Accelerated aging behavior and degradation mechanism of nitrile rubber in thermal air and hydraulic oil environments

Abstract The aging behavior and degradation mechanism of nitrile rubber (NBR) under free and compression states were investigated in simulated air and hydraulic oil environments at various elevated temperatures. The variations in the crosslinking density, volatile components and the chemical structure of NBR during aging were studied using equilibrium swelling testing and dynamic mechanical analysis (DMA), pyrolysis‐gas chromatography–mass spectrometry and attenuated total reflection‐Fourier transform infrared spectroscopy. The migration of additives in different media and the crosslinking density of NBR aged in different conditions were compared. The tensile strength, DMA, and thermogravimetric analysis results were consistent with the changes in the crosslinking density of NBR and the migration of additives. Four effects of the simulated hydraulic system on the thermal aging of NBR were examined. Both the compression stress and the oil medium slowed the aging of NBR. The results can provide new insights into the use of NBR products in lubricating oil environments and NBR lifespan prediction in hydraulic working conditions.