Texas 7871 2 SYNOPSISThe morphology and the mechanical properties of polycarbonate (PC) blends with different acrylonitrile-butadiene-styrene (ABS) materials were investigated. PC/ABS blends based on a mass-made ABS with 16% rubber and large (0.5-1 pm) rubber particles are compared to blends based on an emulsion-made ABS with 50% rubber and small, monodisperse (0.12 pm) rubber particles over the full range of blend compositions. The blends with the bulk ABS showed excellent impact strength for most compositions, and those containing 50 and 70% PC exhibited ductile to brittle transition temperatures below that of PC. The blends with the emulsion ABS showed excellent toughness in sharp notch Izod impact tests a t room temperature and in standard notch Izod impact tests a t low temperatures near the Tg of the rubber. By melt blending the various ABS materials with a styrene-acrylonitrile (SAN 25) copolymer, materials with lower rubber concentrations were obtained. These materials were used in blends with PC to make comparisons at constant rubber concentrations of 5,10, and 15%. The results of this investigation show that brittle ABS materials can produce tough PC-ABS blends. It is apparent that small rubber particles toughen PC-ABS blends a t lower rubber concentrations and a t lower temperatures than is possible with large rubber particles. However, additional work is needed to understand the nature of toughening in these PC-ABS blends with different rubber phase morphologies. It is of particular interest to understand the exceptional ductility of some of the blends at low temperatures.