Fabrication of PVC products requires the addition of thermal stabilizers.  Milling or other processing of unstabilized PVC at elevated temperatures rapidly results in degradation; e.g. discoloration, formation of hydrogen chloride, and irreversible adhesion to equipment surfaces.
 
PVC discoloration is caused by the formation of conjugated double bonds in the PVC polymer chains as a result of the elimination of hydrogen chloride.  The HCl formed during this reaction further catalyzes the decomposition of the PVC.  ADVERA® 401P zeolite scavenges the HCl to reduce this acid concentration so as to decrease PVC discoloration and slow PVC decomposition.  

In stabilization systems based on zinc stearate, the stearic acid groups attach to the PVC polymer chains to stop further formation of the conjugated double bonds.  In that reaction, zinc chloride is formed, which catalyzes PVC decomposition.  Removal of the zinc chloride results in greater stability.  ADVERA® 401P zeolite is very effective as a zinc chloride or tin chloride scavenger.