Atomic Oxygen Erosion Effect Analysis And Protective Coatings Study On Kapton Materials

In low earth orbit （LEO）, atomic oxygen （AO） is considered to be one of the mostsevere hazards to the spacecraft exterior. High energy atomic oxygen attacks spacecraftsurface, can cause severe damages of Kapton, such as irreversible degradation of optical,electric, thermal and mechanical properties. Therefore, systematically analyzing of atomicoxygen erosion effects and studying the mechanism are of great significance for spaceprotection of Kapton materials. Preparing SiO_xcoatings on the surface of materials is oneof the most commonly used methods to improve the atomic oxygen erosion resistance ofKapton materials. However, the instability of adhesive bonding at the interface betweenthe hydrophilic coating and the hydrophobic Kapton surface is a problem to be solved.Then research on adhesive bonding is discussed, atomic oxygen protective technology ofspace materials in severe LEO environment is summarized. Then different protectingcoatings are prepared on Kapton substrate by hydrothermal, solvothermal and plasmapolymerized methods, the atomic oxygen erosion resistance of coatings is evaluated inatomic oxygen ground-based simulation facility. Main results are as follows:（1） AO erosion effect analysis of Kapton surface: SEM, FTIR and UV-Vis analysisresults show that when high active and high energy atomic oxygen attacks theKapton substrate surface, ether bond and C-N bond of Kapton molecular willreact with AO easily. The reactions cause the scission of chain and result in massloss, the increase of surface roughness and the decrease of transmittance.（2） The surface modification of Kapton substrate by hydrothermal method: Theresults show that the hydrophilicity of Kapton is significantly enhanced aftertreated by hydrothermal method, and the adhesion between SiO₂coating andKapton substrate is significantly improved. It is easy to form a uniform andcompact film on the Kapton by either acid sol or base sol. AO irradiation testshows that SiO₂coating has good AO erosion resistance.（3） Preparation of SiO₂coatings by solvothermal and sol-gel method: Different silane coupling agents are used to improve the hydrophilicity of Kapton undersolvothermal condition, then dimethoxydimethysilane （DMDMS） andtetraethoxysilane are chosen as precursors to prepare an organic-inorganicintermediate layer, and finally SiO₂coatings is prepared on the substrate bysol-gel method. The results show that the hydrophilicity of Kapton is significantlyimproved after treated by solvothermal method; the intermediate layer markedlyimproves the cracking phenomenon of inorganic coating in the thermal cycleprocess. The coatings prepared by solvothermal and sol-gel methods possessexcellent AO erosion resistance. After AO exposure the coatings become moreuniform and smoother, no cracks and voids are observed on the surface of thesamples.（4） Deposition of SiO_xcoatings by plasma polymerized method: using gradientdeposition method, from polymer deposition gradually transition to inorganicdeposition, uniform and compact SiO_xcoatings are prepared on Kapton. Thesecoatings not only improve the shortage of traditional inorganic coating such aspoor flexibility, easy to crack; but also overcome the weakness of pureorganosilicone coating such as weak AO erosion resistance. During AO exposure,the organic composition on the coating surface is further oxidized, generatinginorganic silicon oxide and forming porous network structure. This structure isnot easy to react with AO, thus reducing the probability of AO deep erosion onKapton, so the AO erosion resistance of Kapton improves largely.