Preparation Of Nano-sized Zinc Oxide And Its Effect On Anti-ultraviolet And Anti-yellowing Finishing Of Silk Fabrics

As a kind of natural protein fiber,silk is widely used because of its excellent performance.However,silk is very sensitive to light.Research has shown that when exposed to sun,silk will be oxidized by the light,resulting in yellowing,embrittlement and other aging phenomenon.Yellowing is due to the oxidation of amino acids with aromatic ring under the ultraviolet radiation,and the embrittlement,which is a phenomena of mechanical properties decreasing,is caused by the silk fibroin chain degradation and molecular chain being cut off.Both of them attribute to the exposure under ultraviolet light.Therefore,light aging is considered as the biggest shortcoming of silk fiber,and silk fabric surface finishing by blocking the direct impact of ultraviolet light on silk,is of importance to protect silk fibers.In this paper,nano-ZnO particles were prepared by one-step method using sodium hydroxide and zinc chloride raw materials.The prepared nano-ZnO particles were characterized by cold-field scanning electron microscopy(SEM),laser particle size analyzer(Nano Sizer),X-ray diffraction(XRD),transmission electron microscope(TEM)and infrared spectroscopy(FT-IR).The effects of reaction temperature,zinc chloride concentration and reactant concentration ratio on particle size distribution and stability were discussed.The nano-zinc oxide particles with particle size of 68.3nm were prepared successfully,and the aqueous solution was well homogeneous and dispersible.The silk fabric was treated by modified nano-zinc oxide by dip-molding method.The anti-UV,anti-yellowing and antibacterial properties of the fabric were tested,and scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray(XRD)(XRD)were used to analyze the morphology and elements of nano-zinc oxide on silk.The results showed that the weight increased by 0.025 g on 1g silk fabric,and the UPF value was 63.77.After 30 times of washing,the weight of ZnO on the fabric decreased from 0.025 g to 0.012 g,the UPF value was kept at about 30,and it still had good UV protection performance.Whiteness of the untreated fabric decreased from 72.6 % to 38.8 % after ultraviolet radiation for 50 h.The silk fabric treated by the modified nano-zinc oxide has excellent anti-yellowing property.After 50 hours of irradiation under ultraviolet light,the whiteness of the fabric decreased from 76.5 % to 53.6 %,and the mechanical properties were maintained,with the internal structure being undamaged.And the treated sillk fabric has excellent antibacterial properties against Staphylococcus aureus and Escherichia coli.The thermal performance and mechanical properties of treated fabric were basically not affected,with a slight decline in the moisture absorption and permeability.