Physical properties of mma grafted natural rubber film reinforced with in situ silica

Abstract

The improvement in the compatibility and adhesion between natural rubber (NR) grafted with methylmethacrylate (MMA) and silica by two types of vinylated silane, γ-methacryloxypropyltrimethoxysilane (γ-MPS) and vinyltriethoxysilane (VTES) as a coupling agent was reported. In the first step, the NR latex (30%DRC) was grafted with MMA monomer via emulsion polymerization using cumene hydroperoxide/tetraethylene pentamine (CHPO/TEPA) redox system as an initiator. The latex core and PMMA shell feature was found by transmission electron microscopic (TEM) analysis. Graft copolymerization of NR-g-MMA with -MPS or VTES was then proceeded. To generate silica in the grafted NR latex, tetraethoxysilane (TEOS) was mixed with the latex mixture. The composite latex particles appeared to be a core-shell structure with the silica sol forming encompassing the NR core. The silica particles were well dispersed in the rubber matrix as observed by SEM. The conversions of -MPS-TEOS and VTES-TEOS to silica particles in the composite were between 60 to 90%. The results of mechanical test suggested that the vinyl group on the in situ generated silica played an important role in the reinforcement of rubber films.