INFLUENCE OF ACID DYES ON THE PHOTOOXIDATION OF NYLON 6,6 FILM - RELATIONSHIP WITH RATE OF PHOTOFADING AND LUMINESCENT SPECIES

The photofading rates of three azo acid dyes (C.I. Acid Blue 62, C.I. Acid Yellow 135 and C.I. Acid Red 266) and four azo acid metal complex dyes (C.I. Acid Brown 266, C.I. Acid Blue 171, C.I. Acid Orange 162 and C.I. Acid Black 107) were examined in nylon 6,6 film and were compared with the influence of the dyes on the photochemical degradation of the polymer using UV-visible absorption and viscometric analysis. For the first three acid dyes, the relative rates of photofading correlate with the ability of the dyes to photostabilize the polymer, i.e. yellow > blue > red. However, all the dyes are more photostable than the polymer. The acid metal complex dyes also photostabilize the polymer in the order blue > black > orange > brown. The nature of the central metal atom is concluded to be an important factor. In the presence of the dyes the concentration of terminal amine groups has little influence on polymer stability, but dye bath treatment improves the photostability of the polymer due to extraction of photoactive impurities. There is a close correlation between the ability of the dyes to quench the luminescent chromophores and polymer stability; the ability to quench the phosphorescent species at 290 400 nm is most significant as indicated by the correlation coefficients. This suggests that triplet energy transfer may be important in stabilization of the polymer by the dye. © 1990.