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Suspension Grafting Copolymerization of EPM-g-MAN and Its Toughening Effect on SAN Resin

EPM-graft-methyl methacrylate and acrylonitrile (EPM-g-MAN) was synthesized by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto ethylene—propylene bipolymer (EPM) using the method of suspension polymerization. A novel engineering plastic with high impact strength, AEMS, which shows excellent resistance to weatherability and yellow discoloration and aging properties, were prepared by blending EPM-g-MAN with styrene—acrylonitrile (SAN) resin. The influence of the suspension grafting copolymerization technologies, including monomer ratios, EPM ratios, initiator content on monomer conversion ratio, grafting ratio, grafting efficiency, and the impact strength of AEMS, were investigated. The result showed that the optimized reaction conditions were obtained when the mass ratio of AN/MMAAN(fAN) was 15 wt%, the mass ratio of EPM/(EPM + MMA-AN) was 60 wt%, and the mass ratio of BPO/(EPM + MMA-AN) was 0.6 wt%. When the EPM/ AEMS mass ratio was 25 wt%, the notched Izod impact strength of AEMS reached 55.9 kJ/m2. DSC and DMA analysis showed that the compatibility of EPM-g-MAN and SAN resin improved when the grafting chain polarity was appropriate. Transmission electron microscopy analysis showed that EPM phase was the near continuous phase in the shape of bead string with diameter of about 0.15 μm and had good compatibility with SAN resin. Scanning electron microscopy analysis indicated that AEMS fracture surface appeared ‘root beard’ morphology. These phenomena indicated that the toughening mechanism was shear yielding of matrix, which endowed AEMS with remarkable toughness.