Relationship between photofading and chemical structure of disperse azo dyes on nylon fabric^†

Abstract

The initial rates of photofading for 30 disperse azo dyes on nylon fabric upon exposure to a carbon arc in air have been analysed by formulating a kinetic equation that describes azo scission via the disproportionation reactions and intramolecular H‐transfer by two kinds of hydrazinyl radicals and the conversion of a nitro group to a nitroso group via the disproportionation reaction of nitrosyl hydroxide radicals. The five reaction rate constants are discussed in terms of the heats of reaction by calculating the heats of formation for the reactants, intermediates and products of each reaction using the PM5 method. Phenylazo‐ and thiazoleazo‐N,N‐substituted anilines and phenylazo‐pyridones exhibited large rate constants of multiple terms, while phenylazo‐phenols had the highest light fastness and very small rate constants for the disproportionation reactions of hydrazinyl radicals. Photofading on nylon fabric was primarily controlled by the thermal reactions of photo‐induced monohydrogenated dye radicals, which occurred via one or two primary multiple routes.

Radical mechanism of azo cleavage for monoazo reactive dyes, a QSPR study: the similarity between photoreduction on polyamide substrates and thermal reduction in aqueous dithionite solutions

“…In this paper, the formation of aqueous dithionite is explained because the photogeneration of (MHN) was reported in previous papers [30][31][32]. If rearrangement or thermal equilibration of (MHN) after generation had large effects on the AC reaction, the difference between photo-and thermal reactions may be small.…”

“…Thus, (N11) and (N12) formed in the present study may take part in intramolecular H-transfer (disproportionation) and/or redox reactions, as in the case of the photoinduced radicals [30][31][32]. (O13) may immediately rearrange, depending on the stability of (MHN), resulting in (N11) or (N12), whereas ATs may generate (N11) or (N12), depending on their reactivities and stabilities.…”

“…Analysis of thermal reduction in a solution of food dyes using the MO method: similarity between photo-and thermal reduction of dyes The photogeneration of (MHNs) on PA substrates has been reported previously [30][31][32]. Heijkoop and van Beek [19,20] reported the generation of (MHNs) and their AC resulting in the formation of o-iminooxoquinone, aminonaphthoxyl radical, naphthylamine, and aminonaphthol from the flash photolysis study of 1-naphthyl-azo-1naphthol dyes (containing G3 and G4 as their typical dyes) in anaerobic alcoholic solution.…”

“…In the present study, the initial rates of fading on PA (K PA ) of the six azo dyes have been determined using the same procedures as in previous studies [30][31][32], and the order of these K PA values has been interpreted on the basis of thermochemical analysis. In the present study, the initial rates of fading on PA (K PA ) of the six azo dyes have been determined using the same procedures as in previous studies [30][31][32], and the order of these K PA values has been interpreted on the basis of thermochemical analysis.…”

Evaluation of the interactions of DNA with the textile dyes Disperse Orange 1 and Disperse Red 1 and their electrolysis products using an electrochemical biosensor

“…These compounds are applied to fibers such as polyester, polyurethane, polyamide, and nylon [3][4][5]. During the dyeing process, the dye molecule undergoes hydrolysis, and the form that was originally insoluble slowly precipitates over the fiber in the disperse form [1].…”