Thermal degradation of poly(vinyl chloride). II. Degradation mechanism based on decomposition energetics

On the basis of the measured activation energies for radical and HCl generation in four poly(vinyl chlorides) of controlled structures, an overall mechanism of degradation is proposed. The mechanism is a chain reaction involving a β-chloro elimination from a radical-containing polymer molecule. Molecules containing tertiary C? Cl bonds are shown to undergo a fast initiation. Those containing tertiary C? H bonds are also demonstrated to be highly unstable, but the instability is not associated with the initiation step.