The photodegradation behavior of three bifunctional reactive dyes of yellow, red, and blue colors on cotton fiber in the presence of perspiration has been investigated. The original fiber before dyeing and the dyed fiber, respectively treated with acid and alkaline perspiration, were irradiated with monochromatic light of 20 different wavelengths from 201 to 701 nm, using as light source a Xenon lamp divided into 20 wavelength parts. The photodegradation behavior at each wavelength was examined to elucidate the mechanism of the photofading of the dye on the fiber. Original cotton fiber and the dyed fiber were affected markedly by spectroirradiation at a specific wavelength, viz. 259 nm: yellowing of the fiber alone and photofading of the reactive dyes on the fiber occurred maximally at this wavelength. The photodegradation is independent of the color and structure of the dyes. These findings suggest that the photodegradation of the dyes on the fiber is accelerated by the absorbed energy characteristic of the fiber and/or degradation products of the fiber generated at the characteristic wavelength. In the presence of acid or alkaline perspiration the photodegradation of the dye on the fiber also took place maximally at ca. 259 nm. However the original fiber and the dyed fiber were influenced markedly by the added perspiration. The curve of the photodegradation was intensified and broadened significantly by perspiration. Histidine alone in perspiration did not play an important role in the photofading by light and perspiration. The components other than histidine affected the fading cooperatively.

DESCENTE SPORTS SCIENCE Vol.20/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE