NBR is a very commonly used material for o-rings because of its good mechanical properties, its resistance to lubricants and greases. The physical and chemical resistance properties of NBR materials are determined by the acrylonitrile (ACN) content of the base polymer which can vary between 18% and 50%. Low ACN content ensures good flexibility at low temperatures, but offers limited resistance to oils and fuels. As the ACN content increases, the low temperature flexibility reduces and the resistance to oils and fuels improves.

Physical and chemical resistance properties of NBR materials are also affected by the cure system of the polymer. Peroxide-cured materials have improved physical properties, chemical resistance and thermal properties as compared to sulfur-donor-cured materials.

Standard grades of NBR are typically resistant to mineral oil-based lubricants and greases, many grades of hydraulic fluids, aliphatic hydrocarbons, silicone oils and greases and water to about 80ºC.

NBR is generally not resistant to aromatic and chlorinated hydrocarbons, fuels with a high aromatic content, polar solvents, glycol-based brake fluids and non-flammible hydraulic fluids (HFD). NBR also has low resistance to ozone, weathering and aging, but in many applications this has no negative effect. All Buna N and Silicone O-rings shown are 70 Durometer unless noted.