Fabrication and Electrochromic Properties of Electrochromic Composite Materials

In modern power systems, the prolonged operation of high-voltage equipment results in surface charge accumulation on the insulation materials. Therefore, developing visual detection technologies suitable for high-voltage environments is critical for enabling real-time monitoring of insulation status. In this study, we fabricated viologen-doped composite insulators and films based on PVDF-HFP to achieve an electrochromic response under a high voltage. FTIR spectroscopy revealed a distinct absorption peak at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1630 ~\text{cm}^{-1}$</tex>, confirming the successful incorporation of viologen into the PVDF-HFP matrix. The developed composite insulator could withstand electric fields as high as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10^{6} ~\mathrm{V} / \mathrm{m}$</tex> and exhibited reversible color changes that were dependent on both applied voltage and duration. Notably, the material maintained dielectric properties comparable to pure PVDF-HFP (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\varepsilon}_{\mathbf{r}} \approx 10$</tex> at 50 Hz) while showing only a slight increase in dielectric loss (tan <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\delta}&lt;0.2$</tex>). This innovative approach successfully integrated dual functionality: reliable electrical insulation and intuitive visual state indication.