Pure PVA Membrane Research Articles

Poly(vinyl alcohol) mediated bifunctional ZIF-BN nanocomposite for the high-selectivity H2 separation membrane

We combined the advantages of the 2-methylimidazole zinc salt (ZIF-8) and hydroxylated boron nitride (OH-BN) materials to prepare a new bifunctional separation material, namely ZIF-BN. In this, spherical ZIF-8 materials fill the macroporous structure of OH-BN sheets by coordination bonds due to the edge effect. Furthermore, a series of ZIF-BN/PVA membranes were prepared using the vacuum-assisted filtration of the layer-by-layer for the gas separation study. The trace amounts of PVA connect adjacent ZIF-BN sheets through hydrogen bonds, without covering the pore structures of ZIF-8 materials. Based on this exclusive strategy for preparing membranes, the obtained membranes exhibit superior H2 separation performances. Compared with the pure PVA membrane, the H2 permeability, H2/CO2 selectivity, and H2/N2 selectivity of the ZIF-BN/PVA-8 membrane have increased (54, 13, & 12)-fold, to (600 Barrer, 97.2, & 173.6), respectively. This strategy provides a facile way to design new bifunctional membranes for gas separation applications.

Poly (vinyl alcohol)/chitosan/sodium alginate composite blended membrane: Preparation, characterization, and water‐induced shape memory phenomenon

AbstractIn this study, we successfully prepared poly (vinyl alcohol)/chitosan/sodium alginate blended (PCS/SA) composite membranes by a simple solution casting method and solvent evaporation technique. The physicochemical properties and effect of different wt% of sodium alginate (SA) on poly (vinyl alcohol)/chitosan (PCS) membranes were systematically evaluated and studied along with its shape memory properties and mechanism. With increased wt% of SA, the crystallinity of PCS/SA membranes reduced significantly. PCS/SA membrane has better thermal stability than pure PVA membrane but is slightly lower than PCS membrane and decreased with higher SA contents. Dynamic mechanical analysis (DMA) study revealed that water act as a stimulus for the shape recovery behavior. The mechanical study showed that PCS membranes with a small amount of SA (0.1 and 0.2 wt%) have a much better elongation at break than other membranes. The swelling ratio, gel contents, and contact angle results concurred with the results of shape memory effect (SME) of all membranes, where the PCS with higher contents of SA possess better and faster shape recovery speed. The above results demonstrate that SA is a potential additive that can be used for water‐induced shape memory applications.

Preparation and properties of glutaraldehyde crosslinked poly(vinyl alcohol) membrane with gradient structure

Poly(vinyl alcohol) (PVA) is an attractive polymer for various applications based on membranes. To increase water resistance, PVA material has to be adequately crosslinked. However, crosslinking behavior on the whole PVA membrane generally leads to obviously increased brittleness and deteriorated transparency. In the present research, a kind of glutaraldehyde crosslinked PVA membrane with gradient structure has been successfully designed and prepared by the casting membrane of pure PVA aqueous solution and the following surface post-crosslinking processes. The method can endow the PVA membrane with the gradiently decreased crosslinking degree from the surface to inside. Such gradient cross-linked PVA membrane not only keeps good flexibility and transparency, but also possesses satisfactory water-proof property. The structure and properties of the prepared the gradient acetalized PVA (GAPVA) membranes were analyzed and characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscope (SEM), tensile measurement, water resistance test and transparency observation, etc. Compared with pure PVA membrane and uniform acetalized PVA (UAPVA) one, such GAPVA membrane displays excellent performance including good water resistance, transparency and mechanical properties, much higher than those of UAPVA membrane.

Effect of Zn-Cyclen Mimic Enzyme on Mechanical, Thermal and Swelling Properties of Cellulose Nanocrystals/PVA Nanocomposite Membranes

In this work, the effect of Zn-cyclen mimic enzyme on the properties of poly(vinyl alcohol)/cellulose nanocrystals (PVA/CNC) nanocomposite membranes have been studied at three different relative humilities (0%RH, 53%RH and 93%RH). Different amounts of mimic enzyme were incorporated, and membranes were prepared by solution casting. The fabricated nanocomposite films were characterized by X-ray Diffraction, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. The results revealed good interfacial interactions between the constituents. The membranes showed enhanced uptake of moisture, with increasing mimic enzyme concentration as well as humidity. The membranes demonstrated the ability to uptake moisture for almost 4 days. The mechanical properties showed an opposite trend as expected. Tensile strength, tensile modulus and dynamic mechanical properties declined with increase in humidity along with mimic enzyme amount. The highest elastic modulus i.e. 33 MPa was found at the lowest humidity i.e. 0%RH for the pure PVA membrane. Similarly, the maximum tensile strength of 118 MPa was found at the similar conditions for the same formulation. The obtained results suggested the potential application of PVA/CNC and mimic enzyme membranes in CO2 separation.

Chemically and Thermally Crosslinked PVA-Based Membranes: Effect on Swelling and Transport Behavior.

The novel poly(vinyl alcohol) (PVA)-based membranes were prepared using the two-step crosslinking approach: the chemical crosslinking of PVA using sulfosuccinic acid (SSA) (0–50 wt.%) and the thermal treatment (120–160 °C). The membrane composition and crosslinking temperature were optimized in terms of the mechanical and transport properties. The FTIR-ATR analysis revealed that the increase of the SSA concentration and crosslinking temperature resulted in the rise of the ester bond bands intensity due to the esterification reaction between PVA and SSA. As a consequence, the PVA-based membrane with 50 wt % SSA and crosslinked at 140 °C showed the reduced Young’s modulus (from 1266.2 MPa to 1.4 MPa) and elongation at break (from 316% to 66%) in comparison with the pure PVA membrane. The studied swelling behavior of the obtained membranes revealed significantly higher water sorption than that in methanol and propal-2-ol whatever the crosslinking temperature. The performed studies provide a new way of tailoring the membrane physicochemical properties, in particular, the surface hydrophilicity. In addition, the obtained results are crucial for the design and elaboration of the polymer membranes for the pervaporative separation of the liquid-liquid mixtures, in particular, for the alcohol dehydration.

Controllable construction of polymer/inorganic interface for poly(vinyl alcohol)/graphitic carbon nitride hybrid pervaporation membranes

Highly water-selective hybrid pervaporation membranes with excellent water/ethanol separation performance and superior water channels were fabricated by incorporating graphitic carbon nitride (g-C3N4), activated g-C3N4 (O-g-C3N4) and polydopamine modified g-C3N4 (PDA@O-g-C3N4) nanosheets into poly(vinyl alcohol) (PVA) matrix. The nonselective polymer/inorganic interface channels between PVA and g-C3N4, O-g-C3N4 and PDA@O-g-C3N4 in hybrid membranes were controllable constructed through hydrogen bonds, rigid and flexible chemical bonds, respectively. The membrane performances were tested in the pervaporation (PV) process for the dehydration of 90 wt% ethanol/water mixtures at 75 °C. The results revealed that with the increase of binding force among polymer/inorganic interface, from hydrogen bonds (CPVA-g-C3N4), to rigid (CPVA-O-g-C3N4) and flexible chemical bonds (CPVA-PDA@O-g-C3N4), the total flux decreased from 4634 to 2328 g/(m2h) and the separation factor increased from 32.4 to 57.9. It is implied that the nonselective polymer/inorganic interface channels were controlled successfully. Meanwhile, compared with the pure cross-linked PVA (CPVA) membrane (total flux 2325 g/(m2h) and separation factor 18.7), incorporation of g-C3N4, O-g-C3N4 and PDA@O-g-C3N4 could all lead to an increase of surface hydrophilicity of the CPVA membranes along with an increase in membrane tortuosity and membrane water-selective channels that was favorable to the selective permeation of water molecules. Namely, these new hybrid membranes can break the “trade-off effect” effectively. Moreover, due to the ordered alignment of g-C3N4, O-g-C3N4 and PDA@O-g-C3N4 nanosheets and the strong interfacial interactions among these nanosheets, succinic acid (Sa) and the PVA matrix, the hybrid composite membranes showed both high swelling resistance and mechanical stability.

Properties and pervaporation performance of poly(vinyl alcohol) membranes crosslinked with various dianhydrides

ABSTRACTIn this work, three dianhydrides with similar chemical structures, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), 4,4′‐oxydiphthalic anhydride (ODPA), and pyromellitic dianhydride (PMDA), are employed for the crosslinking modification of poly(vinyl alcohol) (PVA) membranes for ethanol dehydration via pervaporation. The changes in crosslinking degree, surface hydrophilicity, and glass‐transition temperature are investigated and compared. Compared to the pure PVA membrane, all crosslinked membranes show higher fluxes but lower separation factors, because of the higher fractional free volume and the lower hydrophilicity by the crosslinking of the PVA matrix, respectively. In addition, all crosslinked PVA membranes exhibit similar flux, and the separation factor presents a decreasing order of PVA/PMDA‐2 > PVA/ODPA‐2 > PVA/BTDA‐2, which is in the reverse order of their hydrophilicity, probably because of the reduction in the swelling resistance. With the PMDA content increasing from 0.01 to 0.04 mol/(kg PVA) in the PVA/PMDA crosslinked membranes, the crosslinking degree is enhanced and the hydrogen bonding is weakened, resulting in a flux increase from 120.2 to 190.8 g m−2 h−1, but the separation factor declines from 306 to 58. This work is believed to provide useful insight on the chemical modification of PVA membranes for pervaporation and other membrane‐based separation applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46159.

Supported silk fibroin/poly(vinyl alcohol) membrane blends: Structure, properties, and ethanol dehydration by pervaporation

Supported hydrophilic silk fibroin/poly(vinyl alcohol) (PVA) films were produced and applied in ethanol dehydration by pervaporation. Silicone treated filter paper acted as a porous layer and dimethylurea was used as crosslinking agent. The morphological and physical characterization indicated that PVA was necessary to obtain an adequate morphology, while the mechanical properties were mainly influenced by the support. In pervaporation tests conducted at 666.6 Pa and 20°C, for a feed content of 14.3 mol%, a permeate water concentration of 74.6 mol% was achieved, corresponding to a separation factor of 23.7, showing a preference for the permeation of water in the blend. The feed composition was found to have a major influence in the pervaporation, swelling, and sorption experiments. The pervaporation experiments showed that the selectivity of the fibroin/PVA blends was higher than that of the pure PVA membranes, suggesting that the selectivity for water was due to the presence of fibroin, the PVA acting mainly as a plasticizer. POLYM. ENG. SCI., 58:1879–1887, 2018. © 2017 Society of Plastics Engineers

Enhancement of the mechanical properties and thermostability of poly(vinyl alcohol) nanofibers by the incorporation of sodium chloride

ABSTRACTThe mechanical properties and thermostability of poly(vinyl alcohol) (PVA) nanofiber mats have been obviously improved by the incorporation of sodium chloride (NaCl). The tensile properties including tensile strength and modulus of membranes with an addition of 1.0 wt % NaCl increased from 2.51 to 4.22 MPa and 33.0 to 176.30 MPa, respectively, more than 160 and 700% of those of the electrospun pure PVA membranes. Moreover, thermogravimetric analysis showed that the initial decomposition temperature (Ti) and the half decomposing temperature (T50%) of PVA nanofibers with the addition of NaCl were at least 26 and 59 °C higher than that of pure PVA nanofibers, respectively, indicating a strong interaction between the PVA and the salt ions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45981.

Mechanical, thermal and swelling properties of cellulose nanocrystals/PVA nanocomposites membranes

Cellulose nanocrystals (CNC) have strong reinforcing properties when incorporated in a compatible polymer matrix. The study was conducted to investigate the effect of addition of different proportions of CNC on the mechanical, thermal and swelling properties of poly(vinyl alcohol) (PVA) nanocomposite membranes for biogas separation. The incorporation of CNC in PVA increased the crystallinity at all investigated relative humidities. No apparent trend is observed for mechanical properties for dry membranes (0% RH) with addition of CNC in PVA matrix. However, at 93% RH the elastic modulus increased 25 times with addition of CNC compared to pure PVA membranes. Moreover, tensile strength also showed twice the values at 53% RH and 93% RH after the addition of CNC. Membranes containing higher CNC content absorbed 9% less moisture. Swelling, thermal and mechanical properties indicate a good potential of CNC/PVA nanocomposite membranes for use in CO2 separation membranes.

Graphitic carbon nitride nanosheets embedded in poly(vinyl alcohol) nanocomposite membranes for ethanol dehydration via pervaporation

Abstract Graphitic carbon nitride (g-C 3 N 4 ) is an innovative soft two-dimensional (2D) nanomaterial. Due to its lamellar structure, similar to graphite layers, g-C 3 N 4 has attracted significant interest as a new class of filler for the fabrication of novel polymeric nanocomposite membranes. In this study, highly water-selective hybrid membranes with excellent water/ethanol separation performance and superior water channels were fabricated by incorporating g-C 3 N 4 nanosheets into a poly(vinyl alcohol) (PVA) matrix. g-C 3 N 4 was synthesized via thermal oxidation “etching”, using melamine as a precursor. The ultrathin and nanoporous structures formed were characterized through transmission electron microscopy, Fourier transform infrared spectra, and X-ray diffraction. Due to the strong interfacial interactions among g-C 3 N 4 , succinic acid (Sa) and the PVA matrix, the hybrid nanocomposite membranes showed both high swelling resistance and mechanical stability. Furthermore, the addition of g-C 3 N 4 can significantly improve the membrane’s hydrophilicity and heat-resistance properties. Importantly, membrane permeability improved greatly because the ordered alignment and the regular pore structure of g-C 3 N 4 resulted in ordered water channels for rapid transportation of water molecules. The total flux and separation factor of this new membrane can reach about 6332 g/(m 2 h), and 30.7 for 90% wt.% ethanol, respectively. Compared with the cross-linked pure PVA membrane (2337 g/(m 2 h) and 11.2), the flux and separation factor can be improved simultaneously. Namely, the composite membrane can break the “trade-off effect” effectively. Furthermore, the nanocomposite membrane exhibited an excellent long-term operating stability. After operating for over 120 h with a 90 wt% ethanol/water system at 75 °C, the total flux and separation factor remained at their initial values. This is a step forward in the application in pervaporation separation processes of organic-inorganic hybrid membranes with superior properties incorporating 2D porous fillers (e.g., g-C 3 N 4 ).

Mixed matrix membranes incorporated with polydopamine-coated metal-organic framework for dehydration of ethylene glycol by pervaporation

In order to solve the issue of incompatibility between metal-organic frameworks (MOFs) and polymer matrix, mixed-matrix membranes (MMMs) on the basis of a hydrophilic polymer poly(vinyl alcohol) (PVA) and a MOF with hydrophilic sulfonic acid group (SO3H-MIL-101-Cr) coated by a thin and uniform polydopamine (PD) layer were prepared for separation of organic solvent from aqueous solutions by taking ethylene glycol (EG) as an example. The PD layer can control the thickness effectively on the surface of SO3H-MIL-101-Cr through a self-polymerization of dopamine and enhance the compatibility between MOF and PVA due to the formation of hydrogen bond between the abundant amine groups in PD and the hydroxyl in PVA matrix. As a result, the prepared SO3H-MIL-101-Cr@PD-PVA MMM exhibits a largely improved water permeability of 7.05×10−5gm−1h−1kPa−1 (the water flux is 540gm−2h−1) and the selectivity is as high as 68.1 (the separation factor is 2864) for EG aqueous solution (water content: 10wt%) separation at 343K. Compared with those in pure PVA membrane, the water permeability and selectivity were increased by 483% and 567% respectively. To the best of our knowledge, this separation performance is superior to those in all of the reported membranes so far. Therefore, this interfacial modification of MOF fillers may be an effective way to enhance the PV separation performance of MMMs, which can be conveniently extended to prepare other kinds of membranes with advanced properties.

CuO nanoellipsoids for superior physicochemical response of biodegradable PVA

PVA nanocomposites comprising of nanoparticles of CuO were prepared and their various physicochemical properties were evaluated. CuO with its impressive array of mechanical, optical, dielectric and hydrophilic properties as well as environmental friendliness is expected to augment the properties of the PVA matrix. The strong interaction between the polymer matrix and the nanofillers was confirmed via XRD and FT-IR investigations. The thermal stability and the mechanical strength of the polymer membranes indeed showed notable improvements in the composites. Thermal conductivity also increased to an extent beyond the theoretical prediction. The dielectric constant of the nanocomposite film was about 2 times higher than that of the pure PVA membrane. The high optical transparency of the PVA membrane also was not compromised with the inclusion of nanosized CuO particles.

Mixed-matrix membrane prepared from crosslinked PVA with NaA zeolite for pervaporative separation of water–butanol mixtures

The NaA zeolite particles are dispersed in a poly(vinyl alcohol)(PVA) matrix to prepare a mixed-matrix membrane (MMM). Pervaporation characteristics such as a permeation flux and a separation factor are investigated in terms of the feed concentration of n-butanol together with a variety of the wt.% of NaA zeolite particles in the membrane. The nano sized zeolite particle of NaA was found to be 63.5 nm. Also, micro sized particle was less than 5 μm. The n-butanol concentration was changed from 0.01 to 0.05 mol fraction with an interval of 0.01 mol fraction, while the pressure of permeation side was about 3 mmHg. The wt.% of the NaA zeolite particles varied between 0 wt.% and 5 wt.%. The effect of the NaA zeolite particles was observed that the flux of water through the MMM was a factor of 2.5 increased compared to the pure PVA membrane at the typical operation condition. When the nanosized of particles was dispersed in the MMM instead of the microsized particles, the flux of water was approximately 20% increased, compared to that through the MMM containing the microsized NaA particles. In addition, the separation factor of water was 5% increased.

Evaluation of cellulose and carboxymethyl cellulose/poly(vinyl alcohol) membranes

Cellulose was isolated from rice straw and converted to carboxymethyl cellulose (CMC). Both polymers were crosslinked with poly(vinyl alcholo) (PVA). The physical properties of the resulting membranes were characterized by FT-IR, TGA, DSC and SEM. The cellulose and CMC were first prepared from bleached rice straw pulp. The infrared spectroscopy of the resulting polymer membranes indicated a decrease in the absorbance of the OH group at 3300–3400cm−1, which is due to bond formation with either the cellulose or CMC with the PVA. The thermal stability of PVA/cellulose and PVA/CMC membranes was lower than PVA membrane. The surface of the resulting polymer membranes showed smooth surface in case of the PVA/CMC membrane and rough surface in case of the PVA/cellulose membrane. Desalination test, using 0.2% NaCl, showed that pure PVA membranes had no effect while membranes containing either cellulose or CMC as filler were able to decrease the content of the NaCl from the solution by 25% and 15%, respectively. Transport properties, including water and chloroform vapor were studied. The moisture transport was reduced by the presence of both cellulose and CMC. Moreover, the membranes containing cellulose and CMC showed significantly reduced flux compared to the pure PVA. The water sorption, solubility and soaking period at different pH solutions were also studied and showed that the presence of both cellulose and CMC influences the properties.

Study of pervaporation for dehydration of caprolactam through PVA/nano silica composite membranes

We investigated nano silica/PVA composite membranes to propose an improved caprolactam pervaporation (PV) dehydration process. The membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and contact angle measurement. Compared with the pure PVA membranes, the nano silica/PVA composite membranes showed different surface morphologies with enhanced hydrophilicity because of their unique formation. To evaluate PV performance and mechanism, we assessed the permeation flux, separation factor, diffusivity/sorptivity selectivity, and activation energy of the composite membranes. The evaluated results indicate that the nano silica/PVA composite membranes induced a breakthrough in the dehydration of a caprolactam-water mixture with a maximum flux of 3.8 kg m − 2 h − 1 and an acceptable separation factor of 150.

Sol–gel derived poly(vinyl alcohol)/maleic acid/silica hybrid membrane for desalination by pervaporation

Highly dispersed homogeneous hybrid polymer–inorganic membranes based on poly(vinyl alcohol) (PVA), maleic acid (MA) and inorganic silica were synthesized via a sol–gel method. Tetraethoxy-silane (TEOS) was used as the silica precursor with MA as an additional crosslinking agent. A range of techniques such as FTIR, SEM, TGA, XRD and DSC were used to characterise the nanostructure and properties of hybrid membranes. Results revealed silica nanoparticles (<10 nm) were well dispersed in the polymer matrix with chemical bonding between the organic and inorganic phases. Thermal properties of the hybrid membranes were significantly enhanced when compared with pure PVA membranes, and swelling of PVA based hybrid membranes was greatly suppressed. The chemically crosslinked PVA with maleic acid and silica resulted in the formation of new hybrid membranes with improved pervaporation properties for desalination application. The pervaporation separation performance of aqueous salt solution was found to be directly related to the diffusion coefficient of water through hybrid PVA/MA/silica membranes. Introduction of MA and silica at given amounts into the polymer chain increased the amorphous region of the membrane and favoured the diffusion of water molecules through the membrane. A water flux of 6.93 kg/m 2 h with salt rejection of >99.5% was achieved at a 6 Torr vacuum and 22 °C.

Preparation and properties of phosphorylated and crosslinked poly(vinyl alcohol)/bisphenol A–epoxy resin membranes for fuel cell applications

AbstractTo overcome the strong dependence of the conductivity on the relative humidity and the lower thermal stability at high temperature of perfluorosulfonate polymers and the leaching‐out problem of phosphoric acid doped membranes, a series of phosphorylated and crosslinked poly(vinyl alcohol) (PVA)/bisphenol A–epoxy resin [diglycidyl ether of bisphenol A (DGEBA)] membranes were prepared. The membrane properties were characterized by Fourier transform infrared spectra, solubility, thermogravimetric analysis, water uptake, swelling ratio, ion‐exchange capacity (IEC), small‐angle X‐ray scattering, and proton conductivity measurements. The results show that the crosslinked PVA/DGEBA membrane had a higher thermal stability (Td ≥ 250°C) than the pure PVA membrane (Td ≥ 220°C) and that the phosphorylated and crosslinked PVA/DGEBA membranes (IEC = 5.54 mmol/g) with a low volume swelling ratio (7.21%) could achieve a maximum proton conductivity of 2.51 × 10−3 S/cm at a temperature as high as 150°C in anhydrous conditions © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis and Characterization of Poly(vinyl alcohol) Membranes with Quaternary Ammonium Groups for Wound Dressing

2-[(acryloyloxy)ethyl]Trimethylammonium chloride (AETMAC) was grafted onto poly(vinyl alcohol) (PVA) using ceric ammonium nitrate (CAN) as a redox initiator. A series of graft co-polymer (PVA-g-PAETMAC) membranes with different contents of AETMAC were prepared with a casting method. The incorporation of AETMAC into PVA chains was confirmed by element analysis and Fourier transform infrared spectroscopy. The effects of grafting on the thermal properties, water take, water vapor transmission rate (WVTR), contact angle, antibacterial activity and cytotoxicity of PVA-g-PAETMAC membranes were investigated. The experiment results showed that PVA-g-PAETMAC membrane has a higher equilibrium swelling ratio, surface hydrophilicity and WVTR than pure PVA membrane. Moreover, the higher the content of AETMAC, the higher were equilibrium swelling ratio, surface hydrophilicity and WVTR. In vitro bacterial adhesion study demonstrated a significantly reduced number of Staphylococcus aureus and Escherichia coli on PVA-g-PAETMAC surfaces when compared to PVA surface. In addition, no significant difference in the in vitro cytotoxicity was observed between PVA and PVA-g-PAETMAC membranes. The presence of quaternary ammonium groups did not reduce L929 cell growth. Therefore, the PVA-g-PAETMAC membranes have the potential for wound-dressing application.

Incorporation of multiwalled carbon nanotubes into poly(vinyl alcohol) membranes for use in the pervaporation of water/ethanol mixtures

AbstractMultiwalled carbon nanotube (MWNT)/poly (vinyl alcohol) (PVA) blend membranes were prepared by the solution‐casting method to determine the effect of MWNTs with nanoscale empty inner space along the tube length on the pervaporation performance of a PVA membrane in the separation of alcohol/water mixtures. The blend membranes were then characterized with several analytical methods such as transmission electron microscopy, differential scanning calorimetry, and X‐ray diffractometry: Transmission electron microscopy showed that the MWNTs were homogeneously distributed through the PVA matrix. The glass‐transition temperature of the PVA membrane was increased from 69.21 to 78.53°C via blending with MWNTs. The crystallinity of the PVA matrix decreased with increasing MWNTs up to 5 wt % from 41 to 36%. The pervaporation properties of the blend membranes were completely different from those of the pure PVA membrane in the separation of water/ethanol mixtures. The flux of the membrane was increased with the amount of MWNTs, whereas the separation factor was maintained up to 1.0 wt % MWNTs. However, beyond that, it was reduced. These results suggested that two factors, the crystallinity of the membrane and the diameters of the MWNTs, affected the performance of the membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009