Recovery of radiation-induced coloration on various polyimides

The polyimide films are colored by radiation exposure. The color of irradiated films, however, fades with the exposure time in air. This discoloration obscures the accurate evaluation of degradation in ground-simulation tests. Therefore, we experimentally clarified the discoloration behaviors for the post-irradiation sample in air. There was a difference in the time constant of air recovery among the three types of polyimides. The recovery behavior depended on the type and thickness of the polyimide. In addition to these, it would be deduced that the behavior of color fading depends on the uniformity of degradation. If the coloration immediately after irradiation is needed to evaluate the degradation, it is necessary to know the recovery behavior on each type and thickness of polymer because the order of radiation resistance varies depending upon the length of time that has elapsed since the air exposure of irradiated sample.