Study on the Stress Softening Effect of Silica Filled Vulcanizates

Abstract

Electron spin resonance measurements under the tensile deformation and transmission electron microscopy observations were carried out for silica filled SBR and polyisoprene vulcanizates to discuss on the mechanism of stress softening effect (Mullins effect).It was found that for unfilled vulcanizates, the breakdown of crosslinks and/or chain scission of rubber molecules are responsible for the Mullins effect. By the incorporation of silica into rubber, the Mullins effect was enhanced possibly due to the partial breakdown of silica agglomerates.