Effect of the Post-Spinning Solvent Exchange on the Performance of Asymmetric, Polyimide Hollow Fibers Prepared by Using a Triple-Orifice Spinneret.

Hollow fibers (HFs) are widely applied in different membrane operations, particularly in gas separation. The present work investigates the effect of post-spinning treatment on the gas transport properties of polyimide-based HFs. The membranes were spun by using both a conventional spinneret and a triple-orifice spinneret. A systematic analysis was carried out by considering different alcohols as the first fluid for the solvent exchange, with or without n-hexane as a second fluid. The HFs were characterized by exploring the change of the morphology and the permselective properties as a consequence of the operation conditions for spinning and post-treatments. According to the morphology, for a specific hollow fiber type, an optimal post-treatment was identified. The HFs prepared with the triple-orifice spinneret, using a solvent-rich shell fluid, can take advantage of the post-treatment using larger alcohols, while smaller alcohols should be preferred for the conventional spun HFs that present inside-outside double skin layers.