Polyvinylidene Fluoride Composite Films Research Articles

Designing of pressure sensor with polyvinylidene fluoride composite films embedded with nickel oxide for energy harvesting

This paper describes the successful fabrication of specially designed piezoelectric pressure sensor by using poly-vinylidene-fluoride (PVDF) films embedded with nickel oxide (NiO). This PVDF-NiO composite film is prepared using the solvent casting method to improve the electro-active β-phase and enhance crystallinity for various sensing and energy harvesting applications. Various tools were used to analyze changes in the crystalline structure, morphology, and dielectric behavior of PVDF-NiO composite films. Structural characterization and Infrared Spectroscopy affirmed the predominance of electro-active β-phase in the PVDF matrix by adding NiO loadings. XRD studies show that the addition of NiO enhances the crystallinity from 45.62 (for pure PVDF) to 59.01 (1 wt% NiO). FTIR analysis shows that the β-phase fraction for PVDF-NiO film reaches to optimum value from 54% (pure PVDF) to 72% (1 wt% NiO). Micrographs from FESEM illustrates the uniform dispersion of NiO particles within the polymer with little agglomeration at the bottom. The I-V characteristic curves investigate the carrier transport mechanism in the composite films which is predominantly governed by Richardson-Schottky in addition to Poole-Frenkel. The maximum dielectric obtained is 25 with relatively low losses which are thrice than pure PVDF. The increase in AC conductivity at higher frequencies makes this novel composite material suitable for various electronic applications.

Preparation of a ferroelectric composite film metal–organic framework/PVDF

With increasing of the intellectualized electronics devices, new kinds of flexible ferroelectric polymer materials with high dielectric constant attracted more and more attention in recent decades. Polyvinylidene fluoride (PVDF), as one of the most studied ferroelectric polymer materials, has been studied in many published works. Among these works, lots of efforts have been employed to promote the generation of β crystal phase. We here introduced a concise and effective way for large-scale fabrication of promising ferroelectric polymer films by doping a metal–organic framework (MOF) particles via costing process. Then effects of the addition of MOF on the ferroelectric, dielectric and mechanical properties of PVDF composite film were systematic researched. By comparing the results of XRD and FTIR, we found that the addition of MOF changed the α crystal phase of PVDF to β crystal phase which helped improve the ferroelectric and dielectric properties of PVDF composites. The new PVDF composite film, with very low addition (5wt.%) of MOF, possessed the highest remanent polarization (22μC/cm2 at 80MV/m and 1 Hz electric field), and the highest dielectric constant (21 at 10 Hz). The data of mechanical properties indicated that the fine dispersion of MOF maintained the flexibility of PVDF.

Enhanced physical, mechanical and protein adsorption properties of PVDF composite films prepared via thermally-induced phase separation (TIPS): Effect of SiO2@PDA nanoparticles

In this work, SiO2@PDA nanoparticles obtained by in-situ coating polydopamine (PDA) on the surface of spherical SiO2 nanoparticles were adopted to prepare the polyvinylidene fluoride (PVDF) composite films via thermally-induced phase separation (TIPS) method with diphenyl carbonate (DPC) as the diluent. PDA was proved to cover evenly on the surface of SiO2 nanoparticles, which was favorable to the dispersion of hydrophilic nanoparticles in the matrix. Effect of the presence of SiO2@PDA nanoparticles on crystallization behavior, thermal stability, mechanical properties and hydrophilicity of the composite films was intensively investigated. Heterogeneous nucleating effect on the crystallization of PVDF coupled with elevated crystallinity was found upon the incorporation of SiO2@PDA without altering the crystal form of PVDF. The rigidity, tensile strength as well as thermal stability of the composite films containing SiO2@PDA were significantly improved in comparison to both neat film and those containing unmodified nanoparticles. In addition, the hydrophilicity of PVDF composite films’ surface was remarkably enhanced with an increasing SiO2@PDA content, which helped to reduce the protein adsorption of the composite films considerably. The present study would supply an insight into the fabrication of PVDF composite films with desirable performance and capabilities.

Fabrication of BaTiO3@super short MWCNTs core-shell particles reinforced PVDF composite films with improved dielectric properties and high thermal conductivity

For present ceramic particles/polymer dielectric composite materials, their dielectric properties and thermal conductivity haven't met the application requirement at the same time. In this research, to achieve this goal, barium titanate@super short MWCNTs (BT@SSCNT) core-shell particle was prepared in a confinement reactive space built by water phase and oil phase. Polyvinylidene fluoride (PVDF) based composite flexible films reinforced by the BT@SSCNT particles possessed desired dielectric and excellent thermal behaviors. Especially for the composite film with 60 wt% (containing less than 17 wt% SSCNT) loading, at 102 Hz and in the wide temperature range of −40–140 °C, dielectric constant and dielectric loss varied from 476 to 764 and from 2.74 to 4.58, respectively. Meanwhile the thermal conductivity of this film reaches 25.43 W/(m K). The promising dielectric properties and high thermal conductivity of the films are attributed to multiple roles of SSCNT shell layer including external electric field applying on BT particles, tremendous interfacial polarization area, restricted electron motion and electron efficient in transporting heat. The BT@SSCNT/PVDF composite films can be a promising candidate for the modern electronic industry.

Two-dimensional sheet-like K0.5Na0.5NbO3 platelets and sandwich structure induced ultrahigh discharge efficiency in poly(vinylidenefluoride)-based composites

Polyvinylidene fluoride (PVDF) -based composites have received great attention in high-energy-density capacitors due to their high breakdown strength and ease of processing. In this work, sandwich structure K0.5Na0.5NbO3(KNN)/PVDF composite films with a middle of PVDF layer containing 2D sheet-like KNN platelets were prepared by a simple layer-by-layer casting process. Experimental results indicate that the reasonably distributed 2D sheet-like KNN platelets and sandwich structured are very effective for reducing the conductivity and dielectric loss of the composite film, manifested by a significant improvement of discharge efficiency (η = 80.2%), which is the highest η value reported so far. In addition, the finite element simulation results confirm that the synergy between the 2D sheet-like KNN platelets and the sandwich structure can effectively hinder the development of electric tree. The high breakdown strength of the composite film and high dielectric constant of KNN platelets result in high discharge energy density of 14.5 J cm−3. This work provides a new reference for PVDF-based polymer composites with excellent comprehensive energy storage performance for capacitive energy storage applications.

PVDF/BaTiO3 films with nanocellulose impregnation: Investigation of structural, morphological and mechanical properties

Polyvinylidene fluoride (PVDF) composite films have witnessed widespread applications in biomedical and flexible electronic devices in recent years. These applications require a material that has enhanced electrical properties, mechanical flexibility along with sufficient strength. A lot of research has been carried out to enhance the piezoelectric and dielectric properties of the PVDF composite films. However, the improvements in the mechanical properties of nano filler reinforced PVDF composite films has not received due attention. In this regard, the present work focuses towards enhancing the mechanical strength and load-bearing capability of PVDF, by preparing composites of PVDF films impregnated with Cellulose Nanocrystals (CNC) and Barium Titanate (BTO) nanoparticles. Solution casting method was adapted to fabricate the PVDF/BTO/CNC films. X-ray diffractograms and FTIR (Fourier Transform infrared spectroscopy) corroborate the presence of ferroelectric γ phase in PVDF. Mechanical and viscoelastic measurements have been carried out to examine the influence of CNC and BTO nano fillers in the PVDF matrix. The addition of CNC and BTO in PVDF film has improved the mechanical strength significantly. The stress achieved for PVDF/5% BTO and PVDF/5% BTO with 0.9% of CNC at 5% strain was 17% and 130% higher than the pristine PVDF, respectively. This study can be helpful for the design engineers to meet custom/specific requirements for a myriad of end-user applications such as piezoelectric nanogenerators.

Flexible and high performance of n-type thermoelectric PVDF composite film induced by nickel nanowires

Nickel nanowires (Ni NW) with high aspect ratio and excellent electrical conductivity were prepared by liquid phase chemical reduction. Polyvinylidene fluoride (PVDF)/Ni NW composite films were fabricated by solution mixing casting and compression molding. The effects of Ni NW with different weight content on the morphology, crystal structure and thermoelectric properties of PVDF/Ni NW nanocomposites were studied. The results show that the nickel nanowires are uniformly dispersed in the PVDF matrix. With the increase of Ni NW content, the conductivity of the composites increases greatly, and the power factor of the composites increases to 24.3μWm−1 K−2 with 75 wt% Ni NW. Although the tensile strength and elongation of the composites decrease gradually, this flexible thermoelectric film still shows great potential for thermoelectric applications.

Enhanced flexible piezoelectric energy harvesters based on BaZrTiO3–BaCaTiO3 nanoparticles/PVDF composite films with Cu floating electrodes

Flexible piezoelectric energy harvesters (FPEHs) were fabricated by employing different types of composite materials based on lead-free piezoelectric nanoparticles (LPNPs) and polyvinylidene fluoride (PVDF) with floating electrodes. The floating electrode effects were analyzed through an experiment and simulation. Different types of LPNPs (BaTiO3, Ba(Zr0.04Ti0.96)O3 (BZT), 1-mol% Cu-doped BZT, Ba(Zr0.2Ti0.8)O3–50(Ba0.7Ca0.3)TiO3 (BZT–BCT), and 1-mol% Cu-doped BZT–BCT)/PVDF composite films were evaluated for FPEH applications. The FPEH based on the BZT–BCT nanoparticles (NPs)/PVDF composite film with floating electrode exhibited a high performance. The highest energy density (2.79 mJ/cm3) was obtained for the FPEH based on the BZT–BCT NPs/PVDF composite film with floating electrode. The results suggest that upon the introduction of the floating electrodes (Cu) into the BZT–BCT NPs/PVDF composite film, charges could be more easily attracted to the floating electrodes that facilitated the collection of charge into the electrodes.

In Situ Measurement of Dielectric Permittivity and Electrical Conductivity of CoCl2/BaCl2 Doped PVDF Composite at Elevated Temperature

This work describes the synthesis and in situ characterization of polyvinylidene fluoride (PVDF) composite films doped with different weight percentage of CoCl2/BaCl2. The solution casting method was used for fabrication of composite films. XRD and SEM were used to analyse the surface morphology of PVDF composite films which confirms the formation of β and α phase predominately. The XRD spectra confirm the reduction in intensities of some peaks associated with α and β phase’s pre dominantly with the insertion of dopants. Dielectric permittivity and ac conductivity of the PVDF composites were measured at elevated temperature. The frequency dependence of dielectric permittivity and ac conductivity behaviour of PVDF composites with different weight percentage of Co/Ba fillers were investigated. The results reveal that the addition of Co/Ba to the host Polymer PVDF affects the dielectric permittivity and conductivity of PVDF composite. The results further reveals that the annealing influences the overall crystallization process and various phases of doped PVDF composite which in turn may affect the piezoelectric behaviour, which is prerequisite for sensing and actuator application of these PVDF composites. Thus the behaviour of sensors and devices based on doped PVDF composite can be predicted at elevated temperature. This study focused to understand the interaction between PVDF and Co/Ba dopants at elevated temperature.

Hydrophilic Fluoro‐Functionalized Graphene Oxide / Polyvinylidene Fluoride Composite Films with High Dielectric Constant and Low Dielectric Loss

AbstractA novel and facile method, to synthesize high‐quality fluoro‐functionalized graphene oxide (F‐GO) and polyvinylidene fluoride (PVDF) composite (F‐GO/PVDF) films prepared by solution blending of F‐GO and PVDF in solution was proposed. The fabricated F‐GO/PVDF nanocomposites with different mass fractions exhibited high dielectric constant and low dielectric loss. Meanwhile, Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy and raman spectroscopy verified the functional groups in the F‐GO. The microstructure analysis using X‐ray diffraction and field‐emission scanning electronmicroscopy were performed to investigate the morphology of F‐GO and F‐GO/PVDF composite films. The thermal, hydrophilic and electrical characterization properties of F‐GO/PVDF composites were investigated by thermal gravimetric analysis, contact angle, and dielectric constant. These results indicate their potential applications for dielectric devices storage devices.

Nucleation effect of unmodified graphene nanoplatelets on PVDF/GNP film composites

Development of polyvinylidene fluoride (PVDF) film composite filled with carbon-based nanomaterials is attracting considerable attention in engineering applications. Numerous studies focus on the enhancement of PVDF properties by adding chemically modified graphene oxide or functionalized carbon nanotubes, or by modifying the polymer chains. On the other hand, in this paper we investigate the nucleation effect of graphene nanoplatelets (GNPs) on morphology and structure of PVDF, without any chemical modification or functionalization either of the GNPs or of the polymer chains. Thus, we fabricate GNP-filled PVDF composite films by the solution casting method. Then, we investigate the effect of GNPs on composite porosity, crystallinity and polymer phases, with special emphasis on the formation of β-phase. To this purpose, the produced PVDF/GNP composite films are characterized through scanning electron microscopy and atomic force microscopy topographies, differential scanning calorimetry, X-ray powder diffraction and Fourier transform infrared spectroscopy. All these experimental characterizations show that GNPs uniformly dispersed in PVDF, without any modification or functionalization, influence significantly the polymer structure and porosity, enhancing the β-phase crystals formation. Finally, the electrical, mechanical and electromechanical properties of the produced PVDF/GNP composite films are characterized.

Investigation of structural, dielectric and sensing properties of MgCl<sub>2</sub>/PVDF composite films prepared via solution casting technique

This article investigates the effect of Mg insertion into the Polyvinylidene fluoride (PVDF). The composite films were prepared using solution casting technique. XRD, and FTIR characterizations were done to study the structural changes in the MgCl 2 /PVDF composite films. The dielectric study reveals the improvement in the dielectric constant and conductivity with the insertion of Mg ions in the PVDF composite. The MgCl 2 /PVDF composite has immense potential in sensing and actuator applications.

Improved lateral heat spreading performance for polyvinylidene fluoride composite film comprising silver nanowire in light-emitting diode

Silver nanowire (AgNW) attracts great attention as a heat dissipation material due to its excellent thermal transfer property which exceeds most traditional heat sink materials.

Effect of titanium dioxide (TiO2) distribution and minute amounts of carbon black on the opacity of PVDF based white composite films

ABSTRACTThere is a contradiction in making completely opaque and white plastic film with a required high TiO2 filling fraction, which resulted in inefficient pigment utilization and high cost. Two methods were used here to overcome the contradiction. Firstly, TiO2 was grafted with poly(methyl methacrylate) (PMMA) by atom transfer radical polymerization to improve the pigment dispersion in poly(vinylidene) fluoride (PVDF). Secondly, minute amounts of carbon black (CB) were added into the PMMA‐g‐TiO2/PVDF system to enhance opacity and decrease TiO2 fraction. The structure, morphology, and properties of PMMA‐g‐TiO2 hybrid particles and composite films were investigated by FTIR, TEM, TGA, SEM, DMA, covering power meter, and UV/VIS spectrophotometer, etc. It was observed that PMMA‐g‐TiO2 was dispersed uniformly as individual particles in PVDF due to the good compatibility between PMMA and PVDF. Therefore, the opacity of PMMA‐g‐TiO2/PVDF films was markedly higher than unmodified‐TiO2/PVDF ones. Adding minute amounts of CB can significantly increase the opacity of the thin film due to its absorption effect on decreasing light transmittance. The contrast ratio (CR) of the PMMA‐g‐TiO2/PVDF film with 20 μm thickness and 25 vol % TiO2 was 97.67%, lower than the critical CR 98% for a complete opacity, however, the CR of sample with 10 vol % TiO2 was 98.1% as the CB concentration was 2 × 10−4 g/cm3, saved more than 15% TiO2. We proposed that a critical thickness d0 existed for the CB/PMMA‐g‐TiO2/PVDF composite films, under which the light reflectance increased as a function of thickness, otherwise, the reflectance kept constant. Besides, d0 could be decreased by increasing CB concentration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43064.

High output piezoelectric nanocomposite generators composed of oriented BaTiO3 NPs@PVDF

Piezoelectric nanocomposites (p-NC) composed of piezoelectric nanoparticles (NPs) and flexible polymer have emerged as outstanding applications for flexible nanogenerators (NGs). In this article, we proposed a p-NC NG by combining the barium titanate nanoparticles (BaTiO3 NPs) with the poly-vinylidene fluoride (PVDF). By a facile and scalable solvent evaporation process, the BaTiO3 NPs and PVDF composite (BaTiO3 NPs @ PVDF) films were fabricated. BaTiO3 NPs dispersed uniformly in the PVDF matrix and formed an oriented structure without aggregations. By using this special oriented BaTiO3 NPs @ PVDF composite film, the highest open-circuit voltage reaches 150V, which is one of the most outstanding output performance in the lead-free piezoelectric field to date. The energy generated from the p-NC NG can light three light-emitting diode (LED) bulbs instantaneously without any storage unit.

Structural, optical and electrical properties of MgCl2 doped polyvinylidene fluoride (PVDF) composites

Pure and Mg doped polyvinylidene fluoride (PVDF) composite films were prepared by solution casting method. The doping concentration of MgCl2 was varied from 2 to 8 wt%. The composite films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–Vis spectroscopy and I–V measurements. The XRD spectra reveal the presence of α and β phase in semi crystalline structure. FESEM indicates the decrease in crystallite size of doped PVDF films with increase in MgCl2 concentration. The optical band gap was calculated using Tauc plot which indicates the increase in value of band gap with subsequent increase in Mg content. The electrical impedance and current measurements were carried out to investigate the piezoelectric response of PVDF composite films.

Fabrication and dielectric properties of the BaTiO 3–polymer nano-composite thin films

To prepare high dielectric thin film of polymer-based materials, nanometer sized barium titanate (BaTiO 3) particles, which should have high dielectric coefficients and low energy dissipation factors due to nano-size effects, were dispersed in polyvinylidene fluoride (PVDF) or siloxane-modified polyamideimide (SPAI). The BaTiO 3 particles with crystal sizes of 10.5–34.6 nm were synthesized with a complex alkoxide method. Polymer/ N-methyl-2-pyrrodinone solution suspending the BaTiO 3 particles was spin-coated on ITO glass substrates to prepare polymer-based composite films with thickness of submicron meters. The BaTiO 3 particles were dispersed more homogeneously in the PVDF film than in the SPAI film. The good dispersion of the particles in the PVDF film brought about a smooth surface of the film that had a root mean square roughness less than 20 nm at a particle volume fraction of 30%. The roughness was less than one-tenth of the roughness of the SPAI composite film. An increase in the BaTiO 3 crystal size from 10.5 to 34.6 nm in the PVDF film at a particle volume fraction of 30% increased the dielectric constant of the film from 20.1 to 31.8. The BaTiO 3–PVDF composite film attained high dielectric constant that had more than twice the dielectric constant of the BaTiO 3–SPAI composite film. The dissipation factor of the PVDF composite film was as low as 0.05 at 10 4 Hz.

Ferroelectric phase stability studies in potassium nitrate: Polyvinylidene fluoride composite films

The structural and thermal properties of potassium nitrate (KNO3): polyvinylidene fluoride composite films have been studied. Differential scanning calorimetry has been employed to characterize the phase transitions in the composite and x-ray diffraction has been used to quantify the crystalline phases. The ferroelectric phase (III) of KNO3 is stabilized relative to the paraelectric phase (II) at room temperature at concentration ⩽50wt%, with the largest proportion at 50wt%. The enthalpies and transition temperature width are also affected in the composite. The polarization hysteresis loops also show that the remanent polarization is largest at 50wt% of KNO3. The capacitance–voltage characteristics exhibit strong hysteresis with pronounced peaks and some asymmetry. The switching current behavior of the composite film was also investigated and supports the presence of ferroelectric phase in the composite film at room temperature.