NBR (Nitrile) is a copolymer of 1,3-butadiene and acrylonitrile. Acrylonitrile content varies in commercial products from 18% to 50%. As the acrylonitrile content increases, resistance to petroleum base oils and hydrocarbon fuels increases, but low temperature flexibility decreases and the rubber can become brittle.
Due to its excellent resistance to petroleum products, and its ability to be compounded for service over a temperature range of -40°C to +120°C (standard stock NBR -30°C to +120°C), NBR is the most widely used elastomer in O-rings today.
Special low temperature NBR is compromising high temperature resistance and the temperature range is typically -40°C to +110°C. NBR compounds compression set, tear resistance and abrasion resistance are superior to most elastomers. On the other hand, ozone, sunlight and weather resistance is poor.