Poss Nanocomposites: Investigating the Dielectric Properties for Insulation Applications

The demand for polymeric insulating materials with enhanced dielectric properties is growing in industries such as power transmission, aerospace engineering, and electric vehicles. However, identifying an optimal insulating polymer remains challenging due to material limitations and varying application requirements. High-temperature superconductor (HTS) power transmission, which operates under cryogenic conditions, poses a unique challenge, as insulating layers can become brittle at low temperatures, leading to structural failures and electrical leakage. To address this, a novel polymer-based nanocomposite was developed using polyamic acid (PAA) as the host polymer and 1 wt.% OctaVinyl-substituted polyhedral oligomeric silsesquioxane (POSS) as the nanofillers. A comparable composite of PAA with sol-gel-generated silicon dioxide (SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>) nanoparticles served as a control. The PAA/POSS samples were processed under a nitrogen environment using tetrahydrofuran (THF) as the primary solvent for uniform POSS dispersion. Dielectric performances of both nanocomposites were evaluated through alternating current (AC) and direct current (DC) breakdown tests at room temperature, followed by post-breakdown characterization using scanning electron microscopy (SEM). The PAA/POSS films exhibited superior dielectric strengths of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$100.97 \text{kV} / \text{mm}$</tex> (AC) and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$155.89 \text{kV} / \text{mm}$</tex> (DC), outperforming the PAA-SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> films, which achieved <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$78.31 \text{kV} / \text{mm}$</tex> (AC) and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$101.81 \text{kV} / \text{mm}$</tex> (DC). This enhancement is attributed to strong interactions between the cage-like silicon structure of OctaVinyl POSS and the PAA matrix. Given these promising results at room temperature, future research will expand the dielectric property investigations of PAA/POSS nanocomposites to cryogenic conditions similar to those used in HTS cable operations.