4. Aniline point

The notion of aniline point was introduced industrially to take account of the fact that two fluids, apparently identical in terms of viscosity, viscosity index, purity, acidity, etc., behave differently towards the same elastomer. As elastomer is widely used in the manufacture of seals, it is important to know how it behaves in contact with the fluid. In the majority of cases where mineral-based fluids are used today, the aniline point is used to predetermine the swelling or shrinkage (shrinkage caused by the extraction of solids from the elastomer composition by the fluid) of a characterized elastomer after immersion in the fluid 5