Light-Perspiration Stability Of Reactive Dyes And Its Influential Factors

The light-perspiration stability of dyes is defined as the resistance of dyeings to fading caused by the synergetic effect of light and human sweat. In hot summer, while sucked with sweat, the textile is also subject to light. In that case, it fades faster than it does when subject to light or sweat alone. Meanwhile, dye and its by-products separated from textile due to light-perspiration could directly contact skin and hurt the human body. But so far, the fading mechanism of dyes under light and perspiration has not been fully disclosed and many factors affecting the stability of dyes still remain unclear.In this paper, three methods for testing the light-perspiration stability of dyes were designed and studied, separately, and during the testing it was found the selected reactive dyes exhibited lowest stability under simultaneous exposure to light, oxygen and perspiration solution. And then three types of standards (ISO, AATCC and ATTS) for preparing for the artificial perspiration were employed and the ATTS standard perspiration which contained more reductive components was found to cause the dyes to fade fastest, and the study on the contribution of components of ATTS standard perspiration showed that some acidic components played the major roles on the fading of reactive dyes and inorganic salts sometimes decelerated the fading extent.Furthermore, to study the effect of dye structure on its light-perspiration stability, a series of substituted azo dyes were synthesized and by analyzing their fading behaviors it was concluded the fading of those dyes under perspiration and light underwent both an oxidative and reductive mechanism. Meanwhile, among ten commercial reactive dyes with different types of chromophores, Cu-complex azo dyes appeared to be the most sensitive under exposure to light and perspiration, whereas anthraquinone dyes showed the best stability. And it was also found that the pH value of perspiration could greatly influence the fading of dyes by affecting the hydrolytic stability of different type of dye-fiber bonding: the fading rate of most chlorotriazinyl reactive dyeings in acidic perspiration is higher than in alkaline perspiration, while the reverse is true for most vinylsulphonyl dyeings.Finally, some technical factors which might affect the stability of reactive dyes during dyeing process were investigated and the results showed that first, in most cases the light-perspiration stability of dyes might increase with the dyeing depth, but sometimes the reverse result could be obtained if the dye-fiber bonding was hydrolyzed to a great extent. And secondly, the difference in light-perspiration stability of the same reactive dye might exist in fabrics of different construction and property. Thirdly, the fabric dyed with matched reactive dyes might have larger color difference under exposure to light and perspiration than it did when dyed with pure dye, probably due to the interaction of the dyes matched together.