Graft copolymerization of styrene onto hydrogenated natural rubber latex

Abstract

Natural rubber (NR), one of biodegradable materials is normally applied in many industries. However, NR has poor thermal and oxidative resistance due to its highly carbon-carbon double bonds in structure caused to limitation in severe conditions. Thus, the chemical structure of NR should be improved via hydrogenation and graft copolymerization for extending its application. In this research, the NR latex was hydrogenated via diimide reduction and then grafted with styrene (ST) or ST/methyl methacrylate (MMA) by using redox initiator. The monomer conversion and grafting properties of hydrogenated NR latex (HNRL) were reported as functions of hydrogenation level, monomer and initiator concentrations, reaction temperature and reaction time. The resulted grafted HNR (GHNR) was then blended with acrylonitrile-butadiene-styrene (ABS) resin with a ratio of GHNR/ABS=10/90 (w/w). The results indicated that the ABS containing HNR grafted with ST (GHNR(ST)) or ST/MMA (GHNR(ST/MMA)) had higher flexural strength (96.9 and 99.8 MPa, respectively) than HNR (78.5 MPa). This result confirms by using a scanning electron microscopy (SEM) of the fractural surfaces exhibited the more homogeneity and compatibility in the ABS containing grafted HNRs. Moreover, the glass transition temperature (T[subscript g]) of ABS decreased when GHNR(ST) or GHNR(ST/MMA) with lower T[subscript g]) values were applied possibly due to the partial miscibility of grafted HNRs in the ABS phase.