The present invention reveals a polymer alloy which is comprised of (a) at least one highly unsaturated rubbery polymer which is covulcanized with at least one N-chlorothio-sulfonamide modified EPDM rubber and (b) at least one thermoplastic resin. A blend of polypropylene with nitrile rubber which has been cocured with an N-chlorothio-sulfonamide modified EPDM rubber is a representative example of such a polymer alloy.