The clearing of poly(lactic acid) fibres dyed with disperse dyes using ultrasound: Part 2 – fastness

Of the three types of clearing processes (water, ECE detergent and reduction clearing) applied to dyeings of six disperse dyes on PLA, water had little effect on fastness to both rubbing and repeated washing; reduction clearing was slightly more effective than ECE detergent in improving wash fastness whilst the detergent imparted higher levels of rub fastness. Both wash and rub fastness were higher when aftertreatment was carried out at 60 °C rather than at 50 °C. Ultrasound enhanced the effectiveness of both reduction clearing and ECE detergent in terms of rub fastness and enabled a modified reduction clearing process to be used that employed lower amounts of alkali and reducing agent. This offers the potential for reducing the BOD, COD, TOD and amount of suspended solids that are generated during the reduction clearing of disperse dyes from dyed PLA. The colour of the five times washed dyeings was unaffected by the aftertreatment used.