Thesis (M.Sc.)--Chulalongkorn University, 2011

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.