Nitrile is a copolymer of butadiene and acrylonitrile and is recommended when excellent resistance to petroleum oils and gasoline is required. Nitrile's resistance to the more aromatic distillates of petroleum is better than neoprene, and it exhibits
excellent resistance to mineral and vegetable oils, but relatively poor resistance to the swelling action of oxygenated solvents such as acetone and the keytones. Nitrile
resists acids and bases with the exception of those having strong oxidizing effects. Resistance to heat aging is good.
Solvent resistance increases and low temperature flexibility decreases in basic polymers with higher acrylonitrile content. Low temperature resistance is inferior to natural rubber, but NBR can be compounded to give adequate performance in this area. Since nitrile does not crystallize on stretching, reinforcing materials, such as
carbon blacks, are required to obtain high strength.
The compounding of nitrile results in a good balance of low creep, good resilience, low permanent set, good abrasion resistance and some ozone resistance. Tear resistance is inferior to natural rubber.
Typical applications of 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 oil and heat are prevalent