Fine In Situ Synthesis of Nano-silica Particles in Natural Rubber

Abstract

The reaction condition for sol-gel reaction of tetraethoxysilane in natural rubber was investigated in order to prepare the green nanocomposite materials. N-hexylamine, n-heptylamine and n-oxtylamine were found to be useful for a high in situ silica filling into natural rubber, where silica particles were generated up to ca. 80 parts per hundred rubber by weight in situ. The formation of reverse micelle by the primary alkylamines with a long hydrocarbon segment was important to increase the in situ silica content in the natural rubber matrix. The primary alkylamines with a long hydrocarbon segment had also an advantage as a surfactant to disperse the generated in situ silica particles homogeneously in the rubber matrix. In the sol-gel method reported here, the solubility of catalyst in water was found to be the most influential point for controlling the in situ silica particles in natural rubber. Not only the direct use but also the diluted use of the obtained high in situ silica filled natural rubber were useful to prepare the various kinds of green nanocomposite elastomers. High stress and low hysteresis loss of these materials were achieved. These materials are expected to be new green nanocomposites for rubber industry and technology.