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Compared with commercial polyolefin membranes, electrospun polymeric membranes have the advantages of higher porosity and better electrolyte wettability, but their poor mechanical performance limits their industrial use as battery separators. In this work, a layer-to-layer electrospinning is used for fabrication of PVdF@PMMA membranes, in which fibers in adjacent layers are arranged at a certain angle (0[degrees], 30[degrees], 60[degrees], 90[degrees]). The as-electrospun membranes are further hot-pressed to boost their mechanical strength. Various techniques are employed to evaluate the membranes, such as scanning electron microscopy, differential scanning calorimetry, contact angle measurement, electrochemical impedance spectroscopy, and linear sweep voltammetry. The results show that polymethyl methacrylate partially melts during the hot-pressing treatment, causing adjacent fibers in the membranes to bridge. The obtained membranes show different tensile strength values with the various angles between fibers. When the angle is 30[degrees], the tensile strength can reach 22.09 MPa and higher porosity (74.68%), greater liquid electrolyte absorption (612.36%) than that of commercial polyolefin membrane are harvested. The lithium-ion cell assembly with the membrane separator exhibits a discharge capacity reaching 142 mAh [g.sup.-1] and an excellent capacity retention of 90.7%. This present study provides an innovative and promising approach for the fabrication of high-performance battery separator by electrospinning. Highlights * PVdF@PMMA membranes are prepared by a layer-to-layer electrospinning. * In the membranes, fiber orientation in adjacent layers is kept at a certain angle. * Hot-pressing further boosts mechanical performance of the membranes. * Membranes with different angle of fibers show various mechanical strengths. KEYWORDS coaxial electrospinning, hot-pressing, lithium-ion battery separator, mechanical reinforcement, 1 | INTRODUCTION Lithium-ion batteries (LIBs) find extensive applications in diverse sectors, particularly the electronics domain, owing to their remarkable attributes encompassing high-energy density, prolonged lifespan, and good for environmental [...]

Shell materials play significant impact on corrosion resistance and mechanical properties on self-healing coating of composite with core-shell nanofiber. In this paper, three promising shell materials were investigated to optimize the performance of self-healing coating. Self-healing core-shell nanofibers with different shell materials were prepared with coaxial electrospinning. The resulting nanofibers were used to prepare self-healing corrosion resistance coating. The tensile test revealed a notable enhancement in the tensile strength of PA6 core-shell nanofiber epoxy composite coatings compared with the epoxy coating, demonstrating increase of 26.92%. Friction and wear test indicated reductions in the friction coefficients of PAN, PVDF, and PA6 core-shell nanofibers by 13.82%, 12.44%, and 26.27%, respectively. The self-healing and anti-corrosion abilities were evaluated through electrochemical impedance spectroscopy (EIS) test. All three coatings exhibited exceptional self-healing efficiencies exceeding 90%, highlighting the substantial potential of the chosen shell materials as nanocontainers for self-healing agent. Results indicate that the nanofibers with PA6 as shell material can achieve the best enhancement performance, which has a greater potential for the corrosion protection and long-lasting use of offshore wind turbine tower coatings. Highlights * Optimizing coating performance by screening coaxial nanofibers for shell materials * Shell material can improve the tensile strength of coating up to 26.92% * Friction coefficient of PA6 nanofiber coating was about 15% lower than PAN and PVDF * All three coatings exhibited exceptional self-healing efficiencies exceeding 90% KEYWORDS coating, core-shell nanofibers, mechanical properties, self-healing, shell material, 1 | INTRODUCTION Offshore wind turbine towers are easy to be corrosive under high humidity and high salt spray marine environments. (1) Application of anti-corrosion coating with self-healing ability is [...]

Suitable air humidity is of great importance for human health, crop growth and the life of buildings. In this work, the polyvinylidene fluoride/calcium chloride (PVDF/Ca[Cl.sub.2]) porous membranes with rich pore structures for adsorption of high-humidity gases were prepared using solvent evaporation-induced phase separation. The results showed that the gap between the PVDF spherical crystals increased with the increase of Ca[Cl.sub.2] content, which increased the porosity of the membrane. When the Ca[Cl.sub.2] content reached 20 wt.%, the water vapor adsorption capacity of the PVDF/Ca[Cl.sub.2] porous membrane was 0.876 [Please download the PDF to view the mathematical expression] and the initial adsorption rate was 0.050 g*[g.sup.-1]*[min.sup.-1]. At this point, the moisture vapor permeance of the membrane was the best at 0.04g*[m.sup.-2]*[h.sup.-1]*[Pa.sup.-1], and the dry strength of the PVDF/Ca[Cl.sub.2] membrane was 0.397 MPa, which was 1.64 times that of the membrane without Ca[Cl.sub.2]. This work provides theoretical and technical guidance for the preparation of air dehumidification materials. Highlights * The porosity of the membranes increased with increasing of calcium chloride content. * The moisture vapor permeance of the M-20 membrane was the best at 0.04 g*[m.sup.-2]*[h.sup.-1]*[Pa.sup.-1]. * The dry strength of the M-20 membrane was 1.64 times that of the M-0 membrane. KEYWORDS Ca[Cl.sub.2], moisture absorption, porous membrane, PVDF, 1 | INTRODUCTION High-humidity gases can be extremely harmful to human health, crop growth and the life of buildings. (1,2) In particular, high-humidity air will speed up the growth and [...]

Abstract Polyvinylidene fluoride (PVDF), a polymer with three common crystal polymorphs ([alpha], [beta], [gamma]), has several practically useful properties, including piezoelectric properties. Accurate measurement of its crystalline polymorphs is important [...]

Polyvinylidene fluoride/boehmite composite membranes with hydrophilic surfaces were prepared using the nonsolvent induced phase inversion technique (NIPS) method to remove arsenate ions from water. The nanoparticles were added with different boehmite filler content. The contact angle of the bare membrane is 85[degrees], and it is reduced to 53[degrees], imparting hydrophilicity due to the presence of boehmite nanoparticles. The mechanical characteristics of the membranes have significantly improved. The BET and SEM results have shown that the average pore diameter gets reduced with boehmite addition, and surface area increases. Additionally, the use of nanoparticles enhanced the membranes' thermal stability. The nanofiltration unit is used to filter the arsenic-contaminated water. The transmembrane pressure of ~4 bar is applied to all the membranes, and arsenic rejection; the flux of the membranes was calculated. The membrane has shown the highest rejection of 55% with a flux of 3.5659 L/[m.sup.2].h. KEYWORDS arsenic removal, membranes, Polyvinylidene fluoride, 1 | INTRODUCTION Groundwater arsenic contamination greater than the permitted limit of 0.05 mg/L has been a serious threat in West Bengal alone. The consumption of arsenic-contaminated groundwater over the [...]

Abstract Highly electro-active P(VDF-HFP)/[Cu.sup.2+] films having more than 99% electroactive phase was prepared by a simple solution casting method. We used this electro-active polymer to make piezoelectric generators (PGs). These [...]

Abstract PI/PVDF-HFP/PI sandwich separators were prepared by electrospinning, and subsequent pressing and heat treatment were used to improve their properties. Morphology, porosity, air permeability, contact angle, and other specifications of [...]

The solubility of boehmite nanoparticles was determined experimentally for 20 different solvents using Hansen solubility parameter method (HSP). The algorithm given by Gharagheizi was optimized using MATLAB. The solubility was found as, [delta] = 33.08 [MPa.sup.1/2] with, [[delta].sub.D] = 16.50 [MPa.sup.1/2], [[delta].sub.D] = 15.54 [MPa.sup.1/2], and [[delta].sub.H] = 24.09 [MPa.sup.1/2]. Flory-Huggin's theory was used to model the quarternary system of a blend polymeric membrane. The thermodynamic equations were solved and optimized using MATLAB and ternary phase diagrams were obtained for different filler compositions. Thermodynamic enhancement and kinetic hindrance parameters were obtained to predict the membrane morphologies. The porosity of the membrane was increased with the addition of nanoparticles. Contact angle of the membrane was decreased from 84.45[degrees] to 50.2[degrees]. KEYWORDS Boehmite, Flory-Huggin's theory, Hansen solubility parameter, phase inversion, Polyvinylidene fluoride, ternary phase diagram, 1 | INTRODUCTION Membrane-based filtration is rapidly expanding due to its ease of scale-up, and it can be coupled with other processes such as adsorption to treat groundwater and industrial [...]

Dielectric materials with thermally responsive property are being pursued in fields such as next-generation sensors, smart switches, and novel actuators. These applications require that the dielectric materials have mechanical durability and stable serviceability besides thermally responsive dielectric behavior. Herein, we report a novel thermally responsive, mechanically durable, and low-cost dielectric composite simply fabricated by vacuum impregnating polyethylene glycol (PEG) into kapok fiber and compounding them with polyvinylidene fluoride. A remarkable dielectric susceptibility, controlled dielectric transition temperature, and obvious thermal hysteresis of the composite films induced by the solid-liquid phase transition of PEG are demonstrated. The effect of molecular weights of PEG on the dielectric response behaviors is evaluated. Such thermally responsive dielectric materials with satisfactory mechanical durability will offer a chance toward constructing thermally responsive systems for reliable and stable operation. KEYWORDS dielectric response, kapok fiber, polarization, polyethylene glycol, polyvinylidene fluoride, temperature, 1 | INTRODUCTION Thermally responsive dielectric materials have received increasing attention in the last decade because of their ability to undergo dielectric transitions in response to temperature stimuli.[1-4] These materials [...]

MWCNT@PDA/PVDF-TrFE and MWCNT@PDA/PVDF-TrFE-CTFE composite films with high dielectric constant, low dielectric loss and excellent energy storage density were prepared by solution casting method. The best component of composite film (2.0 wt% MWCNT@PDA/PVDF-TrFE-CTFE, named C) was selected as the middle layer of the sandwich structure, and the upper and lower layers were made up by pure PVDF-TrFE film (named A) and pure PVDF-TrFE-CTFE films (named B). By testing and comparing the microstructure and performance of the single-layer composite film and the sandwich structure composite film, the influence of the matrix and structure on the performance of the composite film was discussed. The results showed that the dispersion effect of the filler in the matrix became worse, the dielectric constant gradually increased, the dielectric loss of the composite film did not change significantly, and the energy storage density first increased and then decreased with the increasing of the filler content. At a frequency of [10.sup.3] Hz, the dielectric constants of 2.0 wt% MWCNT@PDA/PVDF-TrFE and 2.0 wt% MWCNT@PDA/PVDF-TrFE-CTFE composite films were 9.00 and 13.88, which were 1.9 and 2.9 times of pure films. When the electric field was 1100 kV/cm, the energy storage density of composite film BCB was 6.36 times of film C. KEYWORDS energy storage, MWCNT@PDA, PVDF-TrFE, PVDF-TrFE-CTFE, 1 | INTRODUCTION Electric energy storage equipment has a high-power density due to its ultra-fast charge and discharge capabilities, which can meet the specific needs of various fields, such as [...]

This article reports the design and fabrication of open-cell polyvinylidene fluoride (PVDF) foams as carriers that can promote biofilm growth and organic removal efficiency for biological wastewater treatment in attached growth bioreactors. Open-cell PVDF foams were fabricated by a manufacturing approach that integrated compression molding and particulate leaching. PVDF carriers were structured with two governing factors of leaching agent types (e.g., sodium chloride [NaCl] and sodium acetate [NaOAc]) and contents (e.g., 80 and 90 wt%). Open-cell PVDF foams possessed high porosity and high protected surface area (i.e., more than *10 to *20 of the areas of commercialized carriers), which promoted biofilm growth in these carriers. As a successful advantage, PVDF carriers used in the moving bed biofilm reactors (MBBR) were entirely covered by biofilm in both interior and exterior parts without clogging. This provides strong evidence of the bacterial compatibility of the fabricated open-cell PVDF foam carriers. Moreover, the specific morphology of the PVDF carriers in this article provided superior biofilm protection from the detachment in MBBR. Experimental results revealed that PVDF open-cell foams fabricated by 80 wt% of NaCl demonstrated higher mechanical strength with an organic removal efficiency of 77% [+ or -] 7% in the corresponding bioreactor containing them. KEYWORDS biofilm growth, biological wastewater treatment, moving bed biofilm reactor, open-cell foam, porous media, 1 | INTRODUCTION Polymer foams, which can be classified into closed-cell foams and open-cell foams, are a family of porous materials that possess gas voids in a polymer matrix. [1] [...]

In the present study, a lightweight and flexible polyvinylidene fluoride (PVDF)/zinc oxide (ZnO) nanocomposite was prepared using a lowtemperature phase-inversion process. The synergetic effect of low-temperature, phase-inversion, and the integration of ZnO nanoparticles primes on enhancing the electroactive polar [beta]-phase in the nanocomposite. The transformation of the electroactive phase and its quantification were carried out using Fourier-transform infrared spectroscopy and wide-angle X-ray diffraction. The PVDF/ZnO piezoelectric polymer nanocomposite was utilized for energy harvesting application that showed a better electromechanical response of ca. 69 V (peak to peak) at ~1.6 N, 250 [micro]W/[cm.sup.2] surface power density and 0.25 mA/[cm.sup.2] surface current density. The fabricated piezoelectric polymer nanocomposite is a possible candidate for superior energy scavenging applications for capturing human kinematics. KEYWORDS phase-inversion, piezoelectric nanogenerator, polymer nanocomposite, zinc oxide, p-Phase, 1 | INTRODUCTION With the rapid depletion of fossil-based natural resources, the energy crisis is a matter of great concern in the modern age. [1] Fossil fuels, such as coal, [...]

Polyvinylidene fluoride (PVDF) is a preeminent pyrolytic and piezoelectric polymer. It has been widely studied as an ideal material for wearable flexible sensors or low-power electronic equipment. PVDF/ZnO thin films were prepared by direct writing method, which promoted the ordered arrangement of PVDF molecular chains under the action of electric field and thus improved the crystallinity of the [beta] phase. Meanwhile, the effects of intercalation of ZnO nanoparticles on the crystallinity of PVDF thin films were explored. The results show that appropriate addition of nano-ZnO as nucleating agent can induce the crystallinity of the PVDF film obviously. While the additive amount of nanoparticles was 0.02 wt%, the relative [beta] phase content of the PVDF film can reach 88.92%. Under the double action of adding ZnO nanoparticles and electric field assistance, the dielectric constant of the composite film increases from 6.9 (pure PVDF) to 12.4 (0.03 wt% ZnO) at a frequency of 1 kHz. The [d.sub.33] value of the film without polarization is up to -9.1 pC/N, the output voltage is increased to 351 mV, and the conductivity of the composite film has been improved. KEYWORDS crystallization, dielectric properties, microstructure, thin film, 1 | INTRODUCTION With the vigorous development of the intelligent industry, many wearable electronic products have entered our daily lives. Choosing a suitable sensor is crucial for wearable electronic devices. [...]

Polyvinylidene fluoride (PVDF)-based nanofiber was successfully produced for a high performance and stable humidity sensor via a solution-blowing spinning method. The performances of the manufactured sensors, including the impedance change with relative humidity (RH), moisture stability, and response and recovery times, were investigated. To improve charge carrier transfer, which is the main mechanism of humidity sensing, especially under low RH conditions, lithium chloride was used and displayed the best linearity in the impedance change with RH. Fast response and recovery times of 1.7 and 16.1 s were, respectively, achieved with zinc oxide nanoparticles. Furthermore, the sensors showed excellent moisture stability, owing to the hydrophobicity of PVDF, and this was demonstrated via repeatability testing and scanning electron microscopy. The humidity sensing mechanism was discussed using complex impedance spectra., INTRODUCTION Humidity sensors have been used in various fields, such as modern industry [1], agriculture [2], and smart devices [3-5], Furthermore, there is substantial interest in the precise application of [...]

Polyvinylidene fluoride (PVDF)/polyvinyl alcohol (PVA) ultrafiltration (UF) membranes were prepared via a phase inversion method employing the modification of carboxylated multiwalled carbon nanotubes (MWCNTs-COOH). Various contents of MWCNTs-COOHs (0.00-0.15 wt%, weight of casting solution) were added into PVDF/PVA/dimethyl sulfoxide systems for the fabrication of the plate UF membrane. Fourier transform infrared spectroscopy spectra identified the successful introduction of carboxyl through the C=0 peak at 1730 [cm.sup.-1]. Scanning electron microscopy images exhibited the external surface and the asymmetric morphology with the appearance of a sponge-like inner structure. Atomic force microscopy analysis determined the roughness values and rougher topography. The hydrophilicity of the composite membrane containing 0.09 wt% of MWCNTs-COOHs improved the most. This sample has the highest pure water flux, approximately doubled (126.6 L [m.sup.-2] [h.sup.-1]) compared to the PVDF/PVA membrane (68.6 L [m.sup.-2] [h.sup.-1]), an enhanced bovine serum albumin flux recovery rate, showing an increase of 17%, and the best fouling resistance ability. Meanwhile, the porosity and dynamic contactangle also indicate the enhancement of membrane hydrophilicity. Dextran (DEX) 600k rejection reached 91.0%. Break strength, elongation at break, and Young's modulus also had improvements of 60%, 215.5%, and 56.7%, respectively, when the MWCNTs-COOH content was 0.12 wt%., INTRODUCTION Over the last dozen years, polymeric membranes have been widespread in engineering applications and scientific usage [1], such as the polyamide (PA) membrane for seawater treatment and ethanol purification [...]

We investigated the effects of annealing temperature and vacuum treatment on the crystallinity and ferro-electric properties of solution-casted poly(vinylidene-fluoride-co-trifluoroethylene), P(VDF-TrFE), thick films. We varied the annealing temperature from 70 °C to 150 °C and achieved high-quality ferroelectric thick films annealed at 130 °C. Ferroelectric domains and their properties were confirmed using X-ray diffraction, Fourier transform infrared spectroscopy with attenuated total reflection mode and ferroelectric/piezoelec-tric measurement systems. Drying and/or annealing in the vacuum allowed for the improvement of crystallinity and ferroelectric/piezoelectric properties. Importantly, the piezoelectric coefficient, d33, of our optimal P(VDF-TrFE) films after sufficient poling treatment was 36 pC/N and our P(VDF-TrFE) power generator produced an output voltage of -6 V under periodic bending and unbending motions. POLYM. ENG. SCI., 54:466-471, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION Much attention has been directed towards ferroelectric polymers because they are inexpensive, lightweight, flexible, and easily processed. Ferroelectricity, however, has been found in only a small number of crytstalline [...]

Three series of poly (vinylidene fluoride-chlorotrifluoroethylene)/barium titanate (BT) nanocomposites with varied compositions were fabricated via solution cast process followed by thermally treated in different ways. Quenching the composite samples at lower temperature could effectively enhance their dielectric constant, breakdown strength as well as the energy density. The highest energy density (13.6 J/[cm.sup.3]) is observed in the sample quenched from 200°C to - 94°C with 5 vol% BT, which is much higher than nanocomposites reported in the current literature. The addition of ceramic particles leads to the improvement of dielectric permittivity and energy density measured under the same electric field. However, the dielectric breakdown strength and the energy density measured at breakdown strength of the resultant composites are reduced as a function of BT content. The fixed maximum electric displacement and reduction of saturation electric field suggest that the addition of ceramic particles with high dielectric constant may help increase the energy density of composites under low electric field but not for high electric field. POLYM. ENG. SCI., 53:897-904, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Ferroelectric ceramic has long been investigated and utilized as capacitors, ferroelectric memories, and transducers, for their excellent dielectric, pyro-, and piezoelectric properties (1-4). However, comparing with organic polymeric materials, [...]

Graft copolymer (PVDF-g-PNIPAAm) having poly(vinyli-dene fluoride) (PVDF) backbones and poly(N-isopropyla-crylamide) (PNIPAAm) side chains was synthesized via radical copolymerization and its hollow fiber membrane was fabricated from dry-wet spinning technique with N, N-dimethylformamide as the solvent and poly(ethylene glycol) (10,000) as the additive. The effects of spinning condition (take-up speeds) on the structures and performances of resulting fiber membranes were systematically considered. The structures and performances of fiber membranes were characterized by element analysis, X-ray photoelectron spectroscopy, water contact angle measurement, scanning electron microscope, atom force microscope, and filtration experiments. The results indicate that PNIPAAm side chains tended to enrich on the membrane surface and pore surface and especially tended to aggregate on the inner surface due to the effect of bore fluid. The hollow fiber membrane exhibits an obvious temperature-sensitive property. The pure water flux increases remarkably around 32 °C, while the retention of albumin egg decreases accordingly, when the permeation temperature rises from 20 to 45 °C. As the take-up speed increases, both the inner and outer diameters of fiber membranes decrease. A higher take-up speed favors higher pure water permeation flux, which allows larger molecules to permeate through the fiber membrane. FOLYM. ENG. SC., 53:571-579, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Intelligent membranes show remarkable changes in properties as a response to the surrounding environment changes, such as pH (1-3), ionic field (4), temperature (5-19), and so on. Due to [...]

To improve interactions between carbon nanotubes (CNTs) and poly(vinylidene fluoride) (PVDF) matrix, multiwalled CNTs (MWCNTs) were successfully coated with amphiphilic polyvinylpyrrolidone (PVP) using an ultrasonication treatment performed in aqueous solution. It was found that PVP chains could be attached noncovalently onto the nanotubes' surface, enabling a stable dispersion of MWCNTs in both water and N, N-dimethylformamide. PVP-coated MWCNTs/PVDF nanocomposite films were prepared by a solution casting method. The strong specific dipolar interaction between the PVP's carbonyl group (C=0) and the PVDF's fluorine group C=[F.sub.2] results in high compatibility between PVP and PVDF, helping PVP-coated MWCNTs to be homogenously dispersed within PVDF. Fourier transform infrared and X-ray diffraction characterization revealed that the as-prepared nanocomposite PVDF films exhibit a purely β-polymorph even at a very low content of PVP-wrapped MWCNTs (0.1 wt%) while this phase is totally absent in the corresponding unmodified MWCNTs/PVDF nanocomposites. A possible mechanism of β-phase formation in PVP-coated MWCNTs/PVDF nanocomposites has been discussed. Furthermore, the tensile properties of PVDF nanocomposites as function of the content in PVP-coated MWCNTs were also studied. Results shows that the addition of 2.0 wt% of PVP-coated MWCNTs lead to a 168% increase in Young's modulus and a 120% in tensile strength. POLYM. ENG. SCI., 53:34-43,2013. © 2012 Society of Plastics Engineers, INTRODUCTION Because of its high piezoelectricity, poly(vinylidene fluoride) (PVDF) is a technologically important thermoplastic polymer. While PVDF can exhibits five different crystal polymorphs referred to as α, β, δ, γ, [...]

Nanofibers of polyvinylidene fluoride (PVDF) were prepared using solutions of PVDF with acetone and dimethylacetamide. The solutions were prepared at different concentrations (18, 21.5, and 25% wt) of PVDF. The nanofiber membranes were produced by using the Forcespinning™ method. Parameters such as the orifice size and spinneret angular velocity were varied. The produced membranes were characterized using scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction to determine the effect of varying parameters in the Forcespinning™ process on fiber diameter, bead formation, thermal stability, polymorphism, and morphology of the fibers and overall structure of the membrane. It was observed that polymer concentration played a key role in fiber and bead formation; at higher concentrations (such as 25 wt%), the fiber diameter increased but the bead formation decreased. The prepared composite membranes have potential applications on separators for Li-ion batteries, ultra filtration membranes, and proton conductivity membranes for fuel cells applications. POLYM. ENG. SCI., 52:2260-2265, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION There is significant interest in developing nanofiber membranes due to unique properties that could be obtained with small diameter fibers, such as high surface area to volume ratio and [...]

Zeolite 4A was incorporated into poly(vinylidene fluoride) (PVDF) matrix to prepare mixed matrix membranes (MMMs). The objective of this study was to investigate the effects of the inorganic filler on the structural properties of the MMMs. The resulting membranes were characterized using thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, contact angle tests, and scanning electron microscopy (SEM). The mechanical properties of the membranes were determined using a tensile stress-strain machine. To fully study the interface properties between the inorganic fillers and polymer chains, the densities of the membranes were experimentally determined and compared with the theoretical values. The experimental densities of the composite membranes were lower than those of the theoretical values. The void volume fractions were calculated accordingly. The single gas (He, [CO.sub.2], [O.sub.2], and [N.sub.2]) permeabilities of the resulting membranes were carried out. The highest permeabilities of 14.65, 6.62, 1.01, and 0.3 Barrer for He, [CO.sub.2], [O.sub.2], and [N.sub.2], respectively, were obtained by PVDF/4A 32% composite membrane; whereas the highest selectivities of 105.5, 31.5, and 3.3 for He/[N.sub.2], [CO.sub.2]/[N.sub.2], and [O.sub.2]/[N.sub.2], respectively, were obtained using PVDF/4A 16% composite membrane. POLYM. ENG. SCI., 52:2106-2113, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION It is widely known that polymer membranes for gas separation suffer a trade-off relationship between permeability and selectivity, that is, the enhancement of permeability is always at the expense [...]

Ionic polymer-metal composite (IPMC) actuators that display continuously large actuation displacements without back relaxation and with large blocking force at low direct current (DC) voltages are used as biomimetic sensors, actuators and biomedical devices. This article reports the preparation and actuation performance of new IPMC actuators based on the polyvinylidene fluoride (PVDF)/polystyrene sulfonic acid (PSSA)/ polyvinyl pyrrolidone (PVP) polymer blend membrane, which requires low voltage DC. The performance results of the proposed IPMC actuators are compared with Nafionbased IPMC actuators. In the blend membrane, PVDF is the hydrophobic polymer, PSSA is the polyelectrolyte, and PVP is the hydrophilic basic polymer. The proposed IPMC actuators based on the PVDF/PSSA/PVP blend membrane of polymer mixture ratios of 60/15/25 and 50/25/25 gave higher actuation displacement and higher blocking force at low DC voltages than the Nafion-based IPMC actuator. POLYM. ENG. SCI., 51:1730-1741, 2011. © 2011 Society of Plastics Engineers, INTRODUCTION Ionic polymer-metal composite (IPMC) actuators can be fabricated by plating metal particles on an ion-exchange polymer membrane. IPMCs have received increasing attention in recent years due to their potential [...]

Biological cell injection is laborious work that requires lengthy training and suffers from a low success rate. In this paper, a robotic cell-injection system for automatic injection of batch-suspended cells is proposed. To facilitate the process, these suspended cells are held and fixed to a cell array by a specially designed cell-holding device, and injected one by one through an "out-of-plane" cell-injection process. A micropipette equipped with a polyvinylidene fluoride microforce sensor to measure real-time injection force is integrated in the proposed system. Through calibration, an empirical relationship between the cell-injection force and the desired injector pipette trajectory is obtained in advance. Then, after decoupling the out-of-plane cell injection into a position control in the X-Y horizontal plane and an impedance control in the Z-axis, a position and force control algorithm is developed to control the injection pipette. The depth motion of the injector pipette, which cannot be observed by microscope, is indirectly controlled via the impedance control, and the desired force is determined from the online X-Y position control and cell calibration results. Finally, experimental results demonstrate the effectiveness of the proposed approach. Index Terms--Batch biomanipulation, cell-holding device, position and force control, robotic cell injection.

A corrugated polyvinylidene fluoride (PVDF) bimorph power harvester with harvesting structure fixed at the two edges in the corrugation direction and free at the other edges is proposed. Results concluded that the adaptability of a harvester to operating environment can be improved greatly by designing the harvesting structure with adjustable resonant frequency.

Conductive polymer composites were prepared by melt-mixing of an immiscible blend of poly(vinylidene fluoride) (PVDF), high density polyethylene (HDPE), and carbon black (CB). Three major factors - the carbon black content, the carbon black type, and the composite morphology - were shown to have remarkable effects on the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effect of the composites. The relationship between the morphology and the PTC and NTC effects of the composites was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The OM micrographs indicated that CB was selectively located in the HDPE phase and the SEM micrographs showed that there were some gaps between the two phases. The PTC effect of the composites is caused by the thermal expansion as a result of the melting of the HDPE crystallites. The morphology of the composites greatly affects the PTC and NTC behaviors of the composites. When the CB-filled HDPE formed a continuous phase and the PVDF formed a dispersed phase, the PTC and NTC behaviors of the composites were similar to those of CB-filled neat HDPE composite without crosslinking. When the composite exhibited an interlocking structure, a normal PTC effect could also be observed, but the NTC effect was delayed to higher temperatures. A mechanism was proposed to explain this new physical phenomenon, and the mechanism was verified by another CB-filled polymer blend comprising an alternating copolymer of tetrafluoroethylene-ethylene and HDPE., INTRODUCTION The resistivity of carbon black (CB)-filled semicrystalline polymer composites has been found to increase dramatically when the composite is heated to the melting point of the semicrystalline polymer. Frydman [...]

Removable and reusable sensors are essential in applications like health monitoring or the nondestructive evaluation of newly produced or finished composite structures. In such tests, a major requirement is that the tested structures are not altered during either bonding or removal of the sensor. In this paper, removability and reusability have been introduced to polyvinylindine fluoride (PVDF) film sensors by a very simple process that uses double-sided adhesive tapes. The repeatability of signals generated by such sensors is verified through a series of tests. The use of these removable and reusable sensors is then demonstrated through a selected application where PVDF sensors are ideally suited, namely, detection of defects such as impact damage, saw cuts, and delaminations in elastic structures. These defects change the local curvature in beams, plates, or shell structures, and PVDF sensors are ideally suited to detect these changes in curvatures.

An inexpensive acceleration measurement sensor that uses the piezoelectric polymer poly(vinylidene fluoride) (PVDF) has no moving parts. It achieves a sensitivity of 1.071 V sec sq per meter and a nonlinearity of less than 0.1%, with the limit of detection being 10 micrograms. The pyroelectric effects of the PVDF can be minimized with a symmetrical system. Various measurement ranges of acceleration can be achieved by utilizing the principle of this sensor.

A synthetic array experiment has been used to produce bowtie limited diffraction beams in water, which are in close conformity to those obtained from theory and computer simulations. A broad-band PZT ceramic/polymer composite transducer of one mm diameter is scanned in a raster format and placed at the center of elements of an equivalent two-dimensional array of 50 mm diameter aperture. A polyvinylidene fluoride needle hydrophone of 0.5 mm diameter receives the waves generated by the transducer. A depth of field of 216 mm is achieved for these bowtie beams, along with low sidelobes.

A study of the temperature-dependent dielectric and electromechanical properties of commercial polyvinylidene flouride (PVDF) films reveals their suitability for constructing inexpensive disposable transducers. The measured temperature dependence of the transducer's center frequencies and fractional bandwidths in the -40 to 80 degree celsius range matches very well with the predictions from computer simulations based on Mason's model. Various tests prove the usability of the same disposable transducers for ultrasonic and acoustic emission sensing nondestructive testing purposes.

A membrane hydrophone, capable of characterizing ultrasonic medical transducers, with a minus three dB bandwidth in excess of 150 MHz and spatial resolution of less than 100 micron has been developed. It has been fabricated on a superior coupling piezoelectric copolymer, polyvinylidene fluoride trifluoroethylene film. The frequency response can be evaluated by Bacon's shock wave method only. Absence of a proper technique makes open circuit sensitivity measurement difficult, leaving the only alternative of comparing the loaded end-of-cable sensitivity with a Marconi hydrophone.

Recently, the development in organic ferroelectrics has enabled the design of low-cost electronic devices such as memory cells and radio frequency identification (RFID) systems. The RFID tags do not require [...]

The use of a polyvinylidene fluoride (PVDF) membrane hydrophone in calibrating air-coupled transducers was investigated. The potential and performance of PVDF as a hydrophone material with frequencies between 100 kHz and 5 MHz were examined using a one-dimensional theoretical analytical method. Experimental results showed that PVDF membrane hydrophones are highly suitable for calibration in air and that they offer certain advantages when used in air-coupled calibration. It was also found that the acoustic impedance of PVDF hydrophones is an order of magnitude lower than piezoceramic systems.