Phase Transitions of Polarised PVDF Films in a Standard Curing Process for Composites

Abstract

The article reports on the influence of annealing PVDF in an autoclave process on the PVDF phase composition. DSC, FTIR and XRD measurements serve to observe the phase changes in an already stretched, polarised and β-phase rich film. Annealing was conducted between 90 and 185 ∘C to cover a broad range of curing processes in an autoclave. The β-phase is found to be stable up to near the melting range at 170 ∘C. At 175 ∘C, the non-piezoelectric α-phase dominates and the piezoelectric γ- and γ′-phases appear. The γ-phase grows at elevated temperatures and replaces the β-phase. This observation stresses the importance of developing new methods to reactivate the polarisation after annealing, in particular for the integration of PVDF as a sensor in laminated structures, such as CFRP.

Achieving synergistic improvement in dielectric constant and energy storage properties of all-organic liquid crystal molecule/PVDF composites

“…The suitable addition of 5CB induces heterogeneous nucleation and accelerates the nucleation process, resulting in an increment in the T c value and the degree of crystallinity. 48 It has been reported that the increment of the crystallinity contributes to the enhanced mechanical strength and dielectric insulation performance (such as E b and lifetime). 49 However, 5CB acts as a diluent to hinder the crystallization process and reduce T c when 5CB is over a certain amount.…”

Regulating Conductive Copolymerization Networks in the Polymer Electrolyte for High-Performance Quasi-Solid-State Lithium–Metal Batteries

“…XRD measurements were utilized to examine the crystalline phases of these prepared PVDF-HFP-matrix electrolyte films, and the resulting XRD diffraction patterns are present in Figure a. The untreated PVDF-HFP-F electrolyte film shows the broadening peak between 18 and 20°, indicating the well-known semicrystalline behavior and a combination of crystalline phases α, β, and γ of PVDF . In particular, the diffraction peaks at 18.4°, and 19.9° represent the (020) and (110) crystalline planes of the α phase, while the peak at 20.3° stands for the (101) crystalline plane of the γ phase, and the peak at 20.7° illustrates the (110), (200) crystalline planes of the β phase, respectively .…”

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

“…The dielectric, ferroelectric, and piezoelectric properties are enhanced by the conformations with a larger dipole moment, i.e., in the electroactive phases β and γ. The phase composition was observed to be sensitive to the processing strategy and parameters, to co-polymerisation [ 41 , 42 ], or by nanofiller additions [ 43 , 44 ].…”