Anti-atomic Oxygen Modification Of Polyimide And Design & Simulation Of Scratch-resistant Protective Layer

With the continuous development of my country's aerospace technology,more and more spacecraft are operating in LEO orbit.A large amount of atomic oxygen(AO)existing in LEO orbit has a strong erosive effect on the polymer materials on the surface of the spacecraft.Polyimide has excellent mechanical properties,optical and thermal properties,and chemical stability.It is widely used in the aerospace and aviation fields and is irreplaceable.Because of the existence of AO in LEO that poses a serious threat to spacecraft,all countries are committed to improving the anti-AO performance of polyimide materials.At the same time,considering that the polyimide film is prone to scratches and scratches during transportation and assembly,it is necessary to carry out scratch resistance treatment.In this paper,the surface of the polyimide film is modified by photoactivated silanization process,and the preparation of modified polyimide is studied from the aspects of optical properties,surface morphology,chemical composition,etc.,and the polyimide before and after modification An atomic oxygen exposure experiment was conducted to test the modified polyimide antigenic oxygen capacity.In order to protect the modified layer,the POSS/PDMS system was introduced to use Materials Studio software for molecular dynamics simulation.Different types and ratios of POSS/PDMS system were selected for AO erosion simulation and mechanical performance simulation.From the mass change curve,damage propagation depth and Research on the comparison of mechanical properties,etc.,select the system with the closest performance to polyimide for experimental verification.The research results show that the modified polyimide film prepared by the photoactivated silylation process has improved optical performance and surface quality compared with the original polyimide,and the content of Si and O elements changes continuously,that is,the modified layer is infiltration Growth and epitaxy without changing the original optical,thermal,electrical and mechanical properties of the substrate.There is no interface with the substrate,and it has excellent antigenic oxygen performance,which is 35 times higher than the original polyimide.In order to protect the antigenic oxygen modified layer and improve the scratch resistance of the modified layer,molecular dynamics simulation was used to build a scratch resistant protective layer with different types of POSS and PDMS.The Reax FF force field was used to conduct an atomic oxygen erosion simulation experiment on 8 composite systems composed of POSS and PDMS.The analysis results showed that the POSS-1 system(POSS-1: PDMS=100: 3 and POSS-1: PDMS=100: 6)The ability to resist AO erosion is the best.Carry out mechanical performance simulation(tensile test,nano-indentation experiment and mechanical performance simulation calculation)for each system.The analysis results show that the mechanical performance of system seven(POSS-4:PDMS=100:3)is the best match with polyimide.Using POSS-4(GPOSS),PDMS,photoinitiator,butyl acetate,acetonitrile and propylene carbonate and other reagents,using ultraviolet curing method to prepare the protective layer.Bending test and scratch test results show that the protective layer is well combined with the modified PI.Under the condition of radius of curvature of 10 mm,there is no cracking and peeling,and the surface hardness reaches 7H,which has good bending resistance and scratch resistance.