Metallic soaps that result from the reaction of a metal oxide or a metal hydroxide with a fatty acid are used as co-stabilizers and internal/external lubricants in PVC formulations. Metallic soaps (AKSTAB®, LISTAB®) can be used in PVC formulations either individually or in synergistic combinations (Ca/Zn, Ba/Zn, etc.).
In general, they are the compounds formed by the fatty acids of various lengths (C8 ... C22, etc.) together with metals. Commonly used types are the Al, Ba, Ca, Pb, Mg or Zn soaps of stearic, lauric or benzoic acids.
Calcium stearate, barium stearate, and the laurates of these metals, which are used as internal lubricants in PVC formulations, also act as co-stabilizers that increase the heat stability, revealing their effects through the formation of the CaCl2 salt, which is produced as a result of their reaction with HCl that is released from the thermal degradation of PVC structure.
Among the metal soaps of the zinc that are used as external lubricants in PVC formulations, zinc stearate and zinc laurate also have the reducing effect on the initial colouring. They act as co-stabilizers in the process, revealing their effects through the formation of the ZnCl2 salt, which is produced as a result of their reaction with HCl that is released from the thermal degradation of the PVC structure.