Some Aspects of the Photochemical Degradation of Nylon, Silk, and Viscose Rayon

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Abstract
The vat dyes that are particularly effective in increasing the photochemical degradation of nylon, silk, and viscose rayon are capable of increasing the degradation of undyed cotton that is simultaneously irradiated in their vicinity. The experiments took the form of irradiating a sheet of yarn composed of alternate dyed and undyed threads not in contact with one another. The dyed threads used included nylon, silk, and viscose rayon yarns dyed with various vat dyes. Many of the dyed yarns have a considerable effect upon the degradation of adjacent undyed yarns of cotton or silk, but the same dyed yarns generally have only a small or negligible effect upon the degradation of undyed yarns of nylon or viscose rayon. These results are ap parently due to the greater resistance of the latter textile materials to oxidation by the volatile agent (hydrogen peroxide), which is responsible for the "action at a distance." In some cases- for example, dyed nylon-there is evidence that although the volatile agent is produced by the dye in a relatively large amount it is not responsible for the major proportion of the degradation of the dyed yarn. The effect of humidity on the rate of photochemical degradation of textile materials dyed with active vat dyes appears to be closely related to the ease with which the textile fiber is oxidized by the volatile agent. These results are interpreted in terms of a theory in which the photochemical degradation of the textile material is represented as the result of oxidation by activated oxygen and/or hydrogen peroxide. The relative effectiveness of these two oxidation processes depends upon the particular experimental conditions and the nature of the textile fiber.

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