Patent ID: 8426524

Claim:
An elastomeric composition comprising: (A) from 60 to 67 parts per hundred rubber of a first hydrogenated acrylonitrile-butadiene rubber, (B) from 4 to 15 parts per hundred rubber of a heat resistant additive, and (C) from 25 to 40 parts per hundred rubber of unsaturated acrylonitrile-butadiene rubber; wherein the heat resistant additive is comprised of about 47 percent by weight of a heat resistant agent and about 53 percent by weight of a second hydrogenated acrylonitrile-butadiene rubber; wherein the first hydrogenated acrylonitrile-butadiene rubber is mixed with the heat resistant additive in a non-productive mixing stage before being mixed with the unsaturated acrylonitrile-butadiene rubber; wherein the elastomeric composition is cured after the addition of the unsaturated acrylonitrile-butadiene rubber using a free radical promoting material and a peroxide co-agent, wherein the free-radical promoting material is a peroxide selected from the group consisting of diacyl peroxides, peroxyesters, dialkyl peroxides and peroxyketals and is used in an amount from about 0.5 to about 7 parts per hundred rubber, and wherein the peroxide co-agent is selected from the group consisting of 1,2 polybutadienes, organic acrylates, organic methacrylates, metal salts of an alpha, beta-unsaturated organic acid and mixtures thereof and is used in an amount from about 2 to about 10 parts per hundred rubber; and wherein the elastomeric composition has an original elongation which is within the range of 140% to 153%, and a retained elongation after being heat aged for 72 hours at a temperature of 266° F. which is within the range of 87% to 96% of the original elongation.