Mechanical Engineering Faculty Research


Effect of Rubber Functionality on Mechanical and Fracture Properties of Impact Modified Nylon 6,6/PP Blends

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Tensile and fracture properties of PA6,6/PP blends with 20wt% styrene-ethylene/butylene-styrene triblock copolymers (SEBS) grafted with different levels of maliec anhydride (MA) were studied. It was found that tensile strength and stifness increased with MA level in the 75/25 PA6,6/PP blends but an opposite trend occured in the 50/50 PA6,6/PP regime. The opposite trend in the tensile properties arose from the migration of maleated copolymers from PP phase to the nylon domains when a phase inversion occurred in the 50/50 regime where PP became the dominant phase. An intrinsic strengthening behavior in the interpenetrating network formed by the SEBS copolymers was suggested as the cause for stiffening in the nylon-rich regime PA6,6/PP blends containing 20 wt% SEBS was dramatically altered by the the MA level. It was believed that two competing factors based on the Ramberg-Osgood framework, viz., yield stress (0) and yield strain (E), were responsible for the toughness increase in PA6,6/PP system. When 0 was maintained relatively high and steady, E became the overriding factor in 75/25 PA6,6/PP blends; wheres in the case of relativity low and drastic reduction in 0, toughness became driven by 0 alone.

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