Characteristics and mechanism of low temperature dehydrochlorination of poly(vinyl chloride) in the presence of zinc(II) oxide

Characteristics of low temperature (473 K) dehydrochlorination of PVC powder in the presence of ZnO were studied in nitrogen flow and a reaction mechanism was proposed. It was revealed that a large portion of chlorine (ca. 70%) in PVC powder reacts with ZnO accompanying evolution of water and a slight amount of HCl (ca. 0.5%) without any organic gas. Analysis of the solid product by SEM, XRD and IR suggested that an apparent solid-solid reaction proceeds at 473 K via formation of a liquid phase which acts as reaction promoter and that the solid product is abundant in aliphatic (CH)n polymer. It was concluded that the first step of the dehydrochlorination is cross-linking C-C single bond formation in a polymer chain or among polymer chains followed by isomerization to polyene and aromatics.