Nondestructive modification of aramid fiber based on selective reaction of external cross-linker to improve interfacial shear strength and compressive strength

Abstract Poor adhesion to resin and low axial compressive strength are two prominent problems for application of aramid in fiber-reinforced composites. Simultaneously enhancing interfacial shear strength (IFSS) and compressive strength is still challenging. Herein, 4-(bromomethyl) benzoic acid (BBA) was utilized as external cross-linker to modify (Poly-p-phenylene-benzimidazole terephthalamide) (PBIA) fibers through post-swelling process. It was confirmed that bromomethyl groups of BBA could react with benzimidazole units of PBIA upon 80 °C and carboxyl of BBA could form cross-linking upon 300 °C by decarboxylation coupling reaction. Therefore, both surface grafting and bulk cross-linking can be obtained simultaneously by controlling temperature during modification process. After modification, IFSS and compressive strength of PBIA fibers are enhanced by nearly 27% and 100% respectively while maintaining excellent mechanical properties. Therefore, the method is nearly non-destructive and effective to simultaneously improve IFSS and compressive strength of PBIA fibers.