Thermoplastic elastomer

Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplastic and elastomeric properties. While most elastomers are thermosets, thermoplastics are in contrast relatively easy to use in manufacturing, for example, by injection molding. Thermoplastic elastomers show advantages typical of both rubbery materials and plastic materials. The benefit of using thermoplastic elastomers is the ability to stretch to moderate elongations and return to its near original shape creating a longer life and better physical range than other materials. The principal difference between thermoset elastomers and thermoplastic elastomers is the type of cross-linking bond in their structures. In fact, crosslinking is a critical structural factor which imparts high elastic properties.

There are six generic classes of commercial TPEs:

Examples of TPE products that come from block copolymers group are Thermolast, Hipex, Copec, For Tec E, Santoprene, Termoton, Arnitel, Solprene, Engage, Hytrel, Dryflex, Mediprene, Kraton, and Pibiflex. Examples of TPV are Thermolast A, Thermolast V, Hipex, Forprene, Termoton-V and Vegaprene. Examples of Styrenic block copolymers (TPE-s) are Thermolast K, Thermolast M, Sofprene, and Laprene. An example of Thermoplastic polyurethanes (TPU) compound is Copec. An example of Thermoplastic olefins (TPO) compound is For-Tec E.

In order to qualify as a thermoplastic elastomer, a material must have these three essential characteristics:

It was not until the 1950s, when thermoplastic polyurethane polymers became available, that TPE became a commercial reality. During the 1960s styrene block copolymer became available, and in the 1970s a wide range of TPEs came on the scene. The worldwide usage of TPEs (680,000 tons/year in 1990) is growing at about nine percent per year. The styrene-butadiene materials possess a two-phase microstructure due to incompatibility between the polystyrene and polybutadiene blocks, the former separating into spheres or rods depending on the exact composition. With low polystyrene content, the material is elastomeric with the properties of the polybutadiene predominating. Generally they offer a much wider range of properties than conventional cross-linked rubbers because the composition can vary to suit customer needs.

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