Anti-ultraviolet Properties of Weft-Knitted Textile Composite Materials Based on Modified Aramid and UHMWPE Fabrics

The amide bonds of aramid fibers' prolonged exposure to sunlight leads to the aging of the fibers and poor UV resistance. However, in most of the current studies, the improvement of UV resistance is accompanied by damage to aramid fibers. Four different mass fractions of the silane coupling agent KH550 and anhydrous calcium chloride were used to modify the surface of aramid fibers followed by grafting of zinc oxide nanoparticles onto the aramid fibers. The results showed that the surface free energy increased by 43.61%, and the interfacial shear strength (IFSS) increased by 58.19% when the concentration of KH550 was 20%. The tensile, flexural, and compressive strengths of the composites were higher by 46.81%, 71.05%, and 78.05%, respectively, than those of the unmodified aramid composites. The results showed that the IFSS of the aramid fiber was 16.24% higher than that of AF-20% KH550. The increase could be attributed to the growth of ZnO nanoparticles. The retention rate of the tensile strength of the unmodified aramid fiber was as low as 81.99% after 128 h of UV irradiation, and the retention rate of the aramid fiber after the growth of ZnO nanoparticles was 98.11%. The tensile, flexural, and compressive strength retention rates of aramid composites recorded following the surface growth of nano-ZnO were 98.08%, 91.49%, and 89.56%, respectively, which were significantly higher than the values recorded for unmodified aramid composites (82.19%, 75.44%, and 76.75%, respectively). The growth of nano-ZnO improved the UV resistance of aramid composites and the mechanical properties of aramid composites.