| Abstract: | The rate of sorption of an acid dye by a nylon fabric is strongly influenced by mass–transfer processes in the liquid phase, even at rates of flow far exceeding those to be expected in existing commercial dyeing equipment. It is suggested that concentration gradients exist in the solution within the yam elements of the fabric, and the individual fibres in the yarn elements are shown to differ in their accessibilities to dye; the yarn cross–sections are ‘ring–dyed’. In spite of these complexities the major features of the overall mass–transfer process are well represented by a simple model based on the concept of an equivalent diffusional boundary resistance to mass transfer. The numerical values obtained for δ are comparable with the yarn dimensions, which reflects the ‘coalescence’ of the individual boundary layers to form a region within the yarn elements in which dye transport by convective diffusion in the liquid phase limits the overall mass–transfer rates. |
