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. 2021 Mar 13;14(6):1398.
doi: 10.3390/ma14061398.

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

Yong-Qi Zhang  1 , Xuan Wang  1 , Ping-Lan Yu  2 , Wei-Feng Sun  1
Affiliations

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

Yong-Qi Zhang et al. Materials (Basel). .

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.

Keywords: auxiliary crosslinker; crosslinked polyethylene; dynamic thermo-mechanical analysis; nanodielectrics; water tree growth.

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Conflict of interest statement

Authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic reactions of TMATA grafting onto nanosilica surface.
Figure 2
Figure 2
Schematic water-tree aging experiment with water-knife electrode method.
Figure 3
Figure 3
(a) Hydrogen nuclear magnetic spectrum of MTMPTA and (b) infrared transmission spectra of MPTMS, SiO2 nanoparticles, TMPTA, and TMPTA-s-SiO2 nanoparticles.
Figure 4
Figure 4
Thermogravimetric curves of TMPTA-s-SiO2 nanoparticles which have been prepared by adopting different contents of MTMPTA.
Figure 5
Figure 5
Cross-sectional SEM images: (a) 0.5wt%TMPTA-s-SiO2/XLPE, (b) 1.5wt%TMPTA-s-SiO2/XLPE and (c) 1.5wt%SiO2/XLPE nanocomposites.
Figure 6
Figure 6
Water-tree morphology: (a) XLPE, (b) 0.5 wt%TMPTA-s-SiO2/XLPE, (c) 1.5 wt%TMPTA-s-SiO2/XLPE, (d) 1.5 wt% SiO2/XLPE.
Figure 7
Figure 7
Water-tree characteristic (a) length and (b) width fitted in 2-parameter Weibull statistics.
Figure 8
Figure 8
Schematic mechanism of water micro-beads impacting on amorphous regions under AC electric field in XLPE (top panel) and TMPTA-s-SiO2/XLPE nanocomposite (bottom panel).
Figure 9
Figure 9
Dynamic thermo-mechanical spectra: (a) storage modulus, (b) loss modulus (c) loss factor, and (d) stress-strain characteristics of XLPE and its nanocomposites.
See this image and copyright information in PMC

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