Thermoplastic elastomer composition
 A thermoplastic elastomer composition comprising (A) 10-90 parts by weight of crystalline polypropylene, (B) 10-90 parts by weight of brominated butyl rubber, (C) 10-120 parts by weight of olefinic copolymer rubber to 100 parts by weight of (A)+(B), and (D) 10-150 parts by weight of process oil as plasticizer to 100 parts by weight (A)+(B), all of which are dynamically vulcanized in the presence of a peroxide crosslinking agent. The thermoplastic elastomer composition of this invention has a high gel ratio or gel content in part because brominated butyl rubber is vulcanized with peroxide. The composition has good elasticity, high mechanical strength, low compressively permanent set, excellent long-term heat stability, moldability, and gas impermeability and high damping characteristic. 
Advanced Elastomer Systems, L. P.
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Masaaki Masatoshi Yoshikazu Hisafumi Eiji Shuji
Saito Akami Murakami Endo Sezaki Shimada