IMPACT-MODIFIED NYLON-6 POLYPROPYLENE BLENDS .1. MORPHOLOGY-PROPERTY RELATIONSHIPS

Two types of elastomers grafted with maleic anhydride (MA), an ethylene-propylene random copolymer 9EPR) and a styrene-ethylene/butylene-styrene triblock copolymer (SEBS) were found to function both as impact modifiers and compatibilizers for nylon 6/polypropylene blends. The maleic anhydride grafted to the rubber reacts with the amine end-groups of the polyamide, forming a rubber-nylon 6 graft copolymer that locates at the interface between nylon 6 and polypropylene (PP) and thus acts as a compatibilizer. The SEBS-g-MA material appears to be the most effective compatibilizer. The two rubbers were equally effective for increasing room temperature toughness by dispersing in the nylon 6 phase of the blends. Lower ductile-brittle transition temperatures are obtained when EPR-g-MA rubber is used, owing to its lower T-g and lower modulus at low temperatures compared to SEBS-g-MA rubber. Blend parameters such as rubber content, nylon 6/PP ratio and molecular weight of the components strongly influence the morphology and toughness of the blends. Low ductile-brittle transition temperatures were obtained for blends in which any combination of the above parameters yielded a morphology where nylon 6 was the matrix phase with polypropylene and rubber finely dispersed in it, provided the component molecular weights were high enough to provide adequate intrinsic ductility.