Photodegradation of Acid Dyes in Nylon Films

The photodegradation of three representative acid dyes commonly used to colour nylon was studied in nylon films. It was observed that irreversible photodegradation of the dyes occurs only at wavelengths shorter than 350 nm and that the quantum yield increases as the photolysis wavelength decreases. It was also found that u.v. photolysis of the dyes is partially reversible and that photodegradation is inhibited by oxygen. Evidence is presented that photodegradation occurs by a reductive process, involving hydrogen transfer from the nylon polymer to the excited dye