Structure and Thermoelasticity of Synthetic Rubber/Silica Composites

Abstract

Melt‐compounded composites of synthetic styrene‐co‐butadiene rubber (BUNA SL18) and silica particles (Silica VN3, Degussa) were characterized by wide‐angle and small‐angle x‐ray diffraction and stretching calorimetry. At low elongations, silica particles provided a considerably weaker reinforcement effect of the rubber matrix when compared to organoclay nanoparticles. The overall thermoelastic behavior of both the rubber/silica composites and the rubber/organoclay nanocomposites could be quantitatively accounted for by a model that explicitly assumed the contributions of local strain amplification for the rubber matrix and of successive decay of a spatial network of filler particles with increasing strain, generating the exothermal effects of external friction between particles. Significantly more intensive heat generation, concomitant to higher amplitudes of stress relaxation in the rubber/silica composites at high uniaxial extensions as compared to the rubber/organoclay nanocomposites, was regarded as evidence for a lower mechanical strength of a spatial network of silica particles.