Effects of lead salts on thermal poly(vinyl chloride degradation)

The effect of lead salts (lead stearate, tribasic lead sulfate and tribase/stearic acid) on the thermal degradation of PVC was studied in trichlorobenzene (TCB) solution and under dynamic conditions in a mixing chamber. It was established that lead stearate directly reduces the HCl elimination rate (mainly by diminishing the zip length) whereas the tribase is acting only as HCl acceptor. In presence of stearic acid the tribase becomes a true stabilizer. At the end of the induction period rapid increase of the zip length and transiently high HCl elimination rates were observed. The consequences of these on the possible mechanism of stabilization are discussed.