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As a representative flexible piezoelectric polymer, polyvinylidene fluoride (PVDF) and its copolymers have been widely used in energy harvesters and piezoelectric sensors. In this work, hybrid nanocomposite films were prepared by adding a small amount of carbon black (CB) and Ni nanoparticles to the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix using the solution casting method, followed by stretching and poling to increase the electroactive β-phase content. The results show that the hybrid fillers consisting of 0.3 wt% CB and 0.1 wt% Ni nanoparticles exhibit the best piezoelectric performance. The maximum output voltage of the PVDF-HFP/CB/Ni films reaches 3.5 V under 1 mm micro-vibration, which is 75% higher than that of pure PVDF-HFP films. Characterization results by X-ray diffraction analysis, Fourier-transform infrared spectrometry, and differential scanning calorimeter analysis show that the hybrid fillers are more effective in promoting the phase transformation from the α-phase to the β-phase in the matrix due to synergistic effect.

In recent years, PVDF(polyvinylidene fluoride) and its copolymers have attracted great attention in the development of energy-harvesting devices because of their unique properties such as good flexibility, environmental friendliness, high halogen and acid resistance, lightweight and good biocompatibility. Compared to the most commonly used PZT (lead zirconate titanate), the piezoelectricity of PVDF and its copolymer-based materials is relatively low. To further expand the applications of PVDF, there is an urgent need for efficient methods to prepare high piezoelectric polymers or composites. In this work, the crystal phases are introduced first. Then, the preparation methods of PVDF and its copolymer-based materials are summarized, which are mainly focused on four determining factors of piezoelectricity. The mechanisms of piezoelectric β-phase formation and α- to β-phase transformation are introduced. The influence parameters of each process and their interactions are discussed in detail. In the last section, the progress of the preparation methods is summarized. This work will provide useful information to researchers working on piezoelectric composites.

In this work, eco-friendly superhydrophobic coatings were prepared by dispersing hydrophobic silica nanoparticles and a waterborne silicone-modified polyurethane dispersion into an ethanol solution, which was free of fluorine and volatile toxic solvents. The effects of the silica content on the hydrophobicity and scratch resistance of the hydrophobic surfaces were investigated by WCA measurements and a sandpaper abrasion test, respectively. The experimental results indicated that when the silica content exceeded 30% by mass, the silica/silicone-modified polyurethane coatings had superhydrophobicity. Meanwhile, the superhydrophobic coatings with a silica content of 30% by mass simultaneously had the optimal mechanical stability. We studied the morphology and roughness of the hydrophobic surfaces with different silica content and attempted to briefly explain the influence mechanism of silica content. Furthermore, anti-icing and oil–water separation experiments were carried out on the superhydrophobic coatings, which exhibited good anti-icing performance and high separation efficiency. The eco-friendly superhydrophobic coating is expected to be applied in the fields of oil–water separation, anti-icing, and self-cleaning, etc. [ABSTRACT FROM AUTHOR]

PVDF (poly(vinylidene fluoride)) is a promising piezoelectric polymer which can be applied in sensor or energy harvesting fields. To improve the energy harvesting capability of the PVDF film, we proposed a laminated piezoelectric element consisting of two PVDF films sandwiching a GFRP (glass fiber-reinforced plastic) laminate, named as PVDF/GF/PVDF. Its energy harvesting capability and open circuit voltage were experimentally investigated. Compared with PVDF monolayer and bilayer piezoelectric elements, this newly designed PVDF/GF/PVDF possesses remarkably increased energy harvesting capabilities in both AC and DC circuits. The mechanisms for this phenomenon were explored experimentally, theoretically and numerically in detail. Compared with the PVDF monolayer element, the increases of harvested power in the PVDF bilayer element and the PVDF/GF/PVDF are mainly due to their larger PVDF net volume. Compared with the PVDF bilayer element, the reason for the increase of the energy harvesting capability in the PVDF/GF/PVDF is its higher piezoelectric stress constant caused by the insertion of stiffer GFRP laminate. [ABSTRACT FROM AUTHOR]