Wavelength dependence of light-induced fading and free radical formation in azoreactive dyes

Light-induced stable free radicals (SFRs) were detected in azoreactive dyed cotton fabrics. Extremely slow photofading occurred under exposure to ligh t of relatively long wavelength. The rate of photofading and SFR formation depend on the structure of the dye. Some of them show little drop in the ra te of fading with the increasing wavelength, whereas others show nearly neg ligible changes under incident light of relatively long wavelength. In gene ral a high rate of photofading was found when the SFR concentration was low . (C) 1999 Elsevier Science Ltd. All rights reserved.