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Abstract:
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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.
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