Buna N; NBR; Paracril® (Uniroyal)

Medium density copolymer of butadiene and acrylonitrile

-40 to 250 °F

On a cost basis, nitrile, or NBR, rubber is the least expensive of the oil resistant elastomers. As a result, nitrile is one of the most widely used rubber materials due to its combination of low cost, resistance to many chemicals, and good physical properties. The acrylonitrile content of this highly polar elastomer provides excellent oil and gas permeation resistance which increases as the level of ACN increases. Unfortunately, an increase in the acrylonitrile content compromises low temperature flexibility, and increases compound hardness. Typical ACN content ranges from 18% to 50%. Nitrile should not be exposed to direct sunlight or moderate to high levels of atmospheric ozone, as rapid deterioration will result. However, NBR will accept many antidegradants, most notably PVC, which offer some degree of improvement of these properties. Nitriles are usually sulfur cured, but peroxide curing is also possible, resulting in improved compression set.