Ameliorated Dielectric Performances of UV-Initiated Auxiliary Crosslinking Polyethylene

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.

Download Full-text

Functionalization of Silica Nanoparticles to Improve Crosslinking Degree, Insulation Performance and Space Charge Characteristics of UV-initiated XLPE

Molecules ◽

10.3390/molecules25173794 ◽

2020 ◽

Vol 25 (17) ◽

pp. 3794

Author(s):

Yu-Wei Fu ◽

Yong-Qi Zhang ◽

Wei-Feng Sun ◽

Xuan Wang

Keyword(s):

Space Charge ◽

Silica Nanoparticles ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

High Dispersion ◽

Polyethylene Matrix ◽

Crosslinking Degree ◽

Developed Surface ◽

High Efficient ◽

Insulation Performance

In order to inhibit the outward-migrations of photo-initiator molecules in the ultraviolet-initiated crosslinking process and simultaneously improve the crosslinking degree and dielectric properties of crosslinked polyethylene (XLPE) materials, we have specifically developed surface-modified-SiO2/XLPE nanocomposites with the silica nanofillers that have been functionalized through chemical surface modifications. With the sulfur-containing silanes and 3-mercaptopropyl trimethoxy silane (MPTMS), the functional monomers of auxiliary crosslinker triallyl isocyanurate (TAIC) have been successfully grafted on the silica surface through thiol–ene click chemistry reactions. The grafted functional groups are verified by molecular characterizations of Fourier transform infrared spectra and nuclear magnetic resonance hydrogen spectra. Scanning electronic microscopy (SEM) indicates that the functionalized silica nanoparticles have been filled into polyethylene matrix with remarkably increased dispersivity compared with the neat silica nanoparticles. Under ultraviolet (UV) irradiation, the high efficient crosslinking reactions of polyethylene molecules are facilitated by the auxiliary crosslinkers that have been grafted onto the surfaces of silica nanofillers in polyethylene matrix. With the UV-initiated crosslinking technique, the crosslinking degree, insulation performance, and space charge characteristics of SiO2/XLPE nanocomposites are investigated in comparison with the XLPE material. Due to the combined effects of the high dispersion of nanofillers and the polar-groups of TAIC grafted on the surfaces of SiO2 nanofillers, the functionlized-SiO2/XLPE nanocomposite with an appropriate filling content represents the most preferable crosslinking degree with multiple improvements in the space charge characteristics and direct current dielectric breakdown strength. Simultaneously employing nanodielectric technology and functional-group surface modification, this study promises a modification strategy for developing XLPE nanocomposites with high mechanical and dielectric performances.

Download Full-text

FT-IR Micro Focus Analysis of Additive Content Distribution in XLPE Insulation and Additve Effect on Dielectric Breakdown Strength

IEEJ Transactions on Fundamentals and Materials ◽

10.1541/ieejfms1990.111.6_516 ◽

1991 ◽

Vol 111 (6) ◽

pp. 516-524 ◽

Cited By ~ 2

Author(s):

Masayoshi Ishida ◽

Tatsuki Okamoto ◽

Naohiro Hozumi

Keyword(s):

Content Distribution ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Dielectric Breakdown Strength ◽

Additive Content ◽

Focus Analysis ◽

Ft Ir ◽

Xlpe Insulation

Download Full-text

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

Polymers ◽

10.3390/polym12010062 ◽

2020 ◽

Vol 12 (1) ◽

pp. 62 ◽

Cited By ~ 3

Author(s):

Xin-Dong Zhao ◽

Hong Zhao ◽

Wei-Feng Sun

Keyword(s):

Electric Fields ◽

Carrier Transport ◽

Elevated Temperatures ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Electrical Conductance ◽

Electrical Current ◽

Underlying Mechanism ◽

Polar Group ◽

Frenkel Effect

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.

Download Full-text

Percolation Threshold and Critical Exponent of Dielectric Breakdown Strength of Polyethylene Matrix Composites added Carbon Black

Korean Journal of Materials Research ◽

10.3740/mrsk.2011.21.9.477 ◽

2011 ◽

Vol 21 (9) ◽

pp. 477-481 ◽

Cited By ~ 1

Author(s):

Soon-Gi Shin

Keyword(s):

Carbon Black ◽

Critical Exponent ◽

Percolation Threshold ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Matrix Composites ◽

Polyethylene Matrix ◽

Dielectric Breakdown Strength

Download Full-text

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.

Download Full-text

Morphology and Dielectric Breakdown Strength of XLPE Insulation Affected by Surfactant

IEEJ Transactions on Fundamentals and Materials ◽

10.1541/ieejfms1990.111.11_1013 ◽

1991 ◽

Vol 111 (11) ◽

pp. 1013-1022 ◽

Cited By ~ 1

Author(s):

Masayoshi Ishida ◽

Tatsuki Okamoto

Keyword(s):

Dielectric Breakdown ◽

Breakdown Strength ◽

Dielectric Breakdown Strength ◽

Xlpe Insulation

Download Full-text

Structured Polyethylene Nanocomposites: Effects of Crystal Orientation and Nanofiller Alignment on High Field Dielectric Properties

MRS Advances ◽

10.1557/adv.2016.638 ◽

2016 ◽

Vol 2 (6) ◽

pp. 363-368 ◽

Cited By ~ 12

Author(s):

Bo Li ◽

C. I. Camilli ◽

P. I. Xidas ◽

K. S. Triantafyllidis ◽

E. Manias

Keyword(s):

Crystal Orientation ◽

High Field ◽

Dielectric Breakdown ◽

Breakdown Strength ◽

Film Surface ◽

Nanocomposite Films ◽

X Ray Diffraction ◽

Polyethylene Matrix ◽

X Ray ◽

Orientation Order

ABSTRACTIn previous work we have shown that aligned high aspect-ratio (pseudo-2D) nanofillers can yield large dielectric breakdown strength (EBD) improvements for a nanocomposite with a low-crystallinity polyethylene matrix. Here, we report a systematic study which delineates the contributions of the aligned inorganic fillers and of the aligned polymer crystallites in the overall EBD improvement achieved in the nanocomposites. Specifically, extrusion blown-molded polyethylene/montmorillonite nanocomposite films were cold-stretched to various strains, to further align the nanoparticles parallel to the film surface; this filler alignment is accompanied by a commensurate alignment of the polymer crystallites, especially those heterogeneously nucleated by the fillers. A systematic series of films are studied, with increased extent of alignment of the fillers and of the crystalline lamellae (quantified through Hermans orientation order parameters from 2D X-ray diffraction studies) and the aligned structure is correlated to the electric field breakdown strength (quantified through Weibull failure studies). It is shown that aligned pseudo-2D inorganic nanofillers provide additional strong improvements in EBD, improvements that are beyond, and added in excess of, any EBD increases due to polymer-crystal orientation.

Download Full-text