Impacts of orientation temperature on the insulation properties of biaxial orientated polypropylene film

In recent years, the rapid development of the power grid has put forward higher requirements for power capacitors. As the core dielectric material of capacitors, the insulation performance of biaxially oriented polypropylene (BOPP) film directly determines the energy storage density and operational reliability of capacitors. This article selected the orientation temperatures of 150°C, 160°C and 170°C respectively, and three different BOPP films were obtained. The microstructure of BOPP film was achieved through polarized optical microscope observation, the polarized infrared testing, and the differential scanning calorimetry analysis. At the same time, DC breakdown tests were conducted on BOPP to obtain insulation properties of different sample. Furthermore, the influence of stretching temperature on the aggregated structure of BOPP film was obtained, and the correlation between microstructure and breakdown characteristics were established. The results indicated that the increased stretching temperature was beneficial for the ordered arrangement of molecular chains, but at the same time exacerbated the ordered arrangement of molecular chains. As a result, the rising orientation temperature made the migration of charge carriers much easier and reduced the breakdown strength in consequence.