Mechanochemical dechlorination of polyvinyl chloride by co-grinding with various metal oxides

Polyvinyl chloride powder was ground with one of the oxide powders, i.e. CaO, Fe₂O₃, SiO₂ and Al₂O ₃, in air by a planetary ball mill to investigate the mechanochemical dechlorination of PVC. Grinding causes the size reduction of the each component. The PVC powder sample is degraded by grinding with reduction of molecular weight, forming C=C bonds in its structure. The dechlorination occurs in all the ground mixtures, but its phenomenon is classified into two types. One is the solid-phase reaction to form chlorides, CaOHCl and FeCl₂ · 2H₂O, when CaO and Fe₂O₃ powders are used. The other is the release of HCl gas by degradation when SiO₂ and Al₂O₃ powders are used. All the same, the dechlorination yield increases not only with an increase in grinding time, but also with excess of oxide powder.