Thesis Details

Thesis Title: The effects of critical variables in Superba heat-setting on color uniformity of stock dyed nylon 6,6 staple carpet yarn
Thesis Author: B. Steven Bowen
Abstract: Streakiness continues to be a major quality issue in the production of carpet. The origins of streaks have been studied for years, with many streaks being attributed to the heat-setting process of carpet yarn. Possible causes of streaks in dry and wet heatsetting have been studied using undyed nylon 6,6 filament carpet yarn; however, limited published research exists on the sources of streaks in stock dyed, heat-set nylon 6,6 staple carpet yarn. Two variables that have caused streaks in undyed nylon 6,6 carpet yarn are tunnel temperature and pre-bulker temperature. A study was conducted using the Superba continuous heat-setting system to determine the effect of these variables, along with coil mass density, steam pressure, and belt speed, on stock dyed nylon 6,6, staple carpet yarn. The effects on yarn bulk, yarn shade, fiber morphology, dye migration, and carpet streak intensity were determined from results of testing. The level of coil mass density resulted in the strongest correlation with carpet streaks. Coil mass density had a significant effect on L * values and K/S values. Tunnel temperature had a significant effect only on L * values. Although these effects were statistically significant, the level of color difference was insufficient to create visual color streaks. A comparison of yarn structural characteristics revealed slight changes in yarn bulk and count of streak versus control yarns. Structural differences observed between streak yarn and control yarn were explained by yarn being heat-set using the low level of coil mass density providing more freedom of both fibers in the yarn bundle and the yarn to relax and alter the structure. Thus, coil mass density was determined to be a critical variable to be monitored in the heat-setting process.