Nitrile (NBR) is a copolymer of Acrylonitrile and Butadiene rubbers. The ratio of the two polymers affects the properties of a rubber compound. Raising the acrylonitrile content will increase resistance to oil and solvents and improve abrasion resistance. Lowering the acrylonitrile content improves low temperature properties, compression set and fuel resistance.

While Nitrile rubber is considered to be a general purpose material for O-Rings and many other seals, it can be specifically compounded for many purposes. Grades are available for: food processing, use with milk and edible oils, potable water and other specialty applications. Internal lubricants may be added to reduce frictional properties and extend wear. Specialty Nitrile polymers can be produced by carboxylation (see carboxylated Nitrile) or hydrogenation (see HNBR).

The service temperature for PAI Nitrile compounds varies on the low end from -90º to -15º F (-65º to -25º C) depending on acrylonitrile content. On the high side continuous service varies from 225º F to 300º F depending on the curing agent used. PAI offers NBR compounds in hardness ranges from 30 to 95 durometer. Black is the standard color, but many other colors are available.