Analysis of photofading of phenylazo-indole and phenylazo-N-ethanolaniline disperse dyes on poly(ethylene terephthalate) fabric using the PM5 method

Abstract The photofading behaviors of phenylazo-N-(ethanol)aniline and phenylazo-indole, nitrohetarylazo-N-substituted aniline disperse dyes on poly(ethylene terephthalate) (PET) substrate were analyzed using the Kubelka-Munk (K/S) parameters of the dyed fabrics exposed to a carbon arc in air. The initial experimental slopes (K PET ) of fading on PET were estimated from the time profiles of the K/S values at the λ max . The rates ( k 0, i ) of reaction of these dyes with 1 O 2 were estimated by frontier orbital theory using the PM5 method. The photosensitivities ( f i ) of the dyes were estimated from the K PET assuming that the K PET values are proportional to the product of k 0, i and f i . Dyes with small f i values, irrespective of their k 0, i values, possess excellent lightfastness (LF), while dyes with larger f i values possess poorer LF. The validity of estimating k 0, i values by the MO method was confirmed experimentally by analyzing the mutually photosensitized fading behaviors of combination dyeings.