Nitrile rubber (also called acrylonitrile butadiene rubber, buna, or NBR) is one of the most popular rubber materials in the seal industry. It is well suited for general purpose applications, due to its relatively low cost, its versatility in formulation, and its compatibility with a relatively wide selection of fluids.
The typical temperature range of nitrile rubber is -30F to 250F. It can also be formulated for temperatures as low as -70F, although this occurs at the expense of compression set resistance at higher temperatures
Low temp nitrile also sacrifices compatibility with certain types of oils and hydrocarbons. Aggressive hydrocarbons, such as gasoline, will actually cause “dry out shrinkage,” where the O-ring swells while it is soaked in gasoline, and then shrinks as the gasoline evaporates, or “dries out” (The plasticizers in low temp nitrile dissolve readily in gasoline).
As nitrile is a copolymer of acrylonitrile and butadiene, the acrylonitrile (ACN) portion can be increased. These “high-ACN” nitrile materials can provide a cost-effective seal for gasoline and diesel applications, such as fuel containers, and pumps at the gas station (NOTE: The high temp limit for fuel-resistant nitrile tends to be around 140F, beyond which it starts to swell and degrade).
Typical environments well-suited for nitrile rubber include:
- petroleum and hydrocarbon-based oils
- hydraulic fluids (petroleum-based)
- water and water-based solutions below 212F (100C)
- plumbing, drinking water (for NSF 61 approved compounds)
- food contact (for FDA approved compounds)
gasoline, diesel, gasoline/alcohol blends (fuel-resistant nitriles only).
Applications to avoid include:
- ketones (MEK, acetone)
- brake fluids (DOT 3)
- Gasoline (low ACN nitrile)
- Water above 212F
- steam
- phosphate ester-based hydraulic fluids (Skydrol, Hyjet)
- Environmental seals (susceptible to ozone cracking)
For more information on nitrile materials, or for a quote on nitrile seals, please contact engineering@derbycityseal.com
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