MODELING WEAKLY NONLINEAR 2-STAGE SORPTION KINETICS IN GLASSY POLYMER-FILMS

A model for non-Fickian gradient diffusion in polymer-penetrant system s is studied to assess its capability in predicting experimental resul ts in weakly non-linear differential vapor sorption experiments at con ditions when ''two-stage'' sorption kinetics occur. The effects of six dimensionless parameters in the model on predictions of sorption kine tics are evaluated systematically by numerical simulations. The model predicts a number of observable trends. The predictions are compared s uccessfully with sorption data of acetone vapor in VECTRA(R), a glassy random copolyester of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (HBA/HNA). The results are relevant to the application of VECTRA (R) and related polymers as barrier materials. (C) 1998 Elsevier Scien ce B.V.