Relationship Between Tinctorial Depth and Fiber Fineness in Dyed Polyester Fabrics

The influence of fiber fineness and fabric structure on the tinctorial depth of dyed polyester fabrics was investigated. Plain weave and stitch fabrics composed of polyester filament yarns with different single-fiber finenesses were prepared. The single filaments of the yarn used had finenesses of 0.4, 0.7, 1.0, 2.0, 3.0, and 5.0 denier. The fabrics were dyed with disperse dyes (C. I. Disperse Yellow 5, Red 72 and Blue 148) in various tinctorial depths. The relationship between dye uptake on fabrics (Cf) and K/S value in the Kubelka-Munk function was examined at various wavelengths. Plots of Cf vs. (K/S)d-(K/S)o give a straight line at a particular wavelength for each fabric dyed with the same dye, suffixes d and o refer to dyed and undyed fabrics, respectively. In the K/S region of 10 or less, where Kubelka-Munk function could be applied, the change in the tinctorial depth with Cf and fineness of fiber (D) is expressed by the following equation. This equation shows that a smaller denier leads to lower values for (K/S)d-(K/S)o, which in turn proves that the denier of a single fiber is a significant factor in making the tinctorial depth appear lighter. It was clarified that each fabric has a unique effective surface area and a light-scattering coefficient determined by the fineness of the single fibers and the weaving structure. It was confirmed that the light-scattering coefficient of an undyed fabric could be used to estimate the effect of the fiber substrate on the tinctorial depth.