PVDF/BaTiO3 composite foams with high content of β phase by thermally induced phase separation (TIPS)

Abstract

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  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  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  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  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.

Piezoelectric, mechanical, and crystallographic properties of polyvinylidene fluoride‐hexafluoropropylene based composites reinforced by different dimensional carbon nanomaterials

“…Second, the elastic moduli and yield strengths of PHC films are reduced when excessive carbon nanomaterials are added, and the influence factors of these may be multiple. On the one hand, the crystallinity of PHC also decreases when there are too many nanomaterials 43,44 . On the other hand, too many nanomaterials can agglomerate inside composite film and form some defects 45 …”

“…On the one hand, the crystallinity of PHC also decreases when there are too many nanomaterials. 43,44 On the other hand, too many nanomaterials can agglomerate inside composite film and form some defects. 45 Finally, CB, CNT, and FLG have similar effects on the enhancement of elastic moduli of composite films, but the enhancement in yield strengths of composite films by CB are significantly higher than those by CNT and FLG.…”

Unleashing the piezoelectric potential of PVDF: a study on phase transformation from gamma (γ) to beta (β) phase through thermal contact poling

“…The total crystallinity was calculated using the following equation:where Δ H m is the melting enthalpy of the sample, Δ H o m = 104.7 J g −1 is the enthalpy of the hypothetically 100% crystallized PVDF. 53,55,56 Two samples of each type (poled and unpoled films) were tested.…”

Cold Sintering Process for a BaTiO3/Poly(vinylidene difluoride) Ceramic–Polymer Composite: Evaluation of the Structural and Microwave Dielectric Properties

“…The fabrication of a ceramic–polymer composite was demonstrated for multiple applications like electronics, batteries, energy storage devices, etc. Also, several systems have already been developed by BaTiO 3 /PVDF, which has a high polarization effect and a high energy density. − In the CSP method for the study of composites such as Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 /PVDF–hexafluoropropylene (HFP), LiMoO 4 /poly­(tetrafluoroethylene) (PTFE), SiO 2 /PTFE, and ZnO–Ca 3 Co 4 O 9 /PTFE composites were also examined and achieved better densification. − …”