Carrier Transport and Molecular Displacement Modulated dc Electrical Breakdown of Polypropylene Nanocomposites

Abstract

Dielectric energy storage capacitors have advantages such as ultra-high power density, extremely fast charge and discharge speed, long service lifespan and are significant for pulsed power system, smart power grid, and power electronics. Polypropylene (PP) is one of the most widely used dielectric materials for dielectric energy storage capacitors. It is of interest to investigate how to improve its electrical breakdown strength by nanodoping and the influencing mechanism of nanodoping on the electrical breakdown properties of polymer nanocomposites. PP/Al2O3 nanocomposite dielectric materials with various weight fraction of nanoparticles are fabricated by melt-blending and hot-pressing methods. Thermally stimulated current, surface potential decay, and dc electrical breakdown experiments show that deep trap properties and associated molecular chain motion are changed by incorporating nanofillers into polymer matrix, resulting in the variations in conductivity and dc electrical breakdown field of nanocomposite dielectrics. Then, a charge transport and molecular displacement modulated electrical breakdown model is utilized to simulate the dc electrical breakdown behavior. It is found that isolated interfacial regions formed in nanocomposite dielectrics at relatively low loadings reduce the effective carrier mobility and strengthen the interaction between molecular chains, hindering the transport of charges and the displacement of molecular chains with occupied deep traps. Accordingly, the electrical breakdown strength is enhanced at relatively low loadings. Interfacial regions may overlap in nanocomposite dielectrics at relatively high loadings so that the effective carrier mobility decreases and the interaction between molecular chains may be weakened. Consequently, the molecular motion is accelerated by electric force, leading to the decrease in electrical breakdown strength. The experiments and simulations reveals that the influence of nanodoping on dc electrical breakdown properties may origin from the changes in the charge transport and molecular displacement characteristics caused by interfacial regions in nanocomposite dielectrics.

Finite Element Analysis of the Breakdown Prediction for LDPE Stressed by Various Ramp Rates of DC Voltage Based on Molecular Displacement Model

“…As an alternative to the experimental approach, we proposed a numerical analysis model based on the finite element method (FEM) to predict the breakdown of a polymer insulator, low-density polyethylene (LDPE), and to analyze the effect of the ramp rate of the applied DC voltage. Using this numerical model, the electrical breakdown was systematically analyzed by combining the bipolar charge transport (BCT) model [13][14][15][16] with the molecular displacement model [9,17]. The BCT model describes the behaviors of charge carriers such as holes and electrons inside the insulator, and the molecular displacement model describes the displacement of the molecular chain caused by the trapped charges.…”

Enhancing the filtration efficiency and wearing time of disposable surgical masks using TENG technology

“…As a large activation energy is needed to release this kind of charges, the surface potential of the electret can maintain for a long time. The activation of the trapped charge can be reflected by the location of current peak in the thermally stimulated discharge (TSD) spectrum, higher temperature corresponds to larger activation energy [33] , [34] , [35] . As for the charged PP filter, the current peak at 148 °C ( Fig.…”

Role of Polyvinylpyrrolidone (PVP) on Controlling the Structural, Optical, and Electrical Properties of Vanadium Pentoxide (V2O5) Nanoparticles

“…The carrier trap could become electrically charged for creating a potential barrier between V 2 O 5 nanoparticles that prevent the carrier from moving one particle to another, leading in a reduction in carrier mobility. [68] From the Figure 12, we observe that the resistivity of nanoparticles with PVP is higher than that of nanoparticles without PVP. This high resistivity of nanoparticles synthesized using PVP may be attributed to strong agglomeration.…”