Dielectric relaxation and trap-modulated DC breakdown of polypropylene blend insulation

Li, Zhonglei; Zhong, Zhuoyan; Du, B. X.

doi:10.1016/j.polymer.2019.121935

Cited by 35 publications

(19 citation statements)

References 30 publications

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“…Another simple classification of electrets is hetero-electrets and homo-electrets; where homo-electret mostly occurs by excess charge injection into nonpolar materials, and hetero-electret occurs through the internal charging by orientation of dipoles [3]. Generally, a polymer with high dielectric constant (ε r ) polarizes more in the electric field, giving a high level of initial charges, while its loss with time is another issue [1,5,7].…”

Section: Introductionmentioning

confidence: 99%

“…While various material options were examined to attain the high-quality factor filters [10,25,26], it lacked scrutiny on the material attributes that enable the long-term charge retention. Moreover, the dielectric constant (ε r ) of material has rarely been associated with the charge decay phenomenon in experimental investigation [1,27], while there are implications that ε r is related with the charge stability and conductivity [7,27,28].The purpose of this work is to investigate the polymeric attributes that influence the charge retention capacity of electret filters. In this study, polymers with three different dielectric constants-polypropylene (PP), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN)-were compared for their charge decay phenomena with varied aging conditions.…”

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confidence: 99%

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Material Properties Influencing the Charge Decay of Electret Filters and their Impact on Filtration Performance

Lee

Kim

2020

Polymers

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Electret filters as opposed to mechanical filters display the enhanced ability to capture airborne particles with the electrostatic attraction. However, the environmental aging during shelf-life or use may cancel its benefit by dissipating the charges. This work investigates the polymeric attributes influencing the charge decay and the electrostatic filtration of electret filters, employing polymers with different dielectric constants (εr) and wettability. As accelerated aging, high temperature (120 °C) or high humidity (25 °C, 90% RH) was applied to the electret filters for 48 h. For the humidity aging, wetting property of material was a critical factor affecting the charge decay and the filtration performance, as the absorbed water increases the electrical conductivity. For the thermal aging, the material with the highest εr deteriorated the electric potential and the filtration performance by the largest extent, due to the lower band gap energy for charge transfer. The results of this study implicate that εr and wettability are important material parameters influencing the electric conductivity and chain mobility, and they can be used as convenient predictors for charge retention capacity affecting the robust electrostatic filtration performance.

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Section: Introductionmentioning

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Material Properties Influencing the Charge Decay of Electret Filters and their Impact on Filtration Performance

Lee

Kim

2020

Polymers

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“…It can be seen that IPC30 exhibits the highest shallow trap density and lowest deep trap density. In semicrystalline polymers, the deep traps are often thought to exist in the crystalline regions while the shallow traps are more in the amorphous regions with a low-density [ 27 ]. According to the changes in crystallinity and trap density, it is suggested that the lowest crystallinity is responsible for the high shallow trap density and low deep trap density of IPC30.…”

Section: Discussionmentioning

confidence: 99%

Enhanced Morphology-Dependent Tensile Property and Breakdown Strength of Impact Polypropylene Copolymer for Cable Insulation

et al. 2020

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The decrease in electrical properties caused by the toughening of polypropylene (PP) is a difficult problem for the modification of PP used for cable insulation. In this research, an isotactic PP, a cross-linked polyethylene (XLPE) and two impact PP copolymers (IPCs) with an ethylene–propylene rubber phase content of 15 and 30% were prepared to assess the possibility of IPCs to be used as cable insulating material. The tensile properties and breakdown strength were evaluated, meanwhile, the rubber phase content dependence of the crystalline structure, morphology and trap distribution were also investigated. Results show that IPCs with a 15% rubber phase content (IPC15) can achieve the simultaneous improvement of elongation at break and breakdown strength compared with isotactic PP, which can be attributed to the special crystalline structure. According to the results of differential scanning calorimetry (DSC) and FTIR, it is proposed that the lamella thickness of IPC15 is maximal and some ethylene segments exist in PP crystals of IPC15 as crystalline structure defects, which is responsible for this enhanced breakdown strength. The morphology results reveal that rubber microspheres are found to coexist with spherulites, which can promote the relative sliding among lamellas under external force and further results in the increase in the elongation at break.

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“…On the other hand, these hot electrons with energy as W appl are larger than the potential barrier E t , they can directly cross over deep traps and constantly hit the molecular chain. Moreover, the growth of deep trap density N t will enhance the possibility of hot electrons being captured [46], preventing a large number of hot electrons from directly hitting the molecular chain and causing the molecular chain to rupture, thereby improving the DC breakdown field strength of the HDPE/LDPE blends.…”

Section: Electrical Breakdown Model Of Coupling Molecular Chain Displmentioning

confidence: 99%

Coupling Effect of Molecular Chain Displacement and Carrier Trap Characteristics on DC Breakdown of HDPE/LDPE Blend Insulation

Fan

Zhong

2020

Polymers

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This work focuses on the coupling effect of molecular chain displacement and trap characteristics on direct current (DC) breakdown properties of high density/low density polyethylene (HDPE/LDPE) blend insulation. Frequency domain spectroscopy (FDS) and isothermal discharge current (IDC) are used to characterize the dielectric relaxation and trap characteristics of HDPE/LDPE blends. A DC breakdown model is proposed to reveal the mechanisms of the molecular chain displacement and carrier trap on the DC breakdown strength. The dielectric relaxation α and δ present segmental motions and thermal ion polarization behaviours of HDPE/LDPE blends, respectively. α dielectric relaxation strength (Δεα) increases as the amount of HDPE increases from 0 to 5 wt%, and then declines with a further increase of HDPE content to 20 wt%. According to the velocity equation, the increase of Δεα will increase the molecular chain displacement, resulting in a larger free volume, which will provide electrons with larger free path λ to form hot electrons. A positive correlation exists between the activation energy of the dielectric relaxation process δ and trap density, and the increase of δ dielectric relaxation strength (Δεδ) will adversely affect the breakdown strength of the specimen. HDPE/LDPE blends with 15 wt% HDPE content have lower Δεα and lowest Δεδ, which decreases the mean free path λ of molecular chain and thermal ion polarization. At the same time, it has the highest deep trap density, thus increasing the probability of hot electrons being captured and improving the DC breakdown strength. It is concluded the breakdown of the dielectric is synergistically affected by the molecular chain displacement and carrier trap.

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Dielectric relaxation and trap-modulated DC breakdown of polypropylene blend insulation

Cited by 35 publications

References 30 publications

Material Properties Influencing the Charge Decay of Electret Filters and their Impact on Filtration Performance

Material Properties Influencing the Charge Decay of Electret Filters and their Impact on Filtration Performance

Enhanced Morphology-Dependent Tensile Property and Breakdown Strength of Impact Polypropylene Copolymer for Cable Insulation

Coupling Effect of Molecular Chain Displacement and Carrier Trap Characteristics on DC Breakdown of HDPE/LDPE Blend Insulation

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