Pure Polyvinylidene Fluoride Research Articles

Percolative multi-susceptible PVDF/NZFO composite films with triply controlled high dielectric and magnetic properties

Flexible multi-field susceptible films with remarkable properties and high data storage characteristics are promising in modern electronics. In this work, the percolative Ni0.5Zn0.5Fe2O4 (NZFO)/polyvinylidene fluoride (PVDF) composite films with both high permittivity and significant magnetic properties are prepared by dip coating on ITO/glass substrates. The highest permittivity of 74 is achieved with the NZFO volume ratio close to the percolation threshold, which is 20 times higher than that of pure PVDF. Meanwhile, the dielectric loss is kept below 0.1. The saturation and remanent magnetizations of composite films are 42.04 and 5.70 emu/g and the permeability is ∼3.105, reaching 60%–80% of those in the single phase NZFO. Detailed analysis shows that the high permittivity of the composite film is triply controlled simultaneously by the intrinsic characteristic of the PVDF phase, Kirkpatrick's hybridization model and microcapacitor behavior. It will be of broad interest to control both high dielectric and magnetic properties at the same time of many other flexible and susceptible storage devices.

Piezoelectric and optoelectronic properties of electrospinning hybrid PVDF and ZnO nanofibers

Polyvinylidene fluoride (PVDF) is a unique ferroelectric polymer with significant promise for energy harvesting, data storage, and sensing applications. ZnO is a wide direct band gap semiconductor (3.37 eV), commonly used as ultraviolet photodetectors, nanoelectronics, photonicsand piezoelectric generators. In this study, we produced high output piezoelectric energy harvesting materials using hybrid PVDF/ZnO nanofibers deposited via electrospinning. The strong electric fields and stretching forces during the electrospinning process helps to align dipoles in the nanofiber crystal such that the nonpolar α-phase (random orientation of dipoles) is transformed into polar β-phase in produced nanofibers. The effect of the additional ZnO nanowires on the nanofiber β-phase composition and output voltage are investigated. The maximum output voltage generated by a single hybrid PVDF and ZnO nanofiber (33 wt% ZnO nanowires) is over 300% of the voltage produced by a single nanofiber made of pure PVDF. The ZnO NWs served not only as a piezoelectric material, but also as a semiconducting material. The electrical conductivity of the hybrid PVDF/ZnO nanofibers increased by more than a factor of 4 when exposed under ultraviolet (UV) light.

Frequency dependence of electrical properties of polyvinylidene fluoride/graphite electrode waste/natural carbon black composite

Polyvinylidene fluoride (PVdF) is a semi-crystalline thermoplastic material with remarkably high piezoelectric coefficient and an attractive polymer matrix for micro-composite with superior mechanical and electrical properties. The conductive filler is obtained from Graphite Electrode Waste (GEW) and Natural Carbon Black (NCB). The variation of composite content (%) of PVdF/NCB/GEW were 100/0/0, 95/5/0, 95/0/5, 95/2.5/2.5. This experiment employed dry dispersion method for material mixing. The materials were then moulded using hot press machine with compression parameters of P = 5.5 MPa, T = 150 °C, t = 60 minutes, A = 5×5×(0.2 - 0.4) cm3. The electrical conductivity properties of pure PVdF, as well as PVdF/GEW, PVdF/NCB, and PVdF/NCB/GEW composites were investigated in a frequency range of 100 to 100000 Hz. The PVdF/GEW sample obtained the highest electrical conductivity. It is concluded that GEW and NCB can be incorporated into PVdF as a conductive filler to increase the conductivity of conductive material composite without solvent.

Corrosion behavior of AISI 316 stainless steel coated with modified fluoropolymer in marine condition

In the maritime industry, stainless steel corrosion resistance requires further surface improvement and further enhanced protection using surface coatings. In this study, an engineered copolymer of polyvinylidene fluoride (PVDF) with polymethylmethacrylate (PMMA)-blended coating was found to provide outstanding corrosion resistance for metal surfaces affording protection against severely corrosive marine environments. Electrochemical measurements indicate that corrosion protection of 316 stainless steel was drastically increased when utilizing the KP blend (a combination of PVDF + PMMA), producing a new set of corrosion properties and morphological characteristics. The corrosion protection of the KP coating proved to be very effective in reducing the passive region current density from 2.19 × 10−5 A/cm2 (for bare stainless steel) to 2.63 × 10−10 A/cm2 and the breakdown passive region potential at 0.25 V. This was followed by a significant decrease in corrosion rate, when compared to pure PMMA and PVDF films, during exposure to artificial marine seawater. With the KP film, impedance measurements surpassed those of other films, with a noticeable nonpeak straight line in the phase angle diagram. Optical observation showed that corrosion pits and delamination areas existed under the coatings.

Polymer/metal multi-layers structured composites: A route to high dielectric constant and suppressed dielectric loss

In order to obtain polymer-based composites with a high dielectric constant and suppressed dielectric loss, polyvinylidene fluoride (PVDF)/silver (Ag) multi-layer structured composites were fabricated via vacuum evaporation and hot-press methods. The dielectric constant of the PVDF/Ag(5/4) composite (including five PVDF layers and four Ag layers) is up to 31, and dielectric loss can be suppressed below 0.02 (smaller than that of pure PVDF) at 1 kHz. The enhanced interfacial polarization in multi-layer structured composites is determined via temperature dependence of electrical modulus, which is regarded as the origin of dielectric constant enhancement. The suppressed dielectric loss at low frequency is attributed to the difficulty in the formation of a percolation conductive network in this multi-layer system. This promising multi-layer strategy could be generalized to a variety of polymers to develop polymer-based composites with a high dielectric constant and low dielectric loss.

The influences of polydopamine immersion time on characteristics and performance of polyvinylidene fluoride ultrafiltration membrane

The Polyvinylidene Fluoride (PVDF) membrane has been prepared by phase inversion method using N,N-dimethylacetamide (DMAc) as solvent and Poly Ethylene Glycol (PEG) as additive. The fabricated membrane was modified by Polydopamine (PDA) coating in concentration of 0.5 mg/ml and immersion times of 2 hours, 6 hours, and 24 hours. The characteristics and performance of the PVDF membranes before and after the modification are studied in this paper. The result of the water flux experiment showed that the PDA-coated PVDF membranes showcased a higher flux than that of pure PVDF membrane. Scanning Electron Microscopy (SEM) analysis confirmed that the membrane had an asymmetric structure consisting of two layers. There was no significant influence on the addition of PDA to the morphology of the pore matrix because the modification was done by surface coating. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that PDA was successfully introduced on the surface of PVDF membrane with the appearance of O-H from cathecol and N-H peaks at wavenumber range of 3300-3600 cm-1. Modification with PDA increased the mechanical strength of the membrane which affirmed by the results of the tensile and elongation at break evaluation.

Direct fabrication of a 3D-shape film of polyvinylidene fluoride (PVDF) in the piezoelectric β-phase for sensor and actuator applications

Until now, getting non-porous pure PVDF in the piezoelectric β-phase involved the application of stresses that limit the production of piezoelectric films into a flat form. In this work we present a new method to obtain, directly from the melt, pure β-PVDF which also allows the production of films with a 3D shape. A hydrophilic ionic liquid (IL), C2mim BF4, is used to totally induce the direct crystallization of PVDF in the piezoelectric β-phase during the melt. Afterwards, this IL is completely removed by washing the film in water at 70 °C. The process results in the production of a non-porous pure PVDF film, totally crystallized in the β-phase. Finally and for the first time, the replication of a 3D shape given by a glass form could be demonstrated by using this polymer.

Компьютерное молекулярное моделирование пьезоэлектрических свойств сегнетоэлектрических композитов на основе поливинилиден-фторида с графеном и оксидом графена

Molecular modeling of ferroelectric composites containing polyvinylidene fluoride (PVDF), graphene (G) and/or graphene oxide (GO), was performed using the semi-empirical quantum approximation PM3 in the HyperChem software package. The piezoelectric properties of the composites were analyzed and compared with the experimental data obtained for thin films containing poly(vinylidene-fluoride-trifluoroethylene) with graphene oxide (P (VDF-TrFE)/GO). A qualitative agreement was obtained between the simulation results and the experimental measurements of the piezoelectric coefficient, its decrease in the presence of G or GO was revealed. When models containing one or more layers of graphene with 54 carbon atoms were investigated, it was found that the average piezoelectric coefficient was reduced to -9.8 pm/V for the one-sided PVDF/G model and to -18.98 pm/V for the two-sided sandwich model G/PVDF/G in compare with the calculated piezoelectric coefficient for pure PVDF (-42.2 pm/V). After computer modeling for models incorporating one or more layers of 96 carbon atoms in the oxide graphene, it was found that the piezoelectric coefficient was reduced to a value of -14.6 pm/V for a one-sided PVDF / GO model and to a value of -29.8 pm/V for a two-sided sandwich model GO/ PVDF/GO compared to the piezoelectric coefficient for pure PVDF.

Enhanced breakdown strength of polymer composites by low filler loading and its mechanisms

Dielectric polymer materials with high energy density and low dielectric loss are highly desired for applications in advanced electronic devices and electric power systems. Here, we report on flexible dielectric composites using semiconductor nanoparticles as fillers and polyvinylidene fluoride (PVDF) as a matrix. The introduction of a small amount of ZnO filler results in significantly enhanced voltage breakdown strength and energy density in comparison with pure PVDF. Based on the multi-core model, combining the electric double layer theory and the interface contact theory, we investigate mechanisms and come out with that transportation of carriers under applied voltage is regulated by the charged interface, which delays the formation of the conduction path. Besides, the electric field imposed on the composites is alleviated by the internal micro-electric field.

Improving dielectric properties and energy storage performance of poly(vinylidene fluoride) nanocomposite by surface-modified SrTiO3 nanoparticles

Homogeneous nanocomposites flexible films is fabricated by incorporating surface modified paraelectric SrTiO3 nanoparticles (ST NP) by polyvinylpyrrolidone (PVP) into a polyvinylidene fluoride (PVDF) matrix. A systematic study was investigated on the effect of surface modified ST NP fillers on the dielectric properties and energy storage density of the nanocomposite films. Compared to pure PVDF, nanocomposite films with 5 vol % surface modified ST NP show a maximal energy density of 5.1 J/cm3, which is 182% higher than that of the pure PVDF. Moreover, the nanocomposites films exhibits a high efficiency of 80.7% at electric fields below 1000 kV/cm and still higher than 64.6% at an electric field of 2700 kV/cm. The results demonstrate that the nanocomposites films using the surface modified paraelectric fillers exhibit high energy storage densities and high efficiency.

Durable and self-healing superhydrophobic polyvinylidene fluoride (PVDF) composite coating with in-situ gas compensation function

A durable and self-healing superhydrophobic polyvinylidene fluoride (PVDF)/polyester-modified silicone resin (PMSR)/microspheric Na2CO3@SiO2 coating with WCA of 158±1.5° and low SA of 4±0.5° has been successfully prepared via sol-gel and spraying technique. After 24h hydrolysis of tetraethylorthosilicate (TEOS), microspheric Na2CO3@SiO2 particles with extremely large storage spaces were obtained as reservoirs for the healing agent of POTS. The superhydrophobicity of the prepared coating can be recovered after 10 rubbing/healing test cycles, indicating the excellent self-healing ability. Simultaneously, the prepared coating also possesses gas compensation capability in acidic condition, which can extend superhydrophobic duration by 400%. The gas compensation capability can be mainly attributed to the bubbles generated from the reaction between acid and porous Na2CO3, hindering water wetting the surface. Moreover, the prepared coating can withstand 4217 friction cycles without obvious surface damage, which is approximately 6 times higher than that of pure PVDF coating. This is mainly due to the combined action of the high adhesion of PMSR, the self-lubrication of PVDF and the surface hierarchical nano/micro wrinkles. The prepared coating also shows prominent superhydrophobic stability under the conditions of acid/alkaline solution (pH=1–14) or strong UV exposure (14days). It is believed that this durable and self-healing superhydrophobic coating is anticipated to open a new avenue to enlarge the application range of superhydrophobic coatings.

Preparation and characterization of novel poly (vinylidene fluoride) membranes using flower-like Bi 2 WO 6 for membrane distillation

Abstract In this study, hydrophobic flat-sheet composite membranes of polyvinylidene fluoride (PVDF) were fabricated using non-woven fabrics as a support for direct contact membrane distillation (DCMD) through non-solvent induced phase separation (NIPS). The effects of three-dimensional (3D) Bi 2 WO 6 on membrance morphology, porosity, pore size, pore size distribution, hydrophobicity, thermal properties and permeability were investigated. The flower-like Bi 2 WO 6 could optimize membrane structure and improve the membrane porosity by its unique 3D hollow structure. During the desalination process of 3.5% sodium chloride solution, the salt rejection with nano-Bi 2 WO 6 membranes was higher than the pristine PVDF membrane. The maximum transmembrane permeate flux (about 13.12 kg/m 2 h) was obtained with the feed solution at 60 °C and the cold distillate water at 20.0 °C, which was higher than the commercial PVDF membrane (9.43 kg/m 2 h) and the pure PVDF membrane (12.06 kg/m 2 h). Furthermore, the hybrid membrane exhibited outstanding stability in the 100 h continuous desalination experiments. Our results demonstrated that the prepared PVDF flat-sheet composite membrane with 0.5% flower-like Bi 2 WO 6 has a very good prospect to be utilized in membrane distillation process for desalination.

Carbon Coated Boron Nitride Nanosheets for Polymer Nanocomposites with Enhanced Dielectric Performance.

Carbon coated boron nitride nanosheets (BNNSs@C) hybrids with different carbon contents were synthesized by a chemical vapor deposition (CVD) method. The content of carbon in as-obtained BNNSs@C hybrids could be precisely adjusted from 2.50% to 22.62% by controlling the carbon deposition time during the CVD procedure. Afterward, the BNNSs@C hybrids were subsequently incorporated into the polyvinylidene fluoride (PVDF) matrix to fabricate the BNNSs@C/PVDF nanocomposites through a combination of solution and melting blending methods. The dielectric properties of the as-obtained BNNSs@C/PVDF nanocomposites could be accurately tuned by adjusting the carbon content. The resultant nanocomposites could afford a high dielectric constant about 39 (103 Hz) at BNNSs@C hybrids loading of 30 vol %, which is 4.8 times larger than that of pristine BNNSs-filled ones at the same filler loading, and 3.5 times higher than that of pure PVDF matrix. The largely enhanced dielectric performance could be ascribed to the improved interfacial polarizations of BNNSs/carbon and carbon/PVDF interfaces. The approach reported here offers an effective and alternative method to fabricate high-performance dielectric nanocomposites, which could be potentially applied to the embedded capacitors with high dielectric performance.

Preparation and characterization of Li0.30Cr0.10Ni0.60O/polyvinylidene fluoride composites with high dielectric constants

Abstract Lithium chromium nickel oxide (Li 0.30 Cr 0.10 Ni 0.60 O, LCNO) materials were prepared by sol-gel process and calcined at the temperature of 1000 °C for 3 h. Mechanical mixing process and hot pressing fabricated the composites between LCNO and polyvinylidene fluoride (PVDF). Effects of the amount of LCNO filler on the structure and dielectric properties of LCNO/PVDF composites were investigated. The LCNO/PVDF composites were characterized by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Furthermore, the dielectric properties of the LCNO/PVDF composites were also investigated. From TGA results, the decomposition step of LCNO/PVDF composites depends on the LCNO content and weight loss decrease with increasing LCNO contents due to the presence of LCNO in PVDF. All LCNO/PVDF composites exhibited two-phase structures of cubic rock-salt NiO structure and α-, γ- phases of PVDF. It is revealed that dielectric constant of the polymer composite increases with increasing LCNO content. This might be due to the formation of micro-capacitor network. The LCNO/PVDF composite with amount of 30 wt% showed the best properties with a high dielectric constant of 59.27 and low loss tangent of 0.31 at the frequency of 1 kHz and at room temperature. The composite gave a high dielectric constant, which was 2.82 times higher than that of pure PVDF. Therefore, the flexible high dielectric constant and low loss tangent of the composite were weakly frequency dependent, which might be suitable for capacitor applications.

Application of Ozone-Assisted Membrane Cleaning for Natural Organic Matter Fouled Membranes

ABSTRACTThe popularity of membrane technology in water treatment has been rising for over last 50 years due to wide range of filtration processes and applications, cost effective production and installation as well as safe and efficient water production. However, the development and improvement of membranes is ongoing due to number of weaknesses. Membrane fouling is a major drawback of membrane application in water and waste water treatment. Mostly caused by natural organic matter (NOM), fouling forms a layer on top of the membrane and blocks pores reducing the water permeation and can be potentially destructive to the membrane structure. The issue of membrane fouling can be addressed during membrane manufacturing, maintenance and operation. In the current study, the graphene-based nanomaterials (GBN) were incorporated in polyvinylidene fluoride (PVDF) to manufacture membranes via the phase-inversion technique. The resulting membranes show significant improvement to the properties of the pure PVDF membranes and their antifouling ability. The addition of GBN enhanced the water permeation by over 79% as a result of increased membrane hydrophilicity. Although this enhancement is beneficial, membrane fouling remained an issue despite the observed improvement. In this study, ozone, which is an effective oxidant, was evaluated as a novel technique for the cleaning of humic acid-fouled membranes. When ozone cleaning was applied to the humic acid-fouled membranes, reestablishment of close to original flux values was observed after just 30 min of cleaning. This statement is supported by SEM images that give an insight into the fouling of the membrane surface after the application of the cleaning methods. The data indicate that ozone is an effective technique for membrane cleaning against NOM-induced fouling.

Application of dopamine-modified halloysite nanotubes/PVDF blend membranes for direct dyes removal from wastewater

Membrane technology has been successfully applied for the removal of dyes from wastewater in the textile industry. In this work, halloysite nanotubes (HNTs) were functionalized with dopamine (DA) firstly, and then a series of novel polyvinylidene fluoride (PVDF) membranes were prepared via blending with different dosages of DA grafted HNTs (D-A-HNTs). The characterizations of nanoparticles (NPs) confirmed the reaction between DA and HNTs. The morphologies of membranes were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM), which indicated that D-A-HNTs had a good dispersity in membrane matrix and also improved the microstructure of membranes. The experimental results demonstrated that the D-A-HNTs modified membranes were presented to be more hydrophilic, with a pure water flux (PWF) as high as 42.2Lm−2h−1, which increased by 80.3% compared with pure PVDF membrane. The dye rejection ratios were also improved after adding D-A-HNTs, which reached 86.5% for Direct Red 28, 85% for Direct Yellow 4 and 93.7% for Direct Blue 14, respectively. More importantly, the anti-fouling test revealed that the blend membranes showed excellent anti-fouling property after several cycles. As a result, this study could have a great potential to widen the applications of membrane to treat textile wastewater.

Surface functionalized carbon nanotube with polyvinylidene fluoride: Preparation, characterization, current-voltage and ferroelectric hysteresis behaviour of polymer nanocomposite films

A comparative study of current-voltage characteristics and ferroelectric properties of polyvinylidene fluoride (PVDF) based nanocomposite films with pure multiwall carbon nanotubes (MWCNTs) and surface functionalized MWCNTs by different type of functionalize groups (-COOH, -OH, -NH2) as filler, was reported. The flexible nanocomposite films based on PVDF and surface modified MWCNTs were fabricated via solution casting method. The current voltage characteristics suggests that –COOH and –OH functionalize MWCNT loading PVDF films are semiconducting in nature whereas raw MWCNT and –NH2 functionalize MWNCT loading PVDF films are comparatively conducting in nature. Experimental data of current density-electric field were fitted with different existing theoretical models. It is observed that just by changing the functionalization group the electrical conductivity of the composite films significantly changes which is discernible from the current-voltage characteristic. From ferroelectric study the energy density of –COOH, -OH loaded PVDF films are doubled and tripled compare to the pure PVDF film. This work may provide a rout for using different functionalize MWCNTs into polymer matrix to enhance either the energy density or conducting nature of polymer nanocomposite.

Molecular modeling of the piezoelectric properties of ferroelectric composites containing polyvinylidene fluoride (PVDF) and either graphene or graphene oxide.

Molecular modeling of ferroelectric composites containing polyvinylidene fluoride (PVDF) and either graphene (G) or graphene oxide (GO) were performed using the semi-empirical quantum approximation PM3 in HyperChem. The piezo properties of the composites were analyzed and compared with experimental data obtained for P(VDF-TrFE)-GO films. Qualitative agreement was obtained between the results of the modeling and the experimental results in terms of the properties of the measured effective piezoelectric coefficient d 33eff and its decrease in the presence of G/GO in comparison with the average computed piezoelectric coefficient <d 33>. When models incorporating one or several G layers with 54 carbon atoms were investigated, the average piezoelectric coefficient <d 33> was found to decrease to -9.8pm/V for the one-sided model PVDF/G and to -18.98pm/V for the sandwich model G/PVDF/G as compared with the calculated piezoelectric coefficient for pure PVDF (<d 33> = -42.2pm/V computed in present work, and <d33> = -38.5 pm/V, obtained from J Mol Model 35 (2013) 19:3591-3602). When models incorporating one or several GO layers with 98 carbon atoms were considered, the piezoelectric coefficient was found to decrease to -14.6pm/V for the one-sided PVDF/GO model and to -29.8pm/V for the sandwich GO/PVDF/GO model as compared with the samecalculated piezoelectric coefficient for pure PVDF.

A novel all-organic DIPAB/PVDF composite film with high dielectric permittivity

A novel all-organic composite comprising polyvinylidene fluoride (PVDF) and diisopropylammonium bromide (DIPAB) crystal particles (0–20 mass%) with significant dielectric properties has been synthesized via coating method. The DIPAB crystal nano-particles were prepared in the PVDF matrix by in situ growth method, which were found effective in transforming structure and enhancing the dielectric properties of the composites. X-ray diffraction pattern and Fourier transform infrared spectroscopy confirmed that the DIPAB in situ particles can improve the content of the electroactive β phase nucleation in PVDF matrix, whereas the PVDF matrix could induce the (00l) preferred orientation of the DIPAB nano-crystal. And the dielectric performance of the DIPAB/PVDF composite was significant influenced by the enhanced electroactive β phase and (00l) textured DIPAB. Relative dielectric constants as high as 94 was obtained at 40 Hz with 5 mass% DIPAB filler, which is 11-fold higher than that of the pure PVDF matrix (~8.5). The breakdown strength decreased as the mass fraction of DIPAB increased but still stayed more than 38.9 kV/mm.

Electrospun PVDF fibers and a novel PVDF/CoFe 2 O 4 fibrous composite as nanostructured sorbent materials for oil spill cleanup

Abstract In this work, pure polyvinylidene fluoride (PVDF) and PVDF/cobalt ferrite (CoFe 2 O 4 ) magnetic fibrous composite were successfully prepared by electrospinning method for oil spill sorption applications. The pure spinel phase of CoFe 2 O 4 and PVDF/CoFe 2 O 4 composites were confirmed by X-ray diffraction analysis (XRD). Electrospun sorbent materials were characterized by scanning and transmission electron microscopy (SEM and TEM) as well as by contact angle measurements. In addition, the composite sorbent (PVDF/CoFe 2 O 4 ) was characterized by magnetic measurements. It revealed good magnetic properties that are of real interest to facilitate the separation of the oil-loaded sorbent under the external magnetic field. Finally, the produced electrospun sorbents were tested for sorption of oily liquids, such as: decane, dodecane and commercial motor oils. We obtained good oil sorption capacity (between 9.751–23.615 g/g of pure PVDF) and (8.133–18.074 g/g for the magnetic composite) depending on the nature of oil tested. The present electrospun magnetic PVDF/CoFe 2 O 4 fibrous composite could be potentially useful for the efficient removal of oil in water and recovery of sorbent material.