Molecular Dynamic Simulation of Tribological Properties of Vulcanized Nitrile Rubber with Different Crosslinking Densities

Molecular dynamic tribological models for vulcanized nitrile rubber with different crosslinking densities (0.4, 0.8, 1.2, 1.6)-iron substrate were established, and then the effect of the crosslinking density on the friction coefficient, relative atomic concentration, friction interface temperature and mean square displacement of rubber molecular in shear friction were analyzed. The accuracy of the model was experimentally verified. The results show that with the increase of crosslinking density, the friction coefficient of the friction pair of vulcanized nitrile rubber-iron substrate increased; the change trend was consistent with the test results. Vulcanization cross-linking could effectively improve the stiffness between rubber molecules, and restrict the movement of molecular chains, resulting in a decrease in the relative atomic concentration at the friction interface and the mean square displacement of rubber molecules. The increase in the stiffness of the rubber molecular improved the relative displacement between the rubber matrix and the iron substrate, and the moving of iron substrate needed to overcome more atomic bonding; so the adhesion friction force increased, resulting in an increase in the friction coefficient of the friction interface. The increase in the relative displacement also led to more energy loss, making the friction interface generate more heat; so the temperature of the friction interface rose.