Ground Testing of SCK5 White Silicone Paint for LEO Applications

Abstract

SCK5 is a white antistatic silicone paint developed by CNES and manufactured by MAP (France). The present work summarizes durability tests of this paint in a simulated low earth orbit (LEO) atomic oxygen (ATOX) environment. The paint was applied on various substrates including Kapton film, Duroid 5880 (a glass/Teflon PTFE composite) and TMM3 (a ceramic/thermoset polymer). Two types of ATOX simulation systems were used: an RF oxygen plasma, and a laser detonation source (manufactured by PSI) producing a 5 eV ATOX beam. Both types of simulation facilities generate VUV radiation in addition to oxygen species. Dedicated experiments were performed to distinguish between VUV and ATOX effects. The SCK5 coated samples were also exposed to RF argon plasma, in order to separate between chemical effects of atomic oxygen and physical effects introduced by the RF plasma.The effects of ATOX exposure were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). A comparative study of the erosion yield, the surface morphology and the chemical composition resulting from exposure to equivalent ATOX fluences in both types of simulation systems was performed.The SCK5 exposed to RF plasma showed significant cracking, partial delamination and enhanced embrittlement even for low ATOX fluence, equivalent to 2×1019 atoms/cm2. Similar exposures to the 5 eV ATOX (PSI source) exhibited no cracking. In both cases the exposed samples showed a decrease of the carbon atomic concentration and an increase of the oxygen concentration in the upper surface layer, indicating the formation of a silicon oxide skin, which was more significant for the samples exposed to the RF plasma asher. It may be concluded that the erosion of SCK5 by the RF oxygen plasma is considerably more severe than by the 5 eV ATOX, at least for the specific case of porous coating of siliconic material, tested in the present work.This is most probably associated with a combination of factors, including the nature of the reactive species in the plasma asher, their omnidirectional flux and the high porosity of SCK5 coating, leading to a strong compressive stresses and consequently cracking of the brittle silicon oxide skin.KeywordsMetal Oxide ParticlePTFE CompositeKapton FilmPlasma AfterglowEquivalent Atomic OxygenThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.