Analysis of atomic oxygen erosion resistance mechanism of polyimide composite materials enhanced by polyhydroxysilylazane

Polyimide (PI) has excellent insulating properties and is widely used in aerospace electrical transmission devices and equipment. Polysilazane coatings have demonstrated excellent resistance to reactive atomic oxygen (AO). However, the understanding of the atomic oxygen erosion mechanism for polymer materials mixed with polysilazane components remains limited. In this study, a cage-like polyhydroxysilylazane (PHSN) primarily composed of silicon and nitrogen was designed. Two PI/PHSN hybrid structures were established, and their resistance to AO erosion, reaction pathways, and surface separation products were explored through reactive molecular dynamics simulations. Density functional theory (DFT) was employed to analyze the molecular orbitals of PHSN at different stages, predicting possible reaction sites for AO. The natural binding of generated small molecular fragments to PHSN side chains was studied through binding energy, revealing the volatilization inhibition mechanism of these small molecular fragments. Results indicate that the added cage-like polyhydroxysilylazane enhances the polymer's resistance to AO erosion by absorbing AO and converting it into SiO2. This study explores the protective behavior of PHSN nano-cages at the molecular level, providing a new perspective for the design of AO erosion protection systems.