Polypropylene Hollow Fiber Membrane by Dissolution-Inducing Pore Methods.

Plasma leakage limits the development of polypropylene membranes as oxygenated membranes. Here, a new method named the dissolution-induced pore method was adapted to prepare polypropylene hollow fiber membranes: after polypropylene and polyvinyl chloride were melt-blended and extruded, the polyvinyl chloride was removed by N, N-dimethylacetamide to obtain a porous polypropylene membrane material. The variation of membranes has been explored in detail with respect to the influence of different parameters on the flux and mechanical properties of membranes and the feasibility of the polyvinyl chloride recovery. The resulting polypropylene hollow fiber membrane shows that plasma penetration was zero within 6 h of test, gas flux can reach 189,000 L/(m2·h·0.1 MPa), and its strength at break reaches 65 MPa and the elongation at break is 890%; polyvinyl chloride recovery achieves more than 99%. This research has developed a promising and low-cost extracorporeal membrane oxygenation material, which provides benefits for patients with less capacity for medical expenditure.

Polypropylene Hollow-Fiber Membrane Made Using the Dissolution-Induced Pores Method.

The efficient preparation of hydrophilic polypropylene membranes has always been a problem. Here, a twin-screw extruder was used to melt-blend ethylene-vinyl alcohol copolymer and polypropylene; then, hollow fibers were extrusion-molded with a spinneret and taken by a winder; after this, dimethyl sulfoxide was used to dissolve the ethylene-vinyl alcohol copolymer of the fiber to obtain a polypropylene hollow-fiber membrane. This procedure was used to study the effects of different contents and segment structure of ethylene-vinyl alcohol copolymer on the structure and filtration performance of the membranes; furthermore, the embedded factor and blocked factor were used to evaluate the ethylene-vinyl alcohol copolymer embedded in the matrix without dissolving and or being completely blocked in the matrix, respectively. The results show that the increase in ethylene-vinyl alcohol copolymer could reduce the embedded factor and increase the blocked factor. The increase in the polyethylene segments of ethylene-vinyl alcohol copolymer could increase both the embedded factor and blocked factor. The water permeation of the membrane reached 1300 Lm-2·h-1·bar-1 with a 100% rejection of ink (141 nm) and the elongation at break reached 188%, while the strength reached 22 MPa. The dissolution-induced pores method provides a completely viable alternative route for the preparation of polypropylene membranes.

Fabrication of a loose nanofiltration candidate from Polyacrylonitrile/Graphene oxide hybrid membrane via thermally induced phase separation.

It is still a challenge to design and fabricate a robust nanoporous membrane in large scale and of fundamental importance for practical application. Here, a robust three/two-dimensional polyacrylonitrile/graphene oxide (PAN/GO) homogeneous nanoporous membrane is fabricated in large scale via thermally induced phase separation method, which guarantees the membrane with high mechanical strength and selective separation properties. Differing from conventional nanofiltration (NF) membrane with high rejection to both salt and dye, the resulting hybrid membrane is relative loose, which shows outstanding performances, i.e. high dye rejection and low salt rejection, high permeability and antifouling properties, acting as a promising candidate for dye/salt fractionation. The incorporation of 0.2 wt% GO endows membrane with excellent performance, where high tensile strength, high water permeability (33 L⋅ m-2⋅ h-1⋅ bar-1), selectivity (100% to methyl blue, 99.8% to acid red 18, 26.7% to magnesium sulfate and 10.9% to sodium chloride and flux recovery ratio of 84.4%) are perfectly balanced. Its homogeneous structure and high strength guarantee long term use without the peeling of thin active layer as encountered by conventional NF membranes. The successful fabrication of such a hybrid membrane provides an attractive opportunity for loose NF membrane preparation with performance enhancement in a feasible way for practical application.