1.NBR (Nitrile rubber)
NBR has an oil-resisting property better than other synthetic rubber
and hence is widely applied to oil seals. It has good heat resistance .The
defective problem is poor chemical resistance.

2. PA (Polyacrylate rubber)
Applied specifically to shaft seal of vehicles. Normally the PA rubber
is applied to the shafts of vehicle engine, transmission gears & pinions,
power steering system and won't get hardened by heat or lube oil additives,and the vulnerability is that this material will degrade in water or steam environment, the anti-cold ability and tensile strength is lower than NBR.

3. SI (Silicon rubber)
The SI rubber bears a very weak tensile strength then other polyesters in
dry condition; therefore it's not suitable to become oil seal of rotating
shaft. However, SI could resistance to heat and low temperature.

4. VI (Fluorinated rubber)
The VI rubber can withstand oil temperature up to 150-230^oC and still
be in good state. And also can withstand chemicals. The vulnerability
of VI rubber is that it cannot withstand low temperature and will harden in a temperature at -20~-30^oC. VI rubber is for high temperature use.