Studies of the effects of microstructure on moisture penetration through membranes

A theoretical study has been conducted to investigate the effects of microstructure on the transport properties of water vapor through membranes and a model to predict the moisture flux and moisture resistance was obtained. Experiments were made to measure the moisture resistances in three porous membranes including PVDF, PES and Cellulose membranes. Parameters on membrane structures were determined through regression of the experimental data. The results support that the membrane thickness, pore size distribution, effective porosity and tortuosity all have significant impacts on the moisture penetration through membranes. Based on the parameters, the effects of the mean pore size were studied numerically. The results show that: as the mean pore size increases, the moisture resistance decreases, but the decreasing rate becomes smaller for larger pore size.