Preparation,microstructures,and properties of long-glass-fiber-reinforced thermoplastic composites based on polycarbonate/poly(butylene terephthalate) alloys

This article investigated the preparation, microstructures, and performance of long-fiber-reinforced thermoplastic polycarbonate/poly(butylene terephthalate) alloys through the joint processing of melt blending followed with a melt pultrusion. The mechanical evaluation demonstrated that the resulting composites achieved significant improvements in tensile strength, flexural strength and modulus, and notched impact strength. Such a prominent reinforcement effect is attributed to the feature that the residual fiber length within the injection-molded long-fiber-reinforced thermoplastic composite specimens is much longer than that of the short-fiber-reinforced ones. This takes full advantage of the strength of the reinforcing fibers themselves. The improvement in impact toughness is due to the energy dissipation by both the fiber pullout and fiber fracture as a result of the long-fiber-reinforcing effectiveness. The scanning electron microscopy investigation confirmed that the fiber pullout and fiber breakage concurred on the impact and tensile fracture surfaces, and the former was more significant than the latter. Meanwhile, the scanning electron microscopy observation also indicated a good interfacial adhesion between the thermoplastic matrix and fibers, which results in the subsidiary enhancement of mechanical properties. The study of dynamic mechanical analysis revealed the long-fiber-reinforced thermoplastic polycarbonate/poly(butylene terephthalate) composites achieved a remarkable increase in storage modulus but presented a considerable decrease in loss-factor magnitude compared to the pristine alloys. The thermal stabilities of the composites were also slightly improved in the presence of long glass fibers according to the results of thermogravimetric analysis.