6 - Thermoset Elastomers

Abstract

Elastomers are defined by their very large deformability with essentially complete recoverability. For a material to exhibit such elasticity, it must consist of polymeric chains; these must have a high degree of flexibility and mobility and be joined into a network structure by cross-linking pairs of segments, thereby preventing stretched polymer chains from irreversibly sliding past one another. These elastomers are frequently included in the category of “thermosets,” which are polymers with a network structure that is generated or “set” by thermally induced chemical cross-linking reactions. The term often takes on the more specific meaning of networks that are very heavily crosslinked and below their glass transition temperatures. These are very hard materials with none of the high extensibility associated with typical elastomers. Applications of thermoset elastomers include tires, gaskets, drive belts, biomedical devices (e.g., contact lenses, prostheses, catheters), and parts of living organisms (e.g., skin, veins, heart, and lung tissue).