Studies on the effects of cyclohexylbenzthiazylsulfenamide accelerated sulfur vulcanization of natural rubber. Part-I. Kinetics of vulcanization

Department of Polymer Science and Technology, University of Calcutta, Kolkata-700 009, India E-mail : bidyutbarank@ yahoo.com Fax: 91-33-3519755 Manuscript received 12 November 2002, revised 23 July 2003, accepted 11 August 2003 Cyclohexylbenzthiazylsulfenamide (CBS) is used as delayed action accelerator for the sulfur vulcanization of elastomers. It is now finding increasing application with ultra accelerators like tetramethyl thiuram disulfide (TMTD) and zinc diethyl dithiocarbamate (ZDC) in the vulcanization of natural rubber (NR). The evaluation of kinetic studies on accelerator blends (CBS/ TMTD and CBS/ZDC) is described. The kinetics of crosslink formation by blend systems vary markedly with formulations and the type of ultra accelerator being used. The crosslinking rate of NR gum stock in the absence of ultra accelerator is first order. However, the blend system gives crosslinking rate of dual nature. The rate shows first order at the initial part (low temperature near about 120°) and higher order at the later part of vulcanization (high temperature near about 140°). The activity of ultra accelerator fragments alters the amine moiety of sulfenamide system according to their chemical structure