Thesis (M.Sc.)--Chulalongkorn University, 2009

The in situ generated silica in methyl methacrylate grafted natural rubber (MMA-g-NR) was synthesized through sol-gel reaction of teraethoxysilane (TEOS) using solid rubber method and latex solution method. The graft copolymerization of methyl methacrylate onto natural rubber was carried out using cumene hydroperoxide (CHPO)/tetraethylene pentamine (TEPA) as an initiator. The grafted NR was characterized by FT-IR and NMR analysis. The effects of catalyst concentration, TEOS content, temperature and time on in situ silica content were investigated. For solid rubber method, the in situ silica content increased with increasing the concentration of n-hexylamine, TEOS content, reaction temperature and time and the highest in situ silica content of 48 phr in grafted natural rubber was achieved. For latex solution method, the similar trend of these variables was observed. The in situ silica grafted natural rubber (GNR)/natural rubber (NR) vulcanizates were prepared and the mechanical properties were investigated and compared with commercial silica filled one. The mechanical properties of in situ reinforced NR/GNR vulcanizates were higher than those of commercial silica filled NR/GNR vulcanizate. The TEM micrographs confirmed that the in situ silica particles were well dispersed in GNR matrix while the agglomeration of commercial silica particles was formed in GNR matrix.