Buna Nitrile O-Ring Material Description

 

Nitrile rubber (NBR) o-rings, also known as Buna N, are one of the most commonly used sealing elastomers due to 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 vary from 18% to 50%. Lower ACN content gives better low-temperature properties but inferior resistance to fuels and polar lubricants. Higher ACN content gives lesser quality low-temperature properties but improved fuels and polar lubricants resistance. Standard NBRs typically have 34% ACN content.

Cure system: Sulfur-cured & Peroxide-cured

Standard Nitrile o-rings are usually sulfur-cured. Sulfur-cured compounds offer better low-temperature properties but are more prone to hardening with high temperatures. Peroxide-cured nitrile o-rings have better heat resistance and lower compression sets but are more expensive and more difficult to process. Standard materials in stock include Sulfur-cured 70 & 90 durometer (N70, N90) and Peroxide-cured 90 durometer (N90PC)

Temperature Range (Typical Compounds)

Sulfur-cured:

Standard Low Temp: -40°C (-40°F)
Standard High Temp: 100°C (212°F)

Peroxide-cured:

Standard Low Temp: -29°C (-20°F)
Standard High Temp: 135°C (275°F)

Low-Temp Buna Nitrile O-Rings:

N70LT Low Temp: -55°C (-67°F)
N70LT High Temp: 100°C (212°F)

 

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