Thermal and UV Degradation of Polymer Films Studied In situ with ESR Spectroscopy

Thermal and UV degradation of four common space-grade polymer films have been studied in situ using electron spin resonance (ESR) spectroscopy. By recording subsequent spectra at a sufficient rate, the time dependence of the radical concentration could be followed, allowing more detailed study of the kinetics of the degradation process. The thermal degradation was found to consist of two main processes, one being a stabilization process and the other the actual degradation, whereas the UV experiments showed biexponential degradation kinetics. Additionally, to compare in situ and ex situ experiments, we monitored the stability of the generated radicals after the exposure. The radical concentration decreased only slightly when samples were stored in a vacuum, whereas storage in air led to a significant loss of radicals.