Grafting of styrene and methyl methacrylate onto natural rubber in batch emulsion process

Abstract

The graft copolymerization of styrene/methyl methacrylate mixtures onto diene-based polymer seed latex has been carried out using cumene hydroperoxide redox initiator. The diene-based polymers were natural rubber, styrene-butadiene rubber and polybutadiene. The experiments were designed using two fractional factorial design techniques. The monomer conversion, graft copolymer composition and grafting efficiency were determined. The synthesized graft copolymers were purified and then characterized by proton nuclear magnetic resonance (1H-NMR) analysis and differential scanning calorimetry (DSC). Transmission electron microscopy (TEM) was used to study the morphology of the graft copolymers. Grafting efficiency is discussed with respect to the influence of six process factors and the interaction of these factors. The factors studied include the amount of initiator, emulsifier and chain-transfer agent, styrene-to-methyl methacrylate ratio, monomer-to-rubber ratio, and temperature. The analysis of the results from the design showed that only the amount of chain transfer agent and temperature in the range of test had significant effects on grafting efficiency. The mechanism of graft copolymerization has been studied. It appears that the formation of graft copolymers occurs on the surface of the latex particles through a chain-transfer process. The graft copolymer products could be used as an impact modifier for PVC, thus, blends of the graft copolymer products and PVC were prepared. Izod impact strength and tensile properties of the graft copolymer products were investigated