Photofading of four azo pyridone disperse dyes on polyester fabric and film has been investigated at 254 nm in the presence of air. The results of this research indicate that the same photodegradation products occur in a comparison of the fabric and the film. A photoreduction pathway is involved, which is confirmed by the presence of amines arising from the reduction of the azo group. The fading process follows first-order kinetics, depending on the dye structure. The reaction mechanisms are discussed briefly, and photodegradation products are determined with the aid of TLC comparisons with authentic samples and LC spectra.
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