Elastomers classification

Synonyms Polysulfide elastomer Classification Synthetic polymer... 

Densities and crystallinities of ethylene—a-olefin copolymers mosdy depend on their composition. The classification ia Table 1 is commonly used (ASTM D1248-48). VLDPE resias are usually further subdivided iato PE plastomers of low crystallinity, 10—20%, with densities ia the range of 0.915—0.900 g/cm, and completely amorphous PE elastomers with densities as low as 0.860 g/cm. ... 

The principal component of a mbber compound is the elastomer or blend of elastomers chosen for a specific component appHcation. There are 25—30 different chemical classifications of elastomers six of these classes represent over 90% of all elastomers used (see Elastomers, synthetic). 

Fig. 1. SAE J200 Classification system for ASTM No. 3 oil where in volume swell nr = no requirement. EPDM is ethylene—propylene—diene monomer HR, butyl mbber SBR, styrene—butadiene mbber NR, natural mbber VMQ, methyl vinyl siUcone CR, chloroprene FKM, fluoroelastomer FVMQ, fluorovinyl methyl siUcone ACM, acryUc elastomers HSN, hydrogenated nitrile ECO, epichlorohydrin and NBR, nitrile mbber.

The classification given in Table 1 is based on the process, ie, thermosetting or thermoplastic, by which polymers in general are formed into usehil articles and on the mechanical properties, ie, rigid, flexible, or mbbery, of the final product. AH commercial polymers used for molding, extmsion, etc, fit into one of these six classifications the thermoplastic elastomers are the newest. 

Chapters 10 to 29 consisted of reviews of plastics materials available according to a chemical classification, whilst Chapter 30 rather more loosely looked at plastics derived from natural sources. It will have been obvious to the reader that for a given application plastics materials from quite different chemical classes may be in competition and attempts have been made to show this in the text. There have, however, been developments in three, quite unrelated, areas where the author has considered it more useful to review the different polymers together, namely thermoplastic elastomers, biodegradable plastics and electrically conductive polymers. 

Manufacturer Trade Type Grade name elastomer designation Oil content (phr) Mooney viscosity (T + 8 ) at 127 C Ethylene content Diene type Diene content Molecular weight distribution classification... 

In addition to the broad categories of TPs and TSs, TPs can be further classified in terms of their structure, as either crystalline, amorphous, or liquid crystalline. Other classes (terms) include elastomers, copolymers, compounds, commodity resins, engineering plastics, or neat plastics. Additives, fillers, and reinforcements are other classifications that relate directly to plastics properties and performance. 

Elastomer Comparison ASTM D2000-SAEJ200 Classification... 

The broadest classification for plastics is the old thermoplastic and thermosetting . Examples of the former group are polyethylene, polystyrene, and poly-(methyl methacrylate) examples of the latter are urea-formaldehyde condensation polymers, powder coatings based on polyesters, epoxy resins, and vulcanized synthetic elastomers. 

The two major classifications for RIM products are (1) high-density, high-modulus, flexible elastomers and (2) low-density structural foams. Automotive trim and fascia are usually elastomers. Furniture and equipment housings are frequently molded as structural foams (especially when texture and/or sound deadening are included in the product specifications). 

Other Classification Criteria. Other levels of classification should be superimposed on the above. These include latex, suspension, and bulk type syntheses, all of which result in different properties of the final materials. Uses of plastic-forming and elastomer-forming monomers and crystalline and amorphous structures must be distinguished. The tacticity of the polymers is sometimes important. Of course, the ratio of both polymer masses dictates the overall morphology. Physical operations such as swelling, annealing, and orienting must be considered in any complete treatment. 

In the case of cellular rubber, the ASTM uses several classifications based on the method of manufacture [11,12]. Cellular rubber is a general term covering all cellular materials that have an elastomer as the polymer phase. Sponge rubber and expanded rubber are cellular rubbers produced by expanding bulk rubber stocks, and are open-cell and closed- cell, respectively. Latex foam rubber, which is also a cellular rubber, is produced by frothing a rubber latex or liquid rubber, gelling the frothed latex, and then vulcanizing it in the expanded state. 

Semi-flexible foams (or semi-rigid foams) are sometimes classified as subdivisions of flexible foam because the foams have higher load-bearing properties and good compression recovery. Microcellular flexible foams and integral-skin flexible foams may also be classified in this category. In some classifications, however, microcellular foams are classified as elastomers. 

Industry 2823 entitled Plastics Materials and Elastomers, except Synthetic Rubber is in industry group 282, entitled Industrial Organic Chemicals. This group is a part of major group 28, Chemicals and Allied Products. It is in part 1, The Manufacturing Industry Section of the Standard Industrial Classification Code (7). 

Establishments primarily engaged in manufacturing synthetic rubber by polymerization or copolymerization. An elastomer for the purpose of this classification is a rubber-like material capable of vulcanization, such as copolymers of butadiene and styrene, or butadiene and acrylonitrile, polybutadienes, chloroprene rubbers, and isobutylene-isoprene copolymers. Butadiene copolymers containing less than 50 percent butadiene are classified in Industry 2821. Natural chlorinated rubbers and cyclized rubbers are considered as semifinished products and are classified in Industry 3069. 

Thus, we are proposing such a classification system here. The system presented appears broad enough to encompass all specialized industrial urethanes, including elastomers moldings and also the solvent containing urethanes. But first, we must define the base polyurethane. 

Classification of Plastics, Elastomers, and Rubber (NFPA 231C) NOTE The following categories are based on unmodified plastic materials. The use of fire or flame-retarding modifiers or the physical form of the material may change the classification. 

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