Thesis Details


Thesis Title: The effects of pH buffer, chemical auxiliary concentration, and liquor ratio on the shade repeatability of exhaust dyed polyester using disperse dyes
Thesis Author: Benjamin Espada
Abstract: The most preferred method for dyeing polyester with disperse dyes is at high temperature and high pressure. This process is known as exhaustion dyeing. In the exhaust dyeing of polyester with disperse dyes, dyebath assistants, or auxiliaries are normally added. These auxiliaries are necessary because disperse dyes exhibit limited solubility in water, and a fine, stable dispersion of the dye in solution is an essential requirement in dyeing. The most common auxiliaries are dispersing agents, levelling agents, carriers, sequestering agents, and acid. It is common practice in exhaust dyeing to base the amounts of chemical auxiliaries on the weight of the fiber dyed and to run the jets at a set water level. If the amount of fiber is not kept constant from batch to batch, varying liquor ratios result. When liquor ratios vary, basing the chemicals on the amount of goods causes variations in chemical concentrations. These variations in concentration can change the percent exhaust of the dye, which affects shade repeatability. The use of auxiliaries, the pH of the bath, and the liquor ratio are important in the exhaust dyeing of polyester. When used indiscriminately, poor exhaustion, low color yield g off-shade dyeings, and poor shade repeatability can result. Therefore, it necessary that the influence of the addition of these auxiliary products, the bath pH, and the liquor ratio be understood to maximize shade reproducibility. Two series of experiments were designed to evaluate the influence of a pH buffer, chemical auxiliary concentration, and liquor ratio on the shade repeatability of exhaust dyed polyester using disperse dyes. The first of these series was performed on an Atlas Launderometer and the second series was performed on two Werner-Mathis JFO laboratory jet dye machines. The results of this work showed that changing liquor ratios caused by varying fabric load sizes significantly affected shade variabil. It was also found that basing chemical auxiliaries on the volume of the dyebath significantly reduced the shade variation when these liquor ratios are varied. The use of the buffer system for pH control significantly improved the ability to control the dyebath pH and resulted in reduced variation in depth of shade. It was also found that machine variability between two comparably equipped JFO machines did not significantly affect the shade variability of the dyeings.