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

✍ Scribed by B. Morgan; W. J. McGill

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 175 KB
• Volume: 76
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(20000531)76:9<1413::aid-app6>3.0.co;2-d

✦ Synopsis

2-Bisbenzothiazole-2,2Ј-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°C and residual curatives, intermediates, and products were analyzed by HPLC. ZnO enhances MBTS-accelerated sulfur vulcanization, possibly through its formation of Zn(mbt) 2 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-2,2Ј-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) 2accelerator systems lead to similar crosslink densities; only the rate of the reaction is influenced by Zn(mbt) 2 .