Mechanical, tribological and thermal properties of injection molded short carbon fiber/expanded graphite/polyetherimide composites

In this work, polyetherimide (PEI) modified by short carbon fibers (SCFs) and expanded graphite (EG) composites were fabricated using highly efficient extrusion compounding and injection molding techniques. The effects of SCF-EG hybrid on the mechanical, tribological and thermal properties of PEI composites were examined. It is shown that the tensile and flexural strength as well as fracture toughness of the PEI composites increase monotonically with increasing the relative SCF-EG content. The SCF/EG/PEI hybrid composites show synergies in the Young's modulus and flexural modulus. Moreover, the SCF-EG hybrid leads to the positive synergistic effects in significantly enhancing tribological performance of the PEI hybrid composites. SEM images for the fracture surfaces after tensile testing and the worn surfaces after wear testing of the hybrid composites were employed for explaining the observations for the mechanical and tribological properties. In addition, the PEI composites exhibit a significant reduction in the coefficient of thermal expansion and a moderate increase in thermal conductivity with the incorporation of SCF-EG hybrid. Due to the low cost of EG and its synergistic effects with SCFs, it is promising to fabricate high performance PEI hybrid composites by the simultaneous addition of SCFs and EG.