(295b) Molecular Simulations for the Design and Property Prediction of Elastomer Seals for Sour Gas Environments

Elastomers used as seals in the oil and gas industry must be able to withstand chemical corrosion by hydrogen sulfide that is present in a sour gas environment. Nitrile rubbers, which are otherwise promising in terms of resistance to oil swelling (because of the polar acrylonitrile groups) and low glass transition temperature (that makes them advantageous compared with conventional fluoroelastomers for low-temperature sealing applications), are prone to chemical modification by H₂S, resulting in severe degradation in mechanical properties. This talk will discuss the use of molecular simulations to design novel fluorinated nitrile rubbers resistant to H₂S. The solubilities and diffusion coefficients of the H₂S and CO₂ gases present in sour gas, in fluorinated HNBR elastomers, were predicted using molecular dynamics (MD). The effect of grafting density of the semifluorinated alkyl methacrylate was investigated. Solubilities calculated with MD simulation results were compared with those obtained from Grand Canonical Monte Carlo Simulations. These predictions showed the difference in the behaviors of the polar H₂S and the nonpolar CO₂. The results of molecular simulations were corroborated by measurement of mechanical properties of elastomer specimens aged in a sour gas environment at 250 °F and 1000 psig for 24 hours.