3. Plasticizers

Plasticizers are often considered as processing aids to improve industrial performance. They act by lowering viscosity during mixing to facilitate the incorporation of ingredients. They also facilitate the flow of the mixture through the injection mold channels. However, the damping time of the finished product is increased in their presence, and stiffness is reduced. However, these compounds tend to migrate out of the cured mixture, leading to changes in mechanical properties over time. This is referred to as physical ageing, as opposed to chemical ageing by thermo-oxidation, for example.