Natural rubber/in situ silica nanocomposite of a high silica content

By using n-hexylamine as a catalyst of sol-gel reaction of tetraethoxysilane in uncured natural rubber matrix, spherical silica particles of ca. 46 nm were homogeneously generated in situ at a high content, i.e., 71 parts per one hundred rubbers by weight. The mechanical properties of this soft nanocomposite were very unique comparing with those of conventional silica-filled one. Especially, hysteresis loss and permanent set of the former were much lower than those of the latter. The result will be a breakthrough for practical applications of in situ silica filling.