Dynamically vulcanized blends of nylon, styrene-acrylonitrile copolymer (SAN), and nitrile-butadiene rubber (NBR) were examined for mechanical properties, Shore D hardness, Vicat softening temperature, impact process, and phase morphology. The effect of a curing system such as phenolic formaldehyde resins (PF), dicumylperoxide (DCP), and a sulfur system on the mechanical properties of the nylon/SAN/NBR blends was studied, and dynamic vulcanization with a PF system was found to lead to outstanding toughness of the blends. The effect of PF content on the mechanical properties, Shore D hardness, and heat resistance of the nylon/SAN/NBR blends was also investigated. With increasing PF content the notched-impact strength and Vicat softening temperature (VST) of the nylon/SAN/NBR (50/25/25) blends evidently improved, but tensile strength and Shore D hardness of the blends changed slightly. It can be concluded that the nylon/SAN/NBR (50/ 25/25) blends dynamically vulcanized by high-content PF can attain excellent comprehensive mechanical properties, especially supertoughness, at room temperature. SEM was used to investigate the effect of dynamic vulcanization on disperse-phase particle size, particle size distribution, and phase morphology. It was obvious that disperse-phase particle size decreased with an increasing PF content. Thermal behavior and miscibility of dynamically vulcanized nylon/ SAN/NBR with PF were investigated by DMTA. (C) 2003 Wiley Periodicals, Inc.