Thesis Details


Thesis Title: An investigation of the variables in dyeing textured woven polyester with disperse dyes of different energy levels
Thesis Author: Craig Duhamel
Abstract: Major problems have been encountered in the dyeing of textured woven polyester fabrics. A major portion of the problem is associated with dye shade differences which result in a large number of redyes. Both the use of carriers and high temperature have reduced the shade differences considerably. This technique has especially helped in rereducing the shade differences introduced by variations in the texturing history of yarns. The purpose of this thesis was to investigate the variables in dyeing textured wovens and their contribution to dye shade differences. The variables studied were dyeing temperature, carrier concentration, pH level, time, and dye concentration. The experimental design included the study of different energy level disperse dyes. Disperse dyes are classified according to their molecular size, the high energy dyes being composed of large molecules which are more difficult to enter the polyester fiber. The experiment was designed so that all variables except one were held constant to study the effect of the isolated variable on color difference. Color difference was measured by use of a large sphere I.D.L. Color~Eye. A computerized program was then used to calculate MacAdam units of color difference. One MacAdam unit is defined as a just noticeable difference in color. In addition to MacAdam color difference, KubelkaMunk functions were measured. The function is described by two values, K and S, where K is the coefficient of absorption and S the coefficient of scatter which is written in a ratio K/S. The function is calculated by the following formula: K/S = (l-R)^2 / 2R where, R = reflectance. S 2R The K/S value varies linearly with the concentration of dye on the material. Several conclusions were drawn from the experimental studies. The variable temperature on the average produced significant changes in dye uptake at a change of ten degrees Celsius below the standard. The color changes produced by the variable carrier concentration were dependent on the particular dyestuffs. Certain dyestuff were found to be more sensitive to changes in pH. The time of dyeing was found to be significant in causing color changes dependent on the energy level of the dyestuff. The results of dyeing with different concentration of dye were random color changes in MacAdam units for the yellow colored dyestuffs. The blue and red dyestuffs gave unidirectional changes in color that were directly related to the concentration of dye.