A substance added to materials during the manufacturing process to improve flexibility, workability, etc.
A material of lower molecular weight added to a polymer to separate the molecular chains. This results in a depression of the glass transition temperature, reduced stiffness and brittleness, and improved processability. (Note, many polymeric materials do not need a plasticizer.)
Petroleum derivative or ester-type material added to a mix which increases the processibility, gives control over the hardness and plasticity, and strongly influences the low-temperature characteristics.