Brominated Copolymer of Isobutylene and para-Methylstyrene BIMSM

3 Brominated Copolymer of Isobutylene and para-Methylstyrene (BIMSM) 

Brominated copolymer of isobutylene and para-methylstyrene (DIMS) is the latest new class of synthetic rubber that has been developed for the rubber industry. The sole producer of this new class of elastomer is ExxonMobil, which commercialized it successfully under the trade name Exxpro in the first decade of this new century. The advantage of this new polymer class vs. bromobutyl rubber is that this new elastomer possesses a completely saturated backbone and possesses more reactive benzylic bromine functionality than the bromine sites on the conventional bromobutyl backbone. This means that DIMS reportedly gives superior performance in service vs. BUR. This superiority is shown as better high-temperature resistance, better aging stability than either BUR or EPDM, better weathering resistance, and better ozone resistance. Also, BIMS provides the potential of imparting superior air permeability resistance. 

The quantity of /jara-methylstyrene (PMS) used in this polymerization is small relative to the isobutylene (maybe only 2 to 20 weight percent PMS depending on the grade) while the bromine is even less, perhaps 0.2 to 3 mole percent. The ratio of feedstocks has a great influence on the performance of the BIMSM in rubber compounding. 

BIMSM (official ASTM abbreviation where all rubbers with saturated backbones must end the abbreviation with M) 

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