The formation of microporous polyvinylidene difluoride membranes by phase separation

Bottino, A.; Roda, Giovanni Camera; Capannelli, G.; Munari, S.

doi:10.1016/s0376-7388(00)81159-x

Cited by 367 publications

(204 citation statements)

References 22 publications

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“…In a PES/solvent system during the first stage of membrane formation, solvent evaporates (30s) fast and forms an active top layer. During the second stage, in the immersion process, the PES (polymer rich phase) could be considered practically stable, whereas the solvent and nonsolvent diffuse in the gelation bath [19]. Hence, the mutual diffusion rate of the solvent-nonsolvent has a very significant influence on the sub layer formation.…”

Section: Membrane Hydraulic Resistance (Mhr)mentioning

confidence: 99%

Effect of solvents on performance of polyethersulfone ultrafiltration membranes: Investigation of metal ion separations

2011

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Citation: ARTHANAREESWARAN, G. and STAROV, V., 2010 ABSTRACTThe new polyethersulfone (PES) based ultrafiltration membranes were formed using two stage process of dry and wet phase inversion in non solvent coagulation bath. The effects of three different solvents such as, N-N dimethylformamide (DMF) , N-methyl-2-pyrrolidone (NMP) and Dimethyl sulphoxide (DMSO) of 82.5% and 85% concentrations on the performance of final membranes were extensively investigated. Experimental results proved that PES ultrafiltration membranes with an asymmetric structure were successfully formed which was confirmed by scanning electron microscopy (SEM). The number of pores formed on the top layer of PES membranes using above-mentioned three solvents was the result of the combined effect of the thermodynamic properties of the system (composition, concentrations, phase behaviour) and membrane formation kinetics, whereas, the formation of the macroporous sub layer of those membranes was controlled by the diffusion rate of solvent-nonsolvent. The flux of pure water, membrane resistance, mechanical stability and separation performance of the PES membranes can be varied using different PES concentrations. Separation of metal ions from aqueous solutions was studied for Ni (II), Cu (II) and Cr (III) using two complexing polymer ligands:Polyvinyl alcohol (PVA) and poly(diallyldimethylammonium chloride) (PDDA).The separation and permeate rate (flux) efficiencies of the new membranes are compared using different solvents and different PES/solvents compositions.

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Section: Membrane Hydraulic Resistance (Mhr)mentioning

confidence: 99%

Effect of solvents on performance of polyethersulfone ultrafiltration membranes: Investigation of metal ion separations

2011

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“…[4,9,10] Owing to its importance, the formation of electroactive β crystalline phase has been intensively investigated through various routes, including melt casting, [15] solution deposition, [11] spin coating [12] and phase inversion. [13,14] While, the films or membranes formed by 2 melting/crystallisation are dominated by α-phase, [15] those obtained by spin-coating and further dried at temperature between 30-60 ºC are largely dominated by β-phase crystals. [12] For the phase inversion technique, PVDF films are formed by quenching the casting films into a nonsolvent bath to induce a series of liquid-solid and liquid-liquid phase separation events.…”

mentioning

confidence: 99%

“…[12] For the phase inversion technique, PVDF films are formed by quenching the casting films into a nonsolvent bath to induce a series of liquid-solid and liquid-liquid phase separation events. [5,13,14] The microstructure and crystalline phase of the polymer films in phase-inversion can be controlled by adjusting paramteres like composition, [5,12] type of solvent, [16,17] quenching temperature etc. [18,19] Although PVDF films formed by this technique can have high β-phase contents, they are mostly porous and not suitable for electroactive applications.…”

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Exclusive self-aligned β-phase PVDF films with abnormal piezoelectric coefficient prepared via phase inversion

et al. 2015

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Keywords: PVDF, piezoelectric effect, self-alignment, β-phase, Piezo Force Microscopy Poly(vinylidene fluoride), (PVDF), is one of the most attractive polymers owing to its remarkable pyro-, piezo-and ferro-electroactive properties. [1][2][3][4] These properties stem from its unique polymorphism which also gives rise to its extraordinary mechanical properties, high chemical resistance, good thermal stability and biocompatibility. [5] PVDF shows four significant crystalline phases α, β, δ and γ; [2,6] with the electroactive β-phase being utilized most frequently for the development of sensors, actuators [7,8] and microgenerators. [4,9,10] Owing to its importance, the formation of electroactive β crystalline phase has been intensively investigated through various routes, including melt casting, [15] solution deposition, [11] spin coating [12] and phase inversion. [13,14] While, the films or membranes formed by 2 melting/crystallisation are dominated by α-phase, [15] those obtained by spin-coating and further dried at temperature between 30-60 ºC are largely dominated by β-phase crystals. [12] For the phase inversion technique, PVDF films are formed by quenching the casting films into a nonsolvent bath to induce a series of liquid-solid and liquid-liquid phase separation events. [5,13,14] The microstructure and crystalline phase of the polymer films in phase-inversion can be controlled by adjusting paramteres like composition, [5,12] type of solvent, [16,17] quenching temperature etc. [18,19] Although PVDF films formed by this technique can have high β-phase contents, they are mostly porous and not suitable for electroactive applications. Moreover, the β-phase crystals are randomly oriented in these PVDF films and show no specific directional preference. Polarization under high electric field, [6,20] by Corona poling, [12] or by mechanical stretching [3,6,15] is subsequently carried out to obtain electroactive PVDF films. These operations need to be done at elevated temperatures (>80 o C), requiring high voltage equipment and films with dense structure and high β-phase content. Spontaneous formation of electroactive -phase in PVDF nanofibers formed by drawing was reported to have piezoelectric coefficient up to d33=58.5 pm/V. [25] Similarly, PVDF mesoscale rod arrays, without any poling process, too were also reported to possess good piezoelectric properties due to their high β content. [24] In both these cases, mechanical stretching and stress during the template guiding are believed to be responsible for the piezoelectric effect. Self-polarization of oriented β-phase crystals has also been observed in ultrathin (~20 nm) PVDF copolymer films by spin-coating or by Langmuir-Blodgett (LB) method, and is attributed to the built-in electric field, in-film stress and the strong interaction of PVDF molecules with polar water. [21,22,23] Generally speaking, PVDF films or membrane formed by melt casting, solution deposition, spin coating and phase inversion etc. do not exhibit aligned β-phase crystals without additional t...

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“…It is obvious that the kinetics of phase separation during the immersion of a polymer/ solvent mixture in a nonsolvent bath plays a major role in the control of membrane morphology [44]. The accelerated rate of phase separation due to the addition of nonsolvent additive may be restricted in the rearrangement of polymer aggregates, resulting in the formation of membrane with small macrovoids.…”

Section: Effect Of Some Parameters On Membrane Morphology [43]mentioning

confidence: 99%

Phase Diagram and Membrane Desalination

El–Gendi¹

2015

Desalination Updates

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Desalination technologies have made a significant impact in seawater and brackish water desalination. Recently, the evolution of membrane development has improved performance to lower operating costs and membranes have become the preferred technology for water desalination. Fortunately, different raw materials can be used for preparing membrane sheets which include either organic or inorganic materials, such as cellulose acetate, polyamide, polyimide, ceramic, natural, or artificial polymers. On the one hand, as a result of the variety of the raw materials which already exist in the entire world, different membrane separation processes might be applied dependent on the nature of the membrane sheet and the requirements of treatment process. On the other hand, there are different types of membranes can be used for membrane desalination by using different technologies such as reverse osmosis (RO), membrane distillation (MD), and forward osmosis (FO). The ternary phase diagram for membrane casting solution has an important role to get the required membranes.

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The formation of microporous polyvinylidene difluoride membranes by phase separation

Cited by 367 publications

References 22 publications

Effect of solvents on performance of polyethersulfone ultrafiltration membranes: Investigation of metal ion separations

Effect of solvents on performance of polyethersulfone ultrafiltration membranes: Investigation of metal ion separations

Exclusive self-aligned β-phase PVDF films with abnormal piezoelectric coefficient prepared via phase inversion

Phase Diagram and Membrane Desalination

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