Evaluation of moisture diffusivity in hydrophilic polymer membranes: A new approach

Moisture diffusivity in hydrophilic membranes is measured traditionally by stepwise drying experiments or steady state permeation tests. Problems with these methods are that the convective moisture resistance in membrane boundary layers is seldom taken into account, and the distributed nature of moisture emissions on membrane surface and air concentration above it often give distorted results. In this study, a new method designed to overcome these imperfections is proposed in predicting the diffusivity of moisture in hydrophilic membranes. The key equipment is a filed and laboratory emission cell. The whole technique comprises two steps: in the first step, the cell surface convective mass transfer coefficient is obtained; and in the second step, moisture diffusivity in membrane is measured. The technique also involves a two-dimensional modeling of moisture transport in membranes.