Study On Injection Grade Short Carbon Fiber Reinforced Poly(Phthalazinone Ether Sulfone)s

Thermoplastic composite materials with the advantages of high strength and high tenacity, recyclable, environmentally friendly, etc, have been widely used in aerospace, automobile, electronics and other industrial fields. With the development of high technology, the heat resistant injection grade thermoplastic composite materials are in demand and are becoming a hot spot of research.In this paper, a new heterocyclic thermoplastic resins-poly(aryl ether)s containing phthalazinone moiety which can be used at over 230 ℃, were used to research injection molding heat resistant composite materials reinforced by short carbon fiber.Firstly the Tg and structure of poly(phthalazinone biphenyl ether sulfone) (PPBES) and Poly(phthalazinone ether sulfone ketone) (PPESK) were studied. The rheological properties of the target resins were investigated by HAAKE torque rheometer. The result shows that with the increase of processing temperature, the stability region reduces, and then its torque also reduced. At 370℃, the torque platform of PPBES is about 20min and its torque is about 30NM and the torque platform of PPESK is about 10min and its torque is about 35NM, indicating that they can be processed by injection molding.The results show that PPBES displays good melting rheological properties with a Tg of 265 ℃.Then PPBES composites reinforced by chopped fibers (CF/PPBES) were prepared by extruding and then injection. The continuous carbon fibers are fed directly from vent of extruder. The mechanical properties were detected at different temperature. The test results show that as the carbon fiber content increasing, the mechanical properties of CF/PPBES. increase first before decreasing trend. The maximal tensile strength of 135MPa is found when the carbon fiber content is 25%, with the flexural strength of 151MPa. At low temperature (-55℃), the tensile and flexural strength of CF/PPBES are higher than that of the same proportion of carbon fiber in normal and higher temperature. As the testing temperature increases, the tensile strength and flexural strength are decreased. DSC, TGA and TMA are used to analysis the thermodynamic performance of CF/PPBES. The results show that with the increase of carbon fiber content, the Tg and thermal decomposition temperature of the CF/PPBES does not have a big change. The coefficient of heat expansion of CF/PPBES shows an increasing trend with increasing testing temperature, and shows a decreasing trend with increasing the carbon fiber content in the system of CF/PPBES. A scanning electron microscope was used to study the cross-section and the length and distribution of fiber of the composite materials. The result is that the fiber of section distributes well, and the fiber length is relatively uniform and keeps at about 100μm.