Plasticisers are present in a wide range of applications and everyday products. They are also some of the most widely tested and scrutinised substances in Europe.
In general terms, plasticisation can be carried out as an internal or external process, the latter being the most common one due to affordability and the flexibility to test different formulations. At the same time, external plasticisers can be divided into primary, secondary and extender, very often combined to add specific physical properties to the polymer being plasticised. Several theories have been proposed to explain the action of plasticisers and different ideas must be combined in order to gain a clear understanding of this complex process.