Effects of coating solvent and thermal treatment on transport and morphological characteristics of PDMS/Torlon composite hollow fiber membrane

Abstract

A new approach for formation of the polydimethylsiloxane (PDMS) layer on Torlon polyamide-imide hollow fiber (PAI-HF) support has been developed by directly after fiber spinning without the need to undergo the final conventional solvent exchange and drying step, thereby saving postspinning processing steps. The produced PDMS/PAI-HF composite membranes were found to have high CO 2 permeance (i.e., 1100 GPU) and exhibited good CO 2 /N 2 selectivities of 8-10 which is close to 90% of that of a PDMS dense film. The effects of coating solution, rewetting and crosslinking temperature on the PAI-HF morphological features, that is, gas transport, skin thickness, skin integrity, and substructure resistance are investigated. The rewetting and thermal treatment of the PAI-HF caused the densification of the skin layer and reduced the pore sizes on the top layer. In addition, the potential use of the PAI-HF support with polymers that are insoluble in hexane is also considered. Effects of water, methanol, and hexane exposure of PAI-HF to these solvents are considered. This evaluation calls attention to issues that must be addressed in any eventual use of the PAI-HF with water-soluble or methanol-soluble selective layer polymers, rather than simple hexane-soluble polymers such as PDMS.

Carbon Hollow Fiber‐Supported Metal–Organic Framework Composites for Gas Adsorption

“…The asymmetric hollow fiber spinning was done by a dry‐jet/wet‐quench spinning process using water as a quench bath coagulant. Spun fibers underwent solvent exchange in water for 3 days, followed by methanol and hexane exchange for 1 h each, and then drying in vacuum oven at 130 °C for 3 h. The details of polymer dope composition, the schematic of hollow fiber spinning setup, and Torlon hollow fiber formation have been described in previously . The Torlon hollow fibers used in this study had a length of 5 cm with inner and outer diameters of 300 and 700 μm, respectively.…”

“…Hollow fibers have been shown to be excellent gas–solid contactors for various adsorption‐ and membrane‐based separation processes, mainly due to their unique combination of large surface area and high porosity within a packed volume . While polymeric hollow fibers provide numerous advantages for incorporating inorganic compounds and synthesis of composite materials, they suffer from chemical instability and swelling under various MOF hydrothermal synthesis conditions . This will cause dissolving of the fiber in the strong solvents that are used in the MOF synthesis or diminished properties after exposure.…”

“…[1,[5][6][7][8][9][10][11] While polymeric hollow fibers providen umerous advantages for incorporating inorganic compounds and synthesis of composite materials,t hey suffer from chemical instability and swelling under various MOF hydrothermal synthesis conditions. [12] This will cause dissolving of the fiber in the strong solvents that are used in the MOF synthesis or diminished properties after exposure.O nt he other hand, carbon hollow fibers provideh igh porosity and their structure remainsi ntact under MOF synthesis conditions.T he application of carbon hollow fibers in gas separationp rocesses was pioneered by Koros and co-workers. [5][6][7] To date,t he synthesis of variousM OF-hollow fiber membranesh as been reported.…”

Comparison of hollow fiber and flat mixed-matrix membranes: Theory and simulation

“…Within current challenges in progressing MMMs beyond Robeson's upper bound, the proper selection of the combination of filler and polymer has been largely found to be critical in the attainment of enhanced MMM performance (Chung et al, 2007;Tanh Jeazet et al, 2012). Yet, the membrane geometrical structure has been identified to play a significant role in the implementation of membrane technologies in practical applications (Rownaghi et al, 2017;Sutrisna et al, 2017).…”

“…Alternatively, asymmetric MMMs comprise a selective (composite) dense skin layer coated on a highly porous non-selective core layer (Aroon et al, 2010;Nordin et al, 2014;Zhang et al, 2014). Here, the non-selective support layer is expected to provide mechanical integrity (Galizia et al, 2017;Rownaghi et al, 2017), and the dense composite layer to offer the desired selectivity and permeability (Jiang et al, 2005;Liang et al, 2017). Further, these asymmetric structures are known to have lower fabrication cost than that of symmetric, since they use reduced amounts of expensive materials (e.g.…”