ROLES OF SULFUR AND ACCELERATORS IN THE VULCANIZATION OF SBR COMPOUNDS DEDUCED THROUGH SIMULATION

Abstract

ABSTRACT The roles of curatives such as sulfur (S), N-cyclohexylbenzothiazole sulfenamide (CBS), and diphenylguanidine (DPG) in the vulcanization of SBR compounds were deduced from a quantitative discussion of their contribution to the induction period (tind) of cure and the rate constant (kc) for crosslinking reaction. tind and kc of the SBR compounds with different S, CBS, and DPG were determined in the simulation of their rheocurves using a simple kinetic model with these two parameters. The increase of S content caused an appreciable increase of delta torque (Δτ) with negligible influences on tind and kc. By contrast, the increase of the CBS content increased both kc and Δτ while slightly extending tind. DPG significantly shortened tind by accelerating the generation rate of the active sulfurizing species. The regression analysis of tind, kc, and Δτ provided not only a quantitative comparison of the effect of the curatives on rheocurves but also the optimization of the compositions of the SBR compounds in terms of the rate and extent of cure.