The most commonly used fluids in contact with O-RINGS other than air are the following:
In contact with most of the components listed above, elastomers generally tend to swell.
Temperature and pressure certainly accentuate these phenomena, therefore these effects must be taken into consideration at the moment of the design, to ensure the tightness of the whole system.
Swelling almost always creates a deterioration of the compound which can reach, in extreme cases, even total degradation.
To increase the above is added the effect of the temperature which, at high levels, further increases the effects described above.
There is also the possibility that the phenomenon of Extraction of certain components of the compound occurs.
In this situation there is a loss of volume of the O-RING itself with serious alterations to the seal.
As can be seen from the above, it is very important to verify, at the design level, the fluids used in contact with the O-RING and consequently the compounds to be used in order to obtain a good long-lasting seal.