Thesis Details

Thesis Title: The influence of the degree of preparation on shade consistency, washfastness, and crockfastness properties of a fiber reactive dyed 100% cotton woven fabric
Thesis Author: J. Russell Ogle
Abstract: Cotton remains the most important raw material for textile fabrics, amounting to 51 percent of the world's fiber production. Although polyester is a close second, the production of cotton continues to grow annually. The textile industry has realized the importance of proper preparation of cotton fabrics. The main objective of preparation is to remove all contaminants that could inhibit the uniform absorption of dyes and chemicals in subsequent·', treatments. Recent studies indicate that as many as 70 percent of all defects in the final finished cotton fabric are due to inadequate preparation. An old saying in the textile wet processing industry is "well prepared fabric is half dyed". Typically, the degree of preparation is determined using the following quality indicators: absorbency, extractables (water, enzyme, and solvent), whiteness, fluidity, and ash content. The degree of preparation needed varies according to subsequent dyeing technique. For example, fabrics to be dyed darker shades need not be prepared as extensively as those going into lighter shades. In addition, fabrics to be jet dyed need not be prepared as extensively as those which will be pad/dry-pad/steam dyed. The various dye classes (e.g., reactive, direct, sulfur, etc.) will react differently depending on the degree of preparation. Today, there are general recommended levels of preparation quality indicators that should be obtained to achieve the best dyed fabric quality. However, many of these suggested standards of preparation are not specific to the subsequent dyeing procedure and dyeing technique. The primary objective of this study was to determine the influence of preparation on shade consistency, washfastness, and crockfastness properties of a continuously fiber reactive dyed 100% cotton woven fabric. Cotton twill fabric was desized/scoured/bleached under twenty-five various conditions. Ten of the preparation conditions were mercerized. These prepared and mercerized fabrics were then dyed with Procion H fiber reactive yellow, red, and turquoise dyestuffs on a mini-dye range using a continuous pad/dry-pad/steam procedure. Dyed fabrics were evaluated for depth and levelness of shade, washfastness, and crockfastness properties to set up correlations between these dye parameters and the various preparation quality indicators. The results of this thesis revealed that the degree of preparation influenced depth, hue, and levelness of the final shade. In addition, mercerization only slightly improved the depth and levelness of shade of marginally prepared goods, but not of those poorly prepared. Absorbency and whiteness were the most practical determinants of dye performance. Absorbency was highly associated with the amount of residual water-resistant impurities (ie. fats, oils, waxes, and pectins) which could inhibit uniform dye absorption. Whiteness was also related to the degree in which these contaminants were removed, and to the fmal hue of the goods. Overall, lower levels of absorbency and greater degrees of whiteness resulted in acceptable depths of shade and levelness properties. This study has documented evidence that the degree of preparation can influence the final dyed fabric shade. Therefore, the basis of shade consistency is consistent uniform preparation. Proper preparation of woven cotton fabrics is crucial for successful continuous dyeing with reactive dyes.