Thermoplastic Elastomer

a synthetic polymer that has the properties of a rubber at ordinary temperatures but, like thermoplasts, softens at higher temperatures.

Thermoplastic elastomers have such a combination of properties because they are block copolymers. In the macromolecules of such substances, elastic units, such as polybutadiene, alternate in a specific sequence with thermoplastic units, such as polystyrene. In the processing of thermoplastic elastomers to produce rubber items—for example, footwear—the vulcanization stage is skipped; this is not the case with natural rubbers.