PVDF Substrate Research Articles

ZnO Nanorod Array Modified PVDF Membrane with Superhydrophobic Surface for Vacuum Membrane Distillation Application.

The vacuum membrane distillation (VMD) is a promising technology for lots of applications. To solve the membrane fouling and wetting problems, in this paper, a novel ZnO nanorods 1 H,1 H,2 H,2 H-perfluorodecyltriethoxysilane (PDTS) modified poly(vinylidene fluoride) (PVDF) membrane with a micro/nanoscale hierarchical structure and a superhydrophobic surface has been prepared and applied to the VMD process for distilling highly salty water, for the first time. Among these, a pyrolysis-adhesion method is created to obtain the ZnO seeds and fasten them on the PVDF substrate firmly. The novel modified membrane shows a stable superhydrophobic surface with a water contact angle of 152°, easy cleaning property, excellent thermal and mechanical stability, because of the Cassie's state caused by pocketing much air in the hydrophobized ZnO nanorods, the low surface energy of PDTS coating, and the strong adhesion between ZnO nanorods and PVDF membrane, which has built an ideal structure for VMD application. After 8 h VMD of 200 g L-1 NaCl solution, compared to the virgin PVDF membrane, the novel membrane shows a similar permeate flux but a much higher quality permeated liquid because of its unique antifouling and antiwetting caused by the several microns gap between the feed and the membrane. Due to its easy cleaning property, the novel membrane also exhibits an excellent reusability.

Development of robust fluorinated TiO2/PVDF composite hollow fiber membrane for CO2 capture in gas-liquid membrane contactor

Gas-liquid membrane contactor (GLMC) is a promising method to attain high efficiency for CO2 capture from flue gas, biogas and natural gas. However, membranes used in GLMC are prone to pore wetting due to insufficient hydrophobicity and low chemical resistance, resulting in significant increase in mass transfer resistance. To mitigate this issue, inorganic-organic fluorinated titania/polyvinylidene fluoride (fTiO2/PVDF) composite hollow fiber (HF) membranes was prepared via facile in-situ vapor induced hydrolyzation method, followed by hydrophobic modification. The proposed composite membranes were expected to couple the superb chemical stability of inorganic and high permeability/low cost of organic materials. The continuous fTiO2 layer deposited on top of PVDF substrate was found to possess a tighter microstructure and better hydrophobicity, which effectively prevented the membrane from wetting and lead to a high CO2 absorption flux (12.7 × 10−3 mol m−2 s−1). In a stability test with 21-day operation of GLMC using 1M monoethanolamine (MEA) as the absorbent, the fTiO2/PVDF membrane remained to be intact with a CO2 absorption flux decline of ∼16%, while the pristine PVDF membrane suffered from a flux decline of ∼80% due to membrane damage. Overall, this work provides an insight into the preparation of high-quality inorganic/organic composite HF membranes for CO2 capture in GLMC application.

Decoration of open pore network in Polyvinylidene fluoride/MWCNTs with chitosan for the removal of reactive orange 16 dye

Inspired by the hydrophilic, biocompatible, adsorbent properties of chitosan. A simple, adaptable, green synthesis method was developed to prepare a thin film composite membranes using chitosan as a pore decorating material for the removal of anionic dye-Reactive orange 16 (RO-16). The hydrophilic chitosan was used to fill up the porous hydrophobic PVDF substrate, modified by MWCNTs. The dye rejection was carried out through the formation of a strong electrostatic interaction between the cationic group of chitosan surface and the anionic group of RO-16 dye. The dye molecules accumulate on the chitosan surface, thus promoting the higher retention rate. The TFC membranes were evaluated using dead filtration plant. It is found that the modified membranes showed RO-16 rejection up to 91% with optimum permeation flux of 170kgm−2h−1. Furthermore, the presence of chitosan on MWCNT/PVDF substrate provides a hydrophilic character thus decreasing the active sites available for foulant attachment which is confirmed by the fouling study. The CTAB foulant showed an increase in flux rate even after physical flushing. The modification procedure is performed under mild conditions, thus it is helpful to fabricate TFC membrane at a commercial scale.

Crystallization of Poly(ε-caprolactone) in Poly(vinylidene fluoride)/Poly(ε-caprolactone) Blend.

The crystallization behavior of poly(ε-caprolactone) (PCL) in a poly(vinylidene fluoride) (PVDF)/PCL blend as well as on a highly orientated PVDF substrate was studied by means of POM, DSC and TEM. The results show that the miscibility of the PVDF/PCL blend and the spherulitic morphology of PVDF varies with the blend ratio. For all the compositions, the pre-existing PVDF crystals accelerated the crystallization of PCL because the PVDF exhibits very strong nucleation ability toward PCL as reflected by the occurrence of heteroepitaxy and the transcrystallization of PBA on the PVDF substrate. This is associated with the perfect lattice matching between the PBA and PVDF crystals.

Improvement of the thermal transport performance of a poly(vinylidene fluoride) composite film including silver nanowire

ABSTRACTThe miniaturization trend of electronic devices requires that components have a high heat dissipation in industrial applications and in daily life. In this context, a highly thermally conductive film was fabricated with silver nanowire (AgNW) and poly(vinylidene fluoride) (PVDF) with a bar‐coating method. The thermal transport performance and mechanism of the AgNW/PVDF composite film were investigated. The through‐plane and in‐plane thermal conductivity of the AgNW/PVDF composite film reached 0.31 and 1.61 W m−1 K−1, respectively; these values far exceeded those of the pristine PVDF film. The experiment illustrated that the thermally conductive pathways formed successfully in the PVDF substrate with the addition of AgNW, and the heat tended to transfer along the thermally conductive pathway rather than along the PVDF substrate. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43554.

Preparation and characterization of ZSM-5/PDMS hybrid pervaporation membranes: Laboratory results and pilot-scale performance

ZSM-5 zeolites/Polydimethylsiloxane (PDMS) hybrid membranes were prepared and subsequently applied in ethanol recovery from an ethanol–water mixture by pervaporation (PV) using a pilot-plant with spiral-wound membrane module. The influences of calcination temperature on PV performances as well as zeolites properties were studied. Meanwhile, the optimum zeolites loading was turned out to be 30wt%, the SEM indicated that ZSM-5/PDMS was coated uniformly on the surface of porous PVDF substrate, and the separation layer was dense with the thickness of 8.9μm. The effects of feed temperature and feed flow velocity on the performance of the pilot-scale PV system were investigated. It was found that with increasing feed temperature, the permeation flux increased, whereas the separation factor firstly increased, then it decreased rapidly. As the feed flow velocity increased, both the permeation flux and separation factor increased. Under the optimum process conditions, the pilot-plant showed a total flux of 1170g/m2h with ethanol concentration of 60.00wt% at a feed temperature of 60°C, a feed flow velocity of 3.2cm/s and a permeation side pressure of about 2300Pa with a feed concentration of 10.0wt% ethanol. A long term run consisted of 1000h of continuous PV experiments exhibited satisfying performance stability, indicating that the pilot-plant was a promising approach to separate ethanol from ethanol–water mixture and had long-term stability required for industrial application.

TiO2 Nanotubes/Ionic Liquid Electrolyte System Enhances Li-Ion Battery Performance

High capacity advanced lithium ion batteries (LIBs) utilizes non-volatile ionic liquid (IL) electrolyte is considered a promising candidate to address the safety and durability issues of traditional LIBs. Compared to organic-based electrolyte, however, IL has lower ionic conductivity at almost temperature range and shows less effective contact with the electrodes in absence of organic solvent, thus created barrier of lithium transfer at the electrolyte-electrode interface, which in turn reduce the cell performance 1 . Current study is focused on the design of composite ionic liquid electrolyte which gives higher ionic conductivity coupled with the improved of interface stability. Highly conductive electrolyte could be achieved through optimizing synergistic function between ionic liquids, salt, and the PVdF substrate. By suitable composition of lithium-bis-(trifluoromethyl sulfonyl)imide (Li-TFSI) and 1-butyl-3-methyl imidazolium bis-(trifluoromethyl sulfonyl)imide (BMI-TFSI) ionic liquids in poly-(vyniliden fluoride-hexafluoropropylene) (PVDF-HFP) co-polymeric host material, optimized membrane morphology is achieved through phase inversion technique during membrane casting, where an unique pore structure is formed. High ionic conductivity in the order of 10-3 Scm-2 is observed in PVDF-HFP: BMI-TFSI: Li-TFSI (10:10:2, w/w) electrolyte system, which is found to be higher than that of commercial membrane with liquid electrolyte. . Furthermore, the addition of small amount of TiO2 nanotubes (TiNT) incorporated onto the ionic liquid electrolyte system further raises the ionic conductivity up to ~1.5 x 10-3 Scm-2 (25 oC) and ~8.0 x 10-3 Scm-2 (80 oC), which is attributed both to higher lithium salt dissociation in presence of TiO2 and the establishment of more direct ion conducting pathway 2 . Further addition of TiNT, however, leads to reduction of ionic conductivity, which drops significantly after 5 wt% (relative to the solvent) of TiNT addition, which is probably the result of inorganic self-aggregation. Wider thermal decomposition around ~400 oC from TGA and DSC shows a remarkable improvement in thermal stability of membrane containing TiNT. Battery performance in a Li/electrolyte-TiNT/LiFePO4 coin cells indicates relatively high discharge specific capacity around ~136 mAh/g at 0.05 C moderate electrochemical cycling and shows better cycling performance with almost constant ~ 99% coulombic efficiency as a result of improved electrolyte interface stability to the electrode.

Aniosotropically organized LDH on PVDF: a geometrically templated electrospun substrate for advanced anion conducting membranes.

A bioinspired geometric templating of an electrospun PVDF substrate with hexagonal platelets of Mg-Al layered double hydroxide (LDH), an intrinsic anion conductor, is presented. The distinctive morphology restructures the internal pore geometry and modulates the dynamic wetting profile of PVDF, transforming it into a highly functional substrate for SAFC anion conducting membranes. The membrane fabricated with PVDF-LDH substrate exhibited exceptionally high durability (>140 °C), high anionic conductivity, ion exchange capacity (IEC), restricted swelling, and improved tensile strength, overcoming critical challenges associated with PVDF electrospun substrates and validating its immense potential as a high-temperature-stable and durable substrate for advanced fuel cell membrane applications.

Improved high-frequency soft magnetic properties of FeCo films on organic ferroelectric PVDF substrate

Abstract FeCo films with various thicknesses were fabricated by direct-current magnetron sputtering on corning glass and organic ferroelectric PVDF substrates at the same time with 5 nm Ru seed layer and 5 nm Ta protective layer. The in-plane uniaxial anisotropy field of FeCo on glass substrate increases from 24 to 36 Oe with the increase of FeCo film thickness from 5 to 100 nm. However, a large in-plane anisotropy field of FeCo on PVDF substrate increases with FeCo thickness from 5 to 20 nm and gradually decreases with the FeCo thickness further increasing. Atomic force microscope images of FeCo on glass show quite smooth surface with root-mean-square roughness around 0.5 nm and have none visible granules on the surface for all samples. While, AFM images of FeCo on PVDF show quite rough surface with RMS roughness around 25 nm and have visible granules with the smallest granules appearing at the FeCo thickness of 20 nm. The permeability spectra show the typical ferromagnetic resonance phenomenon and can be well fitted by the LLG equation with the obtained experimental parameters. The ferromagnetic resonance frequency can reach 7.0 GHz for the 20 nm FeCo film on PVDF. Moreover, the quality factor of this sample can respectively reach 26, 12 and 7 at 1.0, 2.0, and 3.0 GHz, indicating the potential real 3G application for high-frequency devices.

Anisotropic highly-conductive films of poly(3-methylthiophene) from epitaxial electropolymerization on oriented poly(vinylidene fluoride)

Electrochemical polymerization of 3-methylthiophene on highly oriented poly(vinylidene fluoride) (PVDF) film was achieved by cyclic voltammetry to yield well-ordered poly(3-methylthiophene) (P3MT) thin films with anisotropic structural and conductivity properties. The conductivity of P3MT along the direction perpendicular to the chain direction of PVDF, after electrochemical dedoping, is 59 ± 3 S cm−1, while that along the PVDF chain direction is 1.2 ± 0.4 S cm−1. The high conductivity of the P3MT is attributed to the well-ordered structure with its flat-on single crystals as confirmed by electron diffraction and Reflection Absorption Infra-red Spectroscopy (RAIRS). The data are consistent with P3MT chains aligned with π–π stacking perpendicular to the chain direction of the PVDF substrate. Epitaxial electropolymerization is an unusual method of preparing highly ordered thin films of organic semiconductors.

Enhancing Membrane Permeability for CO2 Capture Through Blending Commodity Polymers with Selected PEO and PEO-PDMS Copolymers and Composite Hollow Fibres

This paper presents two strategies applied in our study, one involved blending CO2-phillic materials such as PEG and PEG-PDMS copolymer with commodity polymer Matrimid® to improve separation performance, another involved development of composite hollow fibre membranes of high CO2 permeance.Blending of PEG and PEG-PDMS copolymer in Matrimid® resulted in hollow fibre membranes with improved gas separation performance. The modification of the membrane microscopic structure also led to improvements in plasticization resistance and tolerance of water content that are important for industrial applications.Composite hollow fibre membranes of high permeance of 550 GPU and selectivity of 45 were developed by using micro-porous PVDF substrate, with multiple coatings PTMSP gutter layers and Pebax®1074 selective layers. Initial tests with mixed gas and short term aging were encouraging while the tests for the tolerance of water and minor components and tests with real flue gas are ongoing.

Immunoglobulin G immobilization on PVDF surface

Immobilization of antibody molecules onto hydrophobic polymeric surfaces with disordered orientation is something unwanted in many applications. To overcome this drawback, controlled immunoglobulin G (IgG) immobilization onto poly(vinylidene fluoride) surface was investigated in this paper. A two-step process involving radiofrequency plasma pretreatment for polymer surface functionalization, followed by coupling reaction was developed, after which immunoglobulin G was immobilized onto the surface directly or via protein-A. IR and XPS data proved that the process is more efficient when the radiofrequency plasma pretreatment was performed using N2 and N2/H2 as discharge gases. NIR-CI, AFM and XPS surface evaluation revealed that immobilization of IgG onto N2/H2 plasma-treated PVDF via grafted protein-A was achieved with an ends-on orientation, leaving available the antigen binding sites of IgG. This procedure could be a promising route for the preparation of oriented IgG assembly onto PVDF, useful in biomedical, membranes or sensors applications. QCM results showed a better antibody–antigen interaction when IgG immobilization onto PVDF substrate is mediated by protein A.

Development of poly(amidoamine) dendrimer/polyvinyl alcohol hybrid membranes for CO2 capture at elevated pressures

A novel hybrid membrane of poly(amidoamine) (PAMAM) dendrimer/cross-linked poly(vinyl alcohol) (PVA) was developed for the selective separation of CO2 from a mixture of CO2 and H2. PAMAM dendrimers were incorporated into a cross-linked PVA matrix to improve CO2 separation performance at elevated pressures. An organic metal compound di-isopropoxy-bis(triethanol aminato) titanium (Ti cross-linker) was selected as the PVA cross-linker. The effects of cross-linker concentration and membrane thickness on separation performance were discussed. The optimum concentration of Ti cross-linker was from 10 to 25 wt%. CO2 permeance increased with decreasing thickness, but the CO2/H2 selectivity decreased with decreasing thickness. The effect of operating temperature on CO2 separation properties using of the thinnest membrane was discussed. Both QCO2 and CO2/H2 selectivity increased with increasing temperature. The CO2/H2 selectivity reached a maximum of 32 with CO2 permeance of 3.0 × 10-11 m3(STP)/(m2 s Pa) at 60°C under CO2 partial pressure of 560kPa. SEM observation and XPS spectra showed that the selective layer of thickness 6 μm of PAMAM/cross-linked PVA hybrid composite membrane onto a PVDF substrate was formed. The PAMAM dendrimer/cross-linked PVA membrane shows great potential for CO2separation from H2 in high pressure applications, such as IGCC process.

The Microstructure and Electrical Property of Porous Cu Film on Soft PVDF Substrate

The porous Cu film was deposited on soft PVDF substrate by magnetron sputtering at different sputtering pressure. The microstructure and electrical properties of Cu films were investigated as a function of sputtering pressure by X-ray diffraction XRD and Hall effect method. The results show that the surface morphology of Cu film is porous, and the XRD revealed that there are Cu diffraction peaks with highly textured having a Cu-(220) or a mixture of Cu-(111) and Cu-(220) at sputtering pressure 0.5 Pa. The electrical properties are also severely influenced by sputtering pressure, the resistivity of the porous Cu film is much larger than that fabricated on Si substrate. Furthermore, the resistivity increases simultaneously with the increasing of Cu film surface aperture, but the resistivity of Cu film still decreases with the increasing grain size. It can be concluded that the crystal structure is still the most important factor for the porous Cu film resistivity.

Multilayered Poly(vinylidene fluoride) Composite Membranes with Improved Interfacial Compatibility: Correlating Pervaporation Performance with Free Volume Properties

A spin-coating process integrated with an ozone-induced graft polymerization technique was applied in this study. The purpose was to improve the poor interfacial compatibility between a selective layer of poly(2-hydroxyethyl methacrylate) (PHEMA) and the surface of a poly(vinylidene fluoride) (PVDF) substrate. The composite membranes thus fabricated were tested for their pervaporation performance in dehydrating an ethyl acetate/water mixture. Furthermore, the composite membranes were characterized by field emission scanning electron microscopy (FE-SEM) for morphological change observation and by Fourier transform infrared spectroscopy equipped with attenuated total reflectance (ATR-FTIR) for surface chemical composition analysis. Effects of grafting density and spin-coating speed on pervaporation performance were examined. The composite membrane pervaporation performance was elucidated by means of free volume and depth profile data obtained with the use of a variable monoenergy slow positron beam (VMSPB). Results indicated that a smaller free volume was correlated with a higher pervaporation performance of a composite membrane consisting of a selective layer of spin-coated PHEMA on a PHEMA-grafted PVDF substrate (S-PHEMA/PHEMA-g-PVDF). The composite membrane depth profile illustrated that an S-PHEMA layer spin-coated at a higher revolutions per minute (rpm) was thinner and denser than that at a lower rpm.

Enhancement of specific cell-capture efficiency using a reversible dielectrophoresis field

This work proposes using a periodic and reversible DEP (dielectrophoresis) field to improve the immuno-capture efficiency of the rare specific cells in a mixed cell suspension. The forward DEP field gently guides all the cells to interact with the bioprobes that are immobilized on a PVDF substrate in the reactor, and the reverse DEP field redistributes the un-bonded cells into the suspension for next reaction chance. The fluorescence visibility of the specific T-cells was also improved via quantum dots/tetramer complex staining. Accordingly, the specifically stained and captured cells could be imaged and counted. The experimental results indicated that the forward DEP can double the cell-capture efficiency compared with that without DEP enhancement, and the reversible DEP scheme can improve the efficiency about 25% further. This assay is also successively used to detect the population of rare cytotoxic Tc cells in a human blood sample; and the Tc cell has specific receptors on the membrane surface to identify the Epstein–Barr virus (EBV).

Nafion-Doped Polypyrrole as a Supercapacitor Electrode in Ionic Liquid

The supercapacitive properties of flexible Nafion-doped polypyrrole(PPy/Nafion) electrodes prepared using a flexible gold coated porous PVDF substrate were investigated in the presence of an ionic liquid, N-methyl-N-propylpyridinium trifluoromethanesulfonyl imide(P1,3TFSI), by means of cyclic voltammetry for supercapacitors. The PPy/Nafion showed capacitance values in the range of 350–450 F/g at the scan rates of 50–300 mV/s, indicating the ionic liquid is suitable for the electrolyte in supercapacitor.

Characteristics of poly(vinylidene difluoride) modified by plasma-based ion implantation

Surface modification of polymers using radiation effects has been studied in a variety of fields, such as gas barrier or biochemical applications. However, the mechanism of improvement or degradation of polymers induced by radiation has not been well understood. In this study, poly(vinylidene difluoride) (PVDF) of crystalline phase of II (alpha form) was modified by plasma-based ion implantation (PBII) to control its adsorption properties for protein. Helium ions with applied bias voltages ranging from −1 to −20kV were irradiated to the PVDF substrate for one minute and protein adsorption properties on the modified PVDF substrates was evaluated by the Western blotting method. As a result, adsorption of PVDF decreased with increasing the applied bias voltage, whereas the modification with only plasma treatment did not cause a significant change in adsorption properties for protein. The PBII-induced decrease in adsorption can be used for monitoring or patterning the protein. In order to study the mechanism, chemical and physical properties of the modified surfaces were analyzed with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) in attenuated total reflection (ATR) mode. Contact angles on the modified surfaces were also measured and surface free energies were calculated by Owens–Wendt–Rabel–Kaeble method. The surface morphology observed AFM and SEM did not show a significant change after the modification but the concentration of fluorine decreased and the surface energy on the surface increased after the modification. The influential factors in adsorption properties of the modified PVDF for protein are discussed.

Enhanced Pervaporation Performance of Multi-layer PDMS/PVDF Composite Membrane for Ethanol Recovery from Aqueous Solution

Multi-layer PDMS/PVDF composite membrane with an alternative PDMS/PVDF/non-woven-fiber/PVDF/PDMS configuration was prepared in this paper. The porous PVDF substrate was obtained by casting PVDF solution on both sides of non-woven fiber with immersion precipitation phase inversion method. Polydimethylsiloxane (PDMS) was then cured by phenyltrimethoxylsilane (PTMOS) and coated onto the surface of porous PVDF substrate one layer by the other to obtain multi-layer PDMS/PVDF composite membrane. The multi-layer composite membrane was used for ethanol recovery from aqueous solution by pervaporation, and exhibited enhanced separation performance compared with one side PDMS/PVDF composite membranes, especially in the low ethanol concentration range. The maximum separation factor of multi-layer PDMS/PVDF composite membrane was obtained at 60 degrees C, and the total flux increased exponentially along with the increase of temperature. The composite membrane gave the best pervaporation performance with a separation factor of 15, permeation rate of 450 g/m(2)h with a 5 wt.% ethanol concentration at 60 degrees C.

Viscosimetry using a new electromagnetic-acoustic microbalance

The nanostructure evolution of gels, biomaterials or porous media can be characterized by its mechanical properties. Few nondestructive techniques are developed to investigate the viscosity evolution. This paper present a new electromagnetic-acoustic technique using a wireless thickness shear mode transducer. A suitable model of the measurement is also presented to characterize the viscosity of the nanostructure in contact with the transducer. This transducer is a double copper-clad PVDF substrate resonator, designed to operate over a wide radiofrequency range without lumped tuning capacitors. This architecture constitutes an alternative solution to design a high-Q ultrasonic microbalance. To characterize the material at the surface of the transducer, the evolution of the induced complex impedance is measured. From this evolution, the mechanical energy storage and dissipation in the material can be extracted. In order to validate the lumped element model used, a series of glycerol/water mixtures is studied. We show that the resonant frequency shift and damping follow an accurate linear shape (<5%) according to the square root of the liquid viscosity and density product. This result is in good agreement with the classical prediction of Martin and Kanazawa obtained with a quartz crystal microbalance.