Large-Area Flexible Plasma-Polymerized HDMSO Thin-Film Coating for Low-Earth-Orbit Spacecraft Polymers: Excellent Resistance to Atomic Oxygen and UV Erosion

Abstract

It is essential to prepare ultrathin, flexible, and dense coatings with excellent resistance to atomic oxygen (AO) and ultraviolet (UV) erosion on large areas of organic materials on spacecraft surfaces in low Earth orbit. In this paper, a dense plasma-polymerized hexamethyldisiloxane (ppHMDSO) coating with a thickness of about 400 nm and a surface roughness of 0.31 nm was prepared on polyimide surfaces with a width of more than 1000 mm using roll-to-roll compatible PECVD. The synergistic effect and erosion mechanism of AO and UV on the chemical components and structure, erosion depth, morphology, and mass loss of ppHMDSO coatings were revealed by AO and UV exposure experiments, both individually and simultaneously. The results showed that the synergistic effect of AO and UV exacerbated the decarburization and inorganic SiO 2 formation process of the organosilicon coatings, which was attributed to the UV radiation promoting molecular activation and chemical bond breaking and formation. At the same time, the synergistic enhancement between AO and UV promoted the AO erosion depth of the coating and increased the surface roughness. However, no cracks or holes occurred on the surface of the coatings after simultaneous exposure to both AO and UV for 200 h (total AO fluence was 1.12 × 10 22 atoms cm –2, equivalent to 3 years of AO exposure at 400 km circular orbit), and only a slight thinning of the coating thickness was observed. The corresponding AO erosion yield was 9.98 × 10 –27 cm 3 ·atom –1, which is only 0.33% of that of Kapton H. This indicates that although the synergistic effect of AO and UV promotes the degradation and oxidation of the organic components in the coating, the ppHDMSO coating can still effectively protect the Kapton substrate from AO and UV attack in the long term.

Topics & Concepts