Nondestructive growing nano-ZnO on aramid fibers to improve UV resistance and enhance interfacial strength in composites

It is a great challenge in various applications to improve the resistances of aramid fibers (AFs) to harsh environments and enhance the interfacial bonding strength in composites along with maintaining the excellent mechanical properties. Herein, a simple nondestructive method was developed to prepare modified AF with zinc oxide (ZnO) micro-nano structures. Assisted by the adhesion and secondary functionalization of poly L-3,4-dihydroxyphenylalanine (PDOPA), ZnO nanoparticles (NPs) were successfully “seeded” onto the AF surface, and subsequently ZnO nanowires (NWs) were grown on the seed layer. As a result, the surface modification did not cause the significant changes of the tensile strength, and the surface roughness and UV resistance of the modified fibers were significantly improved. After 168 h of UV exposure, the retention of the tensile strength for the modified fiber was as high as 97.2%. Comparing with the pristine AF-reinforced composite, the interfacial shear strengths of AF-PDOPA-ZnO NP/epoxy resin and AF-PDOPA-ZnO NW/epoxy resin composites increased by 31.8% and 37.8%, respectively. Therefore, this effectively nondestructive modification method to grow ZnO nanostructures on a polymer substrate exhibits an extensive application prospect for organic fibers and their composites. [Display omitted] •ZnO nanoparticles were seeded onto the surface of aramid fibers.•ZnO nanowires were further grown on the seed layer.•This is a nondestructive modification with the aid of polydopamine.•The modified fibers exhibit the improved UV resistance and enhanced mechanical properties.