Improved dielectric properties of poly(vinylidene fluoride)–BaTiO₃ composites by solvent‐free processing

Abstract

Composites of poly(vinylidene fluoride) (PVDF) and BaTiO3 nanoparticles (average diameter ca. 125 nm) are fabricated by a solvent‐free and industrially scalable technique, that is, melt blending, followed by compression molding. The effect of processing parameters on the spectroscopic, microstructural, thermal, mechanical and dielectric properties are evaluated as a function of composition (loading up to 30 vol%). The presence of nanoparticle inclusions as well as specific compression molding parameters demonstrate both to affect the molecular relaxations of the PVDF matrix, studied by correlating the results of different techniques, and to induce the PVDF crystallization as β phase. Processing parameters also play a key role for optimizing the dielectric properties. An improved dielectric behavior of the composites is obtained in terms of both permittivity, whose value increases up to four times that of neat PVDF, and dielectric losses, lower than 5% between 10 and 3·104 Hz. The obtained performances resulted enhanced compared to analogous composites prepared with the use of solvents.

Role of Microstructures in the Dielectric Properties of PVDF-Based Nanocomposites Containing High-Permittivity Fillers for Energy Storage

“…The presence of the TiO 2 shell leads to a reduction of the dielectric losses to <0.03 in the range 10 2 –10 4 Hz, the same level observed in the neat polymer . The loss tangent is increased at lower frequencies yet comparable to PVDF.…”

“…16,17,37 The presence of the TiO 2 shell leads to a reduction of the dielectric losses to <0.03 in the range 10 2 −10 4 Hz, the same level observed in the neat polymer. 38 The loss tangent is increased at lower frequencies yet comparable to PVDF. Similar trends are also exhibited by composites containing the BaTiO 3 @SiO 2 inclusions (Figure 3), though the permittivity undergoes a larger decrease.…”

Increasing Permittivity and Mechanical Harvesting Response of PVDF-Based Flexible Composites by Using Ag Nanoparticles onto BaTiO3 Nanofillers

“…The XRD pattern of pure PVDF attests to the co-existence of the α, β, and γ polymorphs by the presence of the peaks at 17.7°, 18.3°, 19.9°, and 26.7° characteristic of the α phase with the diffraction planes (100), (020), (110), and (021), respectively, and the superimposed peaks from 18.5°, 19.2°, and 20.0°, which are specific to the γ phase. The β peak at 20.26° (110) is superimposed also to those of the α and γ phases, but the most relevant β peak corresponding to the (200) diffraction planes can be very well observed at 38.8° [ 45 , 46 , 47 , 48 ]. The X-ray diffractograms for all the PVDF composites confirmed the existence of BT and Ag phases, with a gradual increase of the main Ag peaks (denoted with *) when increasing x .…”

“…The dielectric properties are expected to be affected by the presence of an inorganic hybrid filler, first of all, because of the addition of high permittivity dielectric BaTiO 3 particles in the low-permittivity polymer matrix, as predicted by effective field models [ 68 , 69 ] and by finite element calculations [ 70 , 71 ]. Room temperature permittivity of nanostructured BaTiO 3 is in the range of 800–1000 for dense nanoceramics with a grain size of about ~50 nm [ 72 , 73 ], while for BaTiO 3 nanopowders with a similar diameter range, the permittivity was not reported because its direct measurement or evaluation is subjected to large errors and is dependent on the adopted model for estimation [ 48 ]. Nevertheless, the permittivity in ferroelectric powders is more than one order in magnitude higher than that of polymers and would cause an increase in the effective permittivity in composites.…”

Advantages and limitations of active phase silanization in PVDF composites: Focus on electrical properties and energy harvesting potential

“…Even in pure PVDF, due to structural defects, crystallinity is commonly limited to 50%-60%. 35,[39][40][41] As evident from the results, the addition of filler particles did not greatly reduce the PVDF total crystallinity degree. The unmodified and DDTES-modified samples were found to possess a crystallinity of $50% while the APTES-modified ones have a lower value of crystallinity value, $ 38% (Table 2).…”