Simultaneous reactive dyeing and surface modification of polyamide fabric with TiO₂ precursor finish using a one-step hydrothermal process

In this article, the approach of dyeing polyamide (PA) fabric by using C.I. Reactive Blue 19 dye and simultaneously modifying it with titanium dioxide precursor under hydrothermal conditions is developed. The anthraquinone-based Reactive Blue 19 dye, which is more resistant to biodegradation owing to its fused aromatic structure compared to an azo-based one, is utilized as a model compound in this research to demonstrate the photodegradation effect of TiO₂ on reactive dyes. It is shown that a layer of TiO₂ nanoparticles is homogeneously coated on fiber surfaces and their particle sizes are smaller than those remaining in the residual dyeing liquors. The crystallinity and optical properties of the resultant PA fabrics are changed due to this hydrothermal dyeing process. In comparison with the dyed-only PA fabrics, the PA fabrics dyed and simultaneously modified with anatase TiO₂ nanoparticles exhibit better color fastness against artificial light (xenon) while maintain similar grades of color fastness against washing with soap, wet scrubbing, dry cleaning as well as dry/wet rubbing. While changes in tensile strength, elongation and water absorbency of the resultant PA fabrics were not found, the addition of tetrabutyl titanate in the dyeing liquor is proved to facilitate the reaction of reactive dye with PA fabric and the resultant PA fabric shade. More interestingly, it is noticed that the residual dyeing liquor can be photodegraded after 50 mins of either UV or visible light irradiation, and the dyeing wastewater can thus be released in an eco-friendly manner to the environment.