Mechanical and Tribological Properties of Nitrile Rubber Reinforced by Nano-SiO2: Molecular Dynamics Simulation

Abstract

This paper investigated the mechanism of enhancing the mechanical and tribological properties of nitrile rubber (NBR) via the addition of nano-SiO2 on the molecular scale. Molecular dynamics (MD) simulations were performed on molecular structure models of pure NBR, NBR/SiO2, and three-layer friction pairs. The results showed that the hydrogen bonds and interfacial interaction between nano-SiO2 and NBR molecular chains decreased the fractional free volume of NBR nanocomposites and increased the shear modulus of NBR by 25% compared with that of pure NBR. During the friction process, nano-SiO2 decreased the radius of gyration of NBR molecular chains and effectively lowered the peak atomic velocity, the peak temperature, and the peak friction stress at the interface between NBR and copper atoms. The average friction stress on NBR/SiO2 was 34% lower than that on NBR, which meant the tribological properties of NBR were significantly improved by nano-SiO2. The mechanism of nano-SiO2-reinforcing NBR on a molecular scale can lay a theoretical foundation for the design of water-lubricated rubber bearings.