Dielectric strength and aging performance of polybutylene terephthalate (PBT) under the influence of temperature and humidity

In the present study, the breakdown and aging performance of two PBT materials at different environmental conditions are under investigation. For this purpose, the electrical short-term strength is determined for AC and DC with two different voltage slopes (0,2 kV/s, 2 kV/s). Starting from the dielectric strengths with slow voltage increase, levels for long-term stress were selected. Afterwards, aging investigations under T = 25 ℃, H = 50% relative humidity (r. h.) and T = 85 ℃, H = 85% r. h., took place. The results show clear differences in the short-term and long-term electrical strength of both materials, although they have a nominal identical material composition (glass fibers, flame retardants, etc.). By analyzing the lifetime characteristics, either of both materials shows a significantly better behavior.