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

Modification of natural rubber by graft copolymerization and hydrogenation is the significant method for improving the physical, chemical and thermal properties of diene-based elastomers. Natural rubber latex (NRL) was grafted by emulsion graft copolymerization with styrene monomer, using CHPO/TEPA as redox initiator system. The styrene grafted natural rubber (PS-g-NR) was hydrogenated by diimide reduction system in latex form, using hydrazine and hydrogen peroxide with boric acid as catalyst. The hydrogenation level of hydrogenated styrene graft NR H(PS-g-NR) were determined by nuclear magnetic resonance spectroscopy (1H-NMR). At optimum condition of graft copolymerization, the maximum grafting efficiency was 81.5%. In addition, the highest hydrogenation level of 47.2% was achieved at the ratio of hydrazine to hydrogen peroxide at 1:1.1. The thermogravimetric analysis indicated that the thermal stability of H(PS-g-NR) was higher than their parent polymer. From TEM micrograph of hydrogenated PS-g-NR particles, non-hydrogenated rubber core and hydrogenated rubber layer were observed according to the layer model. From mechanical properties of ABS/H(PS-g-NR) blends, the addition H(PS-g-NR) content at 10 %wt in the ABS blends could increased the tensile strength and impact strength of ABS blends. From thermal aging, the addition of H(PS-g-NR) resulted in the more heat resistance of ABS blends than the addition of NR and PS-g-NR. The ABS/hydrogenated graft NR blend named “Green ABS” would have high potential as a new thermoplastic product in plastic industry.