Influence of thermal dehydrochlorination on the photooxidation kinetics ofPVC samples

A series of PVC samples were thermally dehydrochlorinated under nitrogen. T he amount of HCl was monitored and nine samples with increasing quantity of liberated HCl were obtained (from 0.03 to 2.0% of elimination of HCl, wher e 100% indicates the theoretically total removal of HCl from PVC). These sa mples were characterised with Raman and UV-Vis spectroscopy. Subsequently, the dehydrochlorinated resins were subjected to accelerated weathering with UV-B lamps and the kinetics of formation of the photoproducts were followe d with FTIR spectroscopy, in order to study the influence of the presence o f conjugated sequences on the photooxidation of PVC. The results show that the presence of conjugated sequences into the thermally degraded PVC sample s (Raman spectroscopy indicates the presence of long conjugated sequences a lready at dehydrochlorination rates lower than 0.01%) does not influence ei ther the mechanism or the kinetics of the photooxidation of the PVC chains. The mechanism of photooxidation is discussed. (C) 1999 Elsevier Science Lt d. All rights reserved.