Preparation of high-flux polyimide of intrinsic microporosity for oxygen enrichment membrane
A ternary copolyimide 6FPDM was prepared using 2,4,6-trimethyl M-phenylenediamine(DAM),4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)and pyromellitic anhydride(PMDA)as monomers by one-step high temperature polymerization method.By using non solvent induced phase separation method(NIPS),the completion time of phase separation is controlled by controlling the casting solution composition,coagulation bath temperature,additives and membrane thickness.Then,a PMDS layer is coated on the surface of the membrane to prepare the composite membrane.The oxygen/nitrogen separation performance of the polyimide pristine membrane,asymmetric membrane and composite membrane were tested.By regulating the dope solution and phase inversion conditions(15％absolute ethanol,1％LiNO3,coagulation bath at 45 ℃,and casting knife thickness of 100 μm),the resulted membrane displayed best gas permeability after coating.The oxygen flux reached 96.9 GPU,and the O2/N2 selectivity of 4.3,which has shown great potential in membrane-based oxygen enrichment field.
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