Transport of water vapour and gases in modified cellulose acetate matrices. Influence of the nature of the penetrant on diffusion and relaxation kinetics

Abstract

AbstractMembranes developed by modification of a cellulose acetate (CA) matrix were studied by means of the flow method CA matrix is modified by poly(4‐vinylpyridine) (PVP), or an interpenetrating network (IPN) agent. The obtained diffusion coefficients, permeability coefficients and relaxation kinetic parameters for oxygen, carbon dioxide and water vapour enabled us to consider not only the transport properties of the membranes but also the influence of the relaxation processes on the membrane permeability and stability. The results show that the interactions between water molecules and polar groups on the polymer chains cause the membrane material to swell. This swelling process provokes an increase in the permeation flux of ca. 20–30%. Oxygen causes a consolidation of unstable membranes of the cellulose acetate matrix modified by IPN but not of blends with PVP. The consolidation process reduces the membrane permeability by ca. 38%, while carbon dioxide has no effects on the membrane properties. Membranes based on a modified cellulose acetate matrix have higher permeability than pure CA membranes.