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 improves 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 durometers (N70, N90) and peroxide-cured 90 durometer (N90PC).
Buna Nitrile Compounds
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N50-B101 | 50 |
Black |
-40 to +212 |
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General purpose |
N50-B102 | 50 |
Black |
-40 to +212 |
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UL 157 |
N70-A101 | 70 |
Black |
-22 to +250 |
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General purpose |
N70-B103 | 70 |
Black |
-40 to +212 |
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UL 157 |
N70-B106 | 70 |
Black |
-40 to +212 |
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NSF 61, FDA |
N70-C102 | 70 |
Black |
-40 to +221 |
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General purpose, low temp resistance |
N70-B102 | 70 |
Black |
-35 to +250 |
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General purpose |
N70-C401 | 70 |
Blue |
-40 to +212 |
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Metal/X-ray detectable, FDA-Grade |
N70-B701 | 70 |
Green |
-40 to +212 |
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General Purpose |
N70-B502 | 70 |
White |
-40 to +212 |
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General purpose, FDA-Grade |
N75-F701 | 75 |
Green |
-40 to +212 |
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Metal/X-ray detectable, FDA-Grade |
N80-B102 | 80 |
Black |
-40 to +212 |
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UL 157 |
N90-A101 | 90 |
Black |
-13 to +250 |
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General purpose |
N90-B102 | 90 |
Black |
-65 to +300 |
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Low Temperature |
N90-C901 | 90 |
Green |
-4 to +248 |
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High visibility |
N90-B103 | 90 |
Black |
-40 to +257 |
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Peroxide-Cured |
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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