Macroporous hydrophobic flat-sheet PVDF membranes via vapor induced phase separation

Macroporous hydrophobic flat-sheet PVDF membranes via vapor induced phase separation

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In gas/liquid membrane contactors with aqueous solutions, porous hydrophobic membranes are required. Typically polypropylene, polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) are used. For many emerging applications, contactor membranes should be similar to those already used in membrane distillation. Such membranes should be highly porous and as thin as possible to enhance vapor transport, exhibit low heat conductivity to minimize heat loss, be hydrophobic and have proper pore size for anti-wetting properties [1]. Generally, PTFE membranes show higher hydrophobicity than PVDF membranes. However, considering the difficulty involved in processing PTFE, PVDF is the most promising membrane polymer for scale-up [1].

Vapor Induced Phase Separation (VIPS) is a promising method for obtaining highly porous membranes. In VIPS, phase separation is induced by the dilution of the solvent in the polymer solution with the non-solvent (typically water) taken up from the vapor phase. Factors like relative humidity, exposure time to humid air or airflow velocity influencing mass transfer can be used for tuning VIPS conditions, so that macroporous membranes with high porosity, isotropic cross section and narrow barrier pore size distribution can be achieved. Also polymer concentration and dissolution temperature influence membrane morphology and structure. Using these parameters, PVDF membranes with barrier properties tailored for application in a new three-phase membrane contactor are developed.

References

  1. H. Fan, Y. Peng, Z. Li, et al., J. Polym. Res. 2013, 20, 134
Funding: This work is supported by the EU Horizon 2020 project “XERIC – Innovative Climate-Control System to Extend Range of Electric Vehicles and Improve Comfort” (www.xeric.eu Xeric

Contact:
Prof. Dr.
Mathias Ulbricht