Water-Tree Resistant Characteristics of Crosslinker-Modified-SiO2/XLPE Nanocomposites

Abstract

Trimethylolpropane triacrylate (TMPTA) as a photoactive crosslinker is grafted onto hydrophobic nanosilica surface through click chemical reactions of mercapto double bonds to prepare the functionalized nanoparticles (TMPTA-s-SiO2), which are used to develop TMPTA-s-SiO2/XLPE nanocomposites with improvements in mechanical strength and electrical resistance. The expedited aging experiments of water-tree growth are performed with a water-knife electrode and analyzed in consistence with the mechanical performances evaluated by means of dynamic thermo-mechanical analysis (DMA) and tensile stress–strain characteristics. Due to the dense cross-linking network of polyethylene molecular chains formed on the TMPTA-modified surfaces of SiO2 nanofillers, TMPTA-s-SiO2 nanofillers are chemically introduced into XLPE matrix to acquire higher crosslinking degree and connection strength in the amorphous regions between polyethylene lamellae, accounting for the higher water-tree resistance and ameliorated mechanical performances, compared with pure XLPE and neat-SiO2/XLPE nanocomposite. Hydrophilic TMPTA molecules grafted on the nano-SiO2 surface can inhibit the condensation of water molecules into water micro-beads at insulation defects, thus attenuating the damage of water micro-beads to polyethylene configurations under alternating electric fields and thus restricting water-tree growth in amorphous regions. The intensified interfaces between TMPTA-s-SiO2 nanofillers and XLPE matrix limit the segment motions of polyethylene molecular chains and resist the diffusion of water molecules in XLPE amorphous regions, which further contributes to the excellent water-tree resistance of TMPTA-s-SiO2/XLPE nanocomposites.

Interfacial Click Chemistry Enabled Strong Adhesion toward Ultra‐Durable Crack‐Based Flexible Strain Sensors

“…Other interfacial chemistries in Figure S3a (Supporting Information), such as thiol/double bond click reaction and thiol/epoxy click reaction, have been well characterized, which are helpful for improving the interfacial adhesion. [31,32] Also, in addition to silane treatment of substrate, we also provided three surface modification methods including surface primer, polydopamine (PDA)-coating, and surface initiation to expand the universality of the strategy (Figure S3b, Supporting Information). Taking PDMS as an example, the surface primer method can cure the PDMS precursor with active functional groups (such as amino group, sulfhydryl group, and double bond) on the substrate in situ to obtain the surface with active functional groups.…”

Water-Tree Characteristics and Its Mechanical Mechanism of Crosslinked Polyethylene Grafted with Polar-Group Molecules

“…It has been reported that the larger size and fewer grains of XLPE spherulites conduce to a higher speed of water-tree propagation [ 14 ]. Employing elastomer (SEBS and EVA), inorganic nanofiller (nano MgO) or auxiliary crosslinker (HAV2) for XLPE modifications can ameliorate crystallization morphology, increase crystallinity or crosslink-degree so as to improve water-tree resistance and electrical insulation performances of XLPE material [ 8 , 15 , 16 , 17 ].…”