Abstract: MBS core-shell graft copolymer was synthesized by grafting methyl methacrylate and styrene on poly(butadiene) (PB) rubber particles via seed emulsion polymerization. The MBS particles were introduced into PVC via melt blending and the effects of MMA and St contents in MBS on dispersion and mechanical property of the blends were investigated. With increasing MMA content, the dispersion of the particles was improved，the impact strength of the blends was increased giving high values above 1117 J/m. When the content of St was low, high impact strengths were still observed, however, too high styrene loadings was harmful to the toughness.

Key words: poly(vinyl chloride), methyl methacrylate, styrene, dispersion morphology, toughening, mechanical property