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

Paola Bernardo,Franco Tasselli,Gabriele Clarizia,Giovanni Chiappetta

doi:10.3390/ma12213632

Paola Bernardo, Franco Tasselli + Show 2 more

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https://doi.org/10.3390/ma12213632

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Abstract

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.

Highlights

IntroductionPolymeric materials, such as polyimides [1], play an important role in membrane gas separation
Polymeric materials, such as polyimides [1], play an important role in membrane gas separation. These materials can be shaped as hollow fibers (HFs), which is the most used configuration in this field owing to its superior membrane packing density, leading to compact devices [2]
The HFs prepared without the external fluid in the dry-jet stage (M1) presented a dense layer on the external side, due to the use of water as an external coagulant

Summary

Introduction

Polymeric materials, such as polyimides [1], play an important role in membrane gas separation. These materials can be shaped as hollow fibers (HFs), which is the most used configuration in this field owing to its superior membrane packing density, leading to compact devices [2]. Membrane systems are increasingly considered as appealing alternatives to conventional gas separation methods, such as cryogenic distillation or absorption [3,4]. The spinning process to produce polymeric HFs provides different parameters (composition of dope and bore fluid, flow rates, air gap, temperature of dope and coagulation bath, take-up velocity) that can be varied in order to modify the membrane structure, and its gas transport properties [5]

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