Effect of single-vacancy- and vacancy-adsorbed-atom-defective CNTs on the mechanical and tribological properties of NBR composites: molecular dynamics simulations

Molecular dynamics (MD) simulations were used to map defect-free, single-vacancy (SV)-defective and vacancy-adsorbed-atom (VA)-defective carbon nanotubes (CNTs) using 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant RD) and nitrile-butadiene rubber (NBR) monomer models. Three groups of composites, CNT/RD/NBR, SV-CNT/RD/NBR, and VA-CNT/RD/NBR, were modeled. The mechanical and tribological properties of these composites were investigated, and the thermal-oxidative aging mechanism was analyzed via molecular dynamics (MD) simulations. The results showed that the antioxidant RD had the best protection effect on NBR in the CNT/RD/NBR composite. In addition, the Young's, bulk, and shear moduli of the CNT/RD/NBR composites were significantly improved, and the friction coefficient and wear rate were reduced compared with those of the SV-CNT/RD/NBR and VA-CNT/RD/NBR composites. The mean square displacement, radial distribution function, and relative concentration distribution within the three composites were also calculated separately. The effects of SV-CNTs and VA-CNTs on the NBR composite matrices were elucidated from a microscopic perspective. The results showed that the introduction of SV and VA defects reduced the interfacial interaction of NBR composites and alleviated the antioxidant RD dispersion and migration within the composites.

Automated summary

Molecular dynamics (MD) simulations were used to investigate the properties and aging mechanism of three different composites: defect-free carbon nanotubes (CNTs) with antioxidant RD and NBR; single-vacancy (SV)-defective CNTs with antioxidant RD and NBR; and vacancy-adsorbed-atom (VA)-defective CNTs with antioxidant RD and NBR. The results showed that the antioxidant RD had the best protective effect on NBR in the composites, leading to improved mechanical and tribological properties. The presence of SV and VA defects reduced the interfacial interaction of the composites and affected the dispersion and migration of the antioxidant RD.