Synthesis and atomic oxygen erosion testing of space-survivable POSS (polyhedral oligomeric silsesquioxane) polyimides

The harsh environment present in both low-earth and geosynchronous orbit combined with the need for lighter weight and lower cost man-made orbiting bodies necessitates the design of multi-functional, space-survivable materials. Over the last two decades it has been well established that conventional polymers used in the construction of space vehicles undergo severe degradation resulting in reduced spacecraft lifetimes. In particular, the polyimide Kapton has been studied at length since it is widely used as a flexible substrate for lightweight high power solar arrays because of its inherent strength and desirable thermal properties. In addition to Kapton, thin films of fluorinated polymers such as Teflon FEP are used as the outer layer of multi-layer thermal control insulation because of their superior optical properties, including low solar absorptance and high thermal reflectance. These polymeric materials degrade because spacecraft surfaces must endure a high incident fluences of atomic oxygen (AO), bombardment by low and high-energy charged particles, and thermal cycling along with the full spectrum of solar radiation. Hybrid inorganic/organic polymers have the potential to meet the requirements of space-survivable materials by bridging the gap between ceramics and plastics, resulting in the prevention of AO and radiation damage that has hampered the widespread application of organic polymers in space. The Polymer Working Group at the Air Force Research Laboratory at Edwards AFB has incorporated inorganic POSS (Polyhedral Oligomeric Silsesquioxane) frameworks into traditional polymer systems resulting in hybrid POSS-polymers with dramatic property enhancements. Addition of these POSS nanostructured frameworks into polymers results in increased use and decomposition temperatures, improved mechanical properties, and oxidation resistance.