Significantly Improved Electrical Properties of Crosslinked Polyethylene Modified by UV-Initiated Grafting MAH

Direct current (DC) electrical performances of crosslinked polyethylene (XLPE) have been evidently improved by developing graft modification technique with ultraviolet (UV) photon-initiation. Maleic anhydride (MAH) molecules with characteristic cyclic anhydride were successfully grafted to polyethylene molecules under UV irradiation, which can be efficiently realized in industrial cable production. The complying laws of electrical current varying with electric field and the Weibull statistics of dielectric breakdown strength at altered temperature for cable operation were analyzed to study the underlying mechanism of improving electrical insulation performances. Compared with pure XLPE, the appreciably decreased electrical conductivity and enhanced breakdown strength were achieved in XLPE-graft-MAH. The critical electric fields of the electrical conduction altering from ohm conductance to trap-limited mechanism significantly decrease with the increased testing temperature, which, however, can be remarkably raised by grafting MAH. At elevated temperatures, the dominant carrier transport mechanism of pure XLPE alters from Poole–Frenkel effect to Schottky injection, while and XLPE-graft-MAH materials persist in the electrical conductance dominated by Poole–Frenkel effect. The polar group of grafted MAH renders deep traps for charge carriers in XLPE-graft-MAH, and accordingly elevate the charge injection barrier and reduce charge mobility, resulting in the suppression of DC electrical conductance and the remarkable amelioration of insulation strength. The well agreement of experimental results with the quantum mechanics calculations suggests a prospective strategy of UV initiation for polar-molecule-grafting modification in the development of high-voltage DC cable materials.

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Enhanced Insulation Performances of Crosslinked Polyethylene Modified by Chemically Grafting Chloroacetic Acid Allyl Ester

Polymers ◽

10.3390/polym11040592 ◽

2019 ◽

Vol 11 (4) ◽

pp. 592 ◽

Cited By ~ 3

Author(s):

Xin-Dong Zhao ◽

Wei-Feng Sun ◽

Hong Zhao

Keyword(s):

Space Charge ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Chloroacetic Acid ◽

Dielectric Materials ◽

Electrical Insulation ◽

Polar Group ◽

Charge Accumulation ◽

Allyl Ester ◽

Electrical Insulation Properties

Modified crosslinked polyethylene (XLPE) with appreciably enhanced DC electrical insulation properties has been developed by chemical modification of grafting chloroacetic acid allyl ester (CAAE), exploring the trapping mechanism of charge transport inhibition. The bound state traps deriving from grafted molecule are analyzed by first-principles calculations, in combination with the electrical DC conductivity and dielectric breakdown strength experiments to study the underlying mechanism of improving the electrical insulation properties. In contrast to pure XLPE, the XLPE-graft-CAAE represents significantly suppressed space charge accumulation, increased breakdown strength, and reduced conductivity. The substantial deep traps are generated in XLPE-graft-CAAE molecules by polar group of grafted CAAE and accordingly decrease charge mobility and raise charge injection barrier, consequently suppressing space charge accumulation and charge carrier transport. The well agreement of experiments and quantum mechanics calculations suggests a prospective material modification strategy for achieving high-voltage polymer dielectric materials without nanotechnology difficulties as for nanodielectrics.

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Ameliorated Electrical-Tree Resistant Characteristics of UV-Initiated Cross-Linked Polyethylene Nanocomposites with Surface-Functionalized Nanosilica

Processes ◽

10.3390/pr9020313 ◽

2021 ◽

Vol 9 (2) ◽

pp. 313 ◽

Cited By ~ 1

Author(s):

Yong-Qi Zhang ◽

Ping-Lan Yu ◽

Wei-Feng Sun ◽

Xuan Wang

Keyword(s):

Fractal Dimension ◽

Electric Fields ◽

Tree Growth ◽

Electrical Resistance ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Sio2 Nanoparticles ◽

Polyethylene Matrix ◽

Electrical Tree ◽

Electrical Trees

Given the high interest in promoting crosslinking efficiency of ultraviolet-initiated crosslinking technique and ameliorating electrical resistance of crosslinked polyethylene (XLPE) materials, we have developed the funcionalized-SiO2/XLPE nanocomposites by chemically grafting auxiliary crosslinkers onto nanosilica surfaces. Trimethylolpropane triacrylate (TMPTA) as an effective auxiliary crosslinker for polyethylene is grafted successfully on nanosilica surfaces through thiolene-click chemical reactions with coupling agents of sulfur silanes and 3-mercaptopropyl trimethoxy silane (MPTMS), as characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. The functionalized SiO2 nanoparticles could be dispersively filled into polyethylene matrix even at a high filling content that would generally produce agglomerations of neat SiO2 nanofillers. Ultraviolet-initiated polyethylene crosslinking reactions are efficiently stimulated by TMPTA grafted onto surfaces of SiO2 nanofillers, averting thermal migrations out of polyethylene matrix. Electrical-tree pathways and growth mechanism are specifically investigated by elucidating the microscopic tree-morphology with fractal dimension and simulating electric field distributions with finite-element method. Near nano-interfaces where the shielded-out electric fluxlines concentrate, the highly enhanced electric fields will stimulate partial discharging and thus lead to the electrical-trees being able to propagate along the routes between nanofillers. Surface-modified SiO2 nanofillers evidently elongate the circuitous routes of electrical-tree growth to be restricted from directly developing toward ground electrode, which accounts for the larger fractal dimension and shorter length of electrical-trees in the functionlized-SiO2/XLPE nanocomposite compared with XLPE and neat-SiO2/XLPE nanocomposite. Polar-groups on the modified nanosilica surfaces inhibit electrical-tree growth and simultaneously introduce deep traps impeding charge injections, accounting for the significant improvements of electrical-tree resistance and dielectric breakdown strength. Combining surface functionalization and nanodielectric technology, we propose a strategy to develop XLPE materials with high electrical resistance.

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Feel the force: Bio-electricity and the sensing of electric fields

The Biochemist ◽

10.1042/bio03306026 ◽

2011 ◽

Vol 33 (6) ◽

pp. 26-29

Author(s):

Kene N. Piasta ◽

Christopher Miller

Keyword(s):

Electric Field ◽

Electric Fields ◽

Migratory Birds ◽

Dielectric Breakdown ◽

Electrical Current ◽

Lightning Strike ◽

Electric Force ◽

Science Museums ◽

Hot Flash ◽

Lightning Bolt

In an issue devoted to sensory phenomena, it may seem odd to include an article on sensing something that we cannot consciously perceive: electric force. Of course, we can sense the dramatic power of a lightning bolt: we see the flash, hear the boom, feel the rumble, and, if we're close enough, smell and taste the ozone produced. Lightning is caused by an enormous electric field that develops under a thundercloud due to the separation of electrical charges between the cloud and the earth. Almost 250 years after Benjamin Franklin's kite-in-the-storm experiment, we still don't fully understand how this charge separation is generated. But it's nevertheless a fact that if you are standing under a thundercloud, you are immersed in a large vertically directed electric field, typically a few hundred volts between your head and your feet. Just before a lightning strike, this electric field becomes large enough to literally rip gas molecules in the air apart by pulling negatively charged electrons in one direction – towards the positively charged ground – and positive nuclei towards the negative cloud. Once a column of air becomes ionized in this way, the charged particles zoom to their respective ‘electrodes’, discharging the cloud–ground capacitor in a bright, hot flash of enormous electrical current. Lightning is a manifestation of a phenomenon called ‘dielectric breakdown’, something we've all seen in more controlled contexts, such as cheesy horror movies, Ask-Dr-Science demos at science museums and aluminium foil mistakenly placed in the microwave oven. Dielectric breakdown of most materials occurs at electric fields on the order of a few million volts per metre. But there is a great irony here: whereas we sense all of the secondary consequences of lightning, we are utterly blind to its most fundamental element – the electric field that gets the whole thing going. Humans just never evolved electric-force sensors. (But fish did – and migratory birds and turtles navigate by ‘feeling’ the earth's weak magnetic field.

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Ameliorated Dielectric Performances of UV-Initiated Auxiliary Crosslinking Polyethylene

Journal of Nanoelectronics and Optoelectronics ◽

10.1166/jno.2021.3043 ◽

2021 ◽

Vol 16 (7) ◽

pp. 1037-1046

Author(s):

Ming-Hao Lv ◽

Wei-Chao Zhang ◽

Wei Guo ◽

Liang Du

Keyword(s):

Dielectric Breakdown ◽

Breakdown Strength ◽

Electrical Conductance ◽

Polyethylene Matrix ◽

Crosslinking Degree ◽

Insulation Materials ◽

Crosslinking Process ◽

High Level ◽

Crosslinking Reactions ◽

Xlpe Insulation

In photon-initiated crosslinking reactions of polyethylene molecules, the auxiliary crosslinkers in form of either monomer or homopolymer will cause bridging connections between polymeric molecules by transforming the irradiated photon energy to chemical energy under the assistance of photon-initiators, which can improve photon-initiation quantum efficiency and crosslinking uniformity. In the present study, the auxiliary crosslinkers of TAIC, TAC and TMPTA combining the macromolecular photon-initiator of BPL are employed into the ultraviolet (UV)-initiation technology to develop high-level crosslinked polyethylene (XLPE) insulation materials, whilst elucidating the structural and electrical mechanisms of the dielectric amelioration deriving from auxiliary crosslinking schemes. The specified photosensitive auxiliary crosslinkers can chemically bridge polyethylene molecules in the UV-initiated polyethylene crosslinking process, which can effectively promote polyethylene crosslinking degree but will slightly abate polyethylene crystallinity. Whereas, the orientation polarization and relaxation of molecular electric-dipoles on auxiliary crosslinkers cause additional dielectric permittivity and loss respectively, which will probably reduce insulation performances of XLPE. By contrast to XLPE benchmark, especially for grafting auxiliary crosslinker TAIC with the multiple-coupling carbonyl groups in a ring-conjugation, the preferable deep charge-traps can be introduced into polyethylene matrix to effectively improve electrical conductance and AC dielectric breakdown strength. This study provides experimental basis for developing the photon-initiated XLPE insulation materials with advanced dielectric performances required for manufacturing high-voltage grade cables.

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Dielectric Breakdown in Printed Circuit Boards at Elevated Temperatures

ISTFA 1996: Conference Proceedings from the 22nd International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa1996p0357 ◽

1996 ◽

Author(s):

P. Singh ◽

G.T. Galyon ◽

J. Obrzut ◽

W.A. Alpaugh

Keyword(s):

Experimental Data ◽

Thermal Degradation ◽

Printed Circuit Boards ◽

Printed Circuit Board ◽

Elevated Temperatures ◽

Dielectric Breakdown ◽

Circuit Board ◽

Circuit Boards ◽

Printed Circuit ◽

Data Matching

Abstract A time delayed dielectric breakdown in printed circuit boards, operating at temperatures below the epoxy resin insulation thermo-electrical limits, is reported. The safe temperature-voltage operating regime was estimated and related to the glass-rubber transition (To) of printed circuit board dielectric. The TG was measured using DSC and compared with that determined from electrical conductivity of the laminate in the glassy and rubbery state. A failure model was developed and fitted to the experimental data matching a localized thermal degradation of the dielectric and time dependency. The model is based on localized heating of an insulation resistance defect that under certain voltage bias can exceed the TG, thus, initiating thermal degradation of the resin. The model agrees well with the experimental data and indicates that the failure rate and truncation time beyond which the probability of failure becomes insignificant, decreases with increasing glass-rubber transition temperature.

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Dielectric Breakdown Strength and Energy Storage Density of CCTO-ZBS Electroceramic

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/596/1/012006 ◽

2020 ◽

Vol 596 ◽

pp. 012006

Author(s):

Muhammad Qusyairie Saari ◽

Julie Juliewatty Mohamed ◽

Muhammad Azwadi Sulaiman ◽

Mohd Fariz Abd Rahman ◽

Zainal Arifin Ahmad ◽

...

Keyword(s):

Energy Storage ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Energy Storage Density ◽

Dielectric Breakdown Strength ◽

Storage Density

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Construction of a Three-Dimensional BaTiO3 Network for Enhanced Permittivity and Energy Storage of PVDF Composites

Materials ◽

10.3390/ma14133585 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3585

Author(s):

Xueqing Bi ◽

Lujia Yang ◽

Zhen Wang ◽

Yanhu Zhan ◽

Shuangshuang Wang ◽

...

Keyword(s):

Energy Storage ◽

Polyvinylidene Fluoride ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Sol Gel ◽

Three Dimensional ◽

Low Dielectric ◽

Energy Storage Properties ◽

Discharge Energy Density ◽

Pure Pvdf

Three-dimensional BaTiO3 (3D BT)/polyvinylidene fluoride (PVDF) composite dielectrics were fabricated by inversely introducing PVDF solution into a continuous 3D BT network, which was simply constructed via the sol-gel method using a cleanroom wiper as a template. The effect of the 3D BT microstructure and content on the dielectric and energy storage properties of the composites were explored. The results showed that 3D BT with a well-connected continuous network and moderate grain sizes could be easily obtained by calcining a barium source containing a wiper template at 1100 °C for 3 h. The as-fabricated 3D BT/PVDF composites with 21.1 wt% content of 3D BT (3DBT–2) exhibited the best comprehensive dielectric and energy storage performances. An enhanced dielectric constant of 25.3 at 100 Hz, which was 2.8 times higher than that of pure PVDF and 1.4 times superior to the conventional nano–BT/PVDF 25 wt% system, was achieved in addition with a low dielectric loss of 0.057 and a moderate dielectric breakdown strength of 73.8 kV·mm−1. In addition, the composite of 3DBT–2 exhibited the highest discharge energy density of 1.6 × 10−3 J·cm−3 under 3 kV·mm−1, which was nearly 4.5 times higher than that of neat PVDF.

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