Effect of nitrile butadiene rubber hardness on the sealing characteristics of hydraulic O-ring rod seals

The nitrile butadiene rubber(NBR)hardness effect on the sealing characteristics of hydraulic O-ring rod seals is analyzed based on a mixed lubrication elastohydrodynamic model.Parameterized studies are conducted to reveal the mechanism of the influence of rubber hardness on the static and dynamic behavior of seals.The optimized selections of rubber hardness are then investigated under different conditions.Results show that the low hardness seal is prone to stress concentration due to the extrusion effect under high pressure conditions;it is also more prone to leaking.A high hardness seal can better prevent leakage by reducing film thickness but it will cause large frictional power loss and increase the probability of wear failure.The choice of low hardness is recommended to reduce friction with the premise that leakage requirements are met.

Natural rubber/nitrile butadiene rubber/hindered phenol composites with high-damping properties

New natural rubber(NR)/nitrile butadiene rubber(NBR)/hindered phenol(AO-80)composites with high-damping properties were prepared in this study.The morpholo-gical,structural,and mechanical properties were characterized by atomic force micro-scopy(AFM),polarized Fourier transform infrared spectrometer(FTIR),dynamic mechanical thermal analyzer(DMTA),and a tensile tester.Each composite consisted of two phases:the NR phase and the NBR/AO-80 phase.There was partial compat-ibility between the NR phase and the NBR/AO-80 phase,and the NR/NBR/AO-80(50/50/20)composite exhibited a co-continuous morphology.Strain-induced crystal-lization occurred in the NR phase at strains higher than 200%,and strain-induced orientation appeared in the NBR/AO-80 phase with the increase of strain from 100%to 500%.The composites had a special stress–strain behavior and mechanical properties because of the simultaneous strain-induced orientation and strain-induced crystalliza-tion.In the working temperature range of a seismic isolation bearing,the composites(especially the NR/NBR/AO-80(50/50/20)composite)presented a high loss factor,high area of loss peak(TA),and high hysteresis energy.Therefore,the NR/NBR/AO-80 rubber composites are expected to have important application as a high-perfor-mance damping material for rubber bearing.

Preparation and Characterization of Flame Retardant and Low Smoke Releasing Oil-resistant EVA/NBR Blends

Nano-SiO2 and/or MoO3 were introduced to ethylene-vinyl acetate/nitrile butadiene rubber （EVA/NBR） blends containing magnesium hydroxide （MH） and red phosphorus （RP） to further improve the mechanical properties, oil resistance, smoke suppression and flame retardancy. The results indicated that the tensile strength and oil resistance were significantly improved by incorporating nano-SiO2. Smoke suppression tests for EVA/NBR blend samples showed that both nano-SiO2 and MoO3 can significantly reduce smoke release amount. The flammability characterization indicated that the blended sample with an LOI value of 33.0 could achieve V-0 level in the UL-94 test. Cone calorimetry test data showed the peak heat release rate was 67% lower than that for pure EVA/NBR. Thermal analysis showed that the presence of both nano-SiO2 and MoO3 was beneficial to promoting char formation of the EVA/NBR blends. Char residual analysis suggested that MoO3 aggregated in solid phase during combustion.