Study On PEBA/PPESK Hollow Fiber Composite Membranes For Oxygen Enrichment

Choosing Poly(ether block amide)(PEBA) as the coating material, Poly(phthalazinone ether sulfone ketone)(PPESK) as the membrane material, the PEBA/PPESK composite membranes were prepared and the performance on O2/N2 separation was studied. The solvent post-treatment was used on the PPESK hollow fiber basement-membranes in order to improve the O2/N2 selectivity further, and the results showed that the surface porosity of the membranes was reduced as well as the surface compactness was improved..First, the dense PEBA membranes with pure (n-butane) and mixed (isopropanol and n-butane, mass ratio 3:1) solvents were prepared respectively by solution coating technique and the O2/N2 separation performance was studied severally under the influences of feed pressure and test temperature. The results showed that the performance of oxygen enrichment was better with mixed solvent. The solubility parameter of PEBA and the two styles of solvents were calculated and the solubility of the solvents to PEBA was compared.Second, using the spinning dope recipe of PPESK/DMAc/EtOH/THF, the PPESK hollow fiber membranes were prepared by phase-inverion technique and the PEBA/PPESK composite membranes were made by dip-coating method. The test on mechanical property showed that PPESK hollow fiber membranes had the good mechanicall performance; the PTIR spectraum of PEBA, PPESK and PEBA/PPESK composite membranes indicated that PEBA can be coated on the surface of PPESK hollow fiber membrane; It was studied that the influences of coating technology which contained coating solution concentration, coating temperature, coating time, heat-treating temperature, heat-treating time, second coatings, wet and dry basement membranes, feed pressures and test temperatures on the O2/N2 permselectivity for the PEBA/PPESK composite membranes. It was found that the the O2 permeance of the composite membranes was almost all over 45GPU, and the O2/N2 selectivity was almost all on the top of 2.3, reaching a good O2/N2 separation performance. And the membranes had a long time stability.Finally, the PPESK/DMAc/deionized system basement-membranes were prepared. The surface structure of the membranes was changed and the surface defect was decreased by solvent post-treatment. The membrane structure was observed through scanning electron microscope and the porosity was tested and calculated. The effect of DMAc and NMP aqueous solution concentration,vacuum time,membrane stability and nonsolvent aqueous solution was discussed for the separation of O2/N2. This method was applied to PPESK/DMAc/EtOH/THF system. The results showed that the O2/N2 selectivity was improved after solvent post-treatment.