Inorganic particle enhanced polymer hollow fiber membranes with high mechanical properties

Abstract

Inorganic particle/polymer hollow fiber membranes with different inorganic particle sizes and particle loadings were synthesized and characterized in terms of morphology and mechanical properties. The incorporation of inorganic particles induces the formation of large surface pores in the skin layer yet decreases the pore size of large voids in the support layer. The particle size and particle loading are determining factors in such morphology changes. Moreover, due to the different out-diffusion ability of inorganic particles with different sizes, smaller particles migrated and diffused out from polymer much more easily; therefore nano-sized inorganic particles were usually observed on the top surface of polymer whereas micron-sized inorganic particles were usually partially embedded inside the polymer. As a result of such morphology changes and the intrinsic mechanical properties of inorganic particles, both tensile and compressive properties were improved in such inorganic-polymer composite membranes compared to the pristine membranes. Specifically, the tensile strength can be increased by 47.2% with 1.96 wt% nano-sized alumina whereas the yield compressive strength was enhanced by 55.4% with 76.9 wt% micron-sized alumina in comparison with the pristine polymeric membranes. Besides the improvement of strength, the tensile and compressive Young's modulus was increased and the micron-sized particles are more effective to enhance the Young's modulus than the nano-sized particles. Besides the improvement in mechanical properties, the permeability of polymeric membranes was also enhanced via the inorganic particle incorporation. Therefore, such inorganic-polymer hollow fiber membranes are more promising to be used for practical industrial filtration applications regarding their higher mechanical properties to resist breakage and deformation and their higher permeability in comparison with the polymeric hollow fiber membranes.