Correlations between the chemical structure and the thermal stability of polyvinylchloride. A review

Molecular chain model construction, thermo-stability, and thermo-oxidative degradation mechanism of poly(vinyl chloride)

“…The poly-conjugated systems' constant rate of growth, which is initiated by CAG structure (k p ¼ 0.75 Â 10 À2 s À1 ), is higher by two or more orders of magnitude than the constant containing Cl atoms in the b-position with respect to isolated unsaturated double bonds (k p ¼ 10 À5 s À1 to 10 À4 s À1 ). 20,21 Thus, if thermal degradation followed the CAG mechanism, thermogravimetry (TG) results (Table 4, le) should decrease, which is inconsistent with our experimental results.…”

“…Some researchers 17,18 consider that the formed polyene segments are highly reactive species and that they easily react with oxidizing agents, such as oxygen and ozone. Other researchers [19][20][21] have also proposed that dehydrochlorination of PVC is mainly attributed to the oxygen-containing groups, such as the -C(O)-CH]CH-CHCl-(CAG) group. Furthermore, hydroperoxides, hydroxyls, and carbonyls are generated in polymer molecules during thermal treatment under oxygen atmosphere.…”

“…Minsker 13,20,21 and Lisitskii 19 assumed that the presence of CAG structure causes the instability of PVC resin, whereas Szarka 14 showed that PVC instability can be attributed to the generation of hydroperoxides, carbonyls, and hydroxyl structures under thermal oxidative degradation (Scheme 1). 12,13,16,[20][21][22][23] The main difference between these two typical mechanisms is the position of oxygen molecule attack on the PVC chain. Mechanism I demonstrates that the position of oxygen molecule attack on the main chain of PVC resin is on the unsaturated structure or a carbon atom of the unsaturated sides.…”