Fabrication and Properties of Glass Fiber-Reinforced Composites Using Polyimide Prepregs with Inorganic Nanofillers

Numerous studies have addressed the utilization of polyimide (PI) and silica for improving the properties of hybrid composites. However, the applicability of polyhedral oligomeric silsesquioxanes (POSSs) has not been elucidated. Herein, inorganic nanoparticles containing poly(amic acid)s (PAAs) were synthesized; further, glass fibers (GFs) were impregnated with PAA solutions to obtain PAA prepregs. PI-based fiber-reinforced composites were manufactured with the prepregs by using the hand lay-up technique. The morphology and the thermal, mechanical, and dielectric properties of the composites with inorganic nanoparticles were analyzed to investigate the effects of inorganic additives. The addition of inorganic particles were observed to primarily improve the properties of the PI-based fiber-reinforced composites as compared to those of the neat PI composites. While this improvement was limited in the case of the addition of POSSs owing to the aggregation and a poor interaction with the PI matrix, silica-containing composites exhibited superior thermal, mechanical, and particularly dielectric properties as compared to those of the composites containing POSSs; this was because of the increase in the dispersion of silica nanoparticles that was caused by a silane coupling agent (SCA). The results obtained in this study can be utilized for applications pertaining to the design of PI composites with high mechanical strengths, enhanced thermal stabilities, and low dielectric constants.