The transport properties of a series of ester penetrants through a polyamide-based elastomeric adhesive are reported. The results obtained are compared with those from a similar study on a series of n-alkane penetrants reported previously. It was established that the diffusion of the esters, as in the case of n-alkanes, is Fickian and follows a Henry's law-type mechanism. Furthermore, it was concluded from a combination of activation energy calculations and molecular simulations that the ester penetrants, similar to n-alkanes, diffuse linearly along their long molecular axes. The chemical composition influence of the penetrants was investigated by means of their Flory-Huggins interaction parameter with the elastomer, chi(12). The chi(12) values for the esters were found to be lower than those of the corresponding n-alkanes suggesting the role of favorable contributions from the polymer-ester interactions. Differences in the diffusion coefficients between the n-alkane and ester series were explained on the basis of these chi(12\) values. Finally, correlations between (a) the diffusion parameters, D and E-d, (b) penetrant size (molar volume, V-m) and (c) chemical nature of the penetrant (chi) were established. These correlations account for both penetrant size and chemical effects simultaneously, thereby providing a more general description of the transport properties of the polymer-n-alkane and polymer-ester systems. (C) 2003 Elsevier Science Ltd. All rights reserved.
