Effects of carbon nanotubes functionalization on mechanical and tribological properties of nitrile rubber nanocomposites: Molecular dynamics simulations

Abstract In this research, the effects of the functional group type, degree of sidewall functionalization, and different amido-amines modification of carbon nanotubes (CNTs) on the mechanical and tribological properties of nitrile rubber (NBR)/CNT nanocomposites were comprehensively studied using molecular dynamics (MD) simulations. The Young’s modulus, shear modulus, and bulk modulus of the nanocomposites were estimated by the constant strain method. Three-layer friction models were established to study the coefficient of friction and abrasion rate of CNT/NBR composites under a normal loading. It is found that among these different surface-modified CNTs (i.e., carboxyl, hydrazide, and ethylenediamine), the amide-functionalized CNT behaves the best reinforcing efficiency on the mechanical and tribological capacities of NBR nanocomposites due to the formation of strong dipole–dipole interactions, hydrogen bonding interactions, van der Waals (vdW) interactions, and good interfacial compatibility between CNTs and NBR matrices. Comparing the results obtained with different degree of sidewall functionalization, the vdW force between the amide-functionalized CNT and the NBR matrix plays a major role in determining the interfacial bonding strength. Meanwhile, higher degree of sidewall functionalization (>10%) will lower the enhancement effect by destroying the perfect structure of CNTs. Finally, the reinforcement mechanisms for the interfacial interactions between the functionalized CNTs and NBR matrices were elucidated from an atomic perspective.