The mechanical properties and phase morphology of ternary blends of nylon 6 with rubber, e.g., maleated ethylene-propylene random copolymer (EPR-g-MA) or maleated styrene-(ethylene-co-butylene)-styrene (SEBS-g-MA), and a rigid but brittle imidized acrylic polymer (IA) are explored, The objective was to investigate blends which have independently dispersed rubber and rigid polymer particles in a nylon 6 matrix. The amount of rubber was fixed at 20%, while the IA to nylon 6 ratio was varied. Addition of imidized acrylic polymer particles to nylon 6 toughened by EPR-g-MA particles leads to increased stiffness and room-temperature impact strength and does not change the ductile-to-brittle transition temperatures up to a critical level. Similar improvements in stiffness and room temperature impact strength were found for nylon 6 toughened by SEES-type rubber; however, the low temperature impact properties were not as good. (C) 1999 Elsevier Science Ltd. All rights reserved.401439573969