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Buna-N
Typical
Trade Names:
- Chemigum
- Goodyear Tire & Rubber Co.
- FR-N
- Firestone Synthetic Rubber & Latex Co.
- Paracril
- Uniroyal
- Hycar
- Goodrich Chemical Co.
-
Krynac - Polysar, ltd.
- Ny
Syn - Copolymer Rubber & Chem. Corp.
Nitrile,
chemically, is a copolymer of butadiene and acrylonitrile. Acrylonitrile
content is varied in commercial products from 18% to 48%. As the
nitrile content increases, resistance to petroleum base oils and
hydrocarbon fuels increases, but low temperature flexibility decreases.
Due
to its excellent resistance to petroleum products, and its ability
to be compounded for service over a temperature range of -65 to
+250 degrees F (-54 to +121 degrees C), nitrile is the most widely
used elastomer in the seal industry today. Most military rubber
specifications for fuel and oil resistant MS and AN O-rings require
nitrile base compounds. It should be mentioned, however, that
to obtain good resistance to low temperature with nitrile compounding,
it is almost always necessary to sacrifice some high temperature
fuel and oil resistance.
Nitrile
compounds are superior to most elastomers with regard to compression
set or cold flow, tear and abrasion resistance. Inherently, they
do not possess good resistance to ozone, sunlight or weather but
this can be substantially improved through compounding. However,
since ozone and weather resistance are not always built in, seals
from nitrile bases should not be stored near electric motors or
other equipment which may generate ozone, or indirect sunlight.
A
carboxylate version of high-acrylonitrile butadiene copoylimer
(XNBR) is available for applications requiring the ultimate in
wear resistance. In the reinforced state, this medium-priced rubber
also offers high tensile strength and elongation, as well as high
load bearsing capability. There properties are obtained without
any sacrifice in the other properties of conventional, high acrylonitrile
copolyvers.
Nitrile
is recommended for:
- General
purpose sealing
- Petroleum
oils and fluids
- Water
-
Silicone greases and oils
-
Di-ester base lubricants (MIL-L-7808)
-
Ethylene glycol base fluids (Hydrolubes)
Nitrile
is not recommended for:
- Halogenated
hydrocarbons (carbon letrachloride, trichlor-ethylene)
- Nitro
hydrocarbons (nitrobenzene, aniline)
- Phosphate
ester hydraulic fluids (Skydrol, Fyrquel, Pydruel)
-
Ketones (MEK, acetone)
- Strong
acids
- Ozone
- Automotive
brake fluid
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