Research on property variation and mechanism of NBR immersed in oil

Nitrile butadiene rubber （NBR） is a crucial sealing material for oil-immersed equipment， and its properties have a direct impact on the safe operation of equipment. With elastic strain energy density and hardness as the property parameters， the infrared spectra and tensile fracture characteristics are used to analyze the structural changes in NBR immersed in oil to determine the relationship between its mass-transfer behaviors and the property variations and elucidate the mechanism of property degradation. The findings reveal that NBR experiences swelling when immersed in oil， resulting in a significant reduction in both elastic strain energy density and hardness. These two indices exhibit a strong correlation with oil immersion parameters. Mass transfer behaviors， such as oxidization of functional groups， oil infiltration， and additive dissolution， emerge as the primary drivers behind the property change.