Synthesis of POE-graft-methyl methacrylate and acrylonitrile and its toughening effect on SAN resin

POE-graft-methyl methacrylate and acrylonitrile (POE-g-MAN) was prepared by suspension graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto polyethylene-octene copolymers (POE). POE-g-MAN/SAN resin blends (AOMS) were prepared by blending POE-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The effects of reaction conditions on the graft copolymerization and the toughening effect of POE-g-MAN on SAN resin were discussed. The results showed that the optimized reaction conditions were AN/(MMA + AN) ratio of 15 wt%, POE/(POE + MM − AN) ratio of 60 wt%, BPO/(POE + MMA − AN) ratio of 1 wt%, toluene dosage of 44.4 wt%, PVA dosage of 0.4 wt%, SDS dosage of 0.07 wt%, aqueous phase/oil phase mass ratio of 1.5, at 80 °C for 20 h, and when the POE/AOMS mass ratio was 25 wt% under the optimized reaction conditions, the notched Izod impact strength of AOMS reached 54.0 kJ/m2. Fourier transform infrared spectroscopy provided substantial evidence of grafting of MMA and AN onto POE chains, and differential scanning calorimetry showed that the graft branches affected the crystallization of POE chains and made the melt temperature and the fusion heat be lower. Transmission electron microscopy analysis showed that the highest toughness occured when the size of POE-g-MAN particles and the surface to surface interparticle distance were proper. Scanning electron microscopy analysis indicated that the AOMS fracture surface had plastic flow visible which looked like a fibril morphology when POE content was 25 wt% with the AN/(MMA + AN) ratio (fAN) of POE-g-MAN of 15 wt%. The toughening mechanism of AOMS was shear yielding of matrix, which endowed AOMS with remarkable toughness. Dynamic mechanical thermal analysis showed that the compatibility of the POE phase and SAN phase improved after graft copolymerization of MMA and AN onto POE.