A dynamically vulcanized alloy contains at least one isobutylene-containing elastomer and at least one thermoplastic resin, wherein the elastomer is present as a dispersed phase of small particles in a continuous phase of the thermoplastic resin. The elastomer in the alloy is cured by means of a cure system comprising an increased amount of curative and preferably with no cure accelerators present in the cure system. The elastomer obtains at least seventy five percent cure in not more than 15 minutes at temperatures 220° C. or greater.