Abstract
Dyeing properties of disperse dyes of different energy types were investigated for application with poly(ethylene terephthalate) flat yarn (FY). The maximum exhaustions of low-energy type disperse yellow 54, blue 56, and red 60 were 96%, 94%, and 99%, respectively, and high-energy type disperse orange 30, blue 79, and red 167 were 97%, 98% and 98%, respectively. The exhaustion values of high-energy type disperse dyes on flat polyester yarns were higher than those on normal polyester yarn, while the low-energy type disperse dyes showed no significant differences in dyeability between flat and regular yarns. The build-up properties of various disperse dyes on flat polyester yarn were superior to that of regular polyester. The K/S values of flat polyester yarn linearly increased with the increase in dye concentration in the range of 0.5-8.0 wt.%. The half dyeing times of the flat yarns were approximately 5 min shorter than those of general polyester due to their larger surface area and lower crystallinity. The surface area of flat polyester yarn is larger, which directly results in lower crystallinity. Uneven dyeing properties were observed in the same fabric due to cold crystallization, which was also confirmed using DSC.