Coloration of poly(lactic acid) with disperse dyes. 1. Comparison to poly(ethylene terephthalate) of dyeability, shade and fastness

The dyeability of poly(lactic acid) [PLA] with a range of commercial disperse dye was examined and compared to that of poly(ethylene terephthalate) [PET] in addition to the colour and fastness of the resultant dyeings. A screening exercise in which twenty dyes of differing energy types and chemical classes were applied to PLA revealed a substantial variation between the dyes in terms of dye uptake (12-88% at 4% o.w.f.). Nine dyes exhausted above 70% and were selected for further study, which involved comparison of shade and fastness of PLA dyeings; with those of the corresponding PET dyeings. Differences in shade depended on hue while wet fastness of each of the PLA dyeings was either the same or 0.5-1.0 point lower than its PET counterpart. In all but one case, dye photostability in PLA was found to be very similar to that in PET. Dye build-up profiles on PLA were also investigated and from these results mixtures of compatible dyes identified.