The effect of thermal annealing on the structure and performance of hollow fiber gas separation membranes
In the field of gas membrane separation,hollow fiber membranes(HFMs)are widely used due to their high specific surface area and high filling ratio.In this paper,BTDA-TDI/MDI(P84)co-polyimide hollow fiber membranes were prepared by dry-wet spinning technology.The P84 HFMs were thermally annealed at 250 ℃ and 300 ℃,which were below the temperature of P84 Tg(332.6 ℃),to investigate the effect of thermal annealing procedure on the structure and gas separation performance of the HFMs.Compared with the pristine P84 HFMs,the gas separation properties of the thermally annealed P84 HFMs at 250 ℃ had negligible change,but their tensile strength and the elongation at break decreased significantly.When the thermal annealing temperature was close to Tg(at 300 ℃),the thermal annealing P84 HFMs could maintain the tensile strength and elongation at break.In addition,their gas separation selectivity was significantly improved,and the defects on the surface of P84 HFMs were reduced.To further investigate the effect of the sub-Tg thermal annealing process on the structure of the P84 HFMs,they were characterized by XRD,FTIR,HIM,and so on.
gas separationpolyimidehollow fiber membranethermal annealing
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