Erosion of Kapton® H by hyperthermal atomic oxygen

Organic polymers are subject to erosion from ambient atomic oxygen in low Earth orbit. The linearity or the O-atom fluence dependence of Kapton(R) H erosion and the dependence of Kapton H erosion yield on surface temperature have been investigated. Sample exposures were performed with a pulsed beam containing hyperthermal O atoms that were generated with a laser detonation source. After exposure, samples were removed from the chamber in which the exposures were performed, and postexposure analyses were performed: etch depth (profilometry) and surface topography (atomic force microscopy). A systematic set of exposures, which eroded room-temperature Kapton H from 1.4 to 25 mu m, showed that the erosion yield or Kapton H is linearly dependent on O-atom fluence. This result helps validate the use of Kapton H mass loss (or erosion depth) as a linear measure of the O-atom fluence of a materials exposure. The erosion of Kapton H was strongly temperature dependent. At lower temperatures (<100 degrees C), the erosion yield appeared to be independent of sample temperature. However, above 100 degrees C, the erosion yield exhibited an Arrhenius-like temperature dependence, with an apparent activation energy of 0.31 eV. These observations suggest that O-atom-induced erosion of Kaplan H proceeds through direct, nonthermal, gas-surface reactions and through reactions that depend on surface temperature.