Preparation and gas separation performance of thermally rearranged poly(benzoxazole-co-amide) (TR-PBOA) hollow fiber membranes deriving from polyamides

Flexible poly(benzoxazole-co-amide) (PBOA) gas separation hollow fiber membranes were successfully prepared deriving from ether-containing polyamide precursors by thermal densification with or without a supplementary coating treatment. Compared with polyimide precursors, thermally rearrangement in this work required lower treatment temperature but generated better mechanical properties. Both spinning process and thermal treatment conditions were systemically manipulated to intensify the membrane densification aiming at achieving greatly improved selectivity of the obtained TR-PBOA hollow fiber membranes. It was found that draft ratio had little contribution to selectivity enhancement. Separation performance was substantially improved when precursor fibers were dried using ethanol-hexane exchange method and then thermally treated at 350–390 °C TR hollow fibers obtained by combined thermal treatment with coating method exhibited the highest selectivity values in this study.