The study of 6FDA-polyimide gas separation membranes

Abstract

A systematic study on 6FDA-polyimide membranes for CO2/CH4 gas separation has been carried out in this thesis. It consists of 1) the characterization of the intrinsic properties of dense films, 2) the optimisation of a hollow fiber spinning process, and 3) the chemical cross-linking modification of hollow fibers to improve their resistance to CO2-induced plasticization. In summary, we have 1) studied and compared various definitions of gas diffusion coefficient by means of permeation and sorption apparatus using the dense films of 6FDA-6FpDA polyimide as a model material, 2) investigated the initial plasticization phenomenon based on the extensive database of 6FDA-2, 6-DAT transport properties as functions of pressure and temperature, 3) developed a new and environmental friendly one-polymer and one-solvent spinning system to fabricate 6FDA-2, 6-DAT asymmetric hollow fiber membranes with high performance, 4) demonstrated a simple and practical chemical cross-linking method to improve the plasticization resistance of 6FDA-2, 6-DAT hollow fibers against CO2 using p-xylenediamine and m-xylenediamine cross-linking agents.