Thermal dehydrochlorination and stabilization of poly(vinylchloride) in solution: Part IV—Synergistic effects of β-diketone compounds and metal soap stabilizers

Abstract

Thermal degradation of poly(vinylchloride) (PVC) has been carried out in trichlorobenzene (TCB) solution at 187°C in the presence of zinc and calcium stearates and β-diketone compounds (BDCs). BDCs are able to react alone with PVC through C alkylation, but the reaction is strongly enhanced by the metal soap system. In the initial stages of the reaction, both BDC residues and stearate groups are grafted onto the PVC backbone and some crosslinking may occur due to the double reaction of BDC compounds. The initial dehydrochlorination of PVC, as well as the development of polyene sequences are strongly inhibited in the presence of the total system, but later, the degradation of the polymer is accelerated. The rates of all the processes are strongly dependent on the concentration of structural defects initially present in the polymer. Coordination complexes between BDC and zinc compounds and re-equilibrium keto-enol forms of the BDC are observed in the presence of Ca compounds.