Abstract: PEB-g-MAN, synthesized by suspension grafting copolymerization of methyl methacrylate and acrylonitrile onto PEB, was blended with styrene-acrylonitrile copolymer (SAN). The mechanical properties, phase structure, and toughening mechanism of the SAN/PEB-g-MAN blends were studied using SEM and TEM. The notched impact strength of the blends (25 % PEB) reached 63.3 kJ/m2, which was nearly 60 times that of neat SAN. When the content of PEB was between 15 %-20 %, a brittle ductile transition was observed. TEM and SEM showed that SAN/PEB-g-MAN were partially compatible. When the PEB content was low, the toughening mechanism of the blends was crack branching and termination with slight cavitation. As the PEB content increasing, the toughening mechanism shifted to extensive cavitation, and further to shear yielding accompanied by cavitation.

Key words: styrene-acrylonitrile copolymer, toughening mechanism, poly(ethene-co-1-butene)-graft-methyl methacrylate-acrylonitrile, phase structure, brittle-ductile transition