Investigation of temperature effects on voltage endurance for polyimide/Al2O3 nanodielectrics

In order to investigate the effects of inorganic nanofillers on the electrical properties of polyimide (PI), PI/Al₂O₃ nanocomposites films were prepared via the in-situ polymerization. The hybrids films were characterized by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The dielectric behaviors of pure PI and PI/Al2O3 samples were studied as a function of the measured frequencies and temperatures. Meanwhile, the breakdown strength of pure PI and PI/Al₂O₃samples measured at 25 and 230 °C was analyzed. The corona-resistant lifetime of samples under bipolar continuous square impulse voltage (BCSIV) was performed. With the wt% content of Al₂O₃ nanoparticles increasing, the real (ε\´) and imaginary (ε") of relative permittivity present an increasing tendency, while electrical breakdown strength declines obviously. The Al₂O₃ nanofillers improved the corona-resistant property of PI and the corona-resistant lifetime of PI/Al₂O₃ sample with 25 wt% (weight percent) of nano-Al₂O₃ particles is over 23 times longer than that of the pure PI film. Besides, the temperature is an important factor which would significantly influence the electrical properties of pure PI and PI/Al₂O₃ samples. The elevated temperature would reduce the breakdown voltage and corona-resistant property