Reduction of Ionic Conduction Loss in Multilayer Dielectric Films by Immobilizing Impurity Ions in High Glass Transition Temperature Polymer Layers

Abstract

Current development of advanced power electronics for electric vehicles demands high temperature, high energy density, and low loss polymer dielectrics. Multilayer films (MLFs), which are comprised of alternating high temperature/low loss linear dielectric polymer such as polysulfone (PSF) and high energy density polymer such as poly(vinylidene fluoride) (PVDF), are promising for this application, because high temperature tolerance, high energy density, and low loss can be achieved simultaneously. This study explored the reduction of impurity ion conduction loss in PSF/ PVDF MLFs (e.g., the dissipation factor is as low as 0.003 at 1 Hz and 100 °C) without sacrificing high dielectric constant and high energy density. Various electric poling processes were explored at a temperature slightly below the glass transition temperature (T g ∼ 185 °C) of PSF. Compared with pure alternating current (AC) and pure direct current (DC) poling methods, unipolar (DC + AC) poling was found to be the most effective in polarizing impurity ions from the PVDF layers into the PSF layers. Because of the low segmental mobility below T g , impurity ions were largely "locked" in PSF. The immobilization of impurity ions was thermally stable up to 120 °C. Because DC-link capacitors work with unipolar charge and discharge processes, these PSF/PVDF MLFs with low dielectric losses are promising for the application of advanced power electronics for the automobile industry.

Reducing leakage current and dielectric losses of electroactive polymers through electro-annealing for high-voltage actuation

“…The polymerization agents used in the polymer synthesis of P(VDF-TrFE-CTFE) terpolymer contain ionic impurities that, although only on the order of ppm, contribute to interfacial polarization. 24,[53][54][55] These ionic impurities represent heterocharges that can be driven toward the oppositely charged electrode and accumulate under a constant DC voltage excitation. 56 A schematic representation of this ionic polarization process is shown in Fig.…”

“…[19][20][21][22][23] However, the use of high electric elds with low-glass-transition polymers inevitably results in a high level of leakage current. 24 The control of dielectric losses and their limits in terms of an exponential increase at operating voltage is fundamental to the development of high performing and long-life polymeric actuators. 25 High levels of leakage current also increase energy dissipation 26 and underlies self-heating.…”

Critical Role of Interfacial Diffusion and Diffuse Interphases Formed in Multi-Micro-/Nanolayered Polymer Films Based on Poly(vinylidene fluoride) and Poly(methyl methacrylate)

“…7,8 The markedly improved macroscopic properties in the coextruded multilayer films are generally attributed to the dominating interface/interphase and/or confinement effects. 2,9 Considerable efforts have been made to prepare multilayered films with a great number of interfaces by the combination of alternating layers of immiscible or partially miscible polymer pairs, such as polystyrene (PS)/ poly(methyl methacrylate) (PMMA), 10,11 polycarbonate (PC)/PMMA, 12 PC/poly(vinylidene fluoride) (PVDF), 13,14 polysulfone/PVDF, 15,16 and PS/polycaprolatone (PCL), 17 etc.…”

Bilayer-Structured Polymer Nanocomposites Exhibiting High Breakdown Strength and Energy Density via Interfacial Barrier Design

“…However, the currently reported multi-layered polymer composites are mainly centered on the ferroelectric polymer matrices represented by poly(vinylidene fluoride) (PVDF) and its copolymers and terpolymers. 4,[38][39][40][41][42][43][44][45][46][47][48] Due to the inherent ferroelectric loss and large remnant polarization, the chargedischarge efficiency (η) described in ferroelectric polymers usually ranges from 50 -80%, which signifies that a notable portion of the stored electrical energy in the charging process could not be recovered via discharging but is dissipated in the form of Joule heat. 7,15,16 Compared with the PVDF-based ferroelectric polymers, linear polystyrene (PS) exhibits much low loss, which would assure high η of the polymer nanocomposites.…”