Thesis Details

Thesis Title: The effects of varying package to package density on shade repeatability and levelness of package dyed yarn
Thesis Author: Amy Chandler
Abstract: Increased economic pressures and inflation have resulted in the need for improved uniformity and reproducibility in dyeing. The package dyer is faced with the challenge of equally and evenly penetrating dye liquor to all parts of a package, wi th each yarn layer acting as an obstacle and affecting the levelness and repeatability. Package geometry, especially density, has long been recognized as an important variable in obtaining uniform and reproducible dye uptake in package dyeing. However, the amount of density variation that can be present to still produce acceptably dyed packages is not known. This _. research was conducted to gain a better understanding of the impact of package densi ty on shade repeatability and levelness in package dyeing. variables that were believed to impact density or were believed to be significantly influenced by density were also evaluated. Winding systems used in this study were precision and random, flow rates were 50 psi and 100 psi, and spindle placement was 1 - 4, from top to bottom of.the spindle. Each combination was used wi thin three dyeing systems; polyester disperse, cotton direct, and cotton fiber reactive. Each trial was dyed in a 25 package kier using typical industry dye procedures, wi thout using any enhancing chemicals such as carriers or levelers to promote a worst case scenario. A 5.0 percent difference in K/S values was used as the maximum allowable tolerance for determining levelness and reproducibility. Based on these processing parameters, the following results were disclosed: Within the density ranges studied, the impact of density on shade repeatability and levelness is dependent on the dye system. Density has the largest impact within the polyester disperse dye system and the smallest impact within the cotton fiber reactive system, with medium impact occurring wi thin the cotton direct system. Wi thin the polyester disperse dye system, as package density increases from 0.402 kg/L to 0.516 kg/L, the resultant depth of shade decreases 6.9%. within the direct dye system, as the density increases fromO.314 kg/L to 0.431 kg/L, the depth of shade decreases. For the fiber reactive dye system, as the density increases from 0.314 kg/L to 0.431 kg/L, there was no change in depth of shade. To determine the tolerance levels, or maximum amount of density variation to produce a repeatable shade, the depth of shade values obtained while increasing density were used. The predicted tolerance levels are 18.6% for the disperse system, 38.4% for the direct, and 88.8% for the fiber reactive dye system. However, these values are based on density effect only and no other processing parameters are taken into account. Precision wound packages exhibit consistently higher depth of shade values than random wound packages. These two systems are found to be statistically different from one another, but not when combined with density. Varying flow rate from 50 psi to 100 psi significantly influences depth of shade of dyed packages. Depth increases at high flow rates. When flow and density interactions are combined, the effects on depth of shade are statistically insignificant. Depth of shade is affected by spindle placement indicating that variations in package placement will affect repeatability of shade. When spindle placement and density interactions are combined, the depth of shade is affected. The hardness measurement method, using a Durometer III, is an ~ccurate replacement for calculating density. The correlation is higher than that of the air permeability testing and the average testing time, 5.16 sec, was significantly lower than either the density calculation and the-air permeability testing. As densi ty increases wi thin the polyester and cotton packages, flow decreases. However, an increase in differential pressure can be used to offset increasing density and maintain the same flow. Although air permeability is not an accurate density indication, it is an accurate indication .. of water flow through a package, and is therefore a better indication of package behavior during dyeing.