More Nitrile Seals (O-Rings)
are used than all the other elastomers combined, since nitrile is the most versatile material.
Nitrile is a copolymer of acrylonitrile and butadiene. As the acrylonitrile content of nitriles increases, the oil and fuel resistance increases while the low-temperature flexibility decreases.
Materials can be formulated to perform satisfactorily over the temperature range 65F (18° Celsius) to +300F (149° Celsius), so it is necessary to make sure that the particular nitrile chosen meets the temperature requirements of the application.
Uses of Nitrile
The nitrile materials are recommended for general-purpose sealing of alkaline and salt solutions, petroleum oils and fluids, vegetable and diester oils, silicone greases and oils, ethylene glycol-base fluids, alcohol’s, gasoline’s and water.
They are not suited for use with strong oxidising agents; chlorinated solvents such as carbon tetrachloride or trichlorethylene, nitrated hydro-carbons such as nitrobenzene or aniline; keytones such as methyl ethyl ketone (MEK) and acetone; and aromatic hydrocarbons.
Nitrile has High Profile Uses
Nitrile-based elastomers are usually specified by military MS (military specification) and AN (army, navy) O-rings when used in oil and fuel applications, but because nitrile compounds vary widely within such a large overall temperature range, particular attention should be paid to specifying physical properties.
Ozone will usually attack nitrile materials, but resistance can be greatly improved by the addition of antioxidant compounds.