Nitrile butadiene rubber (NBR), which is also widely known as acrylonitrile butadiene rubber or Buna-N (hence Buna O-Rings), is a synthetic rubber copolymer made up of — you guessed it — butadiene and acrylonitrile. NBR has good mechanical properties and high wear resistance when compared with other elastomers.
The acrylonitrile (or simply nitrile) content of NBR compounds vary considerably — anywhere from 18% to 50% — and influence the physical properties of the finished material. The higher the nitrile content, the better the buna o-ring’s resistance to oil and fuel. However, an increase in nitrile adversely affects the ring’s compression resistance to low temperature. Hence, an o-ring with a lower acrylonitrile content will have higher resistance to low temperature, but a lower resistance to oils and fuels. In view of these opposing realities, a popular compromise is a medium acrylonitrile content rubber.
Unfortunately, nitrile o-rings are 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.
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. When faced with service temperatures higher than 100° C, lifetime will will generally be shortened.
40 to 90 Shore A are available.
Buna O-Ring Colors
Black, brown, green, white, rust, yellow, blue, red, orange, and gray are available, in addition to any customer-assigned color.
NBR O-Rings 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.