Surface modification of polyimide fibers for high-performance composite by using oxygen plasma and silane coupling agent treatment

In this study, the oxygen plasma and silane coupling agent composite treatment was used to modify the polyimide fiber surface to improve the interfacial properties. The oxygen plasma treatment introduced active groups on the fiber surface, which facilitated the grafting of silane coupling agent to the fiber surface. The surface morphology and chemical composition of fibers were characterized by scanning electron microscope and X-ray photoelectron spectroscopy. The results showed that after plasma treatment, the etching spots on the fiber surface increased with the plasma treatment time, and the surface O atom content, O/C ratio and C–O(H) bond ratio reached the highest value at 27 min plasma treatment. After the composite treatment, the surface Si atomic content reached the highest value after 27 min plasma pretreatment. Moreover, polyimide/polyamic acid unidirectional reinforced composites were prepared. In polyimide/polyamic acid composites, the interfacial shear strength of polyimide fibers first increased and then decreased with plasma treatment time, both in oxygen plasma treatment and in composite treatment, and increased by up to 36.98% and 61.68% respectively compared. In addition, the transverse tensile strength of polyimide/polyamic acid composites increased by 103.73% after composite treatment compared with the pristine specimens.