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 ( t ind ) of cure and the rate constant ( k c ) for crosslinking reaction. t ind and k c 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 t ind and k c . By contrast, the increase of the CBS content increased both k c and Δτ while slightly extending t ind . DPG significantly shortened t ind by accelerating the generation rate of the active sulfurizing species. The regression analysis of t ind , k c , 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.