The field of thermoplastic elastomers (TPEs) has been growing rapidly during the last two decades. A number of classes of TPE have been commercialized and have been widely adopted in many applications across most industries. The thermoplastic vulcanizates (TPVs) are the class of TPEs with a cross-linked rubber phase, which has the performance of thermoset rubbers. The TPVs are growing most rapidly of the TPEs and attention to their processing is important to understanding TPEs. The other TPEs generally can be described as block copolymer or a polymer blend. A block copolymer is a TPE where one region is rubber and the other has a rigid nature, and includes styrene block copolymers (SBCs) (e.g. styrene-butadiene-styrene (SBS)), copolyester TPEs (COPEs), thermoplastic urethanes (TPUs), copolyamide TPEs (COPAs) and melt-processible rubber (MPRs). The third division of the classes of TPE are described as rubber / plastic blends. These include thermoplastic olefins (TPOs) where EP rubber and polypropylene are blended and the polyvinyl chloride / nitrile rubber blends (PVC/NBRs).