TPEs and TPVs are such niche items that I seriously doubt that you'll ever find them listed in a printed dictionary or encyclopedia. Therefore, I decided to put my definiton on the Web for all to use as needed.
1) TPE and TPV defined:
a) Thermoplastic Elastomeric Rubber (TPE [sometimes referred to as TPER]) — An alloy of rubber and plastic usually that bridges the price/performance gap of the two parent materials. TPEs have many of the physical properties and characteristics of rubber, but process like plastics.
b) Thermoplastic Vulcanizate Rubber (TPV) — Same as a TPE, but the rubber phase of the product is vulcanized (or cross-linked), which provides the finished elastomer with higher chemical resistance and substantially better mechanical properties.
c) (From Handbook of Thermoplastic Elastomers by Benjamin M. Walker and Dr. Charles P. Rader.) TPEs first appeared as commercial entities during the late 1950s, with the introduction of thermoplastic polyurethane elastomers by both B. F. Goodrich and Mobay Chemical. This was followed by the production of styrene butadiene and styrene isoprene block copolymers by the Shell Chemical Company during the middle and late 1960s. a significant innovation in the TPE field was the commercial introduction of copolyester block copolymers by the Du Pont Company during the 1970s, which was followed by the introduction of a group of rubber-plastic blends — primarily polypropylene and EPDM rubber — by the Uniroyal Chemical Company. The 1980s saw introduction of elastomeric alloy thermoplastic vulcanizates (TPVs), by the Monsanto Chemical Company in 1981, and elastomeric alloy melt processible rubbers (MPRs), by the Du Pont Company in 1985. The Monsanto TPV (now Santoprene by ExxonMobil), based upon a unique process of dynamic vulcanization, consists of a two-phase system — a finely divided dispersion of a highly vulcanized rubber phase in a continuous phase of polyolefin.