Tribological mechanism based on tribo-chemistry and molecular dynamics of polyurea/polyimide shape memory copolymers at high temperature

Exploring the tribological mechanism of the shape memory polymers plays an important role in designing intelligent lubricating materials. Here, a series of shape memory polyurea (PUA)/polyimide (PI) were prepared and their tribological performance were investigated. The result showed that the friction and wear of PUA/PI were higher at shape memory transition temperature (Ttrans) than at 200 degree celsius and room temperature (RT). However, introducing PUA units into PI enhanced its shape memory stability and tribological performance. SEM and XPS analysis revealed that introducing PUA promoted the formation of polymer-based tribofilm. Molecular dynamics simulations further illustrated that the high relative atomic concentration of PUA/6PI at the sliding interface improves the bonding between the tribofilm and the counterpart, thereby improving overall tribological performance.