Benzothiazole-accelerated sulfur vulcanization. V. 2-bisbenzothiazole-2,2 '-disulfide/ZnO and 2-bisbenzothiazole-2,2 '-disulfide/(2-mercaptobenzothiazole)zinc(II) as accelerators for 2,3-dimethyl-2-butene

摘要

2-Bisbenzothiazole-2,2'-disulfide (MBTS)-accelerated sulfur vulcanization in the presence of ZnO and bis(2-mercaptobenzothiazole)zinc(II) [Zn(mbt)(2)] was studied using 2,3-dimethyl-2-butene (TME) as a model for polyisoprene. Reactions were carried out in sealed tubes at 150 degrees C and residual curatives, intermediates, and products were analyzed by HPLC. ZnO enhances MBTS-accelerated sulfur vulcanization, possibly through its formation of Zn(mbt), on reaction with 2-mercaptobenzothiazole (MBT) released on pendent group formation. Zn(mbt)(2) is an accelerator in its own right, but in conjunction with MBTS, a synergistic effect is observed. Interaction between Zn(mbt)(2) and sulfurated MBT and/or 2-bisbenzothiazole-2,2'-polysulfides (MBTP) is proposed to lead to the more rapid sulfuration of Zn(mbt)(2), while Zn(mbt)(2) catalyzes the crosslinking of benzothiazole-terminated pendent groups formed by the interaction of MBTP with the model compound. When ZnO in the formulation is replaced by Zn(mbt)(2), the induction period before the rapid onset of crosslinking is reduced as the release of MBT required for Zn(mbt)(2) formation is eliminated. MBTS-, Zn(mbt)(2)-, and MBTS/Zn(mbt)(2)- accelerator systems lead to similar crosslink densities; only the rate of the reaction is influenced by Zn(mbt)(2). (C) 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1413-1422, 2000. [References: 22]