Abstract: Styrene-EPDM一acrylonitrile tripolymer(EPDM-g-SAN)was prepared by grafting styrene
(St) and acrylonitrile(AN)onto ethylene-propylene-dime mischpolymer ( EPDM) via phase inversion emulsion copolymerization using benzoyl peroxide as an initiator and n-heptane as a solvent. AES was obtained via melt blending the prepared EPDM-g-SAN with SAN resin. the effects of weight ratios of AN/St and EPDM/co-monomers on the monomer conversion and degree of grafting were investigated DSC and DMA showed that EPDM-g-SAN and SAN resin were partially compatible. TEM and SEM indicated that when AN weight percentage was 35 wt，the interface between two phases became smeared, EPDM-g-SAN dispersed finely in the SAN matrix. When AN weight percentage in the comonomers was between 35 wt % and 40 wt，the degree of grafting was about 35%，the notched Izod impact strength of AES reached 50 .7 kJ/m2.the main toughening mechanism was cavitation accompanied with shear yielding.

Key words: ethylene-propylene-dime mischpolymer, phase inversion, graft copolymerization, structore;property;styrene-EPDM一acrylonitrile tripolymer and styrene-acryonitrile copolymer blend