Nitrile rubber (NBR), also know as
Buna-N, is the general term for acrylonitrile butadiene terpolymer.
The acrylonitrile content of nitrile sealing compounds varies
considerably (18% to 50%) and influences the physical properties
of the finished material.
The higher the acrylonitrile content,
the better the resis¬tance to oil and fuel. At the same
time, elasticity and resistance to compression set is adversely
affected. In view of these opposing realities, a compromise
is often drawn, and a medium acrylonitrile content selected.
NBR has good mechanical properties when compared with other
elas¬tomers and high wear resistance. NBR is not resistant
to weathering and ozone.
- Heat resistance
Up to 100°C (212°F) with shorter
life @ 121°C (250°F)
- Cold flexibility:
Depending on individual compound, between
-34°C and -57°C (-30°F and -70°F).
- Chemical resistance
- Aliphatic hydrocarbons (propane,
butane, petroleum oil, mineral oil and grease, diesel
fuel, fuel oils) veg¬etable and mineral oils and
greases.
- HFA, HFB and HFC fluids.
- Dilute acids, alkali and salt
solutions at low temperatures
- Water (special compounds up to
100°C) (212°F).
Not compatible with:
- Fuels of high aromatic content (for
flex fuels a special compound must be used).
- Aromatic hydrocarbons (benzene).
- Chlorinated hydrocarbons (trichlorethylene).
- Polar solvents (ketone, acetone,
acetic acid, ethylene-ester).
- Strong acids.
- Brake fluid with glycol base.
- Ozone, weather and atmospheric aging.
|
