SULFUR VULCANIZATION OF POLYISOPRENE ACCELERATED BY BENZOTHIAZOLE DERIVATIVES .1. COMPARISON OF SULFUR AND 2-MERCAPTOBENZOTHIAZOLE ACCELERATED REACTIONS

Polyisoprene compounds with sulfur and with sulfur and 2-mercaptobenzo thiazole (MET) were volcanized by heating in a differential scanning c alorimeter (DSC) at a programmed rate. The reaction was stopped at var ious temperatures along the thermogram and the product analyzed by det ermining the crosslink density and crosslink type, and by determining the amount of extractable curatives and soluble reaction products by h igh-performance liquid chromatography. DSC cure curves and plots of cr osslink density and extractable sulfur vs. temperature for the unaccel erated and MBT accelerated compounds can be made to coincide by shifti ng them along the temperature axis. It is suggested that MBT accelerat ed sulfur vulcanization occurs by the same mechanism as unaccelerated sulfur vulcanization, with SH+ ions from MBT adding across the carbon- carbon double bond, thus increasing the rate at which the reaction is initiated. (C) 1995 John Wiley & Sons, Inc.