Development of Synergistic Curing Systems for Polychloroprene

Of the dihydric phenols, catechol exhibited a significant synergistic accelerating effect on joint use with TMTD. Aging characteristics of catechol/TMTD accelerated CR vulcanizates were improved when the aromatic nucleus of the catechol was bonded to sulfur. Dicatechol sulfides (XX-125) derived from catechol and S2Cl2 gave improved thermal stability of the vulcanizates. Curing properties of XX-125 seemed enhanced by use with TMTD. A variety of practical CR accelerators has been developed by blending XX-125 with TMTD at the weight ratio to obtain the desired cure rates and physical properties. The essential nature of synergism in these curing systems has yet to be resolved. On detailed practical evaluation of CR vulcanizates cured by these accelerators, XX-125S, -R, -T and -U are suitable substitutes for NA-22 in curing CR.