Ultraviolet Protection And Hydrophilic Finishing Of Poly(Lactic Acid) Fiber

Poly(lactic acid)(PLA) fiber has received considerable attention in textile industry mainly due to its renewablity of source, easy degradability and good dyeability at low temperature. But its hydrophobictiy nature and high UV transmittance limit its application in summer clothes. In this study, one triazine UV absorber, one polyester-polyether block copolymer and two UV shielding agents were used to finish PLA fiber by exhaustion and pad-dry-cure methods with the aim of improving the hydrophilicity and UV protection ability of PLA fiber. In addition, the integrated dyeing and UV protective and hydrophilic functionalization in one bath was discussed. The important conclusions were drawn as follow:(a) The UV absorber bearing triazine ring did not show a high exhaustion, and application temperature exerted greater impact on its adsorption on PET fiber than that on PLA fiber. Using butyl acetate as a accelerant was able to obviously improve the utilization rate of UV absorber. The increment in the adsorption quantity of UV absorber on PLA fiber caused by butyl acetate was higher than that on PET fiber. The accelerating action of butyl acetate to the uptake of UV absorber mainly originated from an increase in the swelling of PLA fiber induced by the accelerant. The tensile strength of PLA fiber decreased with increasing dosage of butyl acetate, and hence the concentration of butyl acetate should be very carefully controlled. The triazine-based UV absorber was capable of increasing the UV protection ability of PLA fiber obviously.(b) ZnO sol was successfully prepared by a sol-gel method. PLA-grafted TiO2 was also prepared via in situ melt polycondensation of lactic acid onto the surface of TiO2 nanoparticles. Then the PLA-TiO2 was capped to the surface of Zn O by a sol-gel method to synthesize ZnO/TiO2 composites(PLA-TiO2-Zn O). The prepared ZnO/TiO2 composites imparted to excellent UV protection capability of PLA fiber.(c) Polyester-polyether block copolymer exhibited higher adsorption capability for PLA fiber than for PET fiber, and it was able to greatly enhance the hydrophilicity of PLA fiber. The adsorption quantity of polyester-polyether block copolymer on PLA fiber increased with its increasing dosage and application temperature. A high temperature modification was capable of increasing the depth of the intercalation of the hydrophobic polyester segments of polyester-polyether block copolymer into PLA fiber, and accordingly improving the laundry resistance of hydrophilicity effect.(d) The integrated dyeing and hydrophilic and UV protective functionalization in one bath was successfully performed. Compared to separate dyeing or finishing, the uptake of disperse dyes and UV absorber by PLA fiber was adversely affected to a much less extent by polyester-polyether block copolymer, but both of them had almost no impact on the hydrophilicity of PLA fabric. The UV absorber in PLA fiber was able to slightly enhance the light resistance of dyeings.