Comparison of disperse dye exhaustion, color yield, and colorfastness between polylactide and poly(ethylene terephthalate)

Ten popular disperse dyes with different energy levels and chemical constitutions were used to compare their exhaustion, color yield, and colorfastness on polylactide (PLA) and poly(ethylene terephthalate) (PET). Only two out of the 10 dyes had exhaustions higher than 80% on PLA at 2% owf. Five out of the 10 dyes had exhaustions less than 50%. All 10 dyes had more than 90% exhaustion on PET, whereas six of them had exhaustions of 98% or higher. There was no obvious pattern as for which energy level or which structure class provided dye exhaustion better than that of others. Although PLA had lower disperse dye exhaustion than that of PET, it had higher color yield. Based on the 10 dyes examined, the color yield of PLA was about 30% higher than that of PET. This means that even with low dye uptake, PLA could have a similar apparent shade depth as that of PET if the same dyeing conditions are applied. Our study supported that the lower reflectance, or reflectivity, of PLA contributes to the higher color yield of PLA than that of PET. A quantitative relation between the shade depth of PLA and PET based on their dye sorption was developed. Disperse dyes examined had lower washing and crocking fastness on PLA than on PET. The differences in class were about 0.5 to 1.0. If the comparison was based on the same dye uptake, the differences might be larger. The differences in light fastness between the two fibers were smaller than that in washing and crocking fastnesses. The light fastness of disperse dyes on PLA is expected to be even better if the comparison is based on the same dye uptake on both fibers. (C) 2003 Wiley Periodicals, Inc.