Maximizing the wash fastness of dyed poly(lactic acid) fabrics by adjusting the amount of air during conventional reduction clearing

In this study we investigate the influences of air content in the sealed reduction-clearing equipment, liquor ratio, sodium dithionite, and sodium carbonate concentrations of an alkaline reduction-clearing bath on wash fastness properties of poly(lactic acid) fabrics dyed with alkali-sensitive and alkali-stable disperse dyes. Lower air content in the sealed reduction-clearing equipment and a greater amount of sodium dithionite present in the clearing bath leads to better wash fastness values. The reduction clearing with a higher liquor ratio resulted in higher wash fastness levels due to the lower amount of air present in the sealed reduction-clearing equipment. The extent of the improvement on wash fastness properties of dyed poly(lactic acid) fabrics depends on the combination of alkali sensitivity of the disperse dye, sodium dithionite concentration, liquor ratio, and air ratio in the clearing equipment. No polymer degradation occurred during the alkaline reduction-clearing process. Poly(lactic acid) fabrics, after reduction-clearing processes, exhibited approximately similar performance for each dyeing compared to the non-cleared control sample, leading to a slight decrease on color yield (f(k)), slightly higher chroma (C*), higher lightness (L*), and therefore brighter appearance without significant shade change.