Investigation of mordant application in direct dyeing of nylon fabrics

Being the first commercially available wholly synthetic textile fiber which was introduced to the market in 1939, nylon fibers are one of the most frequently consumed synthetic fibers. Direct dyes were commercially produced in the early 20th century and had been the preferred method of dyeing of cellulosic fibers together with vat dyes until the discovery of reactive dyes. The most important property of direct dyes is their easy dyeing but with a disadvantage of building up weak bonds within the fiber. Chemical mordants were used mainly in the application of natural dyes to hold and retain the dye molecules in textile fibers. In this research, nylon 6,6 fabric was dyed with four direct dyes of different hues in the presence of mordants (eight metallic and one bio-mordant) to obtain better exhaustion, fixation, and coloration properties. Pre-mordanting, meta-mordanting, and post-mordanting methods were used and the dyeings were performed at 1% owf at pH 5. Percentage of dyebath exhaustion (%E), percentage fixation (%F), and overall fixation (%T) were calculated after pyridine extraction. Wash and light fastness tests were applied on the dyed samples. The results were discussed via color strength (K/S), %E, %F, %T, and CIELAB color differences (ΔE ab *). The results revealed that mordant usage improved the coloration properties of direct dyes on nylon fabrics. The %E, %F, and %T results changed according to the independent variations of dye hue, mordant, and mordanting method. Certain mordants and mordanting method gave the best coloration and fastness results for the dyes under test.