Styrene-assisted grafting of maleic anhydride onto deproteinized natural rubber

Abstract

Grafting of maleic anhydride (MA) onto deproteinized natural rubber (DPNR) was carried out using a differential microemulsion polymerization technique. To improve the grafting efficiency (G.E) and reduce the gel content in the grafts, deproteinizing the NR latex was conducted before the grafting reaction and styrene (ST) comonomer was used to increase the G.E. The effects of initiator and monomer concentration, reaction temperature, reaction time, monomer addition rate, and ST/MA ratio on G.E and gel content were investigated. Kinetics of grafting reaction in either the presence or absence of ST was investigated. The results showed that introduction of copolymerizing styrene could significantly improve both the G.E and the grafting content. The G.E increased with increasing ST/MA ratio. The optimal grafting condition was initiator and MA concentrations of 7wt% and 9wt% of dried rubber content, ST/MA mole ratio of 4:1, and MA addition rate of 0.6ml/min at 60°C for 4h. The addition of styrene to the grafting process enhances the graft copolymerization rate of MA grafting onto DPNR.