Study On Corrosion Mechanism Of Atomic Oxygen To Polymer And Protection Of The Polymer Materials

Atomic oxygen?AO?is the most abundant components in the low earth orbit?LEO?space environment.Atomic oxygen may cause serious impact on the operation of spacecrafts in the LEO.The high temperature oxidation and high speed attack of atomic oxygen would cause serious erosion and even stripping of the most polymer materials used on the surface of spacecrafts,leading to the loss of the mass,the degradation of the electrical,optical and mechanical properties and so on,bring serious threat for the life of the spacecrafts and the execution of space missions.Based on above reasons,starting from the improvement of the atomic oxygen erosion resistance of polymers,the atomic oxygen erosion process and its mechanism were investigated systematically.Using the combination of low concentration of alkali solution under hydrothermal process and the solventhermal process to modify the Kapton surface.The SiOx coating on the surface of Kapton is prepared via sol-gel method.Different polyhedral oligomeric silsesquioxanes?POSS?materials were synthesized and the use of POSS materials in preparation of coating on Kapton surface and the method to use it to modify silicone rubber were explored.Different samples are tesed in the atomic oxygen ground-based simulation device to assess the resistance ability of atomic oxygen erosion.Main research conclusions are as follows:?1?The AO erosion effect analysis of Kapton and silicone rubber: The results show that AO can cause significant influence on the properties of Kapton and silicone rubber.After AO irradiation,Kapton presented a significantly “carpet-like” morphology,the optical transmittance and contact angle are decreased.The interaction between AO and silicon rubber causes cracks on the surface,as well as the decrease of the optical transmittance.After AO irradiation,the main effect is a decrease in carbon atomic concentration together with a increase in silicon and oxygen atomic concentrations.The mass loss of the both polymer materials is mainly due to the destruction of molecular?2?structure when high energy and active atomic oxygen attacks the polymers' surface,which cause the formation of volatile substances?H₂,H₂ O,CO,CO2,etc.?and material wastage.?3?Surface modification of Kapton by alkali solution and its applications to AO protective coating.The results show that the optimal concentration of NaOH under hydrothermal condition to modify Kapton surface was 0.05 mol L-1.Combination of 0.05 mol L-1NaOH with ?-aminopropyltriethoxysilane?APTES?under solvothermal process is an effective surface modification method to improve the adhesion between the SiOx coating and Kapton substrates.Si Ox coating is successfully prepared on the surface of Kapton.After AO exposure,the SiOx coating becomes more uniform,without microcracks and spalling.The results indicate that Si Ox coating can significantly improve the AO resistance ability of Kapton.?4?Different POSS materials are synthesized.Me-POSS and NH₂-POSS are synthesized successfully.The structure and hydrophilicity of POSS are characterized by the infrared spectrum and contact angle measurement instruments.The experiment results show that Me-POSS has strong hydrophobicity while NH₂-POSS has good hydrophilicity.?5?Different POSS coatings are prepared on the surface of Kapton surface.The results show that the Me-POSS can't form a uniform and continuous coating on the surface of Kapton,the coating has strong hydrophobicity.On the contrary,NH₂-POSS can form a continuous,uniform coating on the surface of Kapton,and the coating shows strong hydrophilicity.Compared with pristine Kapton,the optical transmittance of POSS coated Kapton is generally reduced.?6?Modified vulcanized silicone rubber is prepared by physical blending using Me-POSS as filler.The AO resistance ability and erosion mechanism of Me-POSS modified silicone rubber are explored.The results show that adding Me-POSS can change the mechanical properties of the silicone rubber.Cracks appear on the surface of Me-POSS modified silicone rubber and the optical transmittance of Me-POSS modified silicone ruberally increased after AO exposure.Besides,the mass loss of Me-POSS?7?modified silicone rubber increases slightly compared with pristine silicone rubber.It shows that we should improve the preparation and post-processing methods of the materials in the next step.This article lays the foundation for the further research in the future.