Preparation and Characterization of Polymeric Hollow Fibers by Phase-Inversion Techniques

Polymeric hollow fibers are one of the preferred choices of membranes at the industrial level. This chapter illustrates the different techniques employed, both at small and large scale, for their preparation with particular emphasis on the phase-inversion spinning techniques. Hollow fibers, as their flat sheet counterpart, can be prepared by employing traditional phase-inversion techniques even if their preparation can result more challenging. Numerous factors are involved during their preparation process, which affect their final morphology and properties in different ways. The spinning process, employed for the preparation of hollow fibers, consists in five steps: dope solution preparation; dope solution extrusion through the spinneret; possible passage of the nascent fiber into an air-gap region; coagulation; and post-treatment processes. Hollow fibers can be prepared following different methods of spinning, which include melt spinning, dry spinning, wet spinning, and dry/wet spinning. Polymer concentration is undoubtedly one of the most critical parameters that have to be carefully taken into consideration before preparing hollow fibers.