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Curved and structured membrane geometries are known to have the potential to reduce concentration polarization and fouling rates in membrane filtration and membrane contacting applications. However, their production is cumbersome and often comprises various successive processing steps. We present a new direct fabrication process of two new hollow fiber geometries: Curled and meandering hollow fibers. The phenomenon of liquid rope-coiling is adapted to a membrane spinning process resulting in mostly spiralling curly fiber geometries. Parameters influencing geometric properties are evaluated and experimentally obtained structures are presented. Fibers were prepared from a polyethersulfone-based polymer solution in an air gap spinning process. Prepared structured hollow fibers are investigated regarding geometrical measures and pore structures. A comprehensive analysis of the complex interplay between the influencing parameters is suggested. [ABSTRACT FROM AUTHOR]

Abstract: Due to the unique properties of amphiphilic Pluronic block copolymers, they have been blended with other polymers such as PVDF to prepare membranes. Considering the stability issue, the strong pore-forming ability of Pluronic F127, and the mechanical strength of the resultant membranes, Pluronic/LiCl mixed additive consisting of a very low concentration of Pluronic has been used in this study. The effects of spinning conditions on PVDF hollow fiber fabrication have also been studied. It is found that the use of merely 0.2wt% of Pluronic is sufficient to impose significant impacts on the morphology, filtration performance, and mechanical properties of the resultant fibers. Hollow fibers spun using higher coagulant temperature, higher take-up speed, and water as the bore fluid exhibit better mechanical properties and filtration performance. PVDF hollow fiber membranes with PWP of 1180L/m2 hMPa and MWCO of 5kDa were obtained when spun with optimized spinning conditions and using 3wt% of LiCl and 0.2wt% of Pluronic as the mixed additive. The fibers can withstand a pressure of 0.55MPa from the lumen. [Copyright &y& Elsevier]

Abstract: This article describes the research study on exploitation of polymer blending technology and dual-layer hollow fiber spinning process for the fabrication of a novel class of high performance gas separation membranes. The specific functional material employed for this purpose is a polymer blend constructed of the interpenetrated networks of PBI and Matrimid. It is within the scope of this study to unravel the effect of various key parameters on the microstructural evolution, transport properties and separation performance of the developed hollow fiber membranes. The resultant membranes possess desirable morphological and microstructural characteristics, particularly at the outer functional layer, and are free from any delamination at the interface. Analysis of the membranes suggests that both increase in the air-gap distance and application of elongational drawing have promoting effects on the membranes’ permeance. Results also indicate that membranes with H2/CO2 selectivities as high as 11.11 () can be obtained through spinning at sufficiently large air-gap distance. On the other hand, inducing the elongational drawing to the nascent fibers offers membranes with CO2/CH4 selectivities as high as 41.81 (). Therefore, either of these approaches can be employed for desirable tuning of the membrane''s properties to suit the specific application. The variation in outer dope flow rate is identified as another effective technique amenable for tailoring the properties of the hollow fiber membranes. Other findings also show the effectiveness of chemical modification for further enhancing the H2/CO2 separation performance of the membranes. Membranes developed in this research study exhibit a very good resistance toward CO2-induced plasticization and have viable potentials for various gas separation applications including hydrogen purification and natural gas separation. [Copyright &y& Elsevier]