Effect of Curing Additives on the Dispersion Kinetics of Carbon Black in Rubber Compounds)

Abstract

The effect of curing additives on the dispersion kinetics of carbon black (CB) in styrene butadiene rubber (SBR) compounds was investigated by means of the method of the online measured electrical conductance. Addition of curing additives such as stearic acid and diphenylguanidine (DPG) accelerates the CB dispersion process significantly. The viscosity of the rubber matrix was not changed after their addition. The addition of stearic acid and DPG may alter the filler–filler interaction that consequently leads to faster dispersion processes. The obtained difference in morphologies of SBR mixtures containing stearic acid and DPG, respectively, are caused by their different infiltration behavior, which may lead to different dispersion mechanisms. Addition of ZnO could not improve the dispersion process of CB because of its limited interaction with CB. Sulfur and N-cyclohexylbenzothiazole-2-sulfenamide decelerate the CB dispersion process. The strong effect of the rubber microstructure such as styrene content and molecular weight on the CB dispersion in SBR mixtures without additives was found and discussed by taking into consideration the known dispersion mechanisms. The influence of addition of curing additives on the CB dispersion in low styrene-content SBR mixtures is much more pronounced than that in high styrene-content SBR mixtures.

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“…Thus, an outer layer surrounding carbon black particles is formed and reduces the agglomeration. This will lead to a better carbon black dispersion level in rubber matrix (Le et al, 2011). However, rising the concentration of MBTS or CBS along with fixed DPG concentration is insensitive to the viscosity changes as it remains constant.…”