A series of PB-g-SAN impact modifiers (polybutadiene particles grafted by styrene and acrylonitrile) are synthesized by seed emulsion copolymerization initiated by oil-soluble initiator, azobisiobutyronitrile (AIBN). The ABS blends are obtained by mixing SAN resin with PB-g-SAN impact modifiers. The mechanical behavior and the phase morphology of ABS blends are investigated. The graft degree (GD) and grafting efficiency (GE) are investigated, and the high GD shows that AIBN has a fine initiating ability in emulsion grafting of PB-g-SAN impact modifiers. The morphology of the rubber particles is observed by the transmission electron microscopy (TEM). The TEM photograph shows that the PB-g-SAN impact modifier initiated by AIBN is more likely to form subinclusion inside the rubber particles. The dynamic mechanical analysis on ABS blends shows that the subinclusion inside the rubber phase strongly influences the T_g, maximum tan δ, and the storage modulus of the rubber phase. The mechanical test indicates that the ABS blends, which have the small and uniform subinclusions dispersed in the rubber particles, have the maximum impact strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Polybutadiene-g-poly(styrene-co-acrylonitrile) (PB-g-SAN) impact modifiers with different polybutadiene (PB)/poly(styrene-co-acrylonitrile) (SAN) ratios ranging from 20.5/79.5 to 82.7/17.3 were synthesized by seeded emulsion polymerization. Acrylonitrile–butadiene–styrene (ABS) blends with a constant rubber concentration of 15 wt % were prepared by the blending of these PB-g-SAN copolymers and SAN resin. The influence of the PB/SAN ratio in the PB-g-SAN impact modifier on the mechanical behavior and phase morphology of ABS blends was investigated. The mechanical tests showed that the impact strength and yield strength of the ABS blends had their maximum values as the PB/SAN ratio in the PB-g-SAN copolymer increased. A dynamic mechanical analysis of the ABS blends showed that the glass-transition temperature of the rubbery phase shifted to a lower temperature, the maximum loss peak height of the rubbery phase increased and then decreased, and the storage modulus of the ABS blends increased with an increase in the PB/SAN ratio in the PB-g-SAN impact modifier. The morphological results of the ABS blends showed that the dispersion of rubber particle in the matrix and its internal structure were influenced by the PB/SAN ratio in the PB-g-SAN impact modifiers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2165–2171, 2005