The photofading mechanism of commercial reactive dyes on cotton

Photofading in cotton fibers dyed using red, yellow, and blue direct dyes during examination with microspectrophotometry (MSP)

“…In all cases that could be tested, the loss rate of absorbance intensity increased for the lighter shades as compared to the darker shades, approximately doubling for fibers dyed at the lowest concentration (Concentration 3 compared with Concentration 1). This observation is supported by Batchelor’s work [21], where the same enhanced effect on the loss rate of absorbance intensity for lighter shades is reported. However, Batchelor noted that although a greater percentage of dye molecules are destroyed for the darker shades than for the lighter shades, the former case produces a less visually apparent effect on the overall color of the dyed cotton.…”

“…While photofading is a well-known phenomenon in textile fibers [2], [16]–[21], very little information on photofading (sometimes called photobleaching) of fibers during MSP analysis was found in the scientific literature. Efforts to avoid fading of the fiber during MSP analysis in the UV were noted in only a few recent papers, all published in 2015 or 2016 by one group, Was-Gubala and Starczak, from Poland [1], [5], [14], [15].…”

“…The transition via photochemical reactions is considered the mechanism responsible for photofading, and this effect is generally enhanced when dyes are bound to textile substrates [16]. Specific photochemical reactions that have been implicated in photofading include photo-oxidation induced by either singlet oxygen or superoxide, and photo-reductive reactions initiated by UV light [16], [21]. Two recent articles identified the primary mechanism responsible for fading of azo dyes on cotton as photo-oxidation due to superoxide formation [2], [21].…”

“…Specific photochemical reactions that have been implicated in photofading include photo-oxidation induced by either singlet oxygen or superoxide, and photo-reductive reactions initiated by UV light [16], [21]. Two recent articles identified the primary mechanism responsible for fading of azo dyes on cotton as photo-oxidation due to superoxide formation [2], [21]. Schemes for these reactions are given in a paper by Oakes [16], and will not be discussed further here.…”

The Orientation Stability and UV Irradiation of Poly(hexa‐2,4‐diynilene‐1,6‐dioxy)benzoates and Cinnamates ContainingDisperse Red 19

“…In many cases, irradiation of UV or visible light fades color of dyes, although the precise mechanism of photofading or photobleaching, has not been well established. It has been reported that photofading of azo dyes occur by the electron transfer from dye molecules to oxygen by visible light (13). Yamaguchi has reported that the contribution of the singlet oxygen is small (14).…”