Halogenated isobutylene-co-alkylstyrene polymer, preferably halogenated isobutylene-co-methylstyrene polymer, even more preferably brominated isobutylene-co-paramethylstyrene polymer (BIMS), blends thereof, and blends with a second rubber, show improved heat resistance compared to butyl inner tube compositions, and retain the superior barrier properties of butyl inner tube compositions versus inner tube compositions with butyl/EP blends.