Analysis of the photofading of phenylazo-aniline and phenylazo-pyridone disperse dyes on poly(ethylene terephthalate) substrate using the semiempirical molecular orbital PM5 method

The photofading characteristics of six monoazo disperse dyes on polyester fabric upon exposure to a carbon arc in air were analyzed in terms of the reactivity (k0) towards 1O2 and the photosensitivity (f). The photochemical properties of the dyes were estimated by catalytic fading in mixture dyeings of two yellow (pyridone-azo and quinolone-azo) dyes. The k0 ratios for the componential dyes in the 1:1 mixture dyeings varied with the partner yellow dye, implying that they depend upon the f values and the concentrations of the component dyes as well as the superposition of absorption spectra, and the changes in their concentration, even in the initial stages of fading. The relative k0 values, as estimated by the sum of the electrophilic frontier densities using the PM5 method were demonstrated experimentally, while taking the influencing factors into consideration. The assumption that the rates of oxidative fading on PET were proportional to the product of two factors of k0 and f was confirmed as reasonable based on the fading behavior upon exposure to a carbon arc in air of eight disperse azo dyes with a wide range of two factors.