The coloration of poly(lactic acid) fibres with indigoid dyes: Part 2: Wash fastness

The fastness of 5% omf dyeings of three indigoid vat dyes on PLA fabric to repeated washing at 40 °C, 50 °C, and 60 °C increased with increasing temperature of their application (60 °C, 80 °C, 98 °C and 110 °C). Fastness to repeated washing at 40 °C and 50 °C was better than at 60 °C. Of the three dyes used, C.I. Vat Blue 35 displayed lowest fastness to repeated washing and also lowest colour strength. Comparison of the fastness results on PLA fabric with those of dyeings of three disperse dyes on PLA fabric as well as dyeings of three other vat dyes on PA supermicrofibre revealed both similarities and differences in terms of colour loss and staining of adjacent materials, which highlighted the likely importance of subjecting vat dyeings on PLA fabric to a clearing process in order to remove surplus dye.

► Wash fastness of vat dyes on PLA increases with increasing temperature up to 110 °C.
► Fastness also decreases with increasing fastness temperature.
► C.I Vat Blue 35 shows lower build-up and fastness compared to other vat dyes.
► Results imply importance of subjecting dyeings to a clearing process.