Electrical Behavior of PET Films Coated with Nanostructured Organic–Inorganic Hybrids

Hybrid coatings, based on poly(ethylene oxide) (PEO) or polycaprolactone (PCL) and silica (SiO2), at different organic-inorganic compositions have been used to coat PET films employed in the electric industry to produce capacitors. The overall electrical behavior of the coated films has been investigated. The electrical strength of the coated films increases up to 10-15% of the uncoated ones regardless of polymer type (PEO/PCL) and amount of inorganic phase, as far as the thickness of the coating is below 5 μm. A systematic increase of surface electrical conductivity is found in all coated samples which however still behave as insulators. Permittivity and loss factor also increase particularly at low frequencies (< 10 Hz) on account of the presence of ions deriving from the sol-gel process and on the presence of interfacial polarization probably related to the coatings nanostructurated morphology which leads to phase separation.