Tailored chain interaction of binary and ternary PVDF-HFP and PVDF-TrFE-CTFE / graphene nanoplatelets on dielectric properties and charge density capability

Abstract

In this study, a semi-crystalline copolymer, Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), was blended with Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (PVDF-TrFE-CTFE) and Graphene Nanoplatelets (GNP) to fabricate 2-phase and 3-phase composite films. The heterostructure blending enhanced the dielectric constant and polarization. Moreover, the chain interaction between the terpolymer and copolymer improved compatibility with the GNP, reducing charge accumulation and leakage current. The films were prepared using the tape-casting solution method with varying terpolymer loadings. Their bonding, surface structure, and morphology were analyzed using SEM, FTIR, AFM, and contact angle measurements. Electrical properties and energy storage capabilities were evaluated using an LCR meter and a ferroelectric measurement setup. The combination of PVDF-TrFE-CTFE induced significant changes in the morphology, crystallinity, dielectric properties and electrical breakdown strength. Notably, blending with the terpolymer increased the energy storage density from 0.14 J/cm³ (T0) to 0.26 J/cm³ (T70) at 40 kV/mm. Additionally, adding 1 wt% GNP enhanced interfacial polarization, with the T30 + GNP composite nearly 2 times the energy storage density compared to the neat T30 film (0.14 J/cm³ vs. 0.22 J/cm³ at 40 kV/mm). The combination of copolymer and terpolymer also improved the electrical breakdown strength, with T70 reaching 540 kV/mm. These enhancements in polymer-GNP interactions, charge carrier dynamics, and electrical breakdown strength demonstrate the potential of this composite material for high-performance dielectric applications, particularly in capacitive energy storage systems.