Standard elastomer tests

Part 1 Trouser, angle, and crescent test pieces Part 2 Small (delft) test pieces Standard test method for tear strength of conventional vulcanized rubber and thermoplastic elastomers Testing of rubber and elastomers Determination of the tear strength of elastomers Trouser test piece... 

This brief summary report describes the state of the art of all types of cellular materials, particularly plastics and elastomers. The report is organized in the form of a handbook and has an Introduction and sections on Types of Foams (Cellular Materials), Methods of Manufacture, Foam Properties, Solvent Cementing and Adhesive Bonding of Foams, Methods of Making Foams Conductive, and Applications. There are two Appendices, one on Standardization Documents (Test Methods, Practices and Specifications) and the other on Definitions. 

It should be noted that plastics and elastomers have impact strengths that are very dependent on temperature and rate of impact. At low temperatures, below the glass transition temperature, most plastics and elastomers will behave as brittle materials with a significant reduction in impact strength. Likewise, when tested at very fast rates, most plastics and elastomers will act as brittle materials because the polymeric molecules are not allowed to slip by on another but simply break. At times, low temperatures have been used to simulate fast rates of strain (e.g., explosive discharge) that cannot be accomplished easily on standard laboratory test machines. 

The simplest deformations are isotropic compression under hydrostatic pressure, uniaxial extension (or compression), and simple shear. They are used to determine the bulk modulus K, Young s modulus E, and shear modulus G, respectively (37-44). Elastomer testing for commercial applications is highly dependent on the method, the conditions (eg, strain rate, temperature), and the shape of the samples. Therefore, mechanical tests have been standardized for imiformity and simplicity by the American Society for Testing and Materials (ASTM) (45). 

The effects of temperature alone on physical properties are well known. High-temperature test results for several elastomers are shown in Table 16 A. 1 [2]. Note the dramatic loss of tensile strength and elongation for temperatures above the standard laboratory test temperature. 

International Rubber Hardness. The International mbber hardness test (ASTM D1415) (2) for elastomers is similar to the Rockwell test ia that the measured property is the difference ia penetration of a standard steel ball between minor and major loads. The viscoelastic properties of elastomers require that a load appHcation time, usually 30 seconds, be a part of the test procedure. The hardness number is read directly on a scale of 0 to 100 upon return to the minor load. International mbber hardness numbers are often considered equivalent to Durometer hardness numbers but differences ia iadenters, loads, and test time preclude such a relationship. 

Specialty Elastomers. Polychloroprene and polysulfide mbber were the first synthetic specialty elastomers discovered. Since theh invention in the 1930s the total number of classes of synthetic mbbers has grown to almost 30. The foUowing lists standard acronyms by the International Synthetic Rubber Producers (IISRP) and the American Society for Testing and Materials (ASTM) for several specialty elastomers. 

Quahty control testing of siUcones utilizes a combination of physical and chemical measurements to ensure satisfactory product performance and processibihty. Eor example, in addition to the usual physical properties of cured elastomers, the plasticity of heat-cured mbber and the extmsion rate of TVR elastomers under standard conditions are important to the customer. Where the siUcone appHcation involves surface activity, a use test is frequently the only rehable indicator of performance. Eor example, the performance of an antifoaming agent can be tested by measuring the foam reduction when the sihcone emulsion is added to an agitated standard detergent solution. The product data sheets and technical bulletins from commercial siUcone producers can be consulted for more information. 

Prut, E.V., Zelenetskii, A.N., Chepel, L.M., Erina, N.A., Dubnikova, I.L., and Novikov, D.D., Thermoplastic elastomer composition and the way of its manufacturing, Russian Patent 206927/B.I., 32, 1996. ASTM. Standard Test Method for Vickers Hardness of Metallic Materials, 1987. 

Butyl rubber - This material generally had the least endurance in fatigue tests, but it may be adequate for some cardiovascular applications. Advantages include less sensitivity to stress concentrators than Pellethane, a very low permeability to fluids, a moderate creep resistance and widespread availability at low cost. Disadvantages include a relatively low fatigue resistance compared to the elastomers specifically designed for these applications. The rubber tested was not designed for medical applications and had standard rubber additives and modifiers that were cytotoxic unless the material was extracted after manufacture. 

When testing the effect of low temperatures on elastomers it is rarely sufficient merely to enclose the standard apparatus in a refrigerated chamber special procedures are necessary. The relevant standard is BS 903 Part A13. Method for determination of stiffness at low temperatures (Gehman test). 

The TPEs are often tested with elastomer standards some thermoplastics and TPEs are used as adhesives. Sometimes PE and more rarely PVC are crosslinked. Consequently, the following standards, while mainly concerning thermoplastics and composites, also include adhesives and elastomers. 

As it was recognized that the number of variations included in many test method standards was not helpful in respect of obtaining input for databases, there was an initiative in the plastics industry that produced international standards for acquisition and presentation of single and multipoint data. These specify the particular test methods and test conditions to produce strictly comparable data. Very recently, this approach has been taken up in ISO TC 45 and drafts circulated based on British standards4, 5. These standards are not explicit about including thermoplastic elastomers and, as discussed in Chapter 2, Section 9, an acquisition standard for these materials has been proposed in ISO TC 61, Plastics. An example of the problems resulting from lack of consensus on test methods was evident for EPDM polymers and the results of collaboration to rectify this have been published6. 

Whilst thermoplastic elastomers are being included in most test method standards, we do not have a procedure for their preparation and moulding. 

Rubber, vulcanized or thermoplastic Determination of tensile stress-strain properties Standard test methods for vulcanized rubber and thermoplastic elastomers-tension... 

Rubber, vulcanized Determination of the effect of liquids Standard test method for rubber property-effect of liquids Standard test method for rubber property Change in length during liquid immersion Determination of the behavior of rubbers and elastomers when exposed to fluids and vapors Determination of the effect of liquids Determination of equilibrium water vapor absorption... 

The evaluation of erosive wear of elastomers has not been standardized, and most industries test the erosive wear by using methods designed to simulate conditions relevant to their operations. 

Thermal analysis is a useful tool in the quality control of many incoming routine materials, which can be tested against a reference standard developed internally by analysing a large number of samples of known performance criteria to ensure that the quality of supplies is maintained. Solid elastomers can be identified by glass transition temperature (Tg) [70]. The rubber industry uses thousands of different raw materials, and this number is steadily increasing. These materials are listed in [172]. 

To relate the physical properties of carbon black to rubber properties, we tested these tread blacks in the ASTM natural rubber recipe and in an SBR 1500 test recipe. In both elastomers, we checked standard stress/strain properties of modulus, tensile strength, and hardness. In the natural rubber recipe we also tested Firestone running temperature and rebound, and Goodyear rebound. In the SBR we checked percent swell, extrusion rate, viscosity, and laboratory abrasion. 

Fire-Rated Valves that handle flammable fluids may have additional safety-related requirements for minimal external leakage, minimal internal (downstream) leakage, and operability during and after a fire. Being fire-rated does not mean being totally impervious to fire, but a sample valve must meet particular specifications such as those of American Petroleum Institute (API) 607, Factory Mutual Research Corp. (FM) 7440, or the British Standard 5146 under a simulated fire test. Due to very high flame temperature, metal seating (either primary or as a backup to a bumed-out elastomer) is mandatory. 

Fig. 6. Stress-strain diagrams of standard test samples consisting of PMMA and 0, 10, 25, and 100 wt. % (graphs 1-4) of PMMA grafted silicone elastomer particles (powder from Fig. 3a)...

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