Dyeing Properties of a Polyester Ultrafine Fiber

Abstract

Dyeing properties of a polyester taffeta made from ultrafine fibers (0.07 denier) with disperse dyes are clarified through an analysis of sorption isotherms and rate of dye sorption data in comparison with those for microfibers (0.25, 0.32, and 0.44 denier). Ultrafine fibers are made using sea-island-type conjugate spinning techniques, while the microfibers are made by the conventional melt spinning method. Physical properties of the ultrafine fibers relating to the dyeing properties are also measured. The sorption-diffusion behavior of purified disperse dyes in the 0.07 denier (0.07d) fibers at 95°C and the physical properties of these fibers are almost the same as those of the microfibers, except for the 0.25 denier (0.25d) fiber, which contains 0.5% additives to facilitate spinning. Therefore, ultrafine fibers can be dyed by considering only the difference in the fiber radius. Two polyester taffetas are used to measure dyeing kinetics, i.e., 0.07d fibers and 0.25d fibers. Delay of dye sorption at the initial stage is appreciable for the 0.07d taffeta with purified dyes at 95°C and the 0.07d and 0.25d taffetas with commercial dyes at 120°C. This phenomenon is explained in terms of the presence of diffusional boundary layers around the individual filaments caused by the very slow movement of dye liquor through the taffetas. Color yields of the commercial dyes on the two taffetas are discussed.