Effect of carboxyl group introduction and graft modification on the thermal properties and Fe wall adsorption performance of HNBR

Hydrogenated nitrile butadiene rubber (HNBR) has been widely used in petrochemical, aerospace, and other fields for its excellent properties. In this study, molecular dynamics methods were employed to construct molecular models of HNBR and hydrogenated carboxyl butadiene rubber (HXNBR). It was found that the introduction of carboxyl groups significantly enhanced the mechanical properties of the material, whereas the glass transition temperature of the material increased by 9.96% and the thermal conductivity decreased by 17.3%. Subsequently, the grafted hydrogenated carboxylated nitrile butadiene rubber (HXNBR-Rx) model and the HXNBR-Rx/Fe bilayer adsorption model, which incorporate grafting modifications with of C5H11OH, C10H21OH, C15H31OH, C20H41OH and C25H51OH, were constructed. In comparison between their thermal properties and the adsorption properties on the metal walls, we revealed that as the number of grafted side chain carbon atoms increased, both the mechanical properties and the glass transition temperature of the material showed a trend of first decreasing and then increasing, while the thermal conductivity of the material first increased and then decreased. Furthermore, the effect of grafting on the material properties was analyzed at the molecular level in terms of free volume fraction, interfacial interaction energy, and relative atomic concentration. The simulation results can provide some theoretical guidance for optimizing the thermal properties of HNBR materials and the adsorption capacity of the metal walls while maintaining their oil resistance and mechanical properties.