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

Abstract

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.

Bionic ordered structured hydrogels: structure types, design strategies, optimization mechanism of mechanical properties and applications

“…112,184,185,187 This can be achieved by constructing ordered double network hydrogels, 20 introducing metal ions for coordination (Fig. 5A), 172 adding SiO 2 nanoparticles 188 and other methods. These techniques can increase the crosslinking density either directly or indirectly in the bionic ordered structured hydrogels.…”

Dielectric Characteristics of Crosslinked Polyethylene Modified by Grafting Polar-Group Molecules

“…Graft modification is a molecular-level technology of chemically introducing specific functional groups into polymer backbone to promote intrinsic electrical properties of insulation materials used for fabricating HV power cables. Organic compounds with polar groups, such as carbonyl (C=O), used for graft modifications, are competent in reducing charge carrier mobility, ameliorating space charge characteristics, and acting as inhomogeneous nucleation centers to increase polyethylene spherulite density, which account for the holistic improvements in electric-tree resistant performance, insulation strength, and water-tree aging resistance, respectively [ 29 , 30 , 31 , 32 , 33 ]. It is a comprehensive scheme of suppressing the space charge accumulations and enhancing electric resistance of ethylene/α-alkenes copolymers by chemically introducing polar groups, such as ethyl, hydroxyl, nitro, cyanyl, or aromatic ring to improve the electrical performances of power cables under a polar reversal.…”

The synthesis and characterization of polyorganosiloxane nanoparticles from 3-mercaptopropyltrimethoxysilane for preparation of nanocomposite films via photoinitiated thiol-ene polymerization

“…This desirable method of covalently bonding nanoparticles to the polymer matrix prevents the phase separation and particle agglomeration. Moreover, this opportunity contributes greatly to the production of highperformance materials [18][19][20][21][22].In recent decades, most composite materials used in polymer industry contain special resins based on dimethacrylates. Bisphenol A glycerolate dimethacrylate is one of the commonly used dimethacrylate monomers with reinforcing fillers…”

“…This desirable method of covalently bonding nanoparticles to the polymer matrix prevents the phase separation and particle agglomeration. Moreover, this opportunity contributes greatly to the production of highperformance materials [18][19][20][21][22].…”