Influence of aviation hydraulic oil swelling on the mechanical properties of HNBR/EPDM vulcanizates reinforced by carbon black

The study on swelling behaviors of rubber products in liquid media is of great value for life prediction and practical application guidance. In this work, changes in the mechanical properties of hydrogenated nitrile rubber/ethylene propylene diene monomer (HNBR/EPDM) blends caused by swelling in aviation hydraulic oil YH‐15 were studied. Effects of two kinds of carbon black, N220, and N990, on the tensile properties of HNBR/EPDM blends at both unswollen and swollen states were investigated. The results turned out that N220 exhibited better reinforcing effects than N990 on HNBR/EPDM blends. The tensile properties of unfilled and filled HNBR/EPDM blends decreased rapidly at first and then tended to stabilize with the extension of swelling time in YH‐15, while the modulus at 100% declined firstly and then increased. After swelling for 72 h, the tensile strength of HNBR/EPDM blends filled with N220 decreased by more than 35%, and by comparison, it decreased by about 20% for the N990‐filled HNBR/EPDM blends. The cross‐sections of the tensile samples after swelling changed greatly compared with the unswollen samples. In addition, the effect of swelling on the hardness of the HNBR/EPDM blends was not obvious.