Reinforced and Toughened Polyamide 6
Donald R. Paul, D.M. Laura
University of Texas
USA

Keywords: blends, composites , polyamide

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Engineering thermoplastics, ETPs, are versatile matrices for formulating structural materials useful in a variety of applications. Semi-ductile materials, like polyamide 6, can become "super-tough" when appropriately blended with elastomers or other plastics with a rubbery phase. At the other extreme, ETPs can be reinforced with glass fibers to increase strength and stiffness. The addition of rubber alone decreases stiffness/strength while addition of glass fibers causes a loss in toughness. Thus, in some cases, it is attractive to combine the strategies of rubber-toughening and reinforcement to achieve a balance between toughness versus stiffness/strength. There is very little information in the literature on the issues of optimal formulation, processing, and performance of such "blend-composites," which prompted this research using a polyamide 6 matrix. The rubber phase consisted of maleated ethylene/propylene random copolymers or maleated styrene/ethylene/butene block copolymers; the degree of maleation was used to vary rubber particle size over a wide range. The surface of the glass fibers was treated with silanes that left amine, anhydride, epoxy, or no functionality. The interactions between the chemistries used to react the matrix with the rubber and with the glass fibers plus the processing protocols for combining the components were examined. In addition to simple stress/strain and standard Izod measurements, these materials were also characterized by Essential Work of Fracture and Linear Elastic Fracture Mechanics techniques. Transmission electron microscopy was used to determine the morphology of these materials and to understand deformation mechanisms. The effects of processing technique; rubber type, content, and particle size; and glass fiber content and surface finish on the performance of these materials will be discussed in depth. The mechanisms of fracture and toughening will be of particular emphasis.