stark reminder of the risks that infusion therapy poses to patients and health care providers and as the impetus for a strategy to optimize safe and efficient delivery of home infusion therapy. The Academic Center for Evidence-Based Practice Star Model of Knowledge Transformation was used as the evidence-based framework for the implementation of a portable infusion pump that supports home infusion of high-risk medications, leading to increased patient and caregiver satisfaction. Evaluation of this implementation supports the use of an elastomeric infusion device for a high-risk therapy. PMID:22498484

Broadhurst, Daphne

236

Transition to an elastomeric infusion pump in home care: an evidence-based approach.  

UK PubMed Central (United Kingdom)

A fatal overdose of a chemotherapeutic agent delivered to a patient via an electronic infusion device served as a stark reminder of the risks that infusion therapy poses to patients and health care providers and as the impetus for a strategy to optimize safe and efficient delivery of home infusion therapy. The Academic Center for Evidence-Based Practice Star Model of Knowledge Transformation was used as the evidence-based framework for the implementation of a portable infusion pump that supports home infusion of high-risk medications, leading to increased patient and caregiver satisfaction. Evaluation of this implementation supports the use of an elastomeric infusion device for a high-risk therapy.

Broadhurst D

2012-05-01

237

Fully reversible shape transition of soft spheres in elastomeric polymer opal films.  

Science.gov (United States)

Core-interlayer-shell (CIS) beads featuring noncross-linked hard cores were used to prepare large and well-defined elastomeric opal films with remarkably distinct iridescent reflection colors. The matrix of the opal films was cross-linked by UV-irradiation after compression molding of the CIS beads mixed with a bifunctional monomer. Stress-induced deformation of the embedded PS cores lead to hexagonally arranged spheroid oblates with an aspect ratio of 2.5. Optical characterization shows that bead deformation provokes a tremendous photonic band gap shift of about 160 nm. Fully reversible shape transition from the spheroid oblates back to the spherical beads and hence full recovery of the original photonic band gap can be achieved. PMID:23947686

Schäfer, Christian G; Smolin, Daniel A; Hellmann, Goetz P; Gallei, Markus

2013-08-29

238

Correlation of elastomer material properties from small specimen tests and scale-size bearing tests  

International Nuclear Information System (INIS)

Tests were performed on small-size elastomer specimens and scale-size laminated elastomeric bearings to correlate the material properties in shear between the two types of tests. An objective of the tests was to see how well the material properties that were determined from specimen tests could predict the response of scale-size laminated elastomeric bearings. Another objective was to compare the results of specimen test and scale-size bearing test conducted by different testing organizations. A comparison between the test results from different organizations on small specimens showed very good agreement. In contrast, the correlation of scale-size bearing tests showed differences in bearing stiffness

1994-01-01

239

Development of high-temperature joints for thermochemical hydrogen production by IS process. Applicability examination of the coned-disk springs assembly and seal performance test of candidate gaskets  

International Nuclear Information System (INIS)

Thermo-chemical Iodine-Sulfur (IS) process can produce large amount of hydrogen effectively without emission of greenhouse effect gas such as carbon dioxide, where nuclear thermal energy of a high temperature gas-cooled reactor (HTGR) is adopted as a heat source. The IS process uses strong acids such as sulfuric acid and hydriodic acid in high temperature and pressure conditions. Therefore, it is necessary to develop large-size chemical reactors featuring materials that exhibit high temperature and corrosion resistance. A SO3 decomposer, which is one of key components of the IS process, consists of a pressure vessel for high temperature and high pressure helium gas and an internal structure for SO3 decomposition by the latent heat of the helium gas. Since joints of the internal structure will be heated up to 700degC, we designed a high-temperature joint coupled with coned-disk springs and SiC bolts (coned-disk springs assembly) so as to keep seal performance under high temperature condition. This report presents applicability examination results of designed coned-disk springs assembly as well as seal performance test results of candidate gaskets. (author)

2007-01-01

240

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1989-01-01

 
 
 
 
241

Evaluation of the susceptibility to pigmentation of orthodontic esthetic elastomeric ligatures  

Scientific Electronic Library Online (English)

Full Text Available 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 (more) , 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 (pear (more) l 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.

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

2013-04-01

242

Structural investigation of amorphous materials at high pressures  

Energy Technology Data Exchange (ETDEWEB)

A modified diamond anvil cell (DAC) is used for structural studies of amorphous materials at high pressures using a monochromatic synchrotron x-ray beam. The DAC modification includes (1) the use of x-ray transparent seats for a large angular opening for x-ray scattering, and (2) the introduction of a boron gasket insert to increase the sample thickness and to minimize the gasket-hole deformation. A procedure for absorption correction and background subtraction in DAC experiments is described, together with an optimization process for obtaining accurate data of the structure factor and the corresponding pair distribution function. Data for amorphous iron at 67 GPa are presented for demonstration. It is shown that quantitative structural data can be determined for amorphous materials at very high pressures using the DAC. The apparatus should be also useful for structural studies of liquids at high pressures.

Shen, G.; Prakapenka, V.B.; Rivers, M.L.; Sutton, S.R. (UC)

2010-12-06

243

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).

1992-01-01

244

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.

M. Rojek; J. Stabik

2006-01-01

245

Administration of 24-h intravenous infusions of trabectedin in ambulatory patients with mesenchymal tumors via disposable elastomeric pumps: an effective and patient-friendly palliative treatment option.  

UK PubMed Central (United Kingdom)

BACKGROUND: Patients with progressive mesenchymal tumours after standard chemotherapy have poor outcome. Trabectedin is approved in Europe as 24-h intravenous (i.v.) infusion q3w in this setting. We report the use of disposable elastomeric pumps for ambulatory treatment with trabectedin. MATERIAL AND METHODS: Pre-treated sarcoma patients were offered trabectedin 1.5 mg/m(2) as 24-h i.v. infusion via port catheter, either as inpatients using electronic pumps or as outpatients using the Baxter LV10 pump. Co-medication consisted of antiemetics including dexamethasone. RESULTS: 21/28 patients with distant metastasis and/or local relapse elected outpatient therapy and received 130 cycles (median 3, range 1-24). Dose reductions were done in 60 cycles, mainly due to laboratory adverse events (AEs). Best response (Response Evaluation Criteria in Solid Tumours (RECIST)) was 4 cases of confirmed partial remission (PR), 6 cases of stable disease (SD), and 11 cases of progressive disease (PD). Grade 3/4 (Common Toxicity Criteria (CTC)) AEs were limited to 1 case each of haemorrhage and lung embolism; other AEs were in line with published trabectedin experience. 1 port catheter contamination required replacement, 1 catheter thrombosis occurred and 1 extravasation due to needle dislocation was observed. CONCLUSIONS: Outpatient administration of trabectedin as 24-h infusion using Baxter LV10 pumps is preferred by the vast majority of patients; it is feasible, safe, effective, cost efficient, and should be considered as routine practice in this clinical setting.

Schöffski P; Cerbone L; Wolter P; De Wever I; Samson I; Dumez H; Clement P; Wildiers H; Stas M

2012-01-01

246

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.

2006-01-01

247

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

248

Elastomeric composites with high-dielectric constant for use in Maxwell stress actuators  

Science.gov (United States)

Electroactive polymer actuators that utilize the Maxwell stress effect have generated considerable interest in recent years for use in applications such as artificial muscles, sensors, and parasitic energy capture. In order to maximize performance, the dielectric layer in Maxwell stress actuators should ideally have a high dielectric constant and high dielectric breakdown strength. In this study, the effect of high dielectric constant fillers on the electrical and mechanical properties of thin elastomeric films was examined. The fillers studied included the inorganic compounds titanium dioxide (TiO2), barium titanate (BaTiO3), and lead magnesium niobate-lead titanate (Pb(Mg1/3Nb2/3)O3-PbTiO). A high dielectric constant filler based on a polymeric conjugated ligand-metal complex, poly(copper phthalocyanine), was also synthesized and studied. Maxwell stress actuators fabricated with BaTiO3 dispersed in a silicone elastomer matrix were evaluated and compared with unfilled systems. A model was presented which relates filler volume fraction to actuation stress, strain, and elastic energy density at fields below dielectric breakdown. The model and experimental results suggest that for the case of strong filler particle-elastomer matrix interaction, actuation strain decreases with increasing filler content.

Szabo, Jeffrey P.; Hiltz, Johnathan A.; Cameron, Colin G.; Underhill, Royale S.; Massey, Jason; White, Brian; Leidner, Jacob

2003-07-01

249

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

Energy Technology Data Exchange (ETDEWEB)

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.

Kelarakis,A.; Yoon, K.; Somani, R.; Sics, I.; Chen, X.; Hsiao, B.; Chu, B.

2006-01-01

250

Residual thermal stresses in filamentary polymer-matrix composites containing an elastomeric interphase  

Energy Technology Data Exchange (ETDEWEB)

A three-phase micromechanical model based on the method of cells is formulated to characterize residual thermal stresses in filamentary composites containing an interphase between the fiber and the matrix. This is the first such study to incorporate a true three-phase version of the method of cells. The model's performance is critically evaluated using data generated from other micromechanical models. Subsequently, a parametric study is performed to quantify the residual stresses in two hypothetical graphite fiber/epoxy matrix composites: one containing an elastomeric interphase whose Young's modulus is less than that of the fiber and the matrix and one incorporating an interphase whose Young's modulus is intermediate with respect to the fiber and the matrix. The data correlate the residual thermal stresses in the fiber, interphase and matrix as a function of the interphase thickness and fiber volume fraction within each model eomposite. The study makes a broad assessment of the stress-attenuating characteristics that each interphase imparts to the graphite/epoxy composites. Over the range of variables considered, properly dimensioning the elastomer interphase leads to a more favorable reduction of residual thermal stress. 38 refs.

Gardner, S.D.; Pittman, C.U. Jr.; Hackett, R.M. (Mississippi State Univ., Mississippi State (United States) Mississippi Univ., University (United States))

1993-01-01

251

Report on the investigational research on abration/wear resistance using new materials for hydraulic/pneumatic element equipment in fiscal 1994; 1994 nendo yukuatsu yoso kiki no shinzairyo wo mochiita shudo mamo teiko shiken ni kansuru chosa kenkyu hokokusho  

Energy Technology Data Exchange (ETDEWEB)

The paper adopted a new method for measuring friction/wear characteristics of gaskets for hydraulic/pneumatic cylinders of the hydraulic/pneumatic equipment and conducted tests necessary to study and confirm practicality of the gasket. The paper also carries out tests on endurance of the gasket to estimate durability, making an experiment on abrasional/frictional resistance characteristics before and after endurance. The investigation was conducted mainly into measurement and study of a characteristic of frictional resistance and wave forms of abrasional resistance of 28mm-diameter piston rods (the one hard chrome plated and the one shot-blasted after the hard chrome plating) and gaskets, and the endurance tests and study of the test results and the supply of directions as to how to make gaskets to apply to high pressure/speed. As a result, relating to the application of new materials to the seal of the sliding portion and the bearing of hydraulic/pneumatic cylinders which reciprocate, it is thought that guidelines for developing more reliable equipment are obtained as well as the supply of criteria for estimating durability of the equipment under high pressure/speed. 47 figs., 15 tabs.

NONE

1995-03-01

252

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 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.

2013-02-15

253

On the mobility of iron particles embedded in elastomeric silicone matrix  

Science.gov (United States)

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

Rabindranath, R.; Böse, H.

2013-02-01

254

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

Energy Technology Data Exchange (ETDEWEB)

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.

Seidensticker, R.W.; Chang, Y.W.; Kulak, R.F.

1992-05-01

255

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

Energy Technology Data Exchange (ETDEWEB)

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.

Seidensticker, R.W.; Chang, Y.W.; Kulak, R.F.

1992-01-01

256

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; Ju-Seop Kang

2012-01-01

257

Soil stabilization materials and methods  

Energy Technology Data Exchange (ETDEWEB)

For soil stabilization, a liquid applied to the surface of the soil rapidly polymerizes to form an elastomeric resin which bonds the soil particles together to form a tough composite structure within a time span of a few seconds to an hour, depending upon the composition of the soil stabilizer. The stabilizing materials are mixtures of dimer diisocyanate and dimer diamine, which react rapidly, and mixtures of dimer diisocyanate and a derivative of dimer diamine wherein the amine groups have been reacted with a ketone to form ketimine groups. The latter mixture, which reacts more slowly, may be premixed before application to soil surface. 5 claims.

Reed, R. Jr.; Moore, K.L.; Meyers, G.W.

1981-07-07

258

Characterization and degradation of elastomeric four-armed star copolymers based on caprolactone and L-lactide.  

UK PubMed Central (United Kingdom)

Although biodegradable polymers have found extensive applications in medical areas, there are limited reports that show elastomeric behavior. In this work, a biodegradable, elastomeric polymer is demonstrated from a four-armed star copolymer. With a fixed middle core composition, comprising caprolactone (CL) and L-lactide (LA), an elastomer is obtained by increasing the polylactide (PLA) end block lengths to obtain sufficient end block crystallinity. This increase suppressed the middle core's crystallinity yet ensured cocrystallization of the PLA ends of individual star copolymer chains to form a three-dimensional network via physical crosslinking. Cyclic and creep test of the star copolymers showed that at least 75% of recovery was achieved. Degradation study of the copolymer showed that degradation first occurred in the caprolactone-co-lactide (CLLA) core, followed by degradation in the PLA ends. Chain scission in the middle core resulted in immediate formation of CL crystals within the core and increased crystallinity over time, in both CLLA core and PLA ends.

Kong JF; Lipik V; Abadie MJ; Roshan Deen G; Venkatraman SS

2012-12-01

259

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; Ju-Seop Kang

2013-01-01

260

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)

1992-01-01

 
 
 
 
261

Spontaneous Enhancement of Packing Regularity of Spherical Microdomains in the Body-Centered Cubic Lattice upon Uniaxial Stretching of Elastomeric Triblock Copolymers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Block copolymers forming glassy spheres in the matrix of rubbery chains can exhibit elastomeric properties. It is well known that the spherical microdomains are arranged in the body-center cubic (bcc) lattice. However, recently, we have found packing in the face-centered cubic (fcc) lattice, which i...

Takuya Kota; Kimio Imaizumi; Sono Sasaki; Shinichi Sakurai

262

Elastomeric-ligated vs self-ligating appliances: a pilot study examining microbial colonization and white spot lesion formation after 1 year of orthodontic treatment.  

UK PubMed Central (United Kingdom)

AIM: To (1) evaluate the use of adenosine triphosphate (ATP)-driven bioluminescence for quantification of total plaque bacteria in orthodontic patients, (2) compare plaque bacteria amounts at the bracket-tooth interface with use of elastomeric-ligated and self-ligating brackets after 1 year of orthodontic treatment, and (3) analyze formation of white spot lesions by photographic evaluation and laser-light fluorescence (DIAGNOdent). METHODS: Thirteen subjects had fixed orthodontic appliances placed where lateral incisors were bonded with either elastomeric-ligated or self-ligating brackets. Plaque bacteria were collected from incisor surfaces after 1 year and quantified using plating methods and ATP-driven bioluminescence. White spot lesions were evaluated by photographic and DIAGNOdent determinations. A 2 x 2 x 2 mixed-design ANOVA was conducted to determine differences in plaque retention between elastomeric-ligated and self-ligating brackets. RESULTS: ATP-driven bioluminescence values correlated to numbers of total plaque bacteria (r = 0.80). However, unlike findings published in the original pilot study, which described increased plaque retention with elastomeric-ligated brackets at 5 weeks postbonding, there were no significant differences in bacterial numbers or ATP-driven bioluminescence values surrounding the elastomeric-ligated vs self-ligating brackets after 1 year of orthodontic treatment. Based on photographic and DIAGNOdent determinations, white spot lesions were found relatively equally on teeth bonded with either bracket type. DIAGNOdent measurements were found to have moderate sensitivity (0.71) and good specificity (0.88) when compared to white spot lesions determined using photographic evaluation. CONCLUSION: ATP-driven bioluminescence can be used as an accurate assessment of total plaque bacteria in orthodontic patients. After 1 year of orthodontic treatment for patients in this pilot study, there appeared to be no differences in retention of plaque bacteria or white spot lesions comparing the bracket types. The use of DIAGNOdent has some limitations, but may prove to be useful to monitor white spot lesions longitudinally.

Buck T; Pellegrini P; Sauerwein R; Leo MC; Covell DA Jr; Maier T; Machida CA

2011-01-01

263

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

UK PubMed Central (United Kingdom)

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?elastomeric separators. No gender differences were observed in both groups. More pain was recorded in the mandible (P?

Eslamian L; Borzabadi-Farahani A; Hassanzadeh-Azhiri A; Badiee MR; Fekrazad R

2013-01-01

264

Study on the properties of damping bitumen material  

International Nuclear Information System (INIS)

[en] The damping mechanisms of visco-elastomeric materials under the vibration are described, and the dynamic mechanical properties of damping bitumen material are studied.The experimental results show that the kind of raw materials, temperature and vibrational frequency have great influence on the loss factors of damping bitumen materials and that the plasticizers contributed to the range of damping temperature. The shear motion and the internal dissipation of materials increased by adding the planar filler, such as graphites, are also indicated

2002-01-01

265

Mean modulus of elasticity E{sub Gm} for flat gaskets in table 1 of DIN EN 1591. Part 1; Ueber den mittleren E-Modul fuer Flachdichtungen in Tabelle 1 der DIN EN 1591-1  

Energy Technology Data Exchange (ETDEWEB)

A certain confusion currently prevails concerning description of the elastic resilience of gaskets in the European standard for calculation of threaded flanged joints, EN 1591, parts 1 and 2. This is apparent in the occurrence of two variants of the modulus of elasticity, namely modulus of elasticity E{sub G}, on the one hand, and mean modulus of elasticity E{sub Gm}, on the other. This article attempts to clarify these terms. It is shown that there is only one modulus of elasticity for all types of seal and gasket, namely E{sub G} in accordance with equation 2 below. It is also demonstrated that this is, already, tacitly a mean modulus of elasticity in accordance with the test method used. (orig.)

Tueckmantel, H.J. [TMT Technik-Methode-Training, Muellheim an der Ruhr (Germany)

2006-05-15

266

Elastomeric inverse moulding and vacuum casting process characterization for the fabrication of arrays of concave refractive microlenses  

Science.gov (United States)

We present a complete and precise quantitative characterization of the different process steps used in an elastomeric inverse moulding and vacuum casting technique. We use the latter replication technique to fabricate concave replicas from an array of convex thermal reflow microlenses. During the inverse elastomeric moulding we obtain a secondary silicone mould of the original silicone mould in which the master component is embedded. Using vacuum casting, we are then able to cast out of the second mould several optical transparent poly-urethane arrays of concave refractive microlenses. We select ten particular representative microlenses on the original, the silicone moulds and replica sample and quantitatively characterize and statistically compare them during the various fabrication steps. For this purpose, we use several state-of-the-art and ultra-precise characterization tools such as a stereo microscope, a stylus surface profilometer, a non-contact optical profilometer, a Mach-Zehnder interferometer, a Twyman-Green interferometer and an atomic force microscope to compare various microlens parameters such as the lens height, the diameter, the paraxial focal length, the radius of curvature, the Strehl ratio, the peak-to-valley and the root-mean-square wave aberrations and the surface roughness. When appropriate, the microlens parameter under test is measured with several different measuring tools to check for consistency in the measurement data. Although none of the lens samples shows diffraction-limited performance, we prove that the obtained replicated arrays of concave microlenses exhibit sufficiently low surface roughness and sufficiently high lens quality for various imaging applications.

Desmet, L.; Van Overmeire, S.; Van Erps, J.; Ottevaere, H.; Debaes, C.; Thienpont, H.

2007-01-01

267

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

Directory of Open Access Journals (Sweden)

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

E. Calderón; E. Martínez; M. D. Román; A. Pernio; R. García-Hernández; L.M Torres

2006-01-01

268

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

269

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

Science.gov (United States)

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

Rothenbacher, Thorsten; Schwack, Wolfgang

2010-01-01

270

Survey of Impression Materials and Techniques in Fixed Partial Dentures among the Practitioners in India.  

UK PubMed Central (United Kingdom)

Objective. Anecdotal evidence suggests that impression materials and techniques used in general dental practice for fixed partial dentures vary from those taught in dental schools. The aim of this survey was to integrate impression techniques evolved all over the years for fixed partial dentures and to know the techniques and materials which are used in the present day by the practitioners. Materials and Methods. A total of 1000 questionnaires were sent to various practitioners in India, out of which 807 questionnaires were filled. Results. The results showed that 84.8% of prosthodontists (65.56%, urban areas) use elastomeric impression materials as well as irreversible hydrocolloids and 15.2% use irreversible hydrocolloid only. Amongst other practitioners, 55.46% use irreversible hydrocolloid (45%, rural and semiurban areas) and 44.54% use elastomeric impression materials. Elastomeric impression technique practiced most commonly is putty reline with/without spacer (77.2%); other techniques are multiple-mix and monophase techniques. Conclusion. The ideal materials, technique, and armamentarium are required for the long-term success of the treatment for fixed partial denture. Also, if the ideal procedure is not followed, it will lead to a compromised fit of the final prosthesis and failure of the treatment.

Moldi A; Gala V; Puranik S; Karan S; Deshpande S; Neela N

2013-01-01

271

Survey of Impression Materials and Techniques in Fixed Partial Dentures among the Practitioners in India.  

Science.gov (United States)

Objective. Anecdotal evidence suggests that impression materials and techniques used in general dental practice for fixed partial dentures vary from those taught in dental schools. The aim of this survey was to integrate impression techniques evolved all over the years for fixed partial dentures and to know the techniques and materials which are used in the present day by the practitioners. Materials and Methods. A total of 1000 questionnaires were sent to various practitioners in India, out of which 807 questionnaires were filled. Results. The results showed that 84.8% of prosthodontists (65.56%, urban areas) use elastomeric impression materials as well as irreversible hydrocolloids and 15.2% use irreversible hydrocolloid only. Amongst other practitioners, 55.46% use irreversible hydrocolloid (45%, rural and semiurban areas) and 44.54% use elastomeric impression materials. Elastomeric impression technique practiced most commonly is putty reline with/without spacer (77.2%); other techniques are multiple-mix and monophase techniques. Conclusion. The ideal materials, technique, and armamentarium are required for the long-term success of the treatment for fixed partial denture. Also, if the ideal procedure is not followed, it will lead to a compromised fit of the final prosthesis and failure of the treatment. PMID:23691334

Moldi, Arvind; Gala, Vimal; Puranik, Shivakumar; Karan, Smita; Deshpande, Sumit; Neela, Neelima

2013-04-22

272

Study by three techniques of the elastic response of Al(6061) matrix composite material with a high content (40 % vol) of SIC; Estudio mediante tres tecnicas del modulo elastico de un material compuesto de Al(6061) con un alto contenido (40%vol) de SiC  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this investigation is to study the elastic behavior of a discontinuously reinforced composite material, Al(6061)-40vol%SiC, by using three different procedures; Extensometry in uniaxial testing, pendulum elastomeric, and propagation of acoustic signals in the materials. The high ceramic content of this material provides it with a high stiffness without a significant increase in density. Because of this, the material is suitable as structural component in the automotive and aerospace industry. (Author) 8 refs.

Fernandez, R.; Hunicke, U. D.; Mundt, K. H.; Acosta, P.; Kowalski, W.; Schulz, G.; Gonzalez-Doncel, G.

2001-07-01

273

Waste handling: A study of tributyl phosphate compatibility with nonmetallic materials  

Energy Technology Data Exchange (ETDEWEB)

The need for numerous seals, plastic tubing, instrument components, and miles of plastic pipe for transferring process waste streams containing tributyl phosphate (TBP) and petroleum solvents led to an investigation of compatibility. TBP is a solvent for many plastics and elastomers and causes softening, crazing, or cracking of most nonmetallics tested. In this regard it may be considered an external plasticizer for some polymers. TBP also is a surfactant in aqueous solution. Dimension changes and property changes associated with softening will preclude the use of some materials as gaskets. Teflon/trademark/ and Kalrez/trademark/ gaskets appear to be compatible with TBP. Mixed results were obtained with EPDM elastomers, but EPDM O-rings are less costly than Kalrez/trademark/ and are being applied in some areas. Exposure of CPVC rigid piping led to crazing and, ultimately, catastrophic stress cracking, thus precluding its use in the waste services described. High-density polyethylene and PVDF plastic piping were unaffected by the test exposures and are useable for process and process waste service. Applications include 25-30 miles of polyethylene pipe and a large number of EPDM gaskets in the filter assembly of an effluent treatment system at the Savannah River Plant. 3 refs., 7 figs., 3 tabs.

Jenkins, C.F.; Briedenbach, P.J.

1989-01-01

274

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

UK PubMed Central (United Kingdom)

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

Rothenbacher T; Schwack W

2010-01-01

275

[Evaluation of cervical discrepancy of gold crowns in stone dies from various impression materials].  

Science.gov (United States)

A stainless steel master die simulating a dental preparation for crown was used to make 3 gold castings from wax patterns obtained in 3 different ways: a) directly from the naked master die; b) from the same master die with a copper coping 30 microns thick; and c) with a similar copper coping, but 40 microns thick. The discrepancies of fit of the 3 master gold crowns were evaluated in 99 stones dies (33 for each casting) obtained from 11 different elastomeric impression materials (3 replicae of each). The results showed that: 1) stone dies with no coping presented a medium discrepancy of 284 microns, inadequate for clinical use; 2) the 30 microns and 40 microns copings presented medium discrepancies of 18 and 9 microns respectively, both suitable for clinical use. Thus, the use of copings tend to equalize the cervical discrepancy of fit of gold crowns, whatever be the elastomeric impression material used. PMID:2135328

Mantovani, A V; Stephano, C B; Roselino, R F; Roselino, R B; Campos, G M

276

[Evaluation of cervical discrepancy of gold crowns in stone dies from various impression materials  

UK PubMed Central (United Kingdom)

A stainless steel master die simulating a dental preparation for crown was used to make 3 gold castings from wax patterns obtained in 3 different ways: a) directly from the naked master die; b) from the same master die with a copper coping 30 microns thick; and c) with a similar copper coping, but 40 microns thick. The discrepancies of fit of the 3 master gold crowns were evaluated in 99 stones dies (33 for each casting) obtained from 11 different elastomeric impression materials (3 replicae of each). The results showed that: 1) stone dies with no coping presented a medium discrepancy of 284 microns, inadequate for clinical use; 2) the 30 microns and 40 microns copings presented medium discrepancies of 18 and 9 microns respectively, both suitable for clinical use. Thus, the use of copings tend to equalize the cervical discrepancy of fit of gold crowns, whatever be the elastomeric impression material used.

Mantovani AV; Stephano CB; Roselino RF; Roselino RB; Campos GM

1990-01-01

277

Quantification of prosthetic outcomes: elastomeric gel liner with locking pin suspension versus polyethylene foam liner with neoprene sleeve suspension.  

UK PubMed Central (United Kingdom)

For this randomized crossover trial, we compared two common transtibial socket suspension systems: the Alpha liner with distal locking pin and the Pe-Lite liner with neoprene suspension sleeve. Our original hypotheses asserted that increased ambulatory activity, wear time, comfort, and satisfaction would be found with the elastomeric suspension system. Thirteen subjects completed the study. Following 2.5-month accommodation to each condition, ambulatory activity was recorded (steps/minute for 2 weeks), and subjects completed three questionnaires specific to prosthesis use and pain: the Prosthesis Evaluation Questionnaire (PEQ), a Brief Pain Inventory (BPI) excerpt, and the Socket Comfort Score (SCS). Upon completion, subjects selected their favored system for continued use. Ten subjects preferred the Pe-Lite and three the Alpha. Subjects spent 82% more time wearing the Pe-Lite and took 83% more steps per day. Ambulatory intensity distribution did not differ between systems. No statistically significant differences were found in questionnaire results. Subject feedback for each system was both positive and negative.

Coleman KL; Boone DA; Laing LS; Mathews DE; Smith DG

2004-07-01

278

Quantification of prosthetic outcomes: elastomeric gel liner with locking pin suspension versus polyethylene foam liner with neoprene sleeve suspension.  

Science.gov (United States)

For this randomized crossover trial, we compared two common transtibial socket suspension systems: the Alpha liner with distal locking pin and the Pe-Lite liner with neoprene suspension sleeve. Our original hypotheses asserted that increased ambulatory activity, wear time, comfort, and satisfaction would be found with the elastomeric suspension system. Thirteen subjects completed the study. Following 2.5-month accommodation to each condition, ambulatory activity was recorded (steps/minute for 2 weeks), and subjects completed three questionnaires specific to prosthesis use and pain: the Prosthesis Evaluation Questionnaire (PEQ), a Brief Pain Inventory (BPI) excerpt, and the Socket Comfort Score (SCS). Upon completion, subjects selected their favored system for continued use. Ten subjects preferred the Pe-Lite and three the Alpha. Subjects spent 82% more time wearing the Pe-Lite and took 83% more steps per day. Ambulatory intensity distribution did not differ between systems. No statistically significant differences were found in questionnaire results. Subject feedback for each system was both positive and negative. PMID:15558387

Coleman, Kim L; Boone, David A; Laing, Linda S; Mathews, David E; Smith, Douglas G

2004-07-01

279

The significance of pore microarchitecture in a multi-layered elastomeric scaffold for contractile cardiac muscle constructs.  

UK PubMed Central (United Kingdom)

Multi-layered poly(glycerol-sebacate) (PGS) scaffolds with controlled pore microarchitectures were fabricated, combined with heart cells, and cultured with perfusion to engineer contractile cardiac muscle constructs. First, one-layered (1L) scaffolds with accordion-like honeycomb shaped pores and elastomeric mechanical properties were fabricated by laser microablation of PGS membranes. Second, two-layered (2L) scaffolds with fully interconnected three dimensional pore networks were fabricated by oxygen plasma treatment of 1L scaffolds followed by stacking with off-set laminae to produce a tightly bonded composite. Third, heart cells were cultured on scaffolds with or without interstitial perfusion for 7 days. The laser-microablated PGS scaffolds exhibited ultimate tensile strength and strain-to-failure higher than normal adult rat left ventricular myocardium, and effective stiffnesses ranging from 220 to 290 kPa. The 7-day constructs contracted in response to electrical field stimulation. Excitation thresholds were unaffected by scaffold scale up from 1L to 2L. The 2L constructs exhibited reduced apoptosis, increased expression of connexin-43 (Cx-43) and matrix metalloprotease-2 (MMP-2) genes, and increased Cx-43 and cardiac troponin-I proteins when cultured with perfusion as compared to static controls. Together, these findings suggest that multi-layered, microfabricated PGS scaffolds may be applicable to myocardial repair applications requiring mechanical support, cell delivery and active implant contractility.

Park H; Larson BL; Guillemette MD; Jain SR; Hua C; Engelmayr GC Jr; Freed LE

2011-03-01

280

The significance of pore microarchitecture in a multi-layered elastomeric scaffold for contractile cardiac muscle constructs.  

Science.gov (United States)

Multi-layered poly(glycerol-sebacate) (PGS) scaffolds with controlled pore microarchitectures were fabricated, combined with heart cells, and cultured with perfusion to engineer contractile cardiac muscle constructs. First, one-layered (1L) scaffolds with accordion-like honeycomb shaped pores and elastomeric mechanical properties were fabricated by laser microablation of PGS membranes. Second, two-layered (2L) scaffolds with fully interconnected three dimensional pore networks were fabricated by oxygen plasma treatment of 1L scaffolds followed by stacking with off-set laminae to produce a tightly bonded composite. Third, heart cells were cultured on scaffolds with or without interstitial perfusion for 7 days. The laser-microablated PGS scaffolds exhibited ultimate tensile strength and strain-to-failure higher than normal adult rat left ventricular myocardium, and effective stiffnesses ranging from 220 to 290 kPa. The 7-day constructs contracted in response to electrical field stimulation. Excitation thresholds were unaffected by scaffold scale up from 1L to 2L. The 2L constructs exhibited reduced apoptosis, increased expression of connexin-43 (Cx-43) and matrix metalloprotease-2 (MMP-2) genes, and increased Cx-43 and cardiac troponin-I proteins when cultured with perfusion as compared to static controls. Together, these findings suggest that multi-layered, microfabricated PGS scaffolds may be applicable to myocardial repair applications requiring mechanical support, cell delivery and active implant contractility. PMID:21144580

Park, Hyoungshin; Larson, Benjamin L; Guillemette, Maxime D; Jain, Saloni R; Hua, Casey; Engelmayr, George C; Freed, Lisa E

2010-12-08

 
 
 
 
281

Effectiveness of intraoral delivery tips in reducing voids in elastomeric impressions.  

UK PubMed Central (United Kingdom)

Voids in impressions made by five automixed addition silicone elastomers with and without intraoral delivery tips were investigated. The number of voids were counted at a predetermined site on 3 days. Hand-mixed impressions of the automixed materials were made for comparison. There was no statistically significant difference in the mean number of voids produced in each automixed silicone dispensed with the use of intraoral delivery tips and the number of voids produced without the use of the tips. However, there were significant differences in the number of voids among different materials. The rank order of the automixed silicone elastomers was fairly consistent, with Express producing the highest and Reprosil the lowest number of voids. Automixed silicone materials should only be prepared by automixing for optimal results.

Chong YH; Soh G

1991-11-01

282

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

International Nuclear Information System (INIS)

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

2011-01-01

283

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

284

Low-level laser therapy for treatment of pain associated with orthodontic elastomeric separator placement: a placebo-controlled randomized double-blind clinical trial.  

UK PubMed Central (United Kingdom)

OBJECTIVE: The objective of this study was to evaluate the effectiveness of the use of irradiation with a low-level laser therapy (LLLT), wavelength 830?nm, for treating pain inherent to tooth movement caused by orthodontic devices, simulated by positioning interdental elastomeric separators. METHODS: Sixty orthodontic patients were randomly assigned to two groups: GA (ages 12-25 years; mean 17.1 years) was the control, and GB (ages 12-26 years; mean 17.9 years) the intervention group. All patients received elastomeric separators on the mesial and distal surfaces of one of the lower first molars, and immediately after insertion of the separators received irradiation as randomly indicated. The intervention group (GB) received irradiation with LLLT (aluminum gallium arsenide diode), by a single spot in the region of the radicular apex at a dose of 2?J/cm(2) and application along the radicular axis of the buccal surface with three spots of 1?J/cm(2) (wavelength 830?nm; infrared). Control group (GA) received irradiation with a placebo light in the same way. This was a double-blind study. All the patients received a questionnaire to be filled out at home describing their levels of pain 2, 6, and 24?h and 3 and 5 days after orthodontic separator placement, in situations of relaxed and occluded mouth. RESULTS: The patients in the intervention group (LLLT) had lower mean pain scores in all the measures. The incidence of complete absence of pain (score=0) was significantly higher the intervention group. CONCLUSIONS: Based on this study, authors concluded that single irradiation with LLLT of wavelength 830?nm efficiently controlled the pain originating from positioning interdental elastomeric separators, to reproduce the painful sensation experienced by patients when fixed orthodontic devices are used.

Nóbrega C; da Silva EM; de Macedo CR

2013-01-01

285

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

UK PubMed Central (United Kingdom)

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.

Hong Y; Takanari K; Amoroso NJ; Hashizume R; Brennan-Pierce EP; Freund JM; Badylak SF; Wagner WR

2012-02-01

286

Particulate drug interactions with polymeric and elastomeric valve components in suspension formulations for metered dose inhalers.  

UK PubMed Central (United Kingdom)

PURPOSE: To characterise the adhesive interactions between three pulmonary active pharmaceutical ingredient (API) materials and the components of pressurised metered dose inhalers (pMDIs) obtained from two commercially available products (termed 'Prod-1' and 'Prod-2'). This is of potential interest, as a greater understanding of the interactions between specific APIs and surfaces may aid manufacturers in component selection during pMDI system development. METHODS: The theoretical work of adhesion (DeltaG(132)) for each API-pMDI component interaction was calculated using the surface component analysis (SCA) approach. These results were correlated with corresponding API-pMDI component separation energy measurements determined using colloid probe AFM. RESULTS: Strong correlations existed between separation energy and the DeltaG(132) parameters where the polar contribution was accounted for. This highlighted the adhesive influence of polar surface energy on each interaction in this study. Generally the largest adhesive interactions involved APIs and pMDI components which have a bipolar surface energy (i.e. both gamma(-) and gamma(+) >1 mJ m(-2)). CONCLUSIONS: For each API-pMDI interaction in this study, the polar component of surface energy has the greater influence on adhesive events. The bipolar surface energetics of certain APIs and pMDI components were deemed responsible for the increased adhesive interactions observed with these materials. This study highlights that different materials can have different effects on the adhesive interactions with particulate APIs; information that could aid the manufacturer in producing more effective and efficient pMDI systems.

James J; Davies M; Toon R; Jinks P; Roberts CJ

2009-01-01

287

Determination of an optimal magnification for examining voids in elastomeric impressions.  

UK PubMed Central (United Kingdom)

Specimens of one polyether impression material and the resulting stone casts were examined at magnifications from 1X to 10X to determine the optimal magnification for identifying defects. Results showed that the number of defects on impressions and stone dies detected by two operators increased with each corresponding increase in magnification up to magnifications of 9X and 8X, respectively. The magnifications that revealed significantly less defects than the highest mean count were 6X for impression voids and 5X for stone die defects. A magnification of 9X optimized reliability by maximizing void detection while minimizing operator variability.

Soh G; Chong YH

1990-11-01

288

Determination of an optimal magnification for examining voids in elastomeric impressions.  

Science.gov (United States)

Specimens of one polyether impression material and the resulting stone casts were examined at magnifications from 1X to 10X to determine the optimal magnification for identifying defects. Results showed that the number of defects on impressions and stone dies detected by two operators increased with each corresponding increase in magnification up to magnifications of 9X and 8X, respectively. The magnifications that revealed significantly less defects than the highest mean count were 6X for impression voids and 5X for stone die defects. A magnification of 9X optimized reliability by maximizing void detection while minimizing operator variability. PMID:2083026

Soh, G; Chong, Y H

289

ONE-PART STRUCTURAL EPOXY RESIN ADHESIVES CONTAINING ELASTOMERIC TOUGHENERS CAPPED WITH PHENOLS AND HYDROXY-TERMINATED ACRYLATES OR HYDROXY-TERMINATED METHACRYLATES  

UK PubMed Central (United Kingdom)

Structural adhesives are prepared from an elastomeric toughener that contains urethane and/or urea groups, and have some terminal isocyanate groups that are capped with a phenol and other terminal isocyanate groups that are capped with a hydroxy-functional acrylate or a hydroxy-functional methacrylate. In certain embodiments, the presence of both types of capping on the toughener leads to higher impact peel strengths and a greater level of cohesive failure, than when the toughener is capped with a phenol an hydroxy-functional acrylate or hydroxy-functional methacrylate alone.

LUTZ ANDREAS; SCHNEIDER DANIEL

290

Prospective randomized double-blind placebo-controlled trial of postoperative elastomeric pain pump devices used after laparoscopic ventral hernia repair.  

UK PubMed Central (United Kingdom)

BACKGROUND: The laparoscopic repair of ventral hernias can result in significant postoperative pain necessitating a prolonged hospital stay, increased narcotic use, and patient dissatisfaction. Elastomeric pain pump devices with local analgesics may significantly reduce postoperative discomfort after laparoscopic ventral hernia repair. This prospective randomized, double-blind, placebo-controlled study evaluated the effect of local anesthetic continuously infused with an elastomeric pain pump device to reduce postoperative pain. METHODS: After institutional review board approval of the study, all patients undergoing laparoscopic ventral hernia repair consented to participate. Standardized technique included routine transfascial fixation sutures and titanium spiral tacks. Elastomeric pain pumps were placed percutaneously just above the mesh in the hernia sac. For 48 h postoperatively, 100 ml of continuous 0.5% Marcaine or normal saline was used at 2 ml/h. Postoperatively, the patients were evaluated every 8 h for the first 72 h, then after 2 weeks, 6 weeks, and 3 months for pain scores, narcotic usage (both oral and intravenous), return of flatus, length of hospital stay, and postoperative complications. RESULTS: Of the 73 patients enrolled in the study, 37 received 0.5% Marcaine, and 36 received placebo. Despite randomization, the control group had significantly more obese patients (mean body mass index [BMI], 39 vs. 33 kg/m(2); p = 0.005), and more recurrent hernias (40% vs. 19%; p = 0.05), and also tended to have more prior hernia repairs (0.8 vs. 0.3; p = 0.06). There were no significant differences between the two groups in terms of operative times (p = 0.7), hernia size (p = 0.9), mesh size (p = 0.6), number of transfascial fixation sutures (p = 0.4), or number of spiral tacks (p = 0.13). Postoperative visual analog pain scores, usage of oral or intravenous narcotics, and morphine equivalents were similar between the two groups at all study points (p > 0.05). There were no significant differences between the two groups based on return of bowel function, toleration of a regular diet, or length of hospital stay. No postoperative complications directly related to the catheter were observed. CONCLUSIONS: This prospective randomized double-blind, placebo-controlled trial showed no advantage of an elastomeric pain pump device in terms of providing a measurable reduction in postoperative pain scores, narcotic use, time to return of bowel function, or length of hospital stay after laparoscopic ventral hernia repair. Further studies are warranted to determine other alternatives for reducing postoperative pain after laparoscopic ventral hernia repair.

Rosen MJ; Duperier T; Marks J; Onders R; Hardacre J; Ponsky J; Ermlich B; Laughinghouse M

2009-12-01

291

Advanced materials and biochemical processes for geothermal applications  

Energy Technology Data Exchange (ETDEWEB)

Two Geothermal Technology Division (GTD)-sponsored programs: (1) Geothermal Materials Development, and (2) Advanced Biochemical Processes for Geothermal Brines, are described. In the former, work in the following tasks is in progress: (1) high temperature elastomeric materials for dynamic sealing applications, (2) advanced high temperature (300/sup 0/C) lightweight (1.1 g/cc) well cementing materials, (3) thermally conductive composites for heat exchanger tubing, (4) corrosion rates for metals in brine-contaminated binary plant working fluids, and (5) elastomeric liners for well casing. Methods for the utilization and/or the low cost environmentally acceptable disposal of toxic geothermal residues are being developed in the second program. This work is performed in two tasks. In one, microorganisms that can interact with toxic metals found in geothermal residues to convert them into soluble species for subsequent reinjection back into the reservoir or to concentrate them for removal by conventional processes are being identified. In the second task, process conditions are being defined for the encapsulation of untreated or partially biochemically treated residues in Portland cement-based formulations and the subsequent utilization of the waste fractions in building materials. Both processing methods yield materials which appear to meet disposal criteria for non-toxic solid waste, and their technical and economic feasibilities have been established.

Kukacka, L.E.; van Rooyen, D.; Premuzic, E.T.

1987-04-01

292

Preliminary studies of radioactive wastes immobilization, using microwaves, in asphaltic matrices and elastomeric residues  

International Nuclear Information System (INIS)

The present work consists of preliminary studies for immobilization of radioactive waste by using monolithic solid matrices compounded by bitumen (asphalt) and production leftovers of EVA shoe soles (polymeric residues). Those matrices were obtained through high microwave energy heating aiming to reduce possible dispersion of radioactive material in the environment during the stages of intermediate storage, transportation and final disposal. The radioactive waste that was used results from the purification of thorium long made at Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP). The obtained precipitate is named Retoter (thorium residue and rare earth elements). The compounded samples of bitumen and rubber were heated by electromagnetic radiation (high microwave energy); the time was varied and the temperature was controlled. Variables such as mass percent of bitumen/rubber, dosage, microwave power, heating period and temperature were analyzed in order to get the most homogeneous formulations that might be most resistant to environmental agents. The geometry of samples is still being studied to obtain the best distribution of radioactive waste on the polymeric compound (bitumen/rubber). To prove the efficiency of the method, physics and chemistry characterizations have been initially made through assays in order to evidence properties like: porosity, density, leaching rate, resistance to radiation, resistance to aging, thermal, mechanical and structural properties. (author)

2005-09-02

293

Antimicrobial properties of electrically formed elastomeric polyurethane-copper oxide nanocomposites for medical and dental applications.  

UK PubMed Central (United Kingdom)

With the rapidly advancing field of nanotechnology having an impact in several areas interfacing life and physical sciences, the potential applications of nanoparticles as antimicrobial agents have been realized and offer great opportunities in addressing several viral and bacterial outbreak issues. Polyurethanes (PUs) are a diverse class of polymeric materials which also have applications in several areas of biomedical science ranging from blood contact devices to implantable dental technologies. In this report, copper oxide (CuO) nanoparticles (mean size ?50 nm) are embedded into a PU matrix via two electrical fabrication processes. To elucidate the antimicrobial activity, a range of different loading compositions of CuO within the PU matrix (0%, 1%, 5%, and 10% w/w) are electrospun to form thin porous films (thickness < 10 ?m). After washing, the films are tested for their antimicrobial properties against methicillin-resistant Staphylococcus aureus (MRSA). Significant reduction of populations was demonstrated with 10% w/w CuO over a 4-h period. This approach demonstrates the potential of generating tailored antimicrobial structures for a host of applications, such as designer filters, patterned coatings, breathable fabrics, adhesive films (as opposed to sutures), and mechanically supporting structures.

Ahmad Z; Vargas-Reus MA; Bakhshi R; Ryan F; Ren GG; Oktar F; Allaker RP

2012-01-01

294

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Objetivos: Evaluar la eficacia y seguridad de remifentanilo administrado mediante infusor elastomérico con PCA iv en analgesia obstétrica comparado con meperidina intramuscular en parturientas con contraindicación para analgesia epidural. Material y Método: Se seleccionaron aletoriamente 24 parturientas, se asoció infusor elastomérico Baxter® con 250 ml de suero fisiológico con 2,5 mg de remifentanilo y un ritmo de 12 ml·h ¹, lo que supone una infusión media de (more) 0,025 ?g·kg-1·min-1 de remifentanilo, permitiendo la administración de bolos de 5 ml con un tiempo de cierre de 30 minutos (Grupo R) o 1 mg·kg¹ de meperidina y 2,5 mg de haloperidol (Grupo M) vía intramuscular cada 4 h. Valoramos la intensidad del dolor cada 30 min mediante una escala analógica visual (EVA), tiempo de infusión, bolos administrados, el nivel de sedación mediante escala del estado de alerta y sedación evaluada por el observador (OAA/S), efectos adversos y el test de Apgar del recién nacido al minuto y a los 5 min. Resultados: No hubo diferencias en los datos antropométricos de ambos grupos. La duración media de la infusión en el grupo R fue de 280 ± 55 min y las necesidades de bolos de rescate de 1,2 ± 1,5. La dosis media de meperidina intramuscular en el grupo M fue de 120 ± 25 mg. La intensidad del dolor durante el parto fue significativamente menor en el grupo R durante todo el periodo de dilatación y expulsivo (p Abstract in english Objectives: To evaluate the effectiveness and security of remifentanil administered by means of elastomeric infusor with PCA IV compared obstetrical analgesia with intramuscular meperidine in obstetric patients with contraindication for epidural analgesia, Material and Method: 24 patients were randomized, an elastomeric infusor Baxter® with a capacity of 250 ml was filled with 2.5 mg of remifentanil and a 12 mililiter·h-1, was satarted, (average infusion of 0.025·kg-1? (more) ?min-1 of remifentanil, and boluses of 5 ml with a time of closing of 30 minutes (Group R) or 1 mg/kg-1 of meperidine and 2.5 mg of haloperidol (Group M) every 4 h by IM route. We valued the intensity of pain each 30 min by means of a visual analogical scale (EVA), time of infusion, boluses administered, level of sedatión by means of scale of the alert status and sedatión evaluated by observer (OAA/S), adverse effects and the Apgar test of new born to 1 and 5 min. Results: There were no differences in the anthropometric data of both groups. The average duration of the infusion in group R was of 280 ± 55 min and the necessities of boluses of 1.2 rescue of ± 1,5. The average dose of intramuscular meperidine in group M was of 120 ± 25 mg. The intensity of the pain during the childbirth was significantly smaller in group R (p

Calderón, E.; Martínez, E.; Román, M. D.; Pernio, A.; García-Hernández, R.; Torres, L.M

2006-10-01

295

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 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 calidad de estas Unidades. El empleo de técnicas analgésicas invasivas domiciliarias, en todos sus regímenes, puede controlar el dolor postoperatorio en estas intervenciones (more) 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 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 (more) 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

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

2011-06-01

296

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

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

2011-01-01

297

Compression and shear properties of elastomeric bearing using finite element analysis  

Directory of Open Access Journals (Sweden)

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

Kopoonpat, S.; Seadan, M.; 2Faculty of Science and Technology, Chiang Mai Rajabhat University, Muang, Chiang Mai, 50300 Thailand.

2006-01-01

298

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

Directory of Open Access Journals (Sweden)

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

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

2006-01-01

299

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)

1982-01-01

300

Effect of different prosthetic materials on radiation dose distribution in an orbital defect: a clinical report.  

UK PubMed Central (United Kingdom)

It is challenging to treat and irradiate empty cavities with external-beam radiation therapy (EBRT) because body contour irregularities can result in dose heterogeneities. The use of compensator materials to fill the empty cavities can provide a more homogeneous radiation dose distribution. The purposes of this clinical report are to describe the use of 3 different materials (elastomeric material, water-filled balloon, and acrylic resin) in an orbital defect and compare the dosimetric parameters and photon-electron dose distribution during EBRT.

Ozçelik TB; Onal C; Efe E; Yilmaz B

2012-04-01

 
 
 
 
301

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.

2012-11-06

302

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

303

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

Science.gov (United States)

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

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

2012-11-01

304

Spontaneous Enhancement of Packing Regularity of Spherical Microdomains in the Body-Centered Cubic Lattice upon Uniaxial Stretching of Elastomeric Triblock Copolymers  

Directory of Open Access Journals (Sweden)

Full Text Available Block copolymers forming glassy spheres in the matrix of rubbery chains can exhibit elastomeric properties. It is well known that the spherical microdomains are arranged in the body-center cubic (bcc) lattice. However, recently, we have found packing in the face-centered cubic (fcc) lattice, which is easily transformed into the bcc lattice upon uniaxial stretching. In the same time, the packing regularity of the spheres in the bcc lattice was found to be enhanced for samples completely recovered from the stretched state. This reminds us that a cycle of stretching-and-releasing plays an important role from analogy of densification of the packing in granules upon shaking. In the current paper, we quantify the enhancement of packing regularity of spherical microdomains in the bcc lattice upon uniaxial stretching of the same elastomeric triblock copolymer as used in our previous work by conducting small-angle X-ray scattering (SAXS) measurements using high brilliant synchrotron radiation. Isotropically circular rings of the lattice peaks observed for the unstretched sample turned into deformed ellipsoidal rings upon the uniaxial stretching, with sharpening of the peaks in the direction parallel to the stretching direction and almost disappearing of the peaks in the perpendicular direction. By quantitatively analyzing the SAXS results, it was found that the packing regularity of the spherical microdomains was enhanced in the parallel direction while it was spoiled in the perpendicular direction under the stretched state. The enhanced regularity of packing was unchanged even if the stretching load was completely removed.

Takuya Kota; Kimio Imaizumi; Sono Sasaki; Shinichi Sakurai

2010-01-01

305

Morphology and viscoelastic properties of sealing materials based on EPDM rubber.  

UK PubMed Central (United Kingdom)

In this applicative study, the ratio of active and inactive filler loadings was the prime factor for determining the dynamic-mechanical behaviour of ethylene-propylene-diene monomer rubbers. Scanning electron microscopy was used to study the structure of reinforced dense and microcellular elastomeric materials. The effects of filler and blowing agent content on the morphology of composites were investigated. Microcellular samples cured in salt bath show smaller cells and uniform cell size compared with samples cured in hot air. Dynamic-mechanical thermal analysis showed appreciable changes in the viscoelastic properties by increasing active filler content, which could enable tailoring the material properties to suit sealing applications.

Mili? J; Aroguz A; Budinski-Simendi? J; Radicevi? R; Prendzov S

2008-12-01

306

Outgassing tests on materials used in the DIII{endash}D magnetic fusion tokamak  

Energy Technology Data Exchange (ETDEWEB)

In order to achieve high performance plasma discharges in the DIII{endash}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{endash}D vessel. The results of pump-down tests performed on ATJ graphite, thin Grafoil{sup {reg_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&hthinsp;{degree}C, which is the maximum temperature to which the DIII{endash}D vessel is baked. The station was modified to include independent heating control of the sample and a simple load-lock chamber. {copyright} {ital 1999 American Vacuum Society.}

Holtrop, K.L.; Hansink, M.; Kellman, A.G. [Fusion, General Atomics, San Diego, California 92186-5608 (United States)

1999-07-01

307

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

Energy Technology Data Exchange (ETDEWEB)

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.

Holtrop, K.L.; Hansink, M.; Kellman, A.G.

1998-12-01

308

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

International Nuclear Information System (INIS)

[en] 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

1999-01-01

309

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

Directory of Open Access Journals (Sweden)

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

Budinski-Simendi? Jaroslava; Milic Jelena; Cvetkovi? Ivana; Radi?evi? Radmila; Korugi?-Karasz Ljiljana; Vukov Miodrag; Mirkovi? Desa

2006-01-01

310

ELASTIC LAMINATE MATERIAL USEFUL IN CONTACT WITH A HUMAN BODY  

UK PubMed Central (United Kingdom)

An elastic laminate material (multi-layer material, sandwich material) intended to be used for various purposes in which the material may be used in direct contact with human skin, and which comprises a base material (1) of an elastic, porous foam material, preferably a material having closed cells, and a stretchable or elastic surface layer (2) on one side or on both sides thereof, preferably a knitted material like a "stretch material", a tricot/woven material, a piquet material etc., which has been fixed to the base material (1) by means of an intermediate glue layer (3), and in which the base material (1) comprises an elastomeric material which does not contain any chlorine compounds, for instance EPDM rubber, SBR rubber or NBR rubber, and in which the glue layer (3) comprises a thermoplastic melt glue of the type which is dry and non-sticking in cold condition but which has good adhesive properties in heated condition, for instance an EVA glue, a glue of polyolefine, a poylester, a polyethylene or a polyurethane.

PORSGAARD Peter

311

Repair of posterior base of a maxillary complete denture by use of a cast of stone and resilient material.  

UK PubMed Central (United Kingdom)

A method to repair a fractured complete denture and simultaneously augment deficient borders or correct an inadequate posterior palatal seal is described. Corrections were made intraorally with modeling compound and an elastomeric impression material. A resilient impression material was used to block out the undercuts in the denture, and repair was accomplished with visible light-cured resin or an autopolymerizing repair resin. This technique simplifies the laboratory procedures and thereby permits the return of the denture to the patient at the same visit.

Lee S; Morgano SM

1995-11-01

312

Repair of posterior base of a maxillary complete denture by use of a cast of stone and resilient material.  

Science.gov (United States)

A method to repair a fractured complete denture and simultaneously augment deficient borders or correct an inadequate posterior palatal seal is described. Corrections were made intraorally with modeling compound and an elastomeric impression material. A resilient impression material was used to block out the undercuts in the denture, and repair was accomplished with visible light-cured resin or an autopolymerizing repair resin. This technique simplifies the laboratory procedures and thereby permits the return of the denture to the patient at the same visit. PMID:8809264

Lee, S; Morgano, S M

1995-11-01

313

Type B plutonium transport package development that uses metallic filaments and composite materials  

International Nuclear Information System (INIS)

A new package was developed for transporting Pu and U quantities that are currently carried in DOT-6M packages. It uses double containment with threaded closures and elastomeric seals. A composite overpack of metallic wire mesh and ceramic or quartz cloth insulation is provided for protection in accidents. Two prototypes were subjected to dynamic crush tests. A thermal computer model was developed and benchmarked by test results to predict package behavior in fires. The material performed isotropically in a global fashion. A Type B Pu transport package can be developed for DOE Pu shipments for less than $5000 if manufactured in quantity. 5 figs, 6 refs.

1991-01-01

314

Urinary bladder smooth muscle regeneration utilizing bone marrow derived mesenchymal stem cell seeded elastomeric poly(1,8-octanediol-co-citrate) based thin films.  

UK PubMed Central (United Kingdom)

Bladder regeneration studies have yielded inconclusive results possibly due to the use of unfavorable cells and primitive scaffold design. We hypothesized that human mesenchymal stem cells seeded onto poly(1,8-octanediol-co-citrate) elastomeric thin films would provide a suitable milieu for partial bladder regeneration. POCfs were created by reacting citric acid with 1,8-octanediol and seeded on opposing faces with human MSCs and urothelial cells; normal bladder smooth muscle cells and UCs, or unseeded POCfs. Partial cystectomized nude rats were augmented with the aforementioned POCfs, enveloped with omentum and sacrificed at 4 and 10 weeks. Isolated bladders were subjected to Trichrome and anti-human gamma-tubulin, calponin, caldesmon, smooth muscle gamma-actin, and elastin stainings. Mechanical testing of POCfs revealed a Young's modulus of 138 kPa with elongation 137% its initial length without permanent deformation demonstrating its high uniaxial elastic potential. Trichrome and immunofluorescent staining of MSC/UC POCf augmented bladders exhibited typical bladder architecture with muscle bundle formation and the expression and retention of bladder smooth muscle contractile proteins of human derivation. Quantitative morphometry of MSC/UC samples revealed muscle/collagen ratios approximately 1.75x greater than SMC/UC controls at 10 weeks. Data demonstrate MSC seeded POCfs support partial regeneration of bladder tissue in vivo.

Sharma AK; Hota PV; Matoka DJ; Fuller NJ; Jandali D; Thaker H; Ameer GA; Cheng EY

2010-08-01

315

Plaque retention by self-ligating vs elastomeric orthodontic brackets: quantitative comparison of oral bacteria and detection with adenosine triphosphate-driven bioluminescence.  

UK PubMed Central (United Kingdom)

INTRODUCTION: Enamel decalcification is a common problem in orthodontics. The objectives of this randomized clinical study were to enumerate and compare plaque bacteria surrounding 2 bracket types, self-ligating (SL) vs elastomeric ligating (E), and to determine whether adenosine triphosphate (ATP)-driven bioluminescence could be used for rapid assessment of bacterial load in plaque. METHODS: Patients (ages, 11-17 years) were bonded with SL and E brackets in 14 maxillary and 12 mandibular arches by using a split-mouth design. Recall visits were at 1 and 5 weeks after bonding. Plaque specimens were assayed for oral bacteria and subjected to ATP-driven bioluminescence determinations with a luciferin-based assay. RESULTS: In most patients, teeth bonded with SL attachments had fewer bacteria in plaque than did teeth bonded with E brackets. At 1 and 5 weeks after bonding, the means for SL vs E brackets were statistically lower for total bacteria and oral streptococci (P <0.05). ATP bioluminescence values were statistically correlated to the total oral bacteria and oral streptococci, with correlation coefficients of 0.895 and 0.843, respectively. CONCLUSIONS: SL appliances promote reduced retention of oral bacteria, and ATP bioluminescence might be a useful tool in the rapid quantification of bacterial load and the assessment of oral hygiene during orthodontic treatment.

Pellegrini P; Sauerwein R; Finlayson T; McLeod J; Covell DA Jr; Maier T; Machida CA

2009-04-01

316

From deep clays to expanded graphite: towards the modelling of porous materials; De l`argile profonde au graphite expanse: contribution a l`etude des materiaux poreux  

Energy Technology Data Exchange (ETDEWEB)

Compared with standard mechanics, modelling the behaviour of porous materials requires and extended framework. Known as `poro-mechanics`, such an approach has recently been implemented in Aster finite element code. Two examples of its use for engineering purposes are presented in this paper. First, the water pressure rise and the resulting mechanical strains in the clay surrounding a deep disposal of nuclear waste is analysed. The second example concerns the tightness of expanded graphite gaskets which are widely used in the bolted assemblies of EDF nuclear reactors. Other engineering fields such as civil engineering are likely to benefit from this theory, and are mentioned in the conclusion. (authors)

Didry, O.; Patron, E. [Electricite de France, 77 - Moret sur Loing (France). Direction des Etudes et Recherches; Voldoire, F. [Electricite de France (EDF), 92 - Clamart (France). Direction des Etudes et Recherches

1998-10-01

317

Life cycle management of radioactive materials packaging  

International Nuclear Information System (INIS)

The objective of life cycle management of radioactive materials packaging is to ensure the safety functions (i.e. containment of radioactivity, protection against radiation, and criticality safety for fissile contents) during the entire life cycle of the packaging in storage, transportation and disposal. A framework has been developed for life cycle management regarding type B radioactive and fissile materials packaging, drawing upon current US Department of Energy (DOE) storage standards and examples from interim storage of Pu bearing materials in model 9975 transportation packagings. Key issues highlighted during long term storage of Pu bearing materials included gas generation and stability of PuO2+x; other operation safety issues highlighted for interim storage of model 9975 transportation packagings included the need to consider a facility design basis fire event and the long term behaviour of packaging components such as Celotex and elastomeric O-ring seals. The principles of aging management are described, and the key attributes and examples of effective aging management programmes are provided based on the guidance documents for license renewal of nuclear power plants. The Packaging Certification Program of DOE Environmental Management, Office of Safety Management and Operations, plans to expand its mission into packaging certification for storage and aging management, as well as application of advanced technology, such as radiofrequency identification, for life cycle management of radioactive materials packagings.

2007-01-01

318

Life cycle management of radioactive materials packaging.  

Energy Technology Data Exchange (ETDEWEB)

The objective of life cycle management of radioactive materials packaging is to ensure the safety functions (i.e. containment of radioactivity, protection against radiation, and criticality safety for fissile contents) during the entire life cycle of the packaging in storage, transportation and disposal. A framework has been developed for life cycle management regarding type B radioactive and fissile materials packaging, drawing upon current US Department of Energy (DOE) storage standards and examples from interim storage of Pu bearing materials in model 9975 transportation packagings. Key issues highlighted during long term storage of Pu bearing materials included gas generation and stability of PuO{sub 2+x}; other operation safety issues highlighted for interim storage of model 9975 transportation packagings included the need to consider a facility design basis fire event and the long term behaviour of packaging components such as Celotex and elastomeric O-ring seals. The principles of aging management are described, and the key attributes and examples of effective aging management programmes are provided based on the guidance documents for license renewal of nuclear power plants. The Packaging Certification Program of DOE Environmental Management, Office of Safety Management and Operations, plans to expand its mission into packaging certification for storage and aging management, as well as application of advanced technology, such as radiofrequency identification, for life cycle management of radioactive materials packagings.

Liu, Y.; Bellamy, S.; Shuler, J.; Decision and Information Sciences; SRL; DOE

2007-01-01

319

Nanoprobe measurements of materials at megabar pressures  

International Nuclear Information System (INIS)

The use of nanoscale x-ray probes overcomes several key limitations in the study of materials up to multimegabar (> 200) pressures, namely, the spatial resolution of measurements of multiple samples, stress gradients, and crystal domains in micron to submicron size samples in diamond-anvil cells. Mixtures of Fe, Pt, and W were studied up to 282 GPa with 250-600 nm size synchrotron x-ray absorption and diffraction probes. The probes readily resolve signals from individual materials, between sample and gasket, and peak pressures, in contrast to the 5-(micro)m-sized x-ray beams that are now becoming routine. The use of nanoscale x-ray beams also enables single-crystal x-ray diffraction studies in nominally polycrystalline samples at ultrahigh pressures, as demonstrated in measurements of (Mg,Fe)SiO3 postperovskite. These capabilities have potential for driving a push toward higher maximum pressures and further miniaturization of high-pressure devices, in the process advancing studies at extreme conditions.

2010-04-06

320

The effect of diode superpulsed low-level laser therapy on experimental orthodontic pain caused by elastomeric separators: a randomized controlled clinical trial.  

UK PubMed Central (United Kingdom)

The aim of this study was to evaluate the efficacy of diode superpulsed low-level laser therapy (SLLLT) in reducing experimentally induced orthodontic pain. Overall, 120 subjects (23.01?±?1.39 years) were enrolled for a clinical trial. Subjects were randomly assigned to upper (U, N?=?60) or lower (L, N?=?60) jaw groups. All subjects received 4 elastomeric separators mesial and distal to the upper (U group) or lower (L group) right first molar and bicuspids. Each subject of the U and L groups was randomly assigned to laser (Ul, N?=?20 and Ll, N?=?20), placebo (Up, N?=?20 and Lp, N?=?20) or control (Uc, N?=?20 and Lc, N?=?20) sub-groups. Subjects in laser groups received a single GaAs diode SLLLT application (910 nm, 160 mW, beam diameter of 8 mm, applied for 340 s) immediately after placing orthodontic separators. Placebo groups received a simulated SLLLT and controls did not receive any therapy. All participants compiled a survey on pain duration and a 100-mm visual analogue scale immediately after the separators placement and after 12, 24, 36, 48, 72, and 96 h. Pain intensity of laser groups was significantly lower compared to placebo and control groups (p?=?0.0001). In the laser group, 70 % of subjects felt pain, while in the placebo and control groups all subjects felt pain (p?=?0.0001). The end of pain occurred earlier in laser compared to placebo and control groups (p?=?0.021). A single-diode SLLLT application appeared to be effective in reducing the intensity and duration of experimentally induced orthodontic pain and could be used in daily orthodontic practice.

Marini I; Bartolucci ML; Bortolotti F; Innocenti G; Gatto MR; Alessandri Bonetti G

2013-05-01

 
 
 
 
321

The effect of diode superpulsed low-level laser therapy on experimental orthodontic pain caused by elastomeric separators: a randomized controlled clinical trial.  

Science.gov (United States)

The aim of this study was to evaluate the efficacy of diode superpulsed low-level laser therapy (SLLLT) in reducing experimentally induced orthodontic pain. Overall, 120 subjects (23.01?±?1.39 years) were enrolled for a clinical trial. Subjects were randomly assigned to upper (U, N?=?60) or lower (L, N?=?60) jaw groups. All subjects received 4 elastomeric separators mesial and distal to the upper (U group) or lower (L group) right first molar and bicuspids. Each subject of the U and L groups was randomly assigned to laser (Ul, N?=?20 and Ll, N?=?20), placebo (Up, N?=?20 and Lp, N?=?20) or control (Uc, N?=?20 and Lc, N?=?20) sub-groups. Subjects in laser groups received a single GaAs diode SLLLT application (910 nm, 160 mW, beam diameter of 8 mm, applied for 340 s) immediately after placing orthodontic separators. Placebo groups received a simulated SLLLT and controls did not receive any therapy. All participants compiled a survey on pain duration and a 100-mm visual analogue scale immediately after the separators placement and after 12, 24, 36, 48, 72, and 96 h. Pain intensity of laser groups was significantly lower compared to placebo and control groups (p?=?0.0001). In the laser group, 70 % of subjects felt pain, while in the placebo and control groups all subjects felt pain (p?=?0.0001). The end of pain occurred earlier in laser compared to placebo and control groups (p?=?0.021). A single-diode SLLLT application appeared to be effective in reducing the intensity and duration of experimentally induced orthodontic pain and could be used in daily orthodontic practice. PMID:23666533

Marini, Ida; Bartolucci, Maria Lavinia; Bortolotti, Francesco; Innocenti, Giulio; Gatto, Maria Rosaria; Alessandri Bonetti, Giulio

2013-05-11

322

Solar collectors - Sealing and insulating materials outgassing. Outgassing hos taetnings- och isolermaterial i solfaangare  

Energy Technology Data Exchange (ETDEWEB)

One reason for a reduced function in many solar collectors is that the covering plate is fogged by the volatile components in the sealing and insulation products. This so called outgassing also deteriorates the functions of the components. A rubber gasket e.g. hardens when the softener evaporates and the function of the sealing deteriorates. Several investigations of the outgassing tendency in solar collectors have been published. Many materials are unsuitable from the point of outgassing. A method for determination of outgassing has been developed within the scope of this project. The sealing and insulation materials used in solar collectors, made in Sweden, have been examined and investigated. The results show that outgassing from the products even happens at a temperature used by normal use. With a temperature corresponding to a stagnation situation e.g. circulation failure, the quantity of volatile components is considerable.

Eriksson-Widblom, K.

1987-01-01

323

Alkylaminopyridine-modified aluminum aminoterephthalate metal-organic frameworks as components of reactive self-detoxifying materials.  

Science.gov (United States)

Aluminum aminoterephthalate MOF particulate materials (NH(2)-MIL-101(Al) and NH(2)-MIL-53(Al)), studied here as components of self-detoxifying surfaces, retained their reactivity following their covalent attachment to protective surfaces utilizing a newly developed strategy in which the MOF particles were deposited on a reactive adhesive composed of polyisobutylene/toluene diisocyanate (PIB/TDI) blends. Following MOF attachment and curing, the MOF primary amino groups were functionalized with highly nucleophilic 4-methylaminopyridine (4-MAP) by disuccinimidyl suberate-activated conjugation. The resulting MOF-4-MAP modified PIB/TDI elastomeric films were mechanically flexible and capable of degrading diisopropyl fluorophosphate (DFP), a chemical threat simulant. PMID:22871803

Bromberg, Lev; Klichko, Yaroslav; Chang, Emily P; Speakman, Scott; Straut, Christine M; Wilusz, Eugene; Hatton, T Alan

2012-08-21

324

Effects of acid gas on the sealing materials; Einfluss von Sauergas auf die Eigenschaften von Dichtungswerkstoffen  

Energy Technology Data Exchange (ETDEWEB)

Sealing materials in petroleum and natural gas production plants must meet extreme requirements in terms of resistance to chemical substences, high temperatures and pressures. Apart from petroleum and natural gas, they are exposed to extraction aids like aminic corrosion inhibitors and drilling emulstions, and high concentrations of hydrogen sulfide. This gas is particularly problematic because of its toxicity, corrosiveness and aggressiveness towards elastomeric sealing materials. The contribution presents details. [German] Im Allgemeinen werden an Dichtungen, die in Anlagen fuer die Erdoel- und Erdgasfoerderung eingesetzt werden, extreme Anforderungen hinsichtlich Chemikalien-, Temperatur- und Druckbestaendigkeit gestellt. Da ein Dichtungsschaden oder -ausfall die Funktionsfaehigkeit dieser Anlagen stark beeintraechtigen oder gar zum Stillstand der Anlagen fuehren kann, ist die Auswahl geeigneter Dichtungswerkstoffe von elementarer Bedeutung. Hinsichtlich der Chemikalienbelastung ist neben den Grundbestandteilen Erdoel und Erdgas, diversen Foerderhilfen wie aminischen Korrosionsschutzinhibitoren und Bohremulsionen, der Schwefelwasserstoffgehalt von besonderer Problematik. Dieses Gas ist neben der Toxizitaet und seinen korrosiven Eigenschaften auch im Hinblick auf sein aggressives Verhalten gegen elastomere Dichtungswerkstoffe besonders problematisch und aus diesem Grund Gegenstand dieser Abhandlung. (orig.)

Schwarz, T. [Economos Austria GmbH, Judenburg (Austria)

2000-07-01

325

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

Science.gov (United States)

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.

Lee, Jaemyon; Chung, Seungjun; Song, Hyunsoo; Kim, Sangwoo; Hong, Yongtaek

2013-03-01

326

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

International Nuclear Information System (INIS)

[en] 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)

2013-03-13

327

Manipulation of mechanical compliance of elastomeric PGS by incorporation of halloysite nanotubes for soft tissue engineering applications.  

UK PubMed Central (United Kingdom)

Poly (glycerol sebacate) (PGS) is a promising elastomer for use in soft tissue engineering. However, it is difficult to achieve with PGS a satisfactory balance of mechanical compliance and degradation rate that meet the requirements of soft tissue engineering. In this work, we have synthesised a new PGS nanocomposite system filled with halloysite nanotubes, and mechanical properties, as well as related chemical characters, of the nanocomposites were investigated. It was found that the addition of nanotubular halloysite did not compromise the extensibility of material, compared with the pure PGS counterpart; instead the elongation at rupture was increased from 110 (in the pure PGS) to 225% (in the 20 wt% composite). Second, Young's modulus and resilience of 3-5 wt% composites were ?0.8 MPa and >94% respectively, remaining close to the level of pure PGS which is desired for applications in soft tissue engineering. Third, an important feature of the 1-5 wt% composites was their stable mechanical properties over an extended period, which could allow the provision of reliable mechanical support to damaged tissues during the lag phase of the healing process. Finally, the in vitro study indicated that the addition of halloysite slowed down the degradation rate of the composites. In conclusion, the good compliance, enhanced stretchability, stable mechanical behavior over an extended period, and reduced degradation rates make the 3-5 wt% composites promising candidates for application in soft tissue engineering.

Chen QZ; Liang SL; Wang J; Simon GP

2011-11-01

328

Manipulation of mechanical compliance of elastomeric PGS by incorporation of halloysite nanotubes for soft tissue engineering applications.  

Science.gov (United States)

Poly (glycerol sebacate) (PGS) is a promising elastomer for use in soft tissue engineering. However, it is difficult to achieve with PGS a satisfactory balance of mechanical compliance and degradation rate that meet the requirements of soft tissue engineering. In this work, we have synthesised a new PGS nanocomposite system filled with halloysite nanotubes, and mechanical properties, as well as related chemical characters, of the nanocomposites were investigated. It was found that the addition of nanotubular halloysite did not compromise the extensibility of material, compared with the pure PGS counterpart; instead the elongation at rupture was increased from 110 (in the pure PGS) to 225% (in the 20 wt% composite). Second, Young's modulus and resilience of 3-5 wt% composites were ?0.8 MPa and >94% respectively, remaining close to the level of pure PGS which is desired for applications in soft tissue engineering. Third, an important feature of the 1-5 wt% composites was their stable mechanical properties over an extended period, which could allow the provision of reliable mechanical support to damaged tissues during the lag phase of the healing process. Finally, the in vitro study indicated that the addition of halloysite slowed down the degradation rate of the composites. In conclusion, the good compliance, enhanced stretchability, stable mechanical behavior over an extended period, and reduced degradation rates make the 3-5 wt% composites promising candidates for application in soft tissue engineering. PMID:22098880

Chen, Qi-Zhi; Liang, Shu-Ling; Wang, Jiang; Simon, George P

2011-06-06

329

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

2007-01-01

330

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/??GU-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 (?GU-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.

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

2012-01-01

331

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

Science.gov (United States)

...sourced from abroad include: polymer paint, label materials, logo materials, packaging materials, plastic packing, plastic bags, plastic trim pieces and switch covers, rubber spacers, plastic items, rubber gaskets, gaskets, rubber...

2013-07-18

332

"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

333

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 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-propileno-dieno), em formulação ASTM específica para cada tipo de elastômero. Foram avaliadas as propriedades reométricas, mecânicas e morfológicas dos compósit (more) os 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 each elastomer, were prepared. Rheometric characteristics, mechanical properties and the morphology of the compounds developed were evaluated. With the ground scraps incorporati (more) on 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.

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

2007-03-01

334

A DMTA study of the fuel resistance of elastomers  

Energy Technology Data Exchange (ETDEWEB)

One of the major factors that determines the useful lifetime of a polymeric material is the chemical resistance of the polymer to its environment. Knowledge of the chemical resistance of gasket materials to their environment is critical as their failure leads to downtime for the system and increased maintenance costs, as well as fire and safety hazards. In this paper, the results of a dynamic mechanical thermal analysis (DMTA) study of the chemical resistance of several elastomeric materials to naval distillate fuel and aviation turbine fuel are reported. The changes in weight, hardness, mechanical properties and glass transition temperature T[sub g] are used to assess the effect of fuel exposure on the properties of the elastomers

Hiltz, John A.; Morchat, Richard M.; Keough, Irvin A. (Defence Research Establishment Atlantic/Dockyard Laboratory, FMO Halifax, Nova Scotia (Canada))

1993-10-26

335

Study of asbestos exposure in some applications of asbestos materials in the chemical industry.  

UK PubMed Central (United Kingdom)

This study is designed to determine the effects of short-term asbestos exposure on workers in the production of asbestos gaskets and filter materials for technological equipment in the chemical industry. The workers from the "Cathode workshop", "Diaphragm electrolysis", "Polymers" Co., Devnja (12 operators) who operate the installation of asbestos diaphragms manufacture and installation of electrolysis cells, and the staff of the "Mechanical" shop of "Nephtochim" Co., Burgas, engaged in the cutting of gaskets made of pressed asbestos-polymer boards (6 workers), were studied. The hygienic normative standards and methodology for measuring and assessment of the asbestos exposure, used all over the world were applied: mean shift count concentration of respirable asbestos fibres; entire shift personal sampling (BSS 2200-85), PCOM light microscopy (BSS 16909-89). The level of asbestos exposure registered was in the range 0.04 to 0.38 f/cm3 for the operators in the "Diaphragm electrolysis" shop and for the staff in the "Mechanical" shop of "Nephtochim" Co. from 0.04 to 0.43 f/cm3. The established concentrations are acceptable according to the requirements of the official hygienic threshold limit value (TLV) in Bulgaria (1 f/cm3), but because asbestos is a human cancerogen and there is tendency for regular revision with the intention of decreasing the hygienic TLV, the asbestos occupational exposure of these groups of workers cannot be accepted as safe. The statements made increase the necessity of dust control by technical preventive means and the medical control of the workers exposed to asbestos-related injuries.

Strokova B; Evstatieva S; Dimitrova S; Mavrodieva E; Lukanova R

1998-09-01

336

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

UK PubMed Central (United Kingdom)

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

Williams SS; Retterer S; Lopez R; Ruiz R; Samulski ET; DeSimone JM

2010-04-01

337

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-01-01

338

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

Science.gov (United States)

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

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

2010-04-14

339

Optical materials  

CERN Multimedia

Introduction; molecular and crystal structure; physical properties; optical properties of linear materials; optically non-linear materials; laser materials; detector materials; fibre / integrated optics; liquid crystals; power handling capability of optical materials

Wood, Roger M

1993-01-01

340

High-pressure in situ structure measurement of low-Z noncrystalline materials with a diamond-anvil cell by an x-ray diffraction method  

Science.gov (United States)

We have developed techniques for high-pressure in situ structure measurement of low-Z noncrystalline materials with a diamond-anvil cell (DAC) by an x-ray diffraction method. Since the interaction between low-Z materials and x rays is small and the sample thickness in a DAC is also small, the incoherent scattering from the anvils overwhelms the coherent scattering from the sample at a high-Q range. By using a cubic boron nitride gasket to increase the sample thickness and the energy-dispersive x-ray diffraction method with a slit system to narrow the region from which detected x rays are scattered, we can reduce unfavorable effects of the incoherent scattering from the anvils and correct them accurately. We have successfully measured the structure factor of SiO2 glass in a DAC over a relatively wide range of Q under high pressure.

Sato, Tomoko; Funamori, Nobumasa; Kikegawa, Takumi

2010-04-01

 
 
 
 
341

High-pressure in situ structure measurement of low-Z noncrystalline materials with a diamond-anvil cell by an x-ray diffraction method.  

UK PubMed Central (United Kingdom)

We have developed techniques for high-pressure in situ structure measurement of low-Z noncrystalline materials with a diamond-anvil cell (DAC) by an x-ray diffraction method. Since the interaction between low-Z materials and x rays is small and the sample thickness in a DAC is also small, the incoherent scattering from the anvils overwhelms the coherent scattering from the sample at a high-Q range. By using a cubic boron nitride gasket to increase the sample thickness and the energy-dispersive x-ray diffraction method with a slit system to narrow the region from which detected x rays are scattered, we can reduce unfavorable effects of the incoherent scattering from the anvils and correct them accurately. We have successfully measured the structure factor of SiO(2) glass in a DAC over a relatively wide range of Q under high pressure.

Sato T; Funamori N; Kikegawa T

2010-04-01

342

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

343

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

344

Solar Collectors - Sealing and Insulating Materials Outgassing.  

Science.gov (United States)

One reason for a reduced function in many solar collectors is that the covering plate is fogged by the volatile components in the sealing and insulation products. This so called outgassing also deteriorates the functions of the components. A rubber gasket...

K. Eriksson-Widblom

1987-01-01

345

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

Directory of Open Access Journals (Sweden)

Full Text Available Neste trabalho, amostras elastoméricas contendo diferentes tipos de cargas absorvedoras de microondas, sob a forma de pós, foram obtidas para medidas de refletividade. Os materiais utilizados com diferentes composições percentuais em peso foram: ferrocarbonila, negro de fumo, polianilina e ferrita dopadas. 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.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 reflectivity 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

1999-01-01

346

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 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 dopadas. As medidas de refletividade foram determinadas com base nas propriedades magnéticas e dielétricas dos compósitos elastoméricos a partir de dados de espalhamento (more) , 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 reflectivity levels were determined from the magnetic and dielectric properties of the elastomeric composites from scattering data, by fitting the samples in a waveguide, for measu (more) rements 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.

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

1999-12-01

347

Microbial contamination of "as received" and "clinic exposed" orthodontic materials.  

UK PubMed Central (United Kingdom)

INTRODUCTION: Our objective was to determine whether components of fixed orthodontic appliances as received from the manufacturers and after exposure to the clinical environment are free from microbial contamination before clinical use. A pilot molecular microbiologic laboratory study was undertaken at a dental hospital in the United Kingdom. METHODS: A range of orthodontic materials "as received" from the manufacturers and materials "exposed" to the clinical environment were studied for bacterial contamination. After growth on blood-rich media, cultured bacteria were identified by 16S rDNA polymerase chain reaction amplification and sequence phylogeny. RESULTS: Bacteria were isolated from "as received" bands, archwires, and impression trays, but the level of contamination was low (0.5 × 10(1) to 1.825 × 10(2) CFU/mL(-1)). Various bacterial species were isolated from "clinic exposed" bands, archwires, impression trays, coil springs, and elastomeric modules, but the level of contamination was low (0.5 × 10(1) to 8.0 × 10(1) CFU/mL(-1)). The most commonly identified bacterial species was Staphylococcus epidermidis, followed by Kocuria, Moraxella, and Micrococcus species. CONCLUSIONS: New materials "as received" from the manufacturers and those exposed to the clinical environment are not free from bacterial contamination before use in patients, but this contamination is low considering the potential for aerosol and operator contamination and could be considered insignificant. Further studies would be required to determine the level of risk that this poses.

Barker CS; Soro V; Dymock D; Sandy JR; Ireland AJ

2013-03-01

348

Materials science  

International Nuclear Information System (INIS)

[en] The document is a collection of papers on different aspects of materials science. It discusses many items such as surface engineering; physico-chemistry of materials; adhesion; polymers, ceramics and composites; photo materials; microelectronics and fiber optics; nano technology and nano materials; metallic materials, minerals and metallurgy; semiconductors ; civil engineering materials; porous materials and chemistry of environment; biomaterials and biomedical engineering; mechanics, numerical analysis and mathematical modelization

2004-01-01

349

Compatibility of refrigerants and lubricants with elastomers. Quarterly report, 1 October 1992--30 December 1992  

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. 97% of the swell measurements have been made to date. The other 3% of the measurements are contingent on availability of additional 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 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.

1993-01-01

350

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

351

Compatibility of refrigerants and lubricants with elastomers  

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. 97% of the swell measurements have been made to date. The other 3% of the measurements are contingent on availability of additional 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 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.

1993-01-01

352

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

353

Contrast Materials  

Science.gov (United States)

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

354

Nano Materials.  

Science.gov (United States)

Nanomaterials is a new step in the evolution of understanding and utilization of materials. Material science started with the realization that chemical composition is the main factor in determining what a material is. Hereafter it was discovered that the ...

H. Van Heeren

2007-01-01

355

Optical materials  

International Nuclear Information System (INIS)

This book reports on: Diamond films, Synthesis of optical materials, Structure related optical properties, Radiation effects in optical materials, Characterization of optical materials, Deposition of optical thin films, and Optical fibers and waveguides.

1989-01-01

356

Weird materials  

Science.gov (United States)

Heat a material and it gets hotter; heat it enough and it will melt. But some materials will behave rather unexpectedly when heated, and others can act strangely when deformed. Here, three types of weird materials are described - shape memory alloys, Silly Putty® and thermochromic materials - and examples are given of their uses in manufacturing and in the classroom.

Astin, Christina; Talbot, Diane; Goodhew, Peter

2002-11-01

357

Materials management  

Energy Technology Data Exchange (ETDEWEB)

Within the realm of pollution prevention, few approaches offer the diversity in cost and range of opportunities provided by materials management. Improving management of materials generates economic, safety, and environmental benefits within individual departments as well as entire corporations. Efficient and effective materials management includes controlling purchasing, managing materials requirements, minimizing on-site storage, and improving use and reuse of materials--approaches that represent the spirit and intent of pollution prevention.

Bolstridge, J. [GAIA Corp., Silver Spring, MD (United States)

1995-09-01

358

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 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 nos faz indagar: como as tecnologias utilizadas por empresas do setor de polímeros têm feito surgir novos materiais? É possível oferecer soluções de menor impact (more) o 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. T (more) his 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.

Marcos, Haroldo

2012-01-01

359

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

360

Engineered materials  

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-01-01

 
 
 
 
361

Tools & Materials  

Science.gov (United States)

... Tools & Materials. In this section: ... Download educational materials, including a food science curriculum for middle and high school students. ... More results from www.fda.gov/food/foodscienceresearch/toolsmaterials

362

Materials architecture  

Energy Technology Data Exchange (ETDEWEB)

The theme of this sumposium ''Materials Architecture'' should be taken to be a broader from of what is usually understood by microstructure. In this sense materials architecture is concerned with the design of all aspects of the microstructure, texture and also some aspects of the macrostructure. The materreials architecture governs the mechanical and physical properties of engineering materials. All classes of materials are covered within this framwork: metals, ceramics, polymers, amorphous materials, composites. Among the subthemes of the symposium are: mechanical behaviour and deformation mechanicsms, mechanisms of strengthening, annealing processes and engineering properties. The increasing importance of materials in modern society is discussed in a wider framework. The themes covered comprise specific materials and materials processing, resources, industrial research and development, international cooperation and educational aspects. (CLS).

Bilde-Soerensen, J.B.; Hansen, N.; Juul Jensen, D.; Leffers, T.; Lilholt, H.; Pedersen, O.B. (eds.)

1989-01-01

363

Gamma radiation testing methods for organic materials of nuclear use  

International Nuclear Information System (INIS)

Ensuring safe conditions of NPP operation implies identification of environmental conditions of equipment and system operation, developing of refined experimental testing techniques for materials and components, identification of degrading mechanisms. The lifespan of a material can be estimated by theoretical calculations or experimental procedures entailed by operational tests simulating operation conditions. This work presents experimental methods of testing to gamma radiation the organic materials of nuclear use, evaluation of the dose absorbed by the irradiated materials, the degrading effects induced by ionizing radiations. The testing-to-radiation program consists in two stages: - irradiation to gamma fluxes of specific characteristics; - materials characterization by establishing the deterioration level as well as evaluation of lifespan. Still in design phase of Cernavoda NPP the INR Pitesti participated in the program of qualification of materials and equipment with respect to environmental conditions by tests carried out at TRIGA Testing Reactor and SIGMA High Activity Gamma Irradiation Facility. At SIGMA, for instance, in the period 1986-2000 the behavior to gamma radiation was tested for a wide category of products like: motors, cables, illumination systems, plastic and rubber gaskets, adhesives, etc. The aging of these predominantly organic materials usually influenced by ambient conditions (temperature, pressure and humidity) and physical-chemical stresses (vibrations, corrosion, etc) is additionally accelerated by radiation. Depending on destination and operational conditions to which a given material is subjected, the irradiation tests were done in specified conditions, as for instance: - normal ambient parameters; - specified temperature values; - atmospheres different than air; - given pressure values or vacuum; - during a mechanical stress; during an electrical stress. Irradiation capsules of 300 mm diameter and 300 mm height were placed into an irradiation device provided with an external grid able to accommodate a variable number of Co-60 sources in a reproducible geometry. Doses were calculated by aid of Mercurex 3 Code and determined from measurements by the ferrous sulfate standard dosemeter and so the minimum and maximum zones of absorbed doses and consequently Dmax / Dmin dose uniformity ratios were established. The total activity of the SIGMA Irradiation Facility is 91 x 1013 Bq (24,625 Ci), resulting from the 21 Co-60 cassettes each formed of 3 elementary sources encapsulated inside a stainless steel tube of 12 mm diameter and 300 mm length. Testings to dose rates within 1 to 5 kGy/h can be made at SIGMA Facility, while the values of absorbed doses for determining the deterioration level due to irradiation effect are varied within the range 103 to 108 Gy. The results are given for polyethylene, polyamide, vinyle poly-chloride, acryl-nitrilic hydrogenated butadiene rubber and epoxide resins

2001-07-13

364

Audit Materiality  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Materiality is one of the basic and major concepts of auditing. Auditing and Assurance Standard (AAS) (hitherto known as Standard Auditing Practices (SAPs))-13, “Audit Materiality”, states that the concept of materiality recognises that some matters, either individually or in the aggregate, are rela...

Babu, T. R. Ramesh

365

Material problems  

International Nuclear Information System (INIS)

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

1979-10-26

366

Implant material  

UK PubMed Central (United Kingdom)

The invention relates to an implant material based on natural bone, which material is a sintered ceramic material in which the porous fine structure of the bone is present in essentially unchanged form and which comprises more than 99% of hydroxyapatite.

BAUER HANS J; KATZENMEIER BIANCA; KUNTZ MATTHIAS

367

Electrospinning and crosslinking of low-molecular-weight poly(trimethylene carbonate-co-(L)-lactide) as an elastomeric scaffold for vascular engineering.  

UK PubMed Central (United Kingdom)

The growth of suitable tissue to replace natural blood vessels requires a degradable scaffold material that is processable into porous structures with appropriate mechanical and cell growth properties. This study investigates the fabrication of degradable, crosslinkable prepolymers of l-lactide-co-trimethylene carbonate into porous scaffolds by electrospinning. After crosslinking by ?-radiation, dimensionally stable scaffolds were obtained with up to 56% trimethylene carbonate incorporation. The fibrous mats showed Young's moduli closely matching human arteries (0.4-0.8MPa). Repeated cyclic extension yielded negligible change in mechanical properties, demonstrating the potential for use under dynamic physiological conditions. The scaffolds remained elastic and resilient at 30% strain after 84days of degradation in phosphate buffer, while the modulus and ultimate stress and strain progressively decreased. The electrospun mats are mechanically superior to solid films of the same materials. In vitro, human mesenchymal stem cells adhered to and readily proliferated on the three-dimensional fiber network, demonstrating that these polymers may find use in growing artificial blood vessels in vivo.

Dargaville BL; Vaquette C; Rasoul F; Cooper-White JJ; Campbell JH; Whittaker AK

2013-06-01

368

Materials technology assessment of high-temperature solar receivers for fuels and chemicals production  

Energy Technology Data Exchange (ETDEWEB)

Current interest in using solar thermal energy to produce fuels and chemicals has prompted an assessment of materials technology for five proposed designs of solar receivers. The principal process of interest is water splitting. Reaction schemes considered involve the high-temperature decomposition of sulfuric acid, and silicon carbide is the structural ceramic material usually considered most resistant to the conditions of this reaction. Hence we have assessed the fabricability of the designs from SiC for that reaction system, even though most designs envision use with air, helium, or nitrogen as a heat transfer medium. Honeycomb and hemispherical dome receivers have been fabricated from SiC. A receiver using planar coiled tubes has been fabricated from cordierite but not from SiC. Fabrication has not been demonstrated for helical coil and long tube designs. The last three of these should be fabricable with up to two years development. All lack the ultimate test: operational experience. The need for relable seals is common to all designs. Metallic gaskets are subject to corrosion, and ceramic and mechanical seals have not been demonstrated for the anticipated thermal cycling.

Tiegs, T.N.

1981-07-01

369

Materials technology assessment of high temperature solar receivers for fuels and chemicals production  

Science.gov (United States)

Current interest in using solar thermal energy to produce fuels and chemicals has prompted an assessment of materials technology for five proposed designs of solar receivers. The principal process of interest is water splitting. Reaction schemes considered involve the high temperature decomposition of sulfuric acid, and silicon carbide is the structural ceramic material usually considered most resistant to the conditions of this reaction. Hence we have assessed the fabricability of the designs from SiC for that reaction system, even though most designs envision use with air, helium, or nitrogen as a heat transfer medium. Honeycomb and hemispherical dome receivers have been fabricated from SiC. A receiver using planar coiled tubes has been fabricated from cordierite but not from SiC. Fabrication has not been demonstrated for helical coil and long tube designs. The last three of these should be fabricable with up to two years development. All lack the ultimate test: operational experience. The need for reliable seals is common to all designs. Metallic gaskets are subject to corrosion, and ceramic and mechanical seals have not been demonstrated for the anticipated thermal cycling.

Tiegs, T. N.

1981-07-01

370

Composite materials  

International Nuclear Information System (INIS)

[en] 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

1976-01-01

371

Materials engineering  

Energy Technology Data Exchange (ETDEWEB)

This book presents the Proceedings of the Second Materials Engineering Conference. This valuable collection of papers deal with the awareness, creative use, economics, reliability, selection, design, testing and warranty of materials. The papers address topics of both immediate and lasting industrial importance at a readily assimilated level and contain information which will lead speedily to improvements in industrial practice. Topics considered include recent developments in the science and technology of high modulus polymers; computer aided design of advanced composites; a systematic approach to materials testing in metal forming; new cold working tool steels; friction surfacing and its applications; fatigue life assessment and materials engineering; alternative materials for internal combustion engines; adhesives and the engineer; thermoplastic bearings; engineering applications of ZA alloys; and utility and complexity in the selection of polymeric materials.

Bramley, A.N.

1985-01-01

372

Smoking materials  

UK PubMed Central (United Kingdom)

The invention is concerned with a process for improving the smoking properties of a tobacco smoking material in which the tobacco material is subjected to treatment with at least one amylolytic enzyme capable of converting the starch contained in the tobacco into sugar. The amylolytic enzyme or a source thereof may be added to the tobacco material, for example to an aqueous dispersion of the latter.

MITCHELL TERENCE G; PRITCHARD JOHN A

373

Dielectric materials  

Energy Technology Data Exchange (ETDEWEB)

A survey of the application of dielectric materials is given and new developments, problems, and trends are pointed out. Dielectric materials are presented according to their practical application in the field of electrical engineering and communication engineering. Some frequently occurring dielectric materials are characterized more closely at the end of the article. In general, the list of references mentions the studies which have been published within the past 2-3 years.

Fasching, G.M.

1982-02-01

374

Materials development  

International Nuclear Information System (INIS)

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

1976-01-01

375

Scintillator material  

Energy Technology Data Exchange (ETDEWEB)

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography. 4 figs.

Anderson, D.F.; Kross, B.J.

1994-06-07

376

Scintillator material  

Science.gov (United States)

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography. 4 figs.

Anderson, D.F.; Kross, B.J.

1992-07-28

377

Scintillator material  

Energy Technology Data Exchange (ETDEWEB)

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

Anderson, David F. (Batavia, IL); Kross, Brian J. (Aurora, IL)

1992-01-01

378

Scintillator material  

Energy Technology Data Exchange (ETDEWEB)

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

Anderson, David F. (Batavia, IL); Kross, Brian J. (Aurora, IL)

1994-01-01

379

Amorphous materials  

International Nuclear Information System (INIS)

[en] To understand amorphous materials, the difference between crystalline and amorphous materials must be understood, and this requires structure studies. In the first part of this paper X-ray and neutron diffraction by amorphous materials are discussed; the second part is on structure studies for amorphous Si, Se and metals. In the final part some physical properties of amorphous metallic alloys are presented. (author)

1978-06-24

380

Nuclear reactor fuel rod with a tube containing fissile material  

International Nuclear Information System (INIS)

The patent deals with a device to manipulate a fuel rod one end of which contains an opening which can be closed by welding the end gasket after letting in a gas under pressure. The device has a gas-tight end and allows a turn of the fuel rod during welding. (UA/LH)

1975-01-01

 
 
 
 
381

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

International Nuclear Information System (INIS)

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

1983-01-01

382

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

Science.gov (United States)

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

Gauron, Olivier

383

Material Symbols  

Digital Repository Infrastructure Vision for European Research (DRIVER)

What is the relation between the material, conventional symbol structures that we encounter in the spoken and written word, and human thought? A common assumption, that structures a wide variety of otherwise competing views, is that the way in which these material, conventional symbol-structures do ...

Clark, Andy

384

Parachute Materials.  

Science.gov (United States)

The purpose of this paper is to present guidelines for the use of Kevlar and nylon materials in modern parachute systems. Nylon has been used in parachutes for many years, so this discussion will place emphasis upon Kevlar material properties and their ap...

C. W. Peterson D. W. Johnson

1987-01-01

385

Materials; Zairyo  

Energy Technology Data Exchange (ETDEWEB)

Exposed to the menace of foreign cars, Japanese makers are endeavoring vigorously for cost reduction, common use of parts, and review of specifications for parts for manufacturing low-priced cars. Furthermore, strenuous efforts have been made in technological innovation of the engine, weight reduction of the car, and recycling of materials to solve such problems as global warming issue, exhaust gas regulation, and energy saving. In the area of technology for steel material, many kinds of processes are introduced to eliminate heat treatment for contributing to the cost reduction of vehicles, review specifications, eliminate processes, and to improve the yield of materials. In the area of nonferrous metals, aluminum alloy is the most noticeable one for reducing the weight of vehicles even in the future. Magnesium is observed as an excellent material for weight reduction, ranking next to aluminum. In the area of nonferrous metals, research and development have been carried on for ceramic materials, plastic materials, interior materials, rubber materials, glass, and paints. 18 refs.

Kanemaru, H.; Hamano, N. [Hino Motors Co. Ltd., Tokyo (Japan)

1997-08-01

386

Related Materials  

Science.gov (United States)

Related Materials Press Materials NCI Press release: http://www.cancer.gov/newscenter/pressreleases/2011/NLSTprimaryNEJM NCI Q&A on NLST: http://www.cancer.gov/newscenter/qa/2002/nlstqaQA NCI Fast Facts on NLST: http://www.cancer.gov/newscenter/pressreleases/2011/NLSTFastFacts

387

Implant material  

UK PubMed Central (United Kingdom)

The invention relates to an implant material which is based on natural bone and which takes the form of a sintered ceramic material in which the porous fine structure of the bone is essentially unchanged and which has more than 99% hydroxyapatite in its composition.

Bauer Hans-Jörg; Katzenmeier Bianca; Kuntz Matthias Dr.

388

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 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 convencional combinado con ligaduras elastoméricas de baja fricción y ligadura elastomérica convencional. MÉTODOS: se utilizaronbrackets de autoligado SmartClip (3M®) yb (more) rackets 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 bracket and a conventional bracket in combination with low-friction and conventional elastomeric ligatures. METHODS:SmartClip (3M®) self-ligatingbrackets and Gemini (3M®) conventio (more) nal 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.

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

2012-06-01