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 vulcanized or partially vulcanized particles in a continuous phase of the thermoplastic resin. The dynamically vulcanized alloy also contains an anhydride functionalized oligomer. The alloy maintains a high Shore A hardness value while obtaining improved flowability for processing.