Characterization of polybenzimidazole (PBI) film at high temperatures

Polybenzimidazole, a linear thermoplastic polymer with excellent thermal stability and strength retention over a wide range of temperatures, was evaluated for its potential use as the main dielectric in high-temperature capacitors. The film was characterized in terms of its dielectric properties in a frequency range of 50 Hz to 100 kHz. These properties, which included the dielectric constant and dielectric loss, were also obtained in a temperature range from 20°C to 300°C with an electrical stress of 60 Hz, 50 V/mil. The AC and DC breakdown voltages of silicone oil-impregnated films as a function of temperature were also determined. The results obtained indicate that, while the film remained relatively stable up to 200°C, it exhibited an increase in its dielectric properties as the temperature was raised to 300°C. It was also found that conditioning of the film by heat treatment at 60°C for 6 h tends to improve its dielectric and breakdown properties