Low Liquor Microwave Dyeing of Cotton Fabric with a Minimal Amount of Salt and the Effect of Different Reactive Dye Substituents

Demand for textiles is increasing owing to human population growth, social competition, and fashion trends. This growth in demand is met at the cost of contamination of tons of fresh water with dye. In this study, microwave irradiation was used in dyeing of textiles as a method of minimizing this environmental threat. The microwave works through dielectric heating and realizes its effect on different dye structures. Dyeing was performed on six different reactive red dyes based on an H-acid coupling component with dissimilar substituents. UV–visible spectroscopy measurements revealed that auxochromes do not impart color to the dyes, but still have a great impact on color depth and hue. The zeta potential and temperature rise per minute under microwave irradiation were both affected by changes in the dye concentration and structure. The dyeing of cotton samples was performed by the exhaust microwave dyeing technique with an optimized recipe and conventional dyeing with a standard recipe for comparison. The color strength values obtained from the experiments revealed that the microwave technique provides better results by consuming 86.67% less salt with a lower liquor volume. The exhaustion and fixation values further confirmed this assessment. The color fastness against basic conditions was similar with both techniques; hence, the microwave can be considered to be a better technique in all aspects. Furthermore, the dye D195 was found to be more effective in achieving higher color depths with a less concentrated effluent indicating that the synthesis of high-performance dyes requires care in the selection of substituents.

Graphical abstract