Patent ID: 8841383

Claim:
An elastomer composition comprising a blend of: (a) 15 to 25 phr of an ethylene-propylene-diene terpolymer comprising: at least 60 wt % propylene-derived units, from 0.5 to 20 wt % ethylene-derived units, and from 0.3 to 10 wt % diene-derived units, based on the total weight of propylene-derived units, ethylene-derived units, and diene-derived units, wherein the terpolymer has: isotactic propylene triad tacticity of 65 to 95%, a melting point by DSC equal to or less than 110° C., and a heat of fusion of from 5 J/g to 50 J/g; (b) 75 to 85 phr of a blend rubber selected from the group consisting of natural rubbers, polyisoprene rubber, poly(styrene-co-butadiene) rubber, polybutadiene rubber, poly(isoprene-co-butadiene) rubber, styrene-isoprene-butadiene rubber, butyl rubber, star branched butyl rubber, poly(isobutylene-co-alkylstyrene), polychloroprene rubber, nitrile rubber and mixtures thereof; (c) 2 to 20 phr of polybutene processing oil, wherein the polybutene processing oil comprises from 40 to 98 wt % isobutylene derived units, from 2 to 40 wt % 1-butene derived units, and from 0 to 40 wt % 2-butene derived units; and (d) a secondary blend rubber comprising an ethylene-propylene-diene rubber having a crystallinity that is due to ethylene-derived sequences.