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 their resistance to petroleum-based fuels and lubricants and their relatively low price. Nitrile elastomers are copolymers of acrylonitrile and butadiene. (Learn why NBR is a popular choice). There are a number of common variations of nitrile compounds. Nitrile o-rings may also come in a metal-detectable variation while retaining the same qualities as the general Nitrile o-ring compound.

For applications requiring o-rings with high visibility, High-Visibility Nitrile o-rings are recommended. High-Visibility o-rings maintain properties identical to its original compound, with the addition of a distinguishable neon green hue.

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)


Standard Low Temp: -35°C (-31°F)
Standard High Temp: 120°C (248°F)

SPEC SHEET: Nitrile 70 Durometer

SPEC SHEET: Nitrile 75 Durometer – Metal & X-Ray Detectable

SPEC SHEET: Nitrile 90 Durometer

SPEC SHEET: Nitrile 90 Durometer – High-Visibility


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

SPEC SHEET: Nitrile 90 Durometer – Peroxide-Cured

Low-Temp Buna Nitrile O-Rings:

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

N90LT Low Temp: -54°C (-65°F)
N90LT High Temp: 149°C (300°F)

SPEC SHEET: Nitrile 70 Durometer Low-Temp

SPEC SHEET: Nitrile 90 Durometer Low-Temp


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Preferred Environments to Use Buna Nitrile O-Rings

Performs Well In:

  • Petroleum-based oils and fuels
  • Aliphatic hydrocarbons
  • Vegetable oils
  • Silicone oils and greases
  • Ethylene glycol
  • Dilute acids
  • Water up to 100ºC (212ºF)

Doesn't Perform Well In:

  • Aromatic hydrocarbons
  • Automotive brake fluid
  • Chlorinated hydrocarbons
  • Ketones
  • Ethers
  • Esters
  • Phosphate ester hydraulic fluids
  • Strong acids
  • Ozone, weathering, and sunlight