Influence of imidazole derivatives on the dielectric and energy storage performance of epoxy

Abstract

Imidazoles are widely used as curing agents and accelerators for fabricating crosslinked epoxy materials applied in electrical and electronic fields. However, the intrinsic chemical structure of imidazole derivatives would greatly influence the polymerisation process, and further change the electrical properties, which was not emphasised. To achieve an indepth understanding, commonly used imidazole only containing pyridine-type nitrogen and imidazole with both pyridine and pyrrole-type nitrogen were selected in this study. Electrical properties including dielectric properties, volume resistivity, breakdown strength, and especially energy storage performances were systematically investigated. We figured out that higher breakdown strength, glass transition temperature, and lower dielectric loss can be achieved with imidazole containing pyrrole-type nitrogen. Structureinduced curing mechanism diversity and the generated differences in polymer network were highlighted. With the capability to incorporate into the polymer network, the dielectric constant/loss of epoxy cured by imidazole containing pyrrole-type nitrogen is less sensitive with variation in concentration and a high breakdown strength of 577.9 MV/m was achieved. On the contrary, conspicuous decrease in the breakdown strength and increase in dielectric loss of the epoxy cured by imidazole only containing pyridine-type nitrogen were observed, especially at high concentration. Moreover, we also found that the epoxy can be fabricated into films with an attractive energy storage density/efficiency of 1.1 J/cm 3 /97%@200 MV/m, which is twice of the commercial dielectric polypropylene film under the same electric field.

Design and characterization of molecular, crystal and interfacial structures of PVDF-based dielectric nanocomposites for electric energy storage

“…48,59 all-trans TTTT dipoles. The dielectric permittivity of P(VDF-TrFE) at 1 kHz is 18, larger than that of PVDF (6)(7)(8)(9)(10)(11)(12), and the dielectric loss is less than 0.1. 60 Although P(VDF-TrFE) has a high dielectric permittivity, its high residual polarization makes it difficult to be applied in the field of energy storage.…”

“…Compared with P(VDF-HFP)/BT nanocomposites, the P(VDF-HFP)/BT@PANI nanocomposite shows that dielectric properties are notably promoted. As an example, the dielectric constant of BT@PANI/ P(VDF-HFP) is 99.1 at 1 kHz, which is 6.2 times larger than that of 20 vol% BT (16.1) and 9.6 times higher than that of P(VDF-HFP) (10). Zhao et al reported that a conductive carbon shell was coated onto the BT nanoparticles by a hydrothermal method.…”

“…The development of sustainable, [1][2][3] low-cost 4,5 and eco-friendly power conversion 6,7 and storage systems [8][9][10] is an urgent demand for the exploitation of high-density polymer-based dielectric materials. The dramatic improvement of the dielectric permittivity and energy density of dielectric polymers is not only beneficial for reducing the volume and weight of energy storage and conversion devices, but also ensuring that large electrical machines can work under stable conditions.…”

Preparation of fluorinated epoxy‐phthalonitrile resins with excellent thermal stability and low dielectric constant

“…Therefore, materials with low dielectric constants are expected to achieve faster and stable signal transmission in microelectronic devices. 24,25 To address these needs, numerous studies have focused on developing resins with desirable electrical properties and stability at high temperatures. 26 For example, resin properties can be improved by adding inorganic fillers.…”

“…To achieve miniaturization and portability, the size of electronic devices continues to shrink, introducing new obstacles such as signal crosstalk, power consumption and time delays. Therefore, materials with low dielectric constants are expected to achieve faster and stable signal transmission in microelectronic devices 24,25 …”