Research On Atomic Oxygen Protection Technology For Kapton And Silicone Rubber In Low Earth Orbit

Atomic oxygen（AO）with the strong oxidation and high energy is the dominant factor in the low earth orbit.Its reaction with the surface of the polymer can result in sever degradation of polymer,affecting their normal operation and reliability.In this study,sol-gel and wet chemical methods were employed to prepare inorganic protective coatings on the surfaces of Kapton or silicone rubber（SR）.Then the protective efficiency of inorganic coating was tested in a coaxial atomic oxygen simulation facility,besides,the micro-structural changes of the modified surface of polymer and the interface combination between the protective coating and substrate were also studied.The main contents and results are as follows:1.The study on the SiO₂ sol system: to obtain the optimal SiO₂ sol for coating,the influence of the amount of absolute alcohol,catalyst and aging temperature on the particle size and stability of system was studied mainly.The results indicted that: at the lower concentration,the system was relatively stable with smaller particle size and hard to gelation.The system catalyzed by acid generally had larger particle size,and poor stability,nearly gelation particle size rised significantly.While the system catalyzed by alkali in the same condition had smaller particle size,and it was more stable.Besides,the aging temperature also made a difference on the stability of the system,the stability of the acid catalyzed system decreased with the temperature increase.2.A surface modification of Kapton substrate: the alkali solution combined with the silica coupling agent were applied to modify the surface of Kapton,after modified the hydrophilicity of samples was raised obviously,an uniform,adherent and crack-free SnO₂/SiO₂ coating was successfully prepared on the surface of Kapton by using sol-gel process.After eroded by AO in a space environment simulator,the surface of the coatings was still uniform and compact,and the AO erosion yield of sample was sharply down,equivalent to only 4.1% of pristine Kapton,that means the property of AO resistance of the prepared coating was excellent.Meanwhile,SnO₂ also deposited on the Kapton to provided a barrier properties from ESC build-up.3.Study of cracking coating on silicone rubber（SR）: In this chapter,the cracking problem of protective coating on SR was studied from the substrate and surface modification process.The experiment results confirmed that the irregular cracks appeared on the modified SR surface before coating.These cracks were attributed to stress between the SR surface layer and the modified membranes.The bending distortion also aggravated the stress accumulation and caused more cracks.However,SR pretreated by organic solvents can ease the stress concentration and the cracks caused by the modification process and the coating process reduce greatly.4.AO resistance property of SiO₂ doped SR: In this chapter,the AO resistance of SR was improved by doping SiO₂ sol.The research results showed that SiO₂ sol in proper concentration could well dispersed in the non-vulcanized SR.After AO irradiation,the surface of doped SR was still smooth and compact compared with pristine SR,the cracks on the surface decreases greatly.Besides,the mechanical property of doped SR was also improved greatly.