Studies of Recycling of Poly(vinyl chloride) in Molten Na, Ca ‖ NO3, OH Systems

Abstract

The interaction of poly(vinyl chloride) (PVC) with components of molten inorganic systems at the temperature range 200–500°C was studied by a combination of thermogravimetric and differential-thermal methods. The results of this study show that the melts of alkali and alkaline-earth metal nitrates can be used for utilization of wastes of halogen-containing polymeric materials. It was established that unique solid products of interaction of PVC with components of the Ca(NO3)2–Ca(OH)2 mixes are ecologically safe calcium chloride and carbonate. Their formation proceeds in three stages including reactions of PVC dehydrochlorination, interactions of formed hydrocarbon residue and hydrogen chloride with calcium hydroxide and calcium nitrate, oxidation of the hydrocarbon residue, and carbonation of calcium hydroxide. A scheme for the oxidative degradation of PVC and for the binding of chlorine and carbon from the polymer in the reactions with components of Ca(NO3)2–NaNO3 and Ca(NO3)2–Ca(OH)2 mixtures was suggested, involving a series of consecutive and parallel reactions.