Phosphazene-based polymers as atomic oxygen resistant materials

Excerpt

Spacecraft materials in low earth orbit environment (LEO; 200–700 km) are subjected to the combined effects of thermal cycling, far ultraviolet radiation, hard vacuum, micrometeoroid and debris impact, charged particle bombardment, spacecraft charging and atomic oxygen (AO). Of these the dominant chemical constituent of LEO environment is AO formed by the photodissociation of molecular oxygen [1, 2]. AO causes erosion of polyimide films, advanced composites and engineering thermoplastic materials which are extensively used for the construction of satellites and space stations placed in LEO and hence, these materials need protection. Metal oxides, which have negligible erosion rates, can be used as AO resistant protective coatings for materials that are susceptible to AO attack. However, these coatings lack flexibility and are susceptible to pin hole defects and easily crack on thermal cycling due to thermal expansion mismatch of the coating and the substrate [1, 2]. To overcome the above problems, several inorganic and organometallic polymers are considered for AO resistant protective coatings and also as AO resistant material [3‐6]. …