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

Abstract

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.

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

“…Based on the experimental results of electrical conductance and the quantum mechanics calculations, it is reasonable to correlate DBS improvement with the increment of trap level depth and density. These results support the electron trapping model of ameliorating dielectric properties by grafting polar group and suggest that the MAH is the mostly expected graft candidate to improve insulation performances of polymer materials [13]. The tight coupling carbonyl carbon atoms of cyclic anhydride in MAH also essentially account for the enhanced DBS of XLPE-g-MAH.…”

“…It was reported and revealed in an underlying mechanism that modified electrical properties of polypropylene, such as space charge suppression and breakdown strength improvement with abated conductivity, can be achieved by chemically grafting maleic anhydride [12]. Chemically modifying XLPE by grafting chloroacetic acid allyl ester and the correlated space charge accumulation with a trapping mechanism have been reported to explain the palpable improvement of insulation performances [13]. S.H.…”

Elevated-Temperature Space Charge Characteristics and Trapping Mechanism of Cross-Linked Polyethylene Modified by UV-Initiated Grafting MAH

“…The space charges in higher density deriving from the charge-captures by grafting-introduced deep traps only accumulate in a very thin layer region near electrodes. It will not produce large electric field distortion in modified materials even at 80 °C, due to the electrostatic shielding layers near electrodes, which originate from the fixed and densely distributed charges that have been captured into the grafting-introduced deep traps [ 14 ]. It is also proved that the increment of grafting concentration can promote the inhibition of space charge such that the charge injection density and electric field distortion of XLPE-g-0.41wt%MAH are lower than those of XLPE-g-0.33wt%MAH.…”

“…Zhou reported the excellent electrical properties of chemically modified polypropylene by grafting maleic anhydride and analyzed the underlying mechanisms of space charge suppression, breakdown strength improvement, and conductivity abatement [ 13 ]. Zhao developed the chemically modified XLPE by grafting chloroacetic acid allyl ester and correlated space charge accumulation with trapping mechanism to comprehend the achieved insulation performance amelioration [ 14 ]. Lee has successfully grafted maleic anhydride (MAH) onto the macromolecular chain of low-density polyethylene by the generally used chemical methods, indicating that the heteropolar space charge accumulations and electrical conductance can be definitely inhibited in LDPE-g-MAH [ 15 ].…”

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

“…It has been normally recognized that preparing XLPE nanocomposites by filling neat SiO 2 will engender substantial agglomerations of SiO 2 nanofillers when the filling content is higher than about 1.5 wt%. Furthermore, TAIC molecules with polar-groups that have grafted on the surface of SiO 2 nanoparticles will not be evaporated in the crosslinking reaction, thus retaining a higher density of polar-groups that act as effective charge traps to improve DBS by impeding carrier transports and inhibiting space charge accumulation through the trapping mechanism [ 34 ]. The 1.5wt%TAIC- s -SiO 2 /XLPE nanocomposite acquires a higher characteristic 63.2% DBS than the pure XLPE due to the deep traps introduced by the polar-groups of TAIC molecules grafted on nanosilica surfaces, which is consistent with the charge trapping and scattering mechanism in suppressing space charge accumulation and impeding electrical conductance under DC electric field.…”