Phase inversion spinning of ultrafine hollow fiber membranes through a single orifice spinneret

This paper reports a new phase inversion spinning method for the preparation of ultrafine hollow fiber membranes through a single orifice spinneret. An oily additive is pre-added in the polymer dope solution as a bore-forming agent. During the rapid solvent extraction and phase separation processes, the oil is pushed by the external solution (coagulant) to the center of the fiber, and thus the hollow fiber membranes can be obtained by washing away the oil. To demonstrate this new method, ultrafine polysulfone and yttria stabilized zirconia hollow fiber membranes were fabricated using a stainless steel syringe tip as a simple orifice spinneret. The fabrication conditions, including the sizes of syringe tips, contents and types of the oily additives were investigated. Gas permeation test indicates the polysulfone hollow fiber membrane had no large defects. The potential benefits of concave surfaces arising from oil droplets in terms of mechanical properties were also discussed.