Modification of styrene grafted natural rubber by tetraethoxysilane

Abstract

Styrene graft natural rubber (ST-g-NR) was prepared via an emulsion polymerization with redox system of cumene hydroperoxide (CHPO)/ tetraethylene pentamine (TEPA) as initiators. In situ silica filling of ST-g-NR was carried out by using sol-gel reaction of tetraethoxysilane (TEOS) with solid rubber and latex solution method. The effects of reaction condition were studied. For solid rubber method, the effects of catalyst concentration, reaction temperature and reaction time on the in situ silica content were investigated. The in situ silica content increased with the increase of catalyst concentration and reaction time, while the reaction temperature was not affected. The maximum in situ silica content about 50 phr was obtained. For latex solution method, TEOS content, reaction temperature, addition time of TEOS and reaction time were investigated. The in situ silica content increased with the increase of TEOS content and reaction time, while the reaction temperature was not affected. The maximum in situ silica content about 24 phr was achieved when TEOS added after graft copolymerization finished. Moreover, the effects of the conventional silica and in situ silica on the mechanical properties of GNR vulcanizate were also investigated and compared. The mechanical properties of in situ silica filled GNR vulcanizate were higher than those of commercial silica filled GNR vulcanizate. The TEM micrographs indicated that the in situ silica particles were well dispersed in the rubber matrix while the commercial silica particles were agglomerated in the rubber matrix.