2. Lubricants

2.1 Definitions

Thermoplastics can only be processed in the molten state, or at temperatures above their glass transition temperature. Under these conditions, raising the temperature is not enough to lower the viscosity sufficiently, so processing aids, including lubricants, must be used.

These products have a technical and economic importance at least equal to that of thermal stabilizers (article Stabilizers [A 3 232] ).

The expected effects of lubricants are of two kinds.

• Avoid or mitigate the consequences of polymer contact with hot metal tools. To avoid direct contact leading to surface sticking, stagnation...