Nitrile rubber, also known as NBR and Buna-N is a useful gasket material that many buyers refer to as nitrile. Useful though it is, Nitrile Rubber Gaskets are not a solution to every sealing challenge. Here’s some advice on when and when not to use it.
Properties of Nitrile Rubber
Nitrile or NBR is a synthetic rubber with good flexibility and resilience over a temperature range of -30 to +200 °F (-34 to +93 °C). It has good strength and abrasion resistance and a low compression set, all of which make it an effective gasket material. It’s also available as FDA-approved white nitrile for food industry applications.
A particular strength of nitrile is its ability to withstand attack by oils and fuels. Many gasket materials swell and break down when exposed to lubricants, hydraulic fluids or gasoline, but not nitrile. As a result, it’s used extensively with engines, generators, and fuel and hydraulic systems.
It does however have some weaknesses. It’s not for high-temperature applications, it doesn’t have good weather resistance and it will be attacked by polar solvents.
Polar Solvents and Nitrile Rubber Gaskets
Polar solvents are those where the molecules are composed of atoms with significantly different electrical charges. One example is oxygen and hydrogen. Others are acetone, ethanol, and acetic acid. In chemistry terms, these are considered to have a high permittivity or dielectric constant. You might notice that compounds with a high dielectric constant, like pure water, are also good electrical insulators.
Nitrile is susceptible to attack by polar solvents like those listed above. Interestingly though, while water is also polar, it’s a solvent to which nitrile has some resistance. However, for sealing against water, better gasket material choices would be neoprene or EPDM.
Consider Conditions Before Asking for Nitrile
Nitrile Rubber gasket material is a good choice for sealing against fuels, oils, and lubricants. It should not be used with chemicals like acetone, ethanol, and acetic acid. Neither should it be used outdoors or where temperatures exceed 200 °F. If the application involves water, check with a materials specialist at Hennig Gasket before ordering.