Copolymer Poly Vinylidene Fluoride Research Articles

Advancements in Flexible Nanogenerators: Polyvinylidene Fluoride-Based Nanofiber Utilizing Electrospinning.

With the gradual miniaturization of electronic devices and the increasing interest in wearable devices, flexible microelectronics is being actively studied. Owing to the limitations of existing battery systems corresponding to miniaturization, there is a need for flexible alternative power sources. Accordingly, energy harvesting from surrounding environmental systems using fluorinated polymers with piezoelectric properties has received significant attention. Among them, polyvinylidene fluoride (PVDF) and PVDF co-polymers have been researched as representative organo-piezoelectric materials because of their excellent piezoelectric properties, mechanical flexibility, thermal stability, and light weight. Electrospinning is an effective method for fabricating nanofibrous meshes with superior surface-to-volume ratios from polymer solutions. During electrospinning, the polymer solution is subjected to mechanical stretching and in situ poling, corresponding to an external strong electric field. Consequently, the fraction of the piezoelectric β-phase in PVDF can be improved by the electrospinning process, and enhanced harvesting output can be realized. An overview of electrospun piezoelectric fibrous meshes composed of PVDF or PVDF co-polymers to be utilized is presented, and the recent progress in enhancement methods for harvesting output, such as fiber alignment, doping with various nanofillers, and coaxial fibers, is discussed. Additionally, other applications of these meshes as sensors are reviewed.

TSD investigation of P(VDF-TeFE)/Si composites under the gamma irradiation

In the presented work, the charge state of P(VDF-TeFE)/Si-based composites obtained on the basis of nano-Si with a size of 50[Formula: see text]nm and micro-Si particles with a size of 50[Formula: see text][Formula: see text]m and P(VDF-TeFE) copolymer of polyvinylidenefluoride with tetrafluoroethylene from polar polymers, was investigated, the amount of filler and the effect of ionizing radiation on these properties were studied. It has been shown that the observed differences in the charge state parameters of P(VDF-TeFE)/Si composites obtained with nano- and micro-sized Si are due to the higher concentration of nanoparticles and, accordingly, the effective surface area in the composites obtained with nanosized Si, and the change in the mobility of relaxors due to the effects of construction and destruction processes that occur in the polymer matrix and at the interphase boundary after the effect of gamma radiation. The reason for the observed changes in the depolarization processes of polarized P(VDF-TeFE)/nano-Si composites after gamma radiation is the change in the ratio between the construction and destruction processes in the system.

Polyvinylidene Fluoride Copolymers with Grafted Polyethyl Methacrylate Chains: Synthesis and Thermal and Dielectric Properties

Polyvinylidene Fluoride Copolymers with Grafted Polyethyl Methacrylate Chains: Synthesis and Thermal and Dielectric Properties

Impact of stress triaxiality, strain rate, and temperature on the mechanical response and morphology of PVDF

Poly-vinylidene fluoride (PVDF) is a semi-crystalline thermoplastic featuring a high chemical resistance, good thermal stability, and high pressure resistance, rendering it attractive for a wide range of engineering applications. This study assesses the influence of temperature, strain rate, and stress triaxiality on the large-strain response of a commercial PVDF copolymer containing poly-ethylene (PE) particles.The thermo-viscoplastic response of the material was investigated at six temperatures ranging between −20°C and 100°C at a quasi-static strain rate ė of 0.005s−1, and three strain rates ė={0.005,0.1,1.0}s−1 at room temperature. To study the pressure sensitivity of the material, tensile tests using axisymmetric notched tensile specimens with three different notch radii as well as uniaxial compression tests were performed. The mechanical response was assessed in terms of net axial stress and volume strain vs. longitudinal strain, measured using digital image correlation (DIC). To gain insight into the interrelationship between the macroscopic volume strain and void morphology on the microscale, selected cross sections of deformed specimens were imaged employing scanning electron microscopy (SEM).The material exhibited a temperature- and strain-rate-dependent response as well as a pressure-sensitive flow stress. For ambient temperatures up to 60°C, pronounced plastic dilatancy was observed, promoted by increasing the stress triaxiality. The SEM study confirmed that the plastic dilatancy was a result of extensive void nucleation and growth on the microscale. Two sources of void nucleation were identified, namely particle–matrix interface separation as well as cavitation within the matrix material itself. In tests performed at ambient temperatures higher than 80°C, no plastic dilation was observed and no voids or PE particles were identified in the SEM images.Apart from an improved understanding of the material’s mechanical response, this study provides data and insights suitable for the development and calibration of constitutive models, aiding the design of robust and reliable structures using PVDF.

A versatile acoustically active surface based on piezoelectric microstructures

We demonstrate a versatile acoustically active surface consisting of an ensemble of piezoelectric microstructures that are capable of radiating and sensing acoustic waves. A freestanding microstructure array embossed in a single step on a flexible piezoelectric sheet of polyvinylidene fluoride (PVDF) leads to high-quality acoustic performance, which can be tuned by the design of the embossed microstructures. The high sensitivity and large bandwidth for sound generation demonstrated by this acoustically active surface outperform previously reported thin-film loudspeakers using PVDF, PVDF copolymers, or voided charged polymers without microstructures. We further explore the directivity of this device and its use on a curved surface. In addition, high-fidelity sound perception is demonstrated by the surface, enabling its microphonic application for voice recording and speaker recognition. The versatility, high-quality acoustic performance, minimal form factor, and scalability of future production of this acoustically active surface can lead to broad industrial and commercial adoption for this technology.

Impedance Spectroscopy of Charge Conducting Composite Materials Based on Microfibers of Polyvinylidene Fluoride Copolymer with Trifluoroethylene Modified with Polypyrrole

Impedance Spectroscopy of Charge Conducting Composite Materials Based on Microfibers of Polyvinylidene Fluoride Copolymer with Trifluoroethylene Modified with Polypyrrole

Strength and elastic properties of 3D printed PVDF-based parts for lightweight biomedical applications

Research results on 3D printed fluoropolymers are scarce since the filaments were introduced commercially only in the last several years to enable fused filament fabrication (FFF) of structural components for more demanding service conditions, where chemical, UV or fire resistance, high purity, sterilizability or biocompatibility are critical such as in biomedical industry. This experimental study reports on additive manufacturing and quasi-static mechanical testing of polyvinylidene fluoride (PVDF) and in-vitro cytocompatible polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) specimens that were 3D printed with different infill patterns at 75% density (linear, cubic, cross, concentric, octet, zigzag, triangular). Recommendations are provided for addressing issues related to weak adhesion and obtrusive warping, which occur in open-chamber FFF printer due to semi-crystalline and hydrophobic nature of PVDF-based thermoplastics. The measured tensile and flexural stress-strain curves are analyzed to determine the influence of strut-based infills on the strength and elastic performance by including comparisons in ratios between strength, modulus of elasticity and weight of the specimens. The concentric pattern demonstrates the highest tensile strength, while the cross and triangular lattices – the lowest one. In three-point bending, the linear pattern delivers the lowest strength, while the rest exhibit comparable mechanical properties. The results are conducive to the design of 3D printable PVDF homopolymer and copolymer load-bearing structures serving as lightweight high-performance components in biomedical applications.

Multilayered ferroelectric polymer composites with high energy density at elevated temperature

Ferroelectric polymers have been widely explored for film capacitor applications due to their high energy storage densities that are almost an order of magnitude greater than those of the commercial capacitor dielectrics. However, the existing ferroelectric polymers are designed exclusively for room-temperature operation, and suffer from poor capacitive performance at elevated temperature, which falls short of the need in the emerging harsh-environment applications. In this paper, we report multilayered ferroelectric polymer composites exhibiting simultaneous high energy density and high discharge efficiency at elevated temperature. The multilayered composites consist of two copolymers of polyvinylidene fluoride (PVDF) with similar chemical structures but distinct dielectric properties, where one contributes to high electrical polarization and the other offers high thermal stability and suppresses charge injection. More importantly, we demonstrate that the critical issue of charge conduction at elevated temperature in ferroelectric polymers is well tackled by the established highly miscible interlayer interfaces in the multilayered structure set up between the two electrically dissimilar phases. At 70 °C, the maximum discharged energy density above 80% discharge efficiency of the multilayered composites reaches 15.5 J/cm3, far outperforming all the existing ferroelectric polymers. This work sheds light on the design of high-energy-density ferroelectric polymers for high temperature capacitive energy storage.

Nanocomposites of polyvinylidene fluoride copolymer-functionalized carbon nanotubes prepared by electrospinning method

Electrospun nanofiber membranes (ENM) have been utilized in varied applications like filters, sensors, scaffolds for tissue engineering, electronics and so on. In this study, polyvinylidene fluoride (PVDF) copolymer nanofiber was reinforced with functionalized multiwall carbon nanotubes (f-MWCNT) via electrospinning method with N,N-dimethylacetamide (DMAc) as the solvent. To ensure the dispersion of f-MWCNT in polymer solution, it was sonicated prior to addition of PVDF copolymer into the dispersion. The results showed that tensile strength and elongation at break increased by 9 % and 79 %, respectively, with the addition of f-MWCNT, when compared to pure PVDF copolymer nanofiber web. Incorporated f-MWCNT into PVDF copolymer nanofiber also resulted in an increase in the average nanofiber diameter from 312 nm to 445 nm but decrease the hydrophobicity. FTIR spectra and XRD pattern confirmed the increase of PVDF β-phase structure as the results of electrospinning process and addition of MWCNT.

Performance of a Li-Polyimide Battery with Electrolytes of Various Types

—The effect of various types of electrolyte on the behavior of lithium-polyimide batteries was studied. The electrolyte systems used included the liquid 1 M LiPF6 electrolyte in ethylene carbonate/dimethyl carbonate (1: 1), plasticized polymer electrolyte based on the polyvinylidene fluoride copolymer with hexafluoropropylene, and nanocomposite electrolyte with SiO2 nanoparticles introduced in different amounts. The structure rearrangement of polyimide during lithiation—delithiation was studied by cyclic voltammetry (CV), charge—discharge cycling, and quantum—chemical modeling using four types of electrolyte. The use of the polymer and nanocomposite electrolyte was shown to increase the discharge capacity of the polyimide cathode compared to that of the cell with liquid electrolyte, but the structural degradation of the polyimide cathode cannot be avoided.

Tactile-Sensing Based on Flexible PVDF Nanofibers via Electrospinning: A Review.

The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical performance have been widely utilized as functional materials in flexible tactile sensors. Polymer nanomaterials, representing the most promising materials, especially polyvinylidene fluoride (PVDF), PVDF co-polymer and their nanocomposites with ultra-sensitivity, high deformability, outstanding chemical resistance, high thermal stability and low permittivity, can meet the flexibility requirements for dynamic tactile sensing in wearable electronics. Electrospinning has been recognized as an excellent straightforward and versatile technique for preparing nanofiber materials. This review will present a brief overview of the recent advances in PVDF nanofibers by electrospinning for flexible tactile sensor applications. PVDF, PVDF co-polymers and their nanocomposites have been successfully formed as ultrafine nanofibers, even as randomly oriented PVDF nanofibers by electrospinning. These nanofibers used as the functional layers in flexible tactile sensors have been reviewed briefly in this paper. The β-phase content, which is the strongest polar moment contributing to piezoelectric properties among all the crystalline phases of PVDF, can be improved by adjusting the technical parameters in electrospun PVDF process. The piezoelectric properties and the sensibility for the pressure sensor are improved greatly when the PVDF fibers become more oriented. The tactile performance of PVDF composite nanofibers can be further promoted by doping with nanofillers and nanoclay. Electrospun P(VDF-TrFE) nanofiber mats used for the 3D pressure sensor achieved excellent sensitivity, even at 0.1 Pa. The most significant enhancement is that the aligned electrospun core-shell P(VDF-TrFE) nanofibers exhibited almost 40 times higher sensitivity than that of pressure sensor based on thin-film PVDF.

First-principles simulations of PVDF copolymers with high dielectric energy density: PVDF-HFP and PVDF-BTFE

Phase diagrams of polyvinylidene fluoride (PVDF) and its copolymers with hexafluoropropylene (HFP) and bromotrifluoroethylene (BTFE) are investigated via first-principles simulations and compared to previously studied P(VDF-chlorotrifluoroethylene) (CTFE) data. We find that a nonpolar to polar phase transition induced by an electric field also occurs in HFP and BTFE copolymers and the results for P(VDF-HFP) show good agreement with existing experiments. For P(VDF-BTFE) we show that its nonpolar phase remains the ground state for a substantially larger range of concentrations than for P(VDF-CTFE) and P(VDF-HFP), and predict that a high BTFE concentration copolymer will achieve a significantly higher energy density at low field than P(VDF-CTFE) 9%. The transition pathways connecting the polar and nonpolar phases are also calculated and the energy barriers for the transitions turn out to be similar for the three copolymers, even at different co-monomer concentrations. The similarity of barriers indicates that a mixture of these and related copolymers can be used to optimize the properties of the dielectric, such as energy density, processability, and cost.

Surface Shearing Effects on Langmuir–Blodgett Thin Films of P(VDF-TrFE) Ferroelectric Surface

Polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) copolymers, also called Nobel polymers due to their ferroelectric, piezoelectric, and pyroelectric properties, possess non-lineal optical properties and low acoustic impedance that pair with water and living tissue (i.e. are biocompatible). These qualities make them promising for multiple electronic applications. In this paper we explore the effects of applying a shearing force on copolymer of Polyvinylidene Fluoride with Trifluoroethylene (P(VDF-TrFE) thin film has been studied. A shearing technique was used to induce stress on the film, which produced an improvement in crystallization and grain size.

Forming mechanism study of unique pillar-like and defect-free PVDF ultrafiltration membranes with high flux

An intriguing polyvinylidene fluoride (PVDF) membrane with unique pillar-like structures was synthesized. The membrane was synthesized using the phase inversion method by adding the amphiphilic graft copolymer PVDF grafted with poly(ethylene glycol) methyl ether methacrylate (PEGMA) (PVDF-g-PEGMA) to the PVDF backbone material. It had high flux and high sodium alginate rejection ratio under low transmembrane pressure. However, the mechanisms for the formation of pillar-like structures are still unknown. In this paper, we explored the formation mechanism of pillar-like structures from aspects of solvent and additive. Based on the experimental results and analysis of ternary diagram, both NMP and PVDF-g-PEGMA must coexist in casting solution to form pillar-like structures. When NMP is in the solvent, PEGMA segments have enough time to migrate to the surface and repel each other during the phase inversion process. Finally, by using the target plot method, one membrane with the best performance was chosen as the proposed membrane from all membranes that casted under different conditions. The proposed membrane has a pure water flux of 2173L/m2/h/bar. The total organic carbon (TOC, by sodium alginate) removal efficiency is 89%. This membrane may have a good potential in water treatment applications.

Investigation of Ferroelectric Polymer Langmuir Film Properties

ABSTRACTThin films of Polyvinylidene Fluoride (PVDF) copolymers have been incorporated within ferroelectric field effect transistors, all organic thin film transistor devices (OTFTs), piezoelectric actuators, and recently proposed as the ferroelectric layer in a promising multiferroic tunnel junction configuration [1]. The properties of most of these devices would benefit from reduced thickness and better thickness control of the ferroelectric layer during device processing.A proven means for fabricating ultrathin films of the PVDF copolymer is the Langmuir-Blodgett (LB) technique. This technique involves dissolving the polymer in a volatile solvent which is then dispersed dropwise onto a purified water subphase, leaving an ultrathin layer of the copolymer on the water surface. The ability to control the thickness on the molecular level is the most prominent feature of this technique.In some early studies [2], the minimum thickness of these films was found to be about 5 Angstroms, or roughly the same thickness as the intermolecular spacing of the all-trans β phase for the ferroelectric polymers. Later studies have led to the fabrication of films composed of thicker transfer steps: ∼ 1.8 nm per deposition [3]. The discrepancy is likely explained by the nature of the VDF molecule: it is not an amphiphile.In this study, we further investigate the properties of Langmuir films of ferroelectric copolymers and discuss the observation of an apparent monolayer phase transition based on abrupt changes observed in the compressibility of the films. The main goal of this project is to discover the extent to which the device properties (like transfer step thickness) of PVDF films can be modified through processing conditions.

Effective and low fouling oil/water separation by a novel hollow fiber membrane with both hydrophilic and oleophobic surface properties

Membrane filtration for oil/water separation has the potential to provide a simple system with high separation efficiency for oily wastewater treatment. However, conventional membranes are usually subject to severe oil fouling, which has greatly limited the application of membrane technology in oily wastewater management so far. In this study, a novel hollow fiber membrane showing both hydrophilic and oleophobic surface properties was prepared and tested for its oil/water separation performance. The hollow fiber membrane was prepared from polyvinylidene fluoride (PVDF) as the base material and a modified PVDF copolymer with hydrophilic and oleophobic segments as the additive (denoted as AP). The developed hollow fiber membrane was packed into membrane modules for the treatment of artificial oily wastewater samples prepared from hexadecane or crude oil emulsions and real oily wastewater samples collected from a palm oil mill in Malaysia. The experimental results indicate that, as compared to the control PVDF membrane or a modified PVDF membrane with hydrophilic surface property, the developed novel hollow fiber membrane exhibited excellent performances: with much higher water flux, less flux decay during oily wastewater filtration, and significantly higher or almost complete flux recovery from a simple physical cleaning (e.g., water flushing or backwashing) after a filtration run, while achieved the same or usually higher oil removal efficiency. Since the hollow fiber membrane can be easily scaled up to the full module for practical use, there is a great prospect for the developed novel hollow fiber membrane to be used as an effective method for oily wastewater treatment.

Polarization Screening in Multiferroic (Ga,Mn)As/P(VDF-TrFE) Transistors

Ferroelectric copolymers of polyvinylidene fluoride and trifluoroethylene are attractive gate materials because of a rather high remanent polarization, low dielectric permittivity, and easy integration on semiconductors due to the low processing temperature. Recently it was demonstrated that the functionalities of devices with ferroelectric polymer gates can be extended to magnetic field effect transistors with diluted magnetic semiconductor channels. Here we address the critical issue of polarization screening in such transistors quantifying the amount of polarization charge which controls the magnetic channel. The gate effect is shown to be limited by internal polarization screening rather than polarization retention loss.

From Vinylidene Fluoride (VDF) to the Applications of VDF-Containing Polymers and Copolymers: Recent Developments and Future Trends

After an introduction reporting the properties and the applications of fluoropolymers, a first part deals with i) the main routes to produce vinylidene fluoride (VDF) monomer, ii) its homopolymerization, and iii) the advantages and uses of polyvinylidene fluoride (PVDF). In a second section, this review, illustrated by numerous examples, extensively reports the synthesis, properties and applications of the copolymers based on VDF with non-halogenated, fluorinated, commercially available or synthesized comonomers. These comonomers exhibit XYC=CZ-Sp-R structures where X, Y, and Z represent H, F, and CF3 groups, Sp a spacer and R a function such as OH, OAc, SAc, CO2R' (R' being a H atom or an alkyl group), CN, P(O)(OR')2 and SO3H. According to the nature and to the amount of the comonomer, the copolymers can be thermoplastic, elastomeric or thermoplastic elastomers. Introducing reactive R side groups brings complementary properties such as hydrophily, ionic exchange or surface properties, or further crosslinking of the resulting copolymers. Then, the kinetics of radical copolymerization of VDF with M comonomers led to the assessment of the reactivity ratios which are compared. Hence, a reactivity series of these M comonomers with respect to a macroradical terminated by VDF is proposed. Usually, these copolymers exhibit random structures but only three comonomers produced alternating copolymers with VDF: hexafluoroisobutylene, F2C=CFCO2CH3, and H2C=C(CF3)CO2R. The controlled radical copolymerizations of VDF with other comonomers (such as chlorotrifluoroethylene, 3,3,3-trifluoropropene, hexafluoropropylene, perfluoromethyl vinyl ether or-trifluoromethacrylic acid) either in the presence of xanthates, borinates or iodo-compounds are also reported. In addition, new VDF-containing copolymers exhibit well-defined architectures, such as block and graft copolymers. They can be synthesized either by conventional techniques or by controlled radical copolymerization. Chemical modifications of PVDF and poly(VDF-co-monomer) copolymers are also presented. Several properties and applications (such as surfactants, dielectrical polymers, thermoplastic elastomers, fuel cell and ultrafiltration membranes, or polycondensates, the fluorinated segments of which bringing softness and thermal stability) of these VDF-containing copolymers will illustrate this review.

Toward a low-voltage multiferroic transistor: Magnetic (Ga,Mn)As under ferroelectric control

The persistent field effect control of ferromagnetism in a diluted magnetic semiconductor by low-voltage polarizing pulses is demonstrated in a ferroelectric gate field effect transistor configuration. The Curie temperature of the (Ga,Mn)As channel is unambiguously signaled by a cusp in the temperature derivative of resistance. Polarization reversal in the ferroelectric copolymer polyvinylidene fluoride with trifluoroethylene P(VDF-TrFE) by voltage pulses of less than 10 V results in a reproducible nonvolatile shift in the cusp by as much as 7%–9%. The unique combination of a relatively large spontaneous polarization and low dielectric constant of the P(VDF-TrFE) gate promises a further reduction in the operation voltage.

Improving the efficiency of pyroelectric conversion

Pyroelectric conversion utilizes low-grade waste heat as a heat source, and thus produces clean energy. Low-grade heat is abundant in the various industries and it is practically free. It can be converted to high-voltage electricity by pyroelectric conversion. Our pyroelectric converter uses copolymer of poly-vinylidene fluoride with trifluoroethylene [60/40% P(VDF-TrFE)]. Previously, we encountered a substantial power loss due to internal leakage at high temperature and voltage. In order to increase the power output, we examined the effect of polymer purification using solvent extraction. We compared the electrical properties of purified copolymer with those of 'as-received' copolymer. Although we removed only 0.4wt% of the copolymer by solvent extraction, the electrical resistivity of purified copolymer was 35% higher than that of the 'as-received' copolymer. We also observed that thin films produced using purified copolymer were able to withstand 50% higher electric field before they were ruined by the electrical short circuit. Subsequently, we conducted pyroelectric conversion using 25 μm thick 60-40% P(VF 2 -TrFE) copolymer films. Copolymer purification resulted in a three-fold increase in net power output. Net power output per unit volume of the 'as-received' copolymer was 95 J L -1 but it increased to 279 J L -1 for purified copolymer. © Her Majesty the Queen in Right of Canada, as represented by the Minister of Natural Resources, 2007.