Nitrile Back-Up Rings
Nitrile rubber, also known as NBR or Buna N, is one of the most commonly used sealing elastomers due to its resistance to petroleum-based fuels and lubricants and its relatively low price. Nitrile elastomers are copolymers of acrylonitrile and butadiene. There are a number of common variations of nitrile compounds.
- Acrylonitrile Content: The acrylonitrile (ACN) content of the polymer chains can be varied from 18% to 50%. Lower ACN content gives better low-temperature properties but poorer fuels and polar lubricants. Higher ACN content gives poorer low-temperature properties but improved fuels and polar lubricants resistance. Standard NBRs typically have 34% ACN content.
- Cure system: Sulfur-cured
- Standard Nitriles are usually sulfur-cured. Sulfur-cured compounds offer better low-temperature properties but are more prone to hardening with high temperatures.
- Peroxide-cured nitriles have better heat resistance and lower compression sets but are more expensive and more difficult to process.
- Standard Low Temp: -40°C (-40°F)
- Standard High Temp: 100°C (212°F)