What is Nitrile?
Nitrile, or BunaN, is a copolymer of butadiene and acrylonitrile. It is a general purpose oil resistant polymer.
Nitrile has a typical service temperature range between –40° F and +275° F.
Nitrile has excellent resistance to oil, gasoline, solvents, mineral and vegetable oils, hydraulic fluid, and fuels. It is recommended for applications that require good oil and grease resistance as well as moderate ozone resistance. With compounding, it is possible to get a fairly good balance between low creep, good resilience, low permanent set and good abrasion resistance. Nitrile is superior to most elastomers with regard to compression set or cold flow, tear and abrasion resistance. Nitrile resists acids and bases with the exception of those having strong oxidizing effects. Nitrile is resistant to a broader range of aromatic hydrocarbons than neoprene. Resistance to heat aging is good.
Nitrile has poor resistance to ketones, chlorinated hydrocarbons, and nitro hydrocarbons. It does not have good ozone, oxygen or sunlight resistance without the addition of special additives. Nitrile’s low temperature resistance is inferior to natural rubber, and although nitrile can be compounded to give improved performance in this area, the gain is normally at the expense of oil and solvent resistance. Conversely, with higher acrylonitrile contents, the solvent resistance is increased but low temperature flexibility is decreased. Nitrile, like SBR, does not crystallize on stretching. Thus, reinforcing materials, such as carbon blacks, are required to obtain high strength. Tear resistance is inferior to that of natural rubber and electrical insulation is lower.
Nitrile is recommended when excellent resistance to petroleum oils, gasoline, and/or greases is needed. Nitrile is the most widely used elastomer for sealing products due to its excellent resistance to petroleum products and its wide temperature range. More than 50% of the o rings sold are nitrile o rings. Nitrile is also widely used with hydraulic fluid and alcohol applications. Nitrile is commonly used for industrial and automotive applications, in products such as fuel and oil handling hoses, petroleum oil seals, grommets, hydraulic hoses, hydraulic fluid seals, transmission fluid seals, rollers, shock and vibration mounts, and o rings. Typical applications of the premium grades of NBR include carburetor gaskets, fuel pumps, diaphragms and aircraft hose gaskets. The commercial grades of NBR are usually blends of NBR with other polymers. These less costly blends accommodate less demanding applications where oils and heat are prevalent. Ozone resistant nitriles are recommended where extended exposure to air and ozone is anticipated.