Poly(vinylidene fluoride) is widely used as a membrane material for a variety of applications. It has excellent thermal and chemical resistance due to its high fluorine content and its solubility in a number of organic solvents makes it well suited for thermally or non-solvent induced phase inversion. The semi-crystalline character favours the formation of a porous morphology and combined with its strongly hydrophobic character this makes PVDF often the material of choice in applications like microfiltration or membrane contactors. The same physical-chemical properties make PVDF interesting for specific gas, vapour or liquid separations, but the formation of a sufficiently thin active layer is much more difficult1. Recently we demonstrated the possibility to form integrally skinned dense hollow fibre membranes via dry-wet spinning2. The present paper reports the preparation and the gas and vapour transport properties of such membranes. The effect of spinning conditions (solvent type, polymer concentration, inner coagulant composition, coagulation bath temperature) on the morphology and membrane performance will be discussed. Under the proper conditions highly selective and permeable membranes are obtained, with a selective outer skin down to ca. 0.2 ?m, as determined by SEM analysis or gas permeation measurements with six permanent gases (He, H2, N2, O2, CH4, CO2). The ideal selectivity of the fibres approaches or even exceeds that of analogous dense films. DSC and FTIR/ATR analysis reveal that this can be attributed to a high overall crystallinity and to a relatively high fraction of the beta-crystal phase in the selective skin. Vapour permeability studies (see figure) via time lag measurements in a barometric fixed-volume pressure-increase instrument3, combined with vapour sorption analysis in a McBain balances4 and liquid sorption tests reveal fundamentally different behaviour for methanol, acetone and dichloromethane. This is discussed in relation with the membrane structure and the physical-chemical properties of the polymer. Acknowledgements. Funding was received from the EC's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. NMP3-SL-2009-228631, project "DoubleNanoMem" and Italian National project PON01_01840 "MicroPERLA". References 1.K. Jian and P. N. Pintauro, J. Membr. Sci., 1993, 85, 301. 2.S.-H. Choi, F. Tasselli, J.C. Jansen, G. Barbieri, E. Drioli, Eur Polym J. 2010, 46, 1713. 3.M. Macchione, J.C. Jansen, G. De Luca, E. Tocci, et al., Polymer 2007, 48, 2619. 4.K. Friess, J.C. Jansen, O. Vopi?ka, A. Randová, et al., J. Membr. Sci., 2009, 338, 161.
PVDF membranes for gas and vapour separation
JC Jansen;F Tasselli;
2014
Abstract
Poly(vinylidene fluoride) is widely used as a membrane material for a variety of applications. It has excellent thermal and chemical resistance due to its high fluorine content and its solubility in a number of organic solvents makes it well suited for thermally or non-solvent induced phase inversion. The semi-crystalline character favours the formation of a porous morphology and combined with its strongly hydrophobic character this makes PVDF often the material of choice in applications like microfiltration or membrane contactors. The same physical-chemical properties make PVDF interesting for specific gas, vapour or liquid separations, but the formation of a sufficiently thin active layer is much more difficult1. Recently we demonstrated the possibility to form integrally skinned dense hollow fibre membranes via dry-wet spinning2. The present paper reports the preparation and the gas and vapour transport properties of such membranes. The effect of spinning conditions (solvent type, polymer concentration, inner coagulant composition, coagulation bath temperature) on the morphology and membrane performance will be discussed. Under the proper conditions highly selective and permeable membranes are obtained, with a selective outer skin down to ca. 0.2 ?m, as determined by SEM analysis or gas permeation measurements with six permanent gases (He, H2, N2, O2, CH4, CO2). The ideal selectivity of the fibres approaches or even exceeds that of analogous dense films. DSC and FTIR/ATR analysis reveal that this can be attributed to a high overall crystallinity and to a relatively high fraction of the beta-crystal phase in the selective skin. Vapour permeability studies (see figure) via time lag measurements in a barometric fixed-volume pressure-increase instrument3, combined with vapour sorption analysis in a McBain balances4 and liquid sorption tests reveal fundamentally different behaviour for methanol, acetone and dichloromethane. This is discussed in relation with the membrane structure and the physical-chemical properties of the polymer. Acknowledgements. Funding was received from the EC's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. NMP3-SL-2009-228631, project "DoubleNanoMem" and Italian National project PON01_01840 "MicroPERLA". References 1.K. Jian and P. N. Pintauro, J. Membr. Sci., 1993, 85, 301. 2.S.-H. Choi, F. Tasselli, J.C. Jansen, G. Barbieri, E. Drioli, Eur Polym J. 2010, 46, 1713. 3.M. Macchione, J.C. Jansen, G. De Luca, E. Tocci, et al., Polymer 2007, 48, 2619. 4.K. Friess, J.C. Jansen, O. Vopi?ka, A. Randová, et al., J. Membr. Sci., 2009, 338, 161.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
