The concentration distribution of a disperse dye in the multiple layers of nylon fabric is investigated. The surface concentration increases with dyeing time. The increase is attributable to the resistance to dye transport across the diffusional boundary layer. The boundary layer parameter (L.) and the diffusion coefficient (Df) of dye in nylon fabric are estimated in such a way that the experimental data fit in with the theoretical curve of concentration distribution based on the diffusional boundary layer model. The estimated values of thickness of diffusional boundary layer (3d) range from 0.017 to 0.011cm when the dye bath is stirred at 100-150 rpm. As the multiple layer of nylon fabric has spaces or pores between the yarns and also between the individual filaments, it is considered that the dye molecules diffuse through the liquid in the spaces or pores of nylon fabric. Consequently, the observed diffusion coefficient was reasonably explained by assuming the "pore model": the calculated value agreed well with the experimental one.

The diffusion behavior of a disperse dye in a porous membrane was investigated. The surface concentration CB attained its equilibrium value C, only very slowly, varying with time according to the equation where CO is surface concentration at time t=0 and 8 is a constant, 1.387x10-Ss-1.The solution to the diffusion equation may be obtained by superposing the known solutions for the cases of constant surface concentration and time dependent surface concentration as given by Long and Richman. This gives for the concentration distribution where C is the concentration, x is the distance and D is the diffusion coefficient.The experimental data agreed well with the calculated curve.

An equationproposed to describe the diffusion behaviour of reactive dyes was applied to the systems of cellophane rolls and two reactive dyes of Procion M type:Where C is the concentration of active dye at time t at distance x, C' the surface concentration of active dye, K the reaction constant of active dye and D the diffusion coefficient of active dye. In order to determine the diffusion coefficient (D) and the reaction constant (K), eq. (I) was integrated to fit the experimental data by graphical asessment.Effects of pH, dye concentration and dyeing temperature on D and K are discussed. Activation energy of the system is also calculated.The results obtained are as follows: (a) With increase in pH, the diffusion coefficient has a tendency to increase and the reaction constant increases.The diffusion coefficient and the reaction constant are independent of the dye concentration. (c)As dyeing temperature rises, both the diffusion coefficient and the reaction constant increase, while the surface concentration decreases.

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