Diffusion of water through various polymer films: a new high performance method of characterization

Diffusion of water in polymer films has been characterized by using a new h igh performance and reproducible method based on permeation measurements. W ith this method, which uses a fast response water-specific sensor based on dew point measurement, it is possible to determine, from the transient step , the time lag water diffusion coefficient D-L and, when the steady state i s reached, a mean water permeability coefficient P. In this work we have em phasized the water concentration dependence of diffusion coefficient D. Aft er calibration, the technique yields accurate values of P, consistent with literature data. By testing various polymers, different behaviours with res pect to water have been observed, particularly with low density polyethylen e (LDPE) which shows significant hydrophobic properties. (C) 1999 Elsevier Science Ltd. All rights reserved.