MEV PROTON IRRADIATIONS AND ATOMIC OXYGEN EXPOSURE OF SPACECRAFT MATERIALS WITH SIO2 PROTECTIVE COATINGS

Polymeric materials used for the construction of spacecraft include po lymer-matrix composites for structural components, and backface-metall ized plastic films such as DuPont Kapton(TM) H polyimide, and Teflon(T M) FEP fluoropolymer, as thermal control materials. In orbital space-f light, these polymers encounter a very destructive environment compris ing ionizing radiation (keV electrons, MeV protons), ultraviolet photo ns, and hyperthermal atomic oxygen (AO), Therefore, the exposed surfac es of these polymers need to be protected by thin inorganic coatings, such as SiO2. We report preliminary research results on possible syner gistic effects of exposing SiO2-coated polymers, first to MeV proton i rradiation, then followed by high fluences of AO. The coatings, less t han or equal to 0.5 mu m thick, are applied by dual-frequency (MW/RF) plasma-enhanced CVD (PECVD). Samples of Kapton and Teflon were irradia ted with 1-, and 20-year equivalent doses of 1 MeV protons (approximat e to 6.5, and 130 kGy, respectively), followed by greater than or equa l to 10(21) O atoms/cm(2). Irradiation effects are assessed by compari son with witness samples on the basis of microscopy and mechanical pro perty measurements.