Abstract
The best commercial high-voltage insulation material of today is (crosslinked) ultra-pure low-density polyethylene (LDPE). A 100-fold decrease in electrical conductivity can be achieved by adding 1–3 wt.% of well-dispersed inorganic nanoparticles to the LDPE. One hypothesis is that the nanoparticle surfaces attract ions and polar molecules, thereby cleaning the surrounding polymer, and thus reducing the conductivity. LDPE-based nanocomposites with 1–12 wt.% octyl-coated aluminum oxide nanoparticles were prepared and the sorption and desorption of one polar compound (acetophenone, a crosslinking by-product) and one non-polar compound of a similar size (limonene) were examined. Since the uptake of acetophenone increased linearly with increasing filler content, whereas the uptake of limonene decreased, the surface attraction hypothesis was strengthened. The analytical functions for predicting composite solubility as a function of particle size and filler fraction were derived using experimental solubility measurements and Monte Carlo simulations.
Highlights
In order to transport renewable electrical energy across continents with tolerably low energy losses, the voltage levels for the generation of high-voltage direct-current (HVDC) cables must increase from today’s 640 kV to 1–2 MV
The solubility of acetophenone in low-density polyethylene (LDPE)-based nanocomposites was plotted as a function of nanoparticle content in Figure 3a, using desorption data taken at 21 ◦ C (Table 2)
A hypothesis is that ions polar molecules adsorb onto the nanoparticle surfaces, leading to the cleaning of the bulk of the and polar molecules adsorb onto the nanoparticle surfaces, leading to the cleaning of the bulk of polymer, and thereby decreasing the conductivity of the nanocomposite when compared to the pure the polymer, and thereby decreasing the conductivity of the when content compared
Summary
In order to transport renewable electrical energy across continents with tolerably low energy losses, the voltage levels for the generation of high-voltage direct-current (HVDC) cables must increase from today’s 640 kV to 1–2 MV To achieve this voltage increase, improved insulation materials must be developed. A higher thermal stability is achieved by crosslinking the polyethylene (XLPE), but chemical crosslinking with peroxides produces polar species (e.g., acetophenone, cumyl alcohol) which increase the electrical conductivity. 3 , MgO alcohol)polar and that selective(water, adsorption can beperoxide, achieved by coating the nanoparticle heptanecumyl can adsorb molecules dicumyl acetophenone and cumylsurface. A low electrical conductivity is a necessary condition for a good HVDC insulator material, but nanoparticles, but at a high. A low electrical conductivity a necessary condition forcompared a good HVDC material, but nanocomposites typically haveisimproved properties when to pureinsulator. Since the chemical structures and molar masses of limonene (136 g/mol) and acetophenone (120 g/mol) were comparable, the influence of polarity on diffusivity and solubility was expected to be comparatively easy to isolate
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