Suppression of C3 Gas-induced Plasticization in Glassy Polymeric Thin-films

Abstract

C3 gas-induced plasticization is one of the challenges in developing high-performance membranes for olefin/paraffin separation. In particular, plasticization is more severe in thin-film composite (TFC) membranes. The main goal of this dissertation was the suppression of the plasticization in glassy polymer-based TFC membranes by using the protective layer for olefin/paraffin separation. Polyimides, especially 6FDA-DAM and Matrimid, were chosen as a suitable polymer matrix for the fabrication of high-performance C3H6/C3H8 separation membranes. In this study, defect-free 6FDA-DAM TFC membranes were successfully prepared by the spin coating method. We proposed that introducing a protective layer is a good strategy to mitigate the severe plasticization of 6FDA-DAM TFC membranes. This protective layer was spin-coated on the 6FDA-DAM selective layer. Among the different polymers, PEBAX1657 was found the highest performance to suppress the plasticization. Of particular note, 6FDA-DAM TFC membrane with PEBAX1657-based protective layer possessed the highest C3H6/C3H8 permselectivity along with superior anti-plasticization, even comparable to 6FDA-DAM bulk-film. In addition, we confirmed that the protective layer concept can also be applied to Matrimid-based TFC membranes for C3H6/C3H8 separation. Hence, this protective layer strategy holds a great promise for suppressing the plasticization behavior of other glassy polymers-based TFC membranes.