Thermal-oxidative aging and tribological properties of carbon nanotube/nitrile butadiene rubber composites with varying acrylonitrile content: Molecular dynamics simulations

Nitrile butadiene rubber (NBR), a common material used in the stator rubber of screw pumps, usually undergoes severe thermal-oxidative aging and wear at various temperatures and pressures. In this study, 1,2-dihydro-2,2,4-trimethylquinoline (antioxidant RD) and carbon nanotubes (CNTs) were introduced into NBR to improve its thermal-oxidative aging performance and reduce its wear. The thermal-oxidative aging and mechanical and tribological properties of NBR composites with acrylonitrile (ACN) contents of 28%, 33%, and 41% were investigated via molecular dynamics simulations, and the interaction mechanisms of four composites: RD/N28, CNT/RD/N28, CNT/RD/N33, and CNT/RD/N41, were investigated at the atomic level. A three-layer model (Fe-Composites-Fe) was developed to simulate the wear process of the composites. CNT/RD/N41 exhibited better thermal-oxidative aging and tribological properties than those exhibited by CNT/RD/N28 and CNT/RD/N33. This was attributed to an increase in the polar-polar interactions of the nitrile (CN) groups with an increasing ACN content. During friction, a larger frictional force existed between the CNT/RD/N41 molecules, which effectively maintained the stability of the matrix. This study provides a scientific reference for the preparation of high-performance NBR at the microscopic scale, which may extend the service life of screw pumps.