Improvement of natural rubber properties by modification of silica surface using a continuous admicellar polymerization system

Abstract

Fillers such as silica are often added to rubber to improve performance in commercial applications. The use of silica in rubber compounds provides beneficial properties such as improved reinforcement. A major problem with using commercial silica as a filler is that porous structure of silica can adsorb accelerators, leading to deactivate vulcanization. Moreover, adidity of silica surface can retard cure time. Those actions may affect poor compatibility between the silica and rubber. In practical, improvement silica properties can be achieved by admicallar polymerization to modify the surface characteristics. Currently, this process has been successfully performed only in a batch reactor, which is not feasible for industrial applications. In this work, a continuous reactor for the admicellar polymerization was developed. Cetyltrimethylammonium bromide, styrene and isoprene were used as surfactant and co-monomers, respectively. The results showed that modification of the silica surface reduced the BET surface area and increased the mean agglomerate particle size for all samples. Scanning electorn micrographs showed the increase in the particle agglomeration Fourier transform infrared spectroscopy proved the existence of polystyrene and polyisoprene on the modified silica. The use of the modified silica in rubber compounds significantly reduced T90 cure times and improved modulus, abrasion resistance, and resilience. The optimum conditions for silica modification were 5 g co-monomer loading per 1 kg silica at 30 min retention time.