The role of TBLS is to scavenging the molecules of HCl released during degradation or treatment of PVC following the reaction:

 6HCl+3PbO.PbSO4 ===>   3PbCl2+PbSO4+H2O

 Also is the presence of -0-Pb-OH groups that readily exchange -OH for -Cl under conditions that would otherwise lead to degradation of PVC

 Thus the question which arises how to supplement and balanced this reaction according to polyvinylchloride and their stabilizing (tribasic lead sulfate)?