Soluble semi-aliphatic polyimide sizing in CF/PEI composites for improving mechanical performance and hydrothermal aging resistance

Carbon fiber reinforced thermoplastics (CFRTP) inherited special advantages from the thermoplastics, which caused the demand for soaring. However, due to its high molding temperature and the absence of reactive groups, traditional carbon fiber sizing needs to be redesigned. Herein, a suspension formulated from a soluble semi-aliphatic polyimide (S-SA-PI) was used for CF sizing. The effective replacement of the sizing layer on the surface of T300 was clarified by microscopic morphology and surface element content of CFs. The mechanical performance of CF/PEI composites was measured, and the effects of annealing and hydrothermal aging on the mechanical performance were observed. The results show that S-SA-PI sizing can simply improve mechanical performance and hydrothermal aging resistance of CF/PEI. Combining the characteristics of S-SA-PI sizing layer, the mechanism by which S-SA-PI sizing improves the CF/PEI interface was analyzed.