The dielectric response of polyimide to combined radiation, vacuum and thermal aging

Kapton (polyimide) is a material which enjoys a wide usage in space and the present work involves a study of some aspects of its dielectric behaviour after it has been subjected to an aging regime involving electromagnetic radiation, vacuum and temperature, these being some of the principle environmental conditions that materials on a space platform can experience. Following aging for a period of between six and eighteen months, test specimens were transferred to a space simulation chamber that provides an environment that can encompass high vacuum, temperature within the range 80-470 K and a /sup 60/Co gamma dose rate of 7.5 mGy/h at the specimens. Measurements were made of dielectric loss at low frequencies and pre-breakdown transient current pulses under direct stress. The results demonstrate that the different aging regimes produce different dielectric responses.