Electrical properties of polyimide with water absorption

The water content of polyimide film immersed in distilled water for 48 hours and dried was measured, as well as its thermal properties. The PEA method was then used to measure the space charge density after bias voltage was applied, and how the distribution changed. In measuring the water content, the longer the polyimide film dried, the more water content was lost, with hardly any change seen after 12 hours or more. In the measurement of thermal properties, the longer the polyimide film dried, the more water content it lost and the smaller the peak of thermal absorption. For the volume of space charge formed, the longer the polyimide film dried, the more difficult it became to put an electric charge into the specimen while the direct-current bias voltage was applied. This resulted in a smaller volume of space charge, which was closer to the space charge density of the specimen that was not immersed.