Effects of undoped and manganese-doped zinc oxide nanoparticles on the colour fading of dyed polyester fabrics

This paper describes the effects of applying coatings of an acrylic polymer containing nanoparticles of zinc oxide (ZnO) on the fading rate in artificial sunlight of polyester fabrics dyed with disperse dyes containing anthraquinone and benzopyran chromophores. Factors affecting the transparency and UV absorbance of the coatings are discussed. Removing the UV component of sunlight with ZnO nanoparticles markedly decreased the fading rate of the dyes, provided the polymer/ZnO film was not in direct contact with the fabric. When the treatment was applied directly to the fabrics, however, the protection against colour fading was different for the two dyes studied. Whereas the rate of colour fading of a benzopyran dye, of relatively low lightfastness, was decreased by the polymer-ZnO film, the treatment increased the fading rate of the dye of higher lightfastness, based on anthraquinone. This effect has been attributed to the generation of reactive oxygen species (ROS) when ZnO is exposed to UV. The effect of decreasing the photoactivity of ZnO by doping with manganese has been examined. For the benzopyran dye, the UV protection was greatly increased, whereas a much smaller improvement was found for the anthraquinone-based dye.