Modified natural rubber latex by graft copolymerization with styrene and diimide hydrogenation

Abstract

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.