Degradation of polyimide material subjected to a simulated space environment

A series of TSDC spectra was obtained for polyimide which had been subjected to an ageing regime of gamma radiation and temperature under vacuum. The radiation doses, which were delivered at 1 kGy/h, were at a hi and lo level of 500 kGy and 50 kGy respectively and there were two different temperature scenarios which were applied over six months, one cycling with a 24 h period between room temperature and 425 K and the other constant at 425 K. The effects of the ageing were to alter the TSDC spectra from what was seen with fresh material. In general the ageing caused a reduction in the amplitude of the signal, with the hi radiation dose giving a greater signal than the lo and the constant elevated temperature giving a lower signal than the thermal cycling.< >