TRANSPORT OF WATER-VAPOR AND GASES IN MODIFIED CELLULOSE-ACETATE MATRICES - INFLUENCE OF THE NATURE OF THE PENETRANT ON DIFFUSION AND RELAXATION KINETICS

Membranes developed by modification of a cellulose acetate (CA) matrix were studied by means of the flow method CA matrix is modified by pol y(4-vinylpyridine) (PVP), or an interpenetrating network (IPN) agent. The obtained diffusion coefficients, permeability coefficients and rel axation kinetic parameters for oxygen, carbon dioxide and water vapour enabled us to consider not only the transport properties of the membr anes but also the influence of the relaxation processes an the membran e permeability and stability. The results show that the interactions b etween water molecules and polar groups on the polymer chains cause th e membrane material to swell. This swelling process provokes an increa se 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 mem brane permeability by ca. 38%, while carbon dioxide has no effects on the membrane properties. Membranes based on a modified cellulose aceta te matrix have higher permeability than pure CA membranes.