New methods for the determination of the parameters of a concentration-dependent diffusion law for molecular penetrants from transient permeation or sorption data

New methods were developed for the determination of the plasticization para meters and the limit diffusion coefficient of a penetrant whose diffusivity varies exponentially with its concentration. No specific computer software s is required for their use and they are user friendly. The method using di fferential permeation data is based on the correlations between the slope o f the reduced permeation flux versus time plot at the inflexion point, and the two key parameters of the concentration-dependent diffusivity laws. For the transient sorption method, the slope of the penetrant mass uptake vers us square-root of time curve leads to the same parameters of the diffusion law via similar correlations.