EFFECT OF POLYSULFANE SILANIZED SILICA ON THE MORPHOLOGY AND MECHANICAL PROPERTIES OF BROMBUTYL RUBBER VULCANIZATES

Abstract

ABSTRACT Polysulfane silanized white silica particles were prepared by treating with various loadings of bis(3-trie-thoxysilylpropyl)tetrasulfide (TESPT) in a high-speed mixer. Brombutyl rubber (BIIR) vulcanizates filled with the silanized silica were prepared by compression molding. Compared with BIIR/untreated silica vulcanizate, the mechanical properties of BIIR/silanized silica vulcanizates improved prominently with the increase of TESPT loading and reached peak value with the TESPT loading increasing up to 2 phr but declined slightly with the continuous increment of the TESPT. Effects of various loadings of TESPT on the mechanical properties of BIIR vulcanizates were investigated by testing mechanical properties, vulcanizing properties, bound rubber, scanning electron microscopy, and dynamic mechanical analysis (DMA) to determine the extent of rubber-filler interaction. As shown in vulcanizing properties, bound rubber, and DMA measurements, the bound rubber content, cross-link density, and storage and loss modulus of BIIR vulcanizates clearly increased with the TESPT loading increasing from 0 to 2 phr and then reduced somewhat with a continuous increase of TESPT; the tanδmax value decreased significantly with the increment of TESPT loading from 0 to 2 phr and increased sharply with the TESPT content increasing to 4 phr. These experimental results indicate that the improvement in the mechanical properties of BIIR vulcanizates was mostly attributed to a strong BIIR–silica interaction and an effective dispersion of the silica. On the other hand, the decline of mechanical properties can be explained by the excess TESPT, as a kind of physical diluent, having an adverse effect on the silica dispersion and cross-link reaction. By forming the silica aggregates on the mixing, the poor dispersion of silica could cause the decline of relative volume content of silica in the matrix.