Isobutylene-based elastomers include butyl rubber and haloge-nated butyl rubber,and their respective star-branched versions.Due to their impermeability and resistance to heat and oxidation,these polymers find application in tire innerliners and innertubes,curing bladders and envelopes,and other applications where air retention and resistance to heat and oxidation are desired.Butyl rubbers are produced via a cationic polymerization in methyl chloride at temperatures between -90°C and -100°C.These unique attributes and difficult manufacturing requirements place butyl rubbers in the special purpose elastomers category,distinct from general-purpose rubbers such as polybutadiene (BR),natural rubber (NR) and styrene-butadiene rubbers (SBR) (ref.1).
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