The colouration of poly(lactic acid) fibres with indigoid dyes: Part 1 colorimetric analysis

Three vat dyes were applied to poly(lactic acid) fabric at 2–15% omf depths of shade, at 90, 98 and 110 °C for 60–120 min in the presence of alkali and reducing agent. Generally, colour strength increased with increasing application temperature over the range 60–110 °C but, thereafter, further increase in temperature was accompanied by a decrease in colour strength. Colour strength increased with increasing dyeing time up to 60 min but, thereafter, decreased gradually, at each of the three temperatures used, which may be due to alkaline hydrolysis of the fabric. The lower build-up observed for C.I Vat Blue 1 compared to the other two dyes used over the range 2–15% omf may be due to the dye’s lower basicity.

► Colour strength of vat dyes on poly(lactic acid) increase with increasing temperature upto 105 °C.
► Colour strength also increases with increasing dyeing time up to 60 min.
► C.I Vat Blue 1 shows lower build-up compared to other two vat dyes used.