Ultrasonic assisted dyeing - III. Dyeing of wool with lac as a natural dye

The dyeing of wool fabrics using lac as a natural dye has been studied in both conventional and ultrasonic techniques. The extractability of lac dye from natural origin using power ultrasonic was also evaluated in comparison with conventional heating. The results of dye extraction indicate that power ultrasonic is rather effective than conventional heating at low temperature and short time. The effects of dye bath pH, salt concentration, ultrasonic power, dyeing time and temperature were studied and the resulting shades obtained by dyeing with ultrasonic and conventional techniques were compared. Colour strength values obtained were found to be higher with ultrasonic than with conventional heating. The results of fastness properties of the dyed fabrics were fair to good. Dyeing kinetics of wool fibre with lac dye using conventional and ultrasonic conditions was compared. The time/dye-uptake isotherms are revealing the enhanced dye-uptake in the second phase of dyeing (diffusion phase). The values of dyeing rate constant, half-time of dyeing and standard affinity and ultrasonic efficiency have been calculated and discussed. (C) 2004 Elsevier Ltd. All rights reserved.