Preparation of asymmetric polyetherimide hollow fibre membrane with high gas selectivities

Preparation of asymmetric polyetherimide (PEI) hollow fibre membranes with high gas selectivity was studied by introducing volatile organic compounds as additives into the dope solutions. The additives used include methanol, acetone, a mixture of methanol/acetone and tetrahydrofuran (THF). N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc) were used as solvents. The PEI hollow fibre membranes were spun using tap water as the external coagulant and 50 wt.% ethanol aqueous solution as the internal coagulant. The effect of air gap, polymer concentration, solvent and additives on membrane separation properties was investigated. It has been shown that parameters, such as the solvent, additive and air gap affect the dense skin layer formation. Asymmetric PEI hollow fibre membranes with high He/N2 selectivity can be prepared using volatile non-solvent additives and NMP as the solvent at a suitable length of the air gap. The PEI hollow fibre membrane prepared using THF as the additive shows the poor selectivity.