No abstract

No abstract

No abstract

The kinetic perculiarities and mechanism of the nonautocatalytic thermal degradation of PVC with effective removal of HCI are discussed. The papers which are concerned with the mathematical models of the initial stage of the nonautocatalytic thermal dehydrochlorination of idealized PVC, i.e., PVC having no abnormal fragments, the polymer, containing VC units and abnormal groups and the polymer having macromolecules with various stereoregularity, are considered. Mechanism of the autocatalytic thermal degradation of PVC in the presence of HCI is discussed.

The dehydrochlorination of different samples of PVC under vacuum with continuous removal of HCl by freezing, has been studied at 180–210°C. The comparison of the kinetic curves of the dehydrochlorination of various samples of PVC which were obtained by us and other investigators, with the theoretical curves for the thermal degradation of idealized PVC in the absence of HCl has been carried out. This had made it possible to evaluate the influence of unstable fragments present in the original polymer on the initial rate of PVC degradation quantitatively. It has been shown that the distinction between the stationary rates of the dehydrochlorination of various samples of PVC is determined by the difference of the values of the average length of dehydrochlorination chain, lav. The most probable interval of the values of lav has been ascertained to be 4–12. It is established that the most probable value of the constant of the rate of dehydrochlorination of normal links of PVC, k0, is 2.1 × 10−7−2.5 × 10−7 s−1 at 200°C. © 1993 John Wiley & Sons, Inc.