Enhancement of Insulation Properties of Cross-Linked Polyethylene Utilizing Aromatic Voltage Stabilizers with Electron-Withdrawing and Electron-Donating Groups

Abstract

This paper presents the influence of three different voltage stabilizers, 4-n-propylbenzoic acid, 2-methoxyphenylboronic acid, and 3-aminobenzoylmethylamide, on the insulation properties of cross-linked polyethylene (XLPE). The 1 wt % voltage stabilizers are blended with XLPE by a solution method, and then the samples are prepared via a hot pressing method. Electrical and physicochemical properties of the XLPE blends are analyzed by space charge, DC resistivity, DC breakdown strength, thermally stimulated depolarization current, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry experiments. It is found that the addition of the voltage stabilizers enhances the DC resistivity and DC breakdown strength of the XLPE, which also inhibits the accumulation of space charges in the XLPE. The results show that the XLPE blend with the addition of 4-n-propylbenzoic acid has the lowest conduction current and a 23.3% increment in the DC breakdown strength compared to that of the reference XLPE among the used voltage stabilizers. Moreover, it is found that the melting properties and thermal stability of the XLPE are not affected by the addition of the voltage stabilizers. The XLPE blend with 4-n-propylbenzoic acid exhibits a uniform trap depth distribution, which facilitates the migration of the space charge to the anode and reduces the electric field inside the sample bulk. Quantum chemical calculations demonstrate that the matching ability of the electron-withdrawing and electron-donating groups of the three voltage stabilizers effectively enhances the electrical properties of the XLPE. In contrast, the 4-n-propylbenzoic acid has the lowest unoccupied molecular orbital energy level, which can effectively buffer the high-energy electrons and increase the DC breakdown strength. A charge carrier transport mechanism is also proposed to explain the effect of the voltage stabilizer on the space charge movement in the tested samples.

Graftable voltage stabilizer for enhancing insulation performance of crosslinked polyethylene

“…[5][6][7] In order to improve the working stability and service life of XLPE insulation cables, the commonly used modification methods are mainly assigned to nanoparticle modification, [8][9][10][11] blending modification, [12][13][14] grafting modification [15][16][17] and voltage stabilizer modification. [18][19][20][21] Since high-voltage power cable insulation materials require high purity, the easy-to-introduce impurities blending modification method is rarely used. Compared to nanoparticles modification, grafting modification can not only improves the electrical properties of polymer but also has no problems such as agglomeration, plugging and moisture absorption of nanoparticles.…”

“…In order to improve the working stability and service life of XLPE insulation cables, the commonly used modification methods are mainly assigned to nanoparticle modification, 8–11 blending modification, 12–14 grafting modification 15–17 and voltage stabilizer modification 18–21 . Since high‐voltage power cable insulation materials require high purity, the easy‐to‐introduce impurities blending modification method is rarely used.…”

Polystyrene: A Self-Dispersing, Ultralow Loading Additive for Improving the Breakdown Strength of Polypropylene for High Voltage Power Cable Applications

“…17,18 In particular, VSs with benzene derivatives have been found to facilitate the increase of the insulation properties such as volume resistivity and BD strength (BDS) because the benzene ring with delocalized electrons can capture high-energy electrons, thereby inhibiting the impact on polymer molecules. 19,20 Most previous works have utilized aromatic small molecules with benzene derivatives, which could be incorporated into the polymer matrix through physical addition or chemical grafting with the PP matrix. 21,22 However, the physically mixed small molecules are quite volatile, and the chemical grafting requires a quite complicated procedure based on a wet chemical reaction.…”

“…A variety of inorganic nanoparticles (NPs), especially oxide NPs, such as SiO 2 , Al 2 O 3 , TiO 2 , MgO, ZnO, and ZrO, have been widely studied, and the electrical durability could be improved by the addition of a small amount of such NPs that act as trapping sites for charge carriers to lower their mobility. − Nevertheless, there are still many challenges for the use of inorganic NPs because their high surface energy makes them prone to agglomerate, giving rise to poor dispersion in the polymer matrix . Recently, organic additives have attracted much attention as voltage stabilizers (VSs) for PP materials due to their good compatibility with the PP matrix, allowing better dispersion than inorganic additives as well as efficiency in improving electrical durability, even at lower additive levels. , In particular, VSs with benzene derivatives have been found to facilitate the increase of the insulation properties such as volume resistivity and BD strength (BDS) because the benzene ring with delocalized electrons can capture high-energy electrons, thereby inhibiting the impact on polymer molecules. , Most previous works have utilized aromatic small molecules with benzene derivatives, which could be incorporated into the polymer matrix through physical addition or chemical grafting with the PP matrix. , However, the physically mixed small molecules are quite volatile, and the chemical grafting requires a quite complicated procedure based on a wet chemical reaction. , Although one can expect that the polymeric materials would be potential additives to replace such small molecules, only few results on several polymers with aromatic conjugation, such as polypyrrole and poly­(3-hexylthiophene), have been reported and particularly rarely studied for a PP matrix. ,, …”

Invariant electrical conductivity upon thermal ageing of a crosslinked copolymer blend for high voltage insulation

“…XLPE based insulating materials feature a low direct current (DC) electrical conductivity of s DC E 2 Â 10 À14 S m À1 at 70 1Ca typical cable operating temperature -and an electric field exposure of up to 20 kV mm À1 . 5,6 The insulating properties can be improved further by adding conductivity reducing additives, such as metal oxide nanoparticles, [7][8][9] conjugated polymers 10 and aromatic voltage stabilisers, [11][12][13] as well as a small amount of high-density polyethylene. 14 XLPE based insulation materials are obtained by radical crosslinking of low-density polyethylene (LDPE) using peroxides such as dicumyl peroxide (DCP).…”