Vat dye sensitised fibre damage and dye fading by catalytic and activated peroxide bleaching

At equal levels of performance, activated (TAED) and catalytic (Mn-TMTACN) laundry bleaching can differ considerably in terms of the concomitant damag e to fibres and dyes. To quantify this damage, differently dyed cotton fabr ics, and a representative set of eight vat dyes and CI Reactive Brown 7 wer e used. It is shown that dye fading and fibre degradation are dye-specific and are both highly coupled phenomena. The interpretation of the damage dat a is based on dye chemistry, reflectance spectroscopy (UV/VIS and NIR) and EPR measurements. Whereas compelling evidence for a genuine catalytic cycle with the quoted manganese complex is lacking, a possible catalytic role of the dyes is proposed. The dramatic green shift resulting from the catalyti c bleaching of CI Vat Blue 4 is explained in detail. The corresponding oxid ation is reversible and possibly useful as a fibre damage indicator.