Influence of interfacial resistance on kinetics of sorption

Abstract

A model for sorption influenced by rate of transfer to the surface layer of polymeric sheets has been examined. The rate of uptake into the surface layer has been taken to be proportional to the degree of unsaturation of the surface layer. The predicted sorption behaviour has been compared with experimentally observed data which shows a reasonable agreement. A method for calculating diffusion coefficients has been demonstrated. It has been shown that sorption rates could be affected by factors like pressure of the penetrant in the vapour phase and the structure of the surface vis-á-vis that of the bulk. Extension of the model qualitatively, to systems with diffusion coefficients strongly dependent on concentration, indicates the possibility of larger uptake of the penetrant in thinner sheets in an initial time interval. This supports some experimental observations reported earlier. The model supports the experimental work of Long and Richman who observed the time dependence of surface concentrations during sorption. © 1981.