The Insight On Erosion Mechanism Of Spacecraft Surface Material Kapton Exposed To Atomic Oxygen

Low earth orbit?LEO?is the most important place for human to develop and utilize.The largest component of the atmosphere in LEO is atomic oxygen?AO?.When the spacecraft is operating at a high speed,the impact energy of AO is sufficient to cause mass loss,surface erosion and performance degradation of the polymer material on the spacecraft.Kapton is a kind of polyimide material produced by DuPont of the United States.It has excellent chemical stability,wear resistance,high temperature resistance and electrical insulation,so it is widely used in the aerospace field.In recent years,the research on the erosion of Kapton exposed to AO has received extensive attention.Many researchers have conducted experimental research,but the detailed erosion mechanism is poorly understood.The erosion mechanism of Kapton exposed to atomic oxygen was studied by direct dynamics simulation.The results of the direct dynamics simulations can complement the theoretical vacancy in this area,providing a more comprehensive explanation of the experimental results and a theoretical guidance for the development of corrosion resistant materials.In this paper,the erosion mechanism of spacecraft material Kapton exposed to atomic oxygen was studied by direct dynamics simulation.At the collision energy of 4.0⁵.0eV,33 reaction paths were found and 14 reaction paths with higher probability are shown in detail.According to different products,14 reaction pathways can be divided into two categories,the first is the reaction of producing small molecules and free radicals,and the second is the atomic oxygen capture reaction.In the first type of reaction,CO₂ is the main product.In the second type of reaction,C=O bond,C-O-C bond,N-O bond,O-O bond and C-O-H bond are formed.At the same time,in order to better understand the changes of energy and structural parameter in the reaction paths,the transition state was studied in detail under the two methods of RM1 and B3LYP/6-31+G**.Transition states of the four reaction paths are found.According to the energy calculations,these four reactions are all exothermic reactions,indicating that these reaction paths are thermodynamically feasible.Many scientists have studied the erosion effect of atomic oxygen on Kapton through underground experiments.The results showed that the carbonyl in Kapton was attacked by atomic oxygen to form CO₂ and CO.And the C=O bond,C-O-C bond and O=C-N bond could be formed during the exposure to atomic oxygen.In the direct dynamics simulations,there are also trajectories for generating CO and forming O=C-N bond.It can be seen that the results of the direct dynamics simulations are basically matched with the experimental results.However,some dynamics simulation results have not been found in current experiments.These reaction paths are expected to provide a theoretical basis for the erosion of Kapton exposed to atomic oxygen under future laboratory conditions.