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The effect of the aging time on the thermal oil aging behavior of hydrogenated nitrile butadiene rubber (HNBR)/multi-walled carbon nanotube (MWCNT) composites under the free or compression state was investigated. The composites aged under the free state and the IRM 903 oil after aging for different time were characterized by Fourier transform infrared spectroscopy (FTIR) analysis. The surface morphology of the composites aged under the free state was characterized by microscopic analysis. The thermal stability of the composites aged for different time and the edge and inner samples obtained from the composites aged under the free or compression state were characterized by thermal gravimetric analysis. The effect of aging time on the compressive stress and compressive stain energy density of the compressed composites was investigated. The scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis were exercised to the edge and inner samples obtained from the composites. This research facilitates to discover the heterogeneous aging effect on the degradation behavior of HNBR seals under the compression state in the hot oil environment. [ABSTRACT FROM AUTHOR]

Hydrogenated nitrile butadiene rubber (HNBR) is cured by sulfur (S), dicumyl peroxide (DCP), and S donor, respectively. Effect of curing systems on vulcanization, mechanical properties, and cyclic compression of HNBR vulcanizates was investigated. The dependence of storage modulus (G0) on strain was evaluated by Rubber Processing Analysis (RPA) analysis. The Mullins effect and degree of stress softening were also investigated by cyclic compression test. The energy dissipation of cyclic compression was calculated. The presumed mechanism of stress softening of HNBR was presented. The results show that the curing speed, torque, and G0 are higher for S curing system compared with DCP and S donor. The elongation of break and hardness for S system are higher than that of DCP and S donor. The maximum compressive stress, stress softening, and dissipated energy decreased with the increasing number of cycles. The degree of stress softening for S is lower due to the bigger cross-link density and stronger filler- rubber interaction in S-cured HNBR. [ABSTRACT FROM AUTHOR]