Surface functionalization of aramid fibers via constructing different zinc oxide nanostructures for improved UV resistance

Aramid fibers (AFs) with high strength and modulus have a vital application in harsh outdoor bulletproof protection and ship ropes; however, solar radiation, especially ultraviolet (UV) radiation, is one of the main factors for affecting their service life. Herein, different zinc oxide (ZnO) nanostructures were constructed on the surface of AFs by the growth of ZnO nanowires (AF-ZnO NW) and coating of waterborne polyurethane/ZnO nanoparticles composite emulsion (AF/ZnO), respectively. The surface functionalized AFs exhibited enhanced mechanical properties retention after UV radiation. Nevertheless, the tensile strength of AF-ZnO NW before UV aging was already lower than the tensile strength of original AFs due to the surface structure damage from chemical grafting modification. The tensile strength and elongation retention rates of AF/ZnO-5% reached 74.4% and 84.4% after UV exposure for 168 h, respectively, which were much higher than the value of 48.3% and 60.5% of the neat AFs. These results provide an effective and low-cost strategy for improving the UV-resistance of advanced high-performance fibers.