Kazuki Yukumatsu1,Shogo Yamane2,Yuki Horiuchi2,Junji Mizukado2,Hideaki Hagihara2,Yugo Kimoto1
Japan Aerospace Exploration Agency1,National Institute of Advanced Industrial Science and Technology2
Kazuki Yukumatsu1,Shogo Yamane2,Yuki Horiuchi2,Junji Mizukado2,Hideaki Hagihara2,Yugo Kimoto1
Japan Aerospace Exploration Agency1,National Institute of Advanced Industrial Science and Technology2
Polymeric materials are often used as thermal control materials in spacecraft. Many polymeric materials discolored under ultraviolet (UV) irradiation, which changed their solar absorptance affecting the thermal design of spacecraft. For this reason, many ground experiments have been performed to evaluate the solar absorptances during the end of life (EOL) of the spacecraft mission. However, it takes a long time to irradiate the same amount of UV fluence as the actual mission period, and it is difficult to perfectly simulate the UV irradiation conditions such as thermal cycle. Therefore, it is important to study the prediction of the solar absorptance after UV irradiation.<br/>This study aims to quantitatively understand the correlation between the changes in the chemical structures and solar absorptances to make a prediction technique. In this presentation, we report the results of UV irradiation experiments focusing on the presence of oxygen, which has a significant effect on the degradation mechanism of the polymeric materials. We primarily focused on the polyetherimide film which is a relatively transparent material having a good tolerance to the radiation. The surface analysis used by X-ray photoelectron spectroscopy (XPS) and Fourier Transfer Infrared Spectroscopy (FTIR) were performed. We also measured the solar absorptance by a UV-Vis-NIR spectrometer. As a result, the irradiated samples in the air were observed the structure after oxidative deterioration. On the other hand, the irradiated sample in vacuum were not observed such structures. The solar absorptances of the irradiated samples in air were larger than the samples in vacuum. In vacuum, the solar absorptances of samples were not saturated at a maximum of 600 ESD. Moreover, the dependency of the sample temperature in vacuum UV irradiation condition was evaluated, and same analysis was conducted.<br/>Finally, we will discuss the degradation mechanisms based on the surface structure analysis of each of these materials, and the prediction method of solar absorptances.