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In recent years, the demand for filter media has increased dramatically, driven by the need to manufacture personal protective equipment and for various applications in the industrial and civil sectors. Nanofiber‐based membranes are proposed as potential alternatives to commercial filtration devices. This study presents the design and implementation of an innovative pre‐industrial electrospinning setup, combining a negatively charged spinneret and a positively charged counter‐electrode, capable of producing polyvinylidene fluoride (PVDF) nanofibers with an average diameter of 410 nm and electrostatic surface potential values 3.7 times higher compared to a conventional electrospinning process, eliminating the need for further post‐treatment. These properties are essential for improving mechanical and electrostatic filtration of small particles, including infectious droplets. The surface potential of the membranes is also long‐lasting, as evidenced by tests one year after manufacture. As a case‐study, these filters are used to manufacture surgical masks, reporting excellent performance in terms of bacterial filtration efficiency (BFE) up to 99.9%, and breathability (29.8±4.5 Pa cm−2) when compared to commercially available meltblown polypropylene (PP) face masks, and also complied with the stringent European standard (EN14683:2019) for type‐II surgical masks. Furthermore, the pre‐industrial setup allows for increased production capacity of up to 42 000 m2 per year, suitable for large‐scale production. [ABSTRACT FROM AUTHOR]

BaTiO3 nanofibers (BT NFs), prepared by electrospinning, were used as a filler for electrospun poly(vinylidene fluoride‐co‐trifluoroethylene) (PVDF‐TrFE) nanocomposite mats. The phase structure and the effect of poling conditions on the piezoelectric properties of PVDF‐TrFE/BT nanocomposites were investigated. The results showed an improved degree of crystallinity (78.6%) and a high β‐crystal phase (up to 98.3%) in all electrospun samples, independent of the nanofiber content. The two‐step poling method, applying electric fields of opposite polarity, led to significantly improved piezoelectric constants d33 (−31.7 pC N−1), strongly dependent on the added BaTiO3 nanofibers. The inclusion of piezoelectric ceramic nanofibers into a polymer matrix, easily carried out by means of electrospinning, followed by an ad hoc optimized poling treatment, allowed to develop flexible materials with enhanced piezoelectric properties, potentially exploitable in innovative conversion systems used in wearable and sensing devices. [ABSTRACT FROM AUTHOR]

Piezoelectric (PE) materials play an important role in the emerging field of micro and wearable electronics. Achieving high PE response is a key feature for their use in energy harvesting and sensing systems. In this study, highly porous lightweight composite foams composed of PVDF‐TrFE (70/30 and 80/20 mol%) and different BaTiO3 content (5, 10, and 20 wt%) are prepared by thermally induced phase separation method. The PE foams were structurally and thermally examined by using Fourier‐transform infrared spectroscopy, x‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis analyses. All composite foams were characterized by high β‐phase content, while the addition of ceramic particles resulted in higher crystallinity and thermal stability of the investigated foams. Two distinct poling methods were employed due to the different molar compositions of the copolymers. The PE response was measured by the PE strain coefficient (d33) and the output current (Ip). The composite foams based on PVDF‐TrFE 70/30 mol% copolymer, having two well‐separated Curie temperatures for the organic and inorganic phases, can be polarized to achieve the contribution of both components to the PE performance, reaching the highest value of −28.3 pC N−1 and 130 nA at 10 Hz for the composite with 20 wt% BaTiO3. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) displays ferroelectric, piezoelectric and pyroelectric behavior and it is widely used in high-tech applications including sensors, transducers, energy harvesting devices and actuators. The crystallization of this polymer into highly polar β phase is desirable but is hard to achieve without applying specific thermo-mechanical treatments. Indeed, fabrication processes directly affect PVDF molecular chain conformation, inducing distinct polymorphs. In this paper, we present the fabrication of PVDF/BaTiO3 composite foams by thermally induced phase separation method (TIPS). Different compositions are tested and characterized. The crystallinity, and in particular the development of electroactive β crystal phase is monitored by FTIR, DSC and XRD measurements. Dielectric properties are also evaluated. It turns out that TIPS is a straightforward method that clearly promotes the spontaneous growth of the β phase in PVDF and its composite foams, without the need to apply additional treatments, and also significantly improves the degree of crystallinity. BaTiO3 content gives additional value to the development of β phase and total crystallinity of the systems. The low permittivity values (between 2 and 3), combined with the cellular morphology makes these materials suitable as lightweight components of microelectronic circuits. [ABSTRACT FROM AUTHOR]

This article investigates the surface electrical properties of polyether-ether-ketone (PEEK) and cross-linked polyethylene (XLPE) before and after the fluorination modification. The samples are tested for surface conductivity, surface morphology, and surface antiaging characteristics. The samples are also tested for flashover voltage with ramping voltage under 100, 20, and 10 kPa. The results showed that the surfaces of PEEK and XLPE become slightly smoother with the increase in the fluorination time and the conductivity increased with the increase in the fluorination time. After fluorination, the surface of PEEK shows significant hydrophilicity, while the surface hydrophobicity of XLPE is slightly reduced, and there is a trend of recovery with the extension of the fluorination time. After fluorination, the surface antiaging performance is significantly improved. Compared with the untreated samples, the fluorinated PEEK has a higher flashover voltage at 100 kPa, and the flashover voltage is slightly increased at 10 and 20 kPa, while the flashover voltage of XLPE after fluorination shows a downward trend, especially under low pressures. This study provides a reference for fluorinated polymers as promising candidates for the insulation systems for all-electric aircraft. [ABSTRACT FROM AUTHOR]