Aromatic rings as cure sites for EPM elastomers

Terpolymers of ethylene and propylene with 4-phenyl-, 4-o-tolyl, 4-p-tolyl, and 4-(1-naphthyl)-1-butenes were vulcanized with bisbenzylic halides in the presence of highly acidic clays. The halides include bischloromethyldurene, p-bischloromethylbenzene, and p-bisbromomethylbenzene. Since the polymers contain no olefinic unsaturation, the crosslinking is achieved by electrophilic attack of the halide on the pendant aromatic rings. The order of activity is naphthyl > tolyl > phenyl. The new curing system also reacts with olefinic unsaturation. Thus, an EPDM elastomer and SBR rubber, the latter containing both aromatic rings and double bonds, were also readily crosslinked.