TABLE OF CONTENTS Poly(vinyl chloride) (PVC) has enormous commercial applications, which makes it one of the most well-studied polymers. One of the problems associated with the processing and use of PVC is its low thermal stability despite a general agreement that normal PVC with head-to-tail structures should be quite stable {895401} {883236} {805671} This leads to the assumption that there exist several defect sites in the polymer chain that are responsible for the instability. Such possible defects in PVC are branching, chloroallyl groups, endgroups, oxygen-containing groups, unsaturations and head-to-head structures {704210} {704203} [a.84]. It is therefore of great importance to clearly understand the thermal degradation process of PVC to facilitate its processing and usability.
The thermal degradation of PVC is generally accepted to be a two-step process {893672} {871835} {830034} {755845}. The first step (up to 350 C) mainly involves dehydrochlorination of the polymer (Scheme 6), resulting in the formation of conjugated double bonds that break during the second step (up to 550 C).
In the first step HCl is the main volatile product the amount of the other products is very low, including quantities of benzene and some other hydrocarbons {883234}. The main labile sites for dehydrochlorination are the allylic and tertiary chlorines {865099}. Hydrogen chloride may be anticipated as a possible pyrolysis product from chlorine-containing polymeric materials, and, in any quantitative kinetic study of their thermal...
