ESTIMATION OF POTENTIAL PHOTOCHEMICAL PROPERTIES FOR MONOCHLOROTRIAZINYL REACTIVE DYES AND THEIR MANIFESTATIONS IN THE FADING OF DYED CELLULOSE

Cellulose films dyed with 10 monochlorotriazinyl reactive dyes were ex posed to light in various aqueous solutions and the following potentia l photochemical reactivities of dyes estimated: (i) ease with which th e dyes are photo-oxidized, (ii) ease with which dyes are photo-reduced , (iii) apparent photosensitivity, and (iv) the rates of fading in aer ated water. On irradiating the dry reactive cotton dyeings, fading pro ceeded in two steps, viz. many dyes exhibited a considerable initial f ading, accompanied by slow subsequent fading. On exposing the dry dyed cellulose films, little initial fading was observed. The fading behav ior of some dyes could be explained by their potential properties, whi le other dyes underwent slow fading, probably due to a compensation be tween oxidative and reductive photofading processes even though the dy es had high photoreactivity. The concentration dependence on the fadin g behavior of dyed films could be explained by the filter effect with some exceptions, where dyes with high photosensitivity showed larger o r similar fading in deep dyeings than that in the paler dyeings. (C) 1 997 Elsevier Science Ltd.