Service Life Determination of Nitrile O-RINGS in Hydraulic FLUID

Service life prediction of rubber components such as O-rings is critical in many applications, in particular when continuous exposure to fluids is encountered.  In this investigation, nitrile O-rings were exposed to hydraulic fluid at nine different temperatures ranging from 23 to 100°C for four immersion times: 1, 3, 5 and 20 weeks.  Mechanical property test results in the tensile mode were generated using ASTM D1414.  Immersion compression set testing was completed at 100°C. Chemical Crosslink density by solvent swell was used as an independant method to follow the degradation.  Time temperature superposition was employed on all the collected data in order to estimate shift factors.  The Arrhenius approximation provided activation energies from which an estimation of the lifetime of the O-rings at service temperatures was calculated.   Thermogravimetric Analysis together with Energy Dispersive X-Ray Scattering were employed to provide insight into the understanding of the effect of the hydraulic oil on the nitrile rubber.