Buna O-Rings
Acrylonitrile-Butadiene (NBR)
Copolymers of butadiene and acrylonitrile are known by several generic names, Buna N, Nitrile Rubber and NBR. The acrylonitrile content of NBR compounds varies considerably (18% to 50%) and influences the physical properties of the finished material.
The higher the acrylonitrile content, the better the resistance to oil and fuel. At the same time, elasticity and compression set resistance to low temperature is adversely affected. The lower acrylonitrile content obtains, the better low temperature resistance, but at a sacrifice to some resistance to oils and fuels. In view of these opposing realities, a compromise selection is the medium acrylonitrile content rubber. NBR has good mechanical properties when compared with other elastomers and high wear resistance.
NBR is not resistant to weathering and ozone. Some special compounding can improve this defect by the use of a NBR/PVC blending compound which has excellent weathering and ozone resistance and good resistant to fuel but compression set is not good.
Service Temperature
For NBR the service temperature can be designed from -55 C to 100 C or up to 125 C depending on different acrylonitrile content and formula. Generally higher than 100 C, life time will be shortened.
Hardness
40 to 90 Shore A are available.
Color
Black, brown, green, white, rust, yellow, blue, red, orange, and gray are available, or any assigned color from customers.
Application
NBR compounds have excellent resistance to abrasion, non-polar oils and solvent, water and permeation (higher acrylonitrile content will be better). NBR also can be used in conditions of dilute acids, alkalis and salt solution at low temperatures. Applications in aromatic hydrocarbons, chlorinated hydrocarbons and polar solvents are not suitable.