Nitrile, EP/EPDM

May-Lin Silicone Products, Inc.
PO Box 335 • 955 Wooster Road West Barberton, Ohio 44203
Phone: 330-825-9019 • Fax: 330-825-6153

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

EP/EPDM: Two types of EP rubber are available in today's market. They are ethylene propylene (EP) which uses a peroxide cure system and ethylene propylene diene methylene terpolymer (EPDM) which uses a sulfur cure system. These polymers are recognized for their resistance to weathering and high temperatures. The EP rubbers have slightly better heat resistance than the EPDM rubbers; however, the EPDM rubbers are easier to process and manufacture.
EPDM rubbers are used extensively in outdoor applications. They will withstand the abuse of all types of weather including sunlight, ozone and oxidants, and they exhibit excellent resistance to animal and vegetable oils, water steam, oxygenated solvents (acetone, methyl ethyl ketone and other keytones). Color retention in colored compounds is excellent. Compounds exhibit good dielectric qualities and high heat resistance. Low temperature properties are excellent.
The resilience and tensile strengths of EPDM rubbers are low, and resistance to petroleum derivatives is extremely poor.