INITIATED OXIDATION OF POLYENES FORMED IN THERMAL-DEGRADATION OF PVC

Results of an experimental study are presented which show that polyenes formed in the thermal degradation of PVC are readily oxidized in the liquid phase in the presence of a radical initiator. In pure oxygen at a constant rate of initiation, different length polyenes are consumed by a first-order reaction: the rate of consumption is proportional to the polyene length and to the square root of initiator concentration. Applying the relationships given by the theory of chain reactions, we determined the ratio of the rate constant of chain propagation calculated for one double bond k//2 to the square root of the chain-termination rate constant k//4. The value obtained, relatively high in comparison to other unsaturated hydrocarbons, reflects very well the high reactivity of polyenes of the degraded PVC sample towards oxidations. Intramolecular chain propagation steps are also likely to play a role in the oxidation of polyenes.