Styrenic polymers such as ABS are known to be immiscible with polyamides, particularly in the blend ratios of interest ranging from 1:9 to 9:1 (see e.g. Y. V. Lebedev, et al, J. Applied Polymer Science 25, 2493, 1980).
Due to this mutual incompatibility, simple mechanical blends of ABS and nylon 6 tend to be brittle and readily delaminate when the molded parts are flexed or twisted. U.S. Pat. No. 4,496,690 discloses compositions of modified ABS and nylon blends in which the ABS portion was significantly modified through copolymerization with as much as 10% acrylamide monomer units to obtain useful levels of compatibility and properties.
European patent application #202214 (1986) teaches the use of styrene-acrylonitrile-maleic anhydride terpolymers as compatibilizers for ABS-nylon blends.