Paper TF-TuP19
Protecting Polymers from the Natural Space Environment with Films Grown Using Atomic Layer Deposition

Tuesday, October 19, 2010, 6:00 pm, Room Southwest Exhibit Hall

Polymers used on spacecraft are subjected to various threats including hyperthermal oxygen atoms, UV and VUV photons, and ions. These threats can degrade the polymer and lead to static charge accumulation. Nanometer thick inorganic films grown by atomic layer deposition (ALD) can protect polymers including Kapton, Teflon, and PMMA. We are developing multifunctional multilayer ALD films incorporating Al₂O₃ layers for preventing oxygen atom erosion, TiO₂ to minimize UV/VUV radiation damage, and ZnO to dissipate static charge. Such ALD-coated polymeric films are currently being tested in low Earth orbit on the International Space Station on MISSE-7b. In the laboratory, we are further exploring the mechanisms of polymer degradation by atomic oxygen and VUV radiation, as well as the cracking of inorganic films on polymers resulting from different thermal expansion coefficients. Field emission scanning electron microscopy images and profilometry measurements revealed that Kapton H samples coated with 25 ALD cycles (~3 nm) of Al₂O₃ completely resisted atomic oxygen erosion. Quartz crystal microbalance measurements of TiO₂ films deposited on PMMA substrates with an Al₂O₃ interfacial adhesion layer showed that 100 cycles (~6.2 nm) of TiO₂ resisted PMMA degradation upon VUV exposure. Mass losses of VUV-exposed PMMA samples coated with similar overall bilayer thicknesses but different Al₂O₃ thicknesses were compared to decouple the role of the overall Al₂O₃/TiO₂ bilayer coating acting as a physical barrier from the role of TiO₂ acting as a VUV filter.