The atomic oxygen resistant study of a transparent polyimide film containing phosphorus and fluorine

Abstract

As ideal packaging materials for solar cells of low-Earth orbit (LEO) spacecraft, polyimide (PI) films have to withstand various harsh space environment. Here, we investigate the atomic oxygen (AO)-resistant property of a transparent PI film with side diphenylphosphine oxide and trifluoromethyl. After exposed under AO (1.3 × 1020 atoms·cm−2), most excellent properties of the PI film can be maintained except for partial loss of transmittance. Its erosion yield is 0.56 × 10−24 cm3·atom−1, only 18.7% as that of Kapton film at the same condition. To understand the damage mechanism, the surface and bulk performances of the AO exposed PI film were systematically investigated and compared with those of the prinstine PI film. The results indicate that the relative concentration of phosphorus and oxygen near to the AO exposed surface of the PI film increases, which means the formation of a phosphate passivation layer. The thickness of phosphate passivation layer is about 200 nm with the content of PO3− decreasing in vertical direction of itself, which can reduce the further erosion of the PI film by AO. Such PI films containing P and F are much more AO resistant and expected a candidate as packaging material for LEO spacecraft.