Degradation behavior and mechanism of polyurethane coating for aerospace application under atmospheric conditions in South China Sea

The polyurethane coating for aerospace application was exposed to the marine atmospheric environment for different time period, and the degradation behavior and mechanism of the coating were evaluated by morphology, appearance, chemical changes, adhesion, barrier properties and thermal stability. The results revealed that the appearance of the polyurethane coating was quickly degraded in the early exposure stage, and then changed slowly in the late exposure stage. ATR-FTIR and XPS analysis demonstrated that ultraviolet radiation was an important cause of the rupture of chemical bonds, the chain scission of the polyurethane was dominated by the C-N bond rupture. There were good corresponding relationships between the adhesion and barrier properties of the coating during the degradation process. Furthermore, the thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis showed that the marine atmospheric environment obviously reduced the thermal stability of the coating.