Six disperse dyes were applied at 0.5%,1% and 2% omf depths of shade to poly(lactic acid) fabric at 30e80 C
for 20, 50 and 90 min in both the presence and absence of ultrasound. Whilst ultrasound enhanced the
colour strength obtained for three of the six disperse dyes used at temperatures upto 70 C, ultrasound did
not always result in enhanced colour strength being achieved in the case of the three other dyes.
The observed intensification of colour strengthwas attributed to dye disaggregation. Dyeing at 80 C in the
presence of ultrasound resulted in pale, dull dyeings of reduced colour strength, which was attributed to
breakdown of the dye dispersions at this particular temperature.