Improved interfacial properties and electrical insulation in aramid fiber/epoxy vitrimer composites by plasma treatment

Abstract Epoxy-based vitrimers with dynamic covalent network provide a promising strategy for the recycling of fiber-reinforced composites. Nevertheless, due to the smooth surface and inherent chemical inertness of aramid fiber (AF), the issue of weak interfacial bonding remains a challenge limiting the application and performance optimization of AF/epoxy vitrimer (AF/EP) composites. In this work, dielectric barrier discharge plasma is adopted for AF surface modification, aiming to enhance the interfacial properties between AF and boronic ester-based EPs. The effects of gas atmospheres (argon and air) and treatment durations on the surface characteristics of AF, as well as the interfacial properties, insulation performance, degradation behavior and recyclability of the composites are investigated. The results show that plasma treatment endows AFs with rougher surface morphology and abundant oxygen-containing functional groups, thereby enhancing the mechanical and insulation performance of the AF/EP composites. Air plasma treatment exhibits superior effects in enhancing interfacial shear strength (IFSS) and dielectric breakdown strength of the composites, yet inevitably reduces the degradation efficiency and results in obvious performance degradation after reutilization. In contrast, argon plasma treatment achieves an excellent balance between improved performance and recyclability. The IFSS and breakdown strength can be increased by 31.22% and 12.51% respectively after 2 min of argon plasma treatment. Moreover, the modified composites maintain structural and performance stability during reuse, and the breakdown strength of the recycled composites remains at 91.25% of the original value.