Effect of thermal stabilizers (Ba/Cd/Zn metal salts carboxylate and dibasic lead stearate), on the photodegradation of PVC films.

Abstract

The photodegradation of polyvinylchloride (PVC) modified by the incorporation of thermal stabilizers namely dibasic lead stearate (DLS) and a mixture of (Ba/Cd/Zn) metal salts carboxylate, was investigated by means of thermal analyses methods: differential scanning calorimetry (DSC) and thermogravimetry (TG). By using DSC it has been shown that the addition of stabilisers to PVC affects its thermal behaviour. Eight (8) different formulations have been prepared for this purpose. It has been shown that DLS and Ba / Cd / Zn, which are both heat stabilizers, operate differently their stabilization effects on PVC. During processing, the former is only moderately consumed, while the latter reacts almost entirely. The DSC analysis and the oxidative induction time (OIT) measurements have shown that the unreacted DLS concentration interacts with UV light leading to its progressive consummation with ageing time. OIT measurements have also revealed that a very small amount of unreacted Ba/Cd/Zn, not detected by the other characterization methods, remains after processing. The respective effects of each stabilizer and those of their different combinations on PVC stability were discussed in the light of DSC, TG and OIT measurements.

Key words: PVC - UV – Photodegradation - Thermal stabilizer – DSC – OIT - TG.