Clearing of dyed poly(lactic acid) fabrics under acidic and alkaline conditions

This study has been conducted to examine the influence of different clearing treatments, following dyeing using different clearing agents under acidic and alkaline pH conditions, on the colour fastness and colour properties of poly(lactic acid) fabrics dyed with alkali-sensitive and alkali-stable disperse dyes. Wet-fastness properties of poly(lactic acid) fibres dyed with both alkali-sensitive and alkali-stable disperse dyes were improved to the commercially acceptable levels with a clearing treament at 60 degrees C for 15 minutes using the right combination of the chemistry of the dye, clearing agent type and pH condition (pH 5 and pH 10.7) of the applied clearing bath. Overall, successful clearing treatments, judged by high wet fastness results, exhibited approximately similar performances for each dyeing compared to a non-cleared control sample. These clearing treatments led to a very slight decrease in colour yield (f(k)), slightly higher chroma (C*), higher lightness (L*) and therefore brighter appearance without significant shade change. No poly(lactic acid) polymer degradation occurred during clearing whichever clearing agent is used, and whether the conditions are acidic or alkaline.