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A poly(vinylidene fluoride)-based composite film with higher piezoelectric properties was prepared by the solvent mixing method of adding liquid crystal small molecules to create defects among polyvinylidene fluoride (PVDF) molecular chains. The composite obtained by simple uniaxial stretching and thermal polarization exhibits higher piezoelectric properties (d33 = 29.0 pC/N) than neat PVDF (d33 = 24.3 pC/N). The defects reduce the grain size of PVDF to some extent, thus reducing the coercivity field of PVDF from 64.6 to 58.1 MV/m. This strategy could endow PVDF with higher piezoelectric coefficient and lower polarization field, which is attractive for piezoelectric applications. [ABSTRACT FROM AUTHOR]

The development of flexible and high‐performance dielectric materials is of critical importance in energy storage devices. Since energy density of a dielectric capacitor is determined by the dielectric constant and breakdown strength, in this work, a simple and effective way is provided to increase the energy storage density of polymer matrix dielectric film via adding exfoliated mica nanosheets. Few‐layered mica nanosheets were successfully exfoliated by a facile one‐step method and incorporated with Poly(vinylidene fluoride) (PVDF) matrix. The mica nanosheets could act as the insulating barriers, which help to increase the breakdown strength of the PVDF/mica composites. The maximum discharged energy density of the prepared composite film was 7.93 J cm−3 at 450 MV m−1 with only 5 vol% of mica nanosheets, which is about three times higher than pure PVDF. This study introduced an economic and effective approach to get flexible and high energy density polymer composite films and broadened the application of mica. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The preparation and dielectric properties of silver-polydopamine/poly (vinylidene fluoride) (Ag-PDOP/PVDF) composite films with suppressed dielectric loss are reported. The dielectric loss tangents of the composite films were found to be rather low similar to that of pure PVDF over the frequency range 100 Hz to 30 kHz, almost regardless of the Ag content, and even lower than that of pristine PVDF in the relatively high frequency region. The nanoscale structure comprised of Ag nanoparticles (Ag NPs), isolated by the PDOP coating and the PVDF matrix, hindered the formation of percolative networks, resulting in the decreased conduction loss in the composite films, even at a high filler loading. The strong interfacial interaction between the Ag@PDOP particles and the PVDF matrix also contributed to the restrained interfacial loss. Consequently, these composite films had higher permittivity and smaller dielectric loss than the PVDF matrix at relatively high frequencies, and would thus be attractive for physically small capacitor applications in electronics and electric power systems. [ABSTRACT FROM AUTHOR]

This paper selected typical polar polymers which are polyvinylidene fluoride (PVDF) and polyamide (PA) to prepare PA/PVDF blend for energy storage material. Three kinds of PA (PA6, PA66 and PA11) with representative characters were chosen as the main research polymers for blending with PVDF. The electrical properties of three kinds of all-polymeric blends were tested and the microstructure was characterized by X-ray diffractometer (XRD), Fourier transform infrared instrument (FTIR), Scanning electron microscope (SEM) and Differential scanning calorimetry (DSC). Our finding suggests that the created high-ε polymeric blends represent a novel type of material that is easy to process. In addition, the dielectric constant and breakdown strength of PA/PVDFs are relatively high so that it can be applied to electronic components. [ABSTRACT FROM AUTHOR]

The dependence of the dielectric properties of micro- (m-) and nano- (n-) silver (Ag)/poly(vinylidene fluoride) (PVDF) composites on the Ag particle size was determined. The magnitude of dielectric constant and conductivity for the PVDF/n-Ag composites was much higher than that of the PVDF/m-Ag composites at the same Ag volume loading. Our results suggest that the percolative behaviors were quite different for the m- and n-systems owing to the Ag particle size effect. The dielectric property depends on the synergistic effects of interfacial area, interparticle distance, and interfacial adhesion, all of which are highly dependent on the Ag particle size. The increased interfacial area, reduced interparticle distance, and improved interfacial adhesion contributed to the better dielectric properties of the PVDF/n-Ag composites. [ABSTRACT FROM AUTHOR]

Compared to polyvinylidene fluoride (PVDF) and its copolymers, castor-oil-derived nylon-11 has been less explored over the past decades, despite its excellent piezoelectric properties at elevated temperatures. To utilize nylon-11 for future sensor or vibrational energy harvesting devices, it is important to control the formation of the electroactive δ′ crystal phase. In this work, nylon-11 films were first fabricated by solution-casting and were then uniaxially stretched at different stretching ratios (SR) and temperatures (Ts) to obtain a series of stretched films. The combination of two-dimensional wide-angle X-ray diffraction (2D-WAXD) and differential scanning calorimetry (DSC) techniques showed that the fraction of the δ′ crystal phase increased with the stretching ratio and acquired a maximum at a Ts of 80 °C. Further, it was found that the ferroelectric and piezoelectric properties of the fabricated nylon-11 films could be correlated well with their crystalline structure. Consequently, the stretched nylon-11 film stretched at an SR of 300% and a Ts of 80 °C showed maximum remanent polarization and a remarkable piezoelectric coefficient of 7.2 pC/N. A simple piezoelectric device with such a nylon-11 film was made into a simple piezoelectric device, which could generate an output voltage of 1.5 V and a current of 11 nA, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boron nitride nanosheet with N-doped carbon modification as novel dielectric filler. • Enhanced compatibility and interfacial polarization between filler and PVDF matrix. • Simultaneously increased dielectric constant and breakdown strength. • Outstanding energy density and efficiency achieved in sandwich-structured film. It is a challenge to simultaneously enhance dielectric constant and breakdown strength of dielectrics and achieve a greatly elevated energy density. Herein, polyaniline was first coated onto the surface of boron nitride nanosheets (BN), and then nitrogen-doped carbon (NC) was formed through a carburization process, resulting in BN@NC composite, which was subsequently added to poly(vinylidene fluoride) (PVDF) to prepare a composite film with high dielectric performance. The characterization showed that BN@NC effectively preserved the nanosheet structure of BN and formed strong hydrogen bonding interactions with the PVDF matrix, promoting the β-PVDF formation. This not only improved the compatibility but also enhanced the interfacial polarization between conductive NC and the polymer, leading to a high dielectric constant. Moreover, the electrically insulating BN prevented the formation of leakage current, resulting in a high breakdown strength. Finally, a sandwich-structured film was constructed, and exhibited a dielectric constant of 10.2 (at 1 kHz), a breakdown strength of 380 MV m−1, and an energy density of 6.1 J cm−3, which were 20%, 36%, and 74% higher, respectively, than those of pure PVDF film (8.5, 280 MV m−1, and 3.5 J cm−3). This work highlights significant potential for applications in low-cost and high-energy density dielectric composites. [ABSTRACT FROM AUTHOR]

The design and preparation of novel renewable biomass-based dielectric composites have drawn great attention recently. Here, cellulose was dissolved in NaOH/urea aqueous solution, and Al 2 O 3 nanosheets (AONS) synthesized by hydrothermal method were used as fillers. Then the regenerated cellulose (RC)-AONS dielectric composite films were prepared by regeneration, washing and drying. The two-dimensional AONS had a better effect on improving the dielectric constant and breakdown strength of the composites, so that the RC-AONS composite film with 5 wt% AONS content reached an energy density of 6.2 J/cm3 at 420 MV/m. Furthermore, in order to improve the dielectric energy storage properties of cellulose films in high humidity environment, the hydrophobic polyvinylidene fluoride (PVDF) was innovatively introduced to construct RC-AONS-PVDF composite films. The energy storage density of the prepared ternary composite films could reach 8.32 J/cm3 at 400 MV/m, which was 416 % improvement against that of the commercially biaxially oriented polypropylene (2 J/cm3), and could be cycled for >10,000 times under 200 MV/m. Concurrently, the water absorption of the composite film in humidity was effectively reduced. This work broadens the application prospect of biomass-based materials in the field of film dielectric capacitor. [ABSTRACT FROM AUTHOR]

Temperature responsive dielectrics provide the opportunity to obtain permittivity tunable materials, which is particularly useful in modern electrical and electronic devices. However, the applications of the tunable dielectric materials are largely limited owing to the low dielectric transition temperature and/or insufficient shape stability during phase transition. Herein we present the first example of poly(vinylidene fluoride)/polyethylene glycol/graphene oxide (PVDF/PEG/GO) composites with tunable dielectric permittivity based on temperature-dependent phase transition of PEG. The permittivity switching of shape-stabilized PVDF/PEG/GO composites can be triggered above room temperature. This report may provide a roadmap of fabricating new tunable or switchable dielectrics with relatively high dielectric transition temperatures based on polar organic phase change materials. [ABSTRACT FROM AUTHOR]