Azo/Epoxy Copolymer and Nano-ZnO Hybrid Coating as an Effective UV Radiation Shielding and UV Protection Method for Silk Fabrics

Silk possesses excellent flexibility, moisture absorption, breathability, antistatic properties, mechanical strength, biocompatibility, biodegradability, and aesthetic appeal, making it suitable for textile and biomedical applications. However, UV exposure breaks silk's molecular peptide bonds, weakening strength and hampering long-term use. In this study, we synthesized an organic-inorganic composite protective layer for the enhancement of UV resistance of silk fibers. The method combines an azobenzene photoresponsive monomer with a glycerol ester containing epoxy groups to form a photoresponsive polymer, which was then blended with zinc oxide (ZnO) nanoparticles. The research results indicate that the UV protection performance of modified silk fabrics has been improved. After 192 h of UV exposure, silk fabrics treated with azobenzene/epoxy-ZnO composite coating retained 72.7% of its tensile strength, higher than the 49.7% of untreated fabric. Additionally, the ratio of pigment absorption coefficient to scattering coefficient (K/S) was 0.408, higher than the 0.343 of the original silk fabrics. The ultraviolet protection factor (UPF) measures a material or garment's UV protection ability. The azobenzene/epoxy-ZnO-treated silk fabric has a UPF exceeding 100. This azobenzene-modified silk fabric also shows better light fastness than the original. The study offers an active and efficient way to reduce silk's photodegradation in daily use.

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