Natural rubber-g-methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber u sing potassium persulfate as an initiator was carried out by emulsion polym erization. The rubber macroradicals reacted with MMA to form graft copolyme rs. The morphology of grafted natural rubber (GNR) was determined by transm ission electron microscopy and it was confirmed that the graft copolymeriza tion was a surface-controlled process. The effects of the initiator concent ration, reaction temperature, monomer concentration, and reaction time on t he monomer conversion and grafting efficiency were investigated, The grafti ng efficiency of the GNR was determined by a solvent-extraction technique. The natural rubber-g-methyl meth acrylate/poly(methyl methacrylate) (NR-g-M MA/PMMA) blends were prepared by a melt-mixing system. The mechanical prope rties and the fracture behavior of GNR/PMMA blends were evaluated as a func tion of the graft copolymer composition and the blend ratio. The tensile st rength, tear strength, and hardness increased with an increase in PMMA cont ent. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. (C) 2001 John Wiley & Sons, Inc.