Development of Space-Qualified Photocurable-Silsesquioxane-Coated Polyimide Films

Abstract

Silsesquioxane () has been researched as a potential atomic-oxygen protective-coating material for spacecraft applications. To this end, the present study focuses on the development of photocurable silsesquioxane ( series, manufactured by Toagosei Co., Ltd.) coating on polyimide base films. Photocurable silsesquioxanes “ series” are a new type of organic–inorganic hybrid materials that feature photoinitiated polymerizable groups (organic units) introduced into silsesquioxane frameworks (inorganic units) as multifunctional groups at an intramolecular level. This coating has the following excellent properties for use as a protective coating for space materials: 1) high atomic-oxygen tolerance, 2) high adhesion to substrate material (polyimide), 3) high transparency, 4) low outgassing and low recondensability, and 5) ease of handling. In a previous research, fundamental space-application data for two types of coatings have been presented. In this study, two types of space-qualified polyimide films have been selected, both of which were thick and aluminized on the rear. Roll-to-roll wet-coating technology has been adopted for this product with a width of 1 m. The -coated films thus obtained were evaluated for their resistance to space environmental factors, such as atomic oxygen, electron beam, and ultraviolet irradiations; thermal cycling; and high-temperature-vacuum conditions. The acquired outgassing properties complied with the American Society for Testing and Materials E 595 standard. Volume-resistivity data were also acquired. The results indicate excellent space environmental tolerance in the prepared coatings. Thus, the present study established a facile roll-to-roll wet-coating process for developing coating on two types of polyimide base films.