1,3-BUTADIENE, 2-METHYL-, POLYMER WITH 2-METHYL-1-PROPENE 2-Methyl-1,3-butadiene polymer with 2-methyl-1-propene 62493-92-9 9006-49-9 9010-85-9 Butyl rubber Isobutylene/isoprene copolymer Poly(isobutylene-co-isoprene)