MANOMETRIC TECHNIQUES FOR DETERMINATION OF GAS-TRANSPORT PARAMETERS IN MEMBRANES - APPLICATION TO THE STUDY OF DENSE AND ASYMMETRIC POLY(VINYLTRIMETHYLSILANE) MEMBRANES

An experimental manometric arrangement has been suggested for the study of membrane transport properties based on new techniques for the estimation of diffusion, sorption and permeation coefficients. Different variants of the transient regime and steady regime permeation of gases through polymer films have been proposed for the determination of membrane transport parameters. These techniques make possible measurements either from a steady initial condition or with variable boundary conditions. Transport parameters in quite different conditions (e.g., in the high pressure range, or in transitions between two steady permeation states) can be obtained from various permeation variables, with some advantages over the classical time-lag and modified time-lag methods. The methods have been applied to the study of transport properties of CO2, O2 and N2 in dense and asymmetric membranes made from poly(vinyltrimethylsilane). Transport parameters of different gases obtained for dense membranes are consistent with those found in some of the literature. The CO2 permeabilities are found to depend on the pressures applied on the two sides of the membranes: the CO2 permeability decreases in the case of dense membranes, but increases in the case of asymmetric membranes, with increase in the applied pressure.