Thesis (M.Sc.)--Chulalongkorn University, 1997

The graft copolymerization of methyl methacrylate and styrene onto natural rubber in the emulsion process was studied. The graft copolymerization was carried out by varying concentration of methyl methacrylate and styrene monomers, emulsifier concentration, initiator concentration, and reaction temperature. The grafting efficiency, graft ratio and degree of monomers conversion were reported. The molecular weights of free S/MMA and the frequency of graft chain on backbone rubber were determined by the gel permeation chromatography (GPC) technique. The copolymer composition was determined by nuclear magnetic resonance spectroscopy (NMR), and elemental analyzer. The optimum conditions of graft copolymerization were 100 parts by weight of monomer per 100 parts by weight of natural rubber latex, the emulsifier concentration of 1.5 parts by weight, the initiator concentration of 1.5 parts by weight, and temperature of 70 ํC for 8 hours. The grafted natural rubber product could be used as an impact modifier for PVC was studied. The grafted natural rubber product (5, 10, 15, and 20 phr) and PVC blend were prepared. The effect of grafted natural rubber product and PVC ratio on tensile properties, lzod impact strength, and hardness were investigated. The tensile strength and hardness decreased with increasing the grafted natural rubber product, but the elongation at break and impact strength increased with increasing the grafted natural rubber. The appropriate grafted natural rubber product used were 10 and 15 phr.