Molecular Structure Modulated Trap Distribution and Carrier Migration in Fluorinated Epoxy Resin

Abstract

<jats:p>Surface charge accumulation on epoxy insulators is one of the most serious problems threatening the operation safety of the direct current gas-insulated transmission line (GIL), and can be efficiently inhibited by the surface modification technology. This paper investigated the mechanisms of fluorination modulated surface charge behaviors of epoxy resin through quantum chemical calculation (QCC) analysis of the molecular structure. The results show that after fluorination, the surface charge dissipation process of the epoxy sample is accelerated by the introduced shallow trap sites, which is further clarified by the carrier mobility model. The electron distribution probability of the highest occupied molecular orbitals (HOMO) under positive charging and the lowest unoccupied molecular orbitals (LUMO) under negative charging shows distinctive patterns. It is illustrated that electrons are likely to aggregate locally around benzenes for the positively charged molecular structure, while electrons tend to distribute all along the epoxy chain under negatively charging. The calculated results verify that fluorination can modulate surface charge behaviors of epoxy resin through redesigning its molecular structure, trap distribution and charging patterns.</jats:p>

Space Charge Behavior in Epoxy‐Based Dielectrics: Progress and Perspective

“…[84] So far, researchers have mainly focused on key parameters such as the molecular orbital, the density of states, and the electrostatic potential to gain insight into the charge injection and charge trapping process. [83,85,78,236] In this section, simulation studies on space charge characteristics from both macroscopic and microscopic views will be discussed to provide a multidimensional perspective on understanding charge dynamics and exploring advanced methods of suppressing charge accumulation. While comparative studies on EP-based dielectric materials are systematically summarized and presented, the focus is not limited to EP since most models and theories are universal.…”

“…With the rapid development of computational science, simulation studies on space charge behavior have been attracting increased attention. The recent space charge simulations can mainly be divided [78] into macroscopic simulations (based on bipolar charge transport (BCT) models [79][80][81] ) and microscopic simulations (based on quantum chemistry [82][83][84][85][86] or classical molecular dynamics). The former focused on simulating multiple physical processes, including charge injection, charge transport, and charge recombination, which has been promoted to reproduce the experimental results to the maximum extent [81,87,88] and forecast charge behavior in specific samples limited by sample size or thickness that are inappropriate for PEA tests.…”

Introducing Chlorine Into Epoxy Resin to Modulate Charge Trap Depth in the Material

“…7, the surface of the sphere covering segment C of DGEBA molecule is concentrated in red, and the surface of the The electron trap depth of the molecule affects the hopping probability of electrons, thus affecting the electron mobility in the transport process and the electrical conductivity of the material. Their relationships are shown in (3), ( 4) and ( 5), where θhop is hopping probability, φt is charge trap depth, k is Boltzmann constant, T is absolute temperature, μ is carrier mobility, μ0 is intrinsic mobility, σ is electrical conductivity, n is electron concentration, q is electron charge quantity, p is hole concentration [12,16] 3) and ( 4) that the hopping probability of the electrons is higher, resulting in a higher electron mobility μn. However, the introduction of the chlorine does not cause a significant change in the hole trap depth, so the hole mobility μp does not change obviously.…”

“…J. Li et al investigated the modulating mechanism of the fluorination treatment to the surface charge transfer on epoxy resin through quantum chemical calculation (QCC) analysis. The results show that the fluorination treatment generates shallow trap sites on the epoxy material surfaces, which improves the surface conductivity and subsequently accelerates the process of surface charge dissipation [16]. S. Akram et al modified the polyimide film surface with fluorine gas-phase and investigated the surface conductivity of fluorinated polyimide films.…”

Explorative Study on a Novel Ellipsometry Detection Method for Space Charge Inside Solid Insulation: Towards High Temporal and Spatial Resolutions

“…As the two key performance indicators of measurement technology, the measurement speed and spatial resolution can directly determine the measured charge information and its trap distribution range. Different insulating materials also show varying trap characteristics [7]- [9]. The existing researches under special electrical stresses within 500 Hz and polarity reversal conditions show that the accumulation of space charge can form instantaneously at the moment of voltage application or state transition [10]- [12].…”