Determination of diffusion parameters for polymer spheres undergoing high volume liquid transfer

In high volume liquid transfer inlo or oul of a polymer, swelling and shrinkage phenomena oecur. Simultaneously, the diffusivity for the liquid transfer is concentration dependent, increasing exponenlially. An investigation into the process of diffusion-absorption and diffusion-evaporation has been carried oul. Five parameters intervene: the diffusivily; its concentration dependency through the polymer: the coefficients of eonvective transfer at the surface during absorption; or desorption: and the extent of liquid absorbed. At the beginning of the absorption stage, the convective coefficient and the diffusivity of the liquid in the polymer free from liquid were determined. At the onset of evaporation from the pre-salurated polymer, the convective coefficient and the diffusivity in the polymer were also determined. Finally, the concentration dependency of the diffusivity was obtained from the values of the diffusivity in the polymer free from liquid and saturated. Rather good agreement is shown between the kinetics determined either experimentally or calculated using these parameters and a numerical model.