Bromobutyl (BIIR) is a copolymer of isobutylene and small amounts of brominated isoprene which provides unsaturated sites for vulcanization. This elastomer has many of the attributes of butyl rubber, including low gas and moisture permeability, good vibration damping, low glass transition temperature, excellent resistance to ageing and weathering, and wide vulcanization versatility. The introduction of bromine increases adhesion to other rubbers and metals and provides much higher curing rates (i.e. lower amount of curative are required). Furthermore, brominated butyl can be co-vulcanized with general purpose high-unsaturation elastomers, such as natural rubber, polybutadiene, and styrene-butadiene rubber, while maintaining the mostly saturated backbone structure.