Kinetics of dyeing acrylic acid-grafted cotton, fabric with basic dyes

The effect of graft yield, dye concentration and dyeing temperature on the colour strength of acrylic acid-grafted cotton fabric has been studied for Sandocryl Blue (SB) and Rhodamine Red (RR) basic dyes. It is observed that the colour strength increases with the increase in graft yield and levels off at higher degrees of grafting. The best dyeing is achieved at pH 3.9 and 2.72 for SB and RR aqueous solutions respectively. The colour strength of grafted fabrics increases rapidly with the increase in dyeing time and levels off within few minutes, depending on the dye concentration (C-o) and temperature of the dye bath. The initial dyeing rates (R-d) for SB dye Are higher than those for RR dye. The dyeing process follows a 0.62 order kinetics and is almost independent of the dyeing temperature or the type of dye. Dyeing rate and rate constant increase considerably with the increase in dyeing temperature. Activation energies of 11.2 and 14.36 kJ/mole were calculated for SB and RR dyes respectively. The mechanism of the dyeing process for the two dyes is diffusion controlled and their dyeing rates depend on the type of basic dye. Considerably high dyeing rates are found even at temperatures as low as 282 K and the completion of the dyeing process takes place in a matter of, minutes. About 70-99% of the colour strength of the samples dyed at 90degreesC for 1h is obtained at dye bath temperatures ranging from 9degreesC to 55degreesC and a dyeing time of 80s.