Effects of an electrospun Janus structure on enhanced UV resistance performance

Thermoplastic polyurethane (TPU) fabrics often possess good mechanical, waterproofing, and breathability properties. However, the resistance of TPU to excessive ultraviolet (UV) irradiation is poor and often does not meet the UV resistance requirements of fabrics. Electrospun nanofibers with a side-by-side structure can combine the advantages of different materials. Therefore, in this study, a series of Janus composite nanofiber membranes with side-by-side structures were prepared by eccentric electrospinning using polyacrylonitrile (PAN), titanium dioxide (TiO₂), and TPU as raw materials. The Janus structure of the nanofibers was evident in scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Wettability and breathability tests showed that the nanofiber membranes exhibited waterproofing and breathability properties. The Janus composite nanofiber membrane with 1 wt% titanium dioxide TiO₂ exhibited a UV-protection factor (UPF) as high as 1962 and a UV transmittance of less than 2.5%, with the amount of TiO₂ added being proportional to the UV resistance. Additionally, the UV resistance of the nanofiber membranes did not decrease substantially after seven days of immersion in solutions at different pH values. Finally, this study analyzed the mechanism by which the Janus structure enhanced the UV resistance. The UV light was reflected, refracted, and absorbed many times on the crescent side with excellent UV-absorption performance, which greatly improved the UV resistance of the membrane.