Etude de la stabilisation du polychlorure de vinyle avec des molecules modeles—IV. Composes epoxydes

Chloro-4-hexene-2 (C4H2), a model compound for the study of polyvinylchloride stabilization, reacts with epoxy compounds in dichloroethane but not in tetrahydrofuran. In the latter case, the reaction is catalysed by zinc chloride but this compound is also a catalyst for the polymerization of the epoxy function. The zinc chloride is then modified so that the kinetic laws for etherification and dehydrochlorination of C4H2 are more complex than when the catalyst is CdCl₂, as previously studied by Anderson and McKenzie. With zinc and calcium stearate, one also observes esterification of C4H2, the three reactions being competitive. The synergistic effect of epoxy in the presence of stearate is induced chiefly by modification of ZnCl₂ through the initiation reaction for the polymerization. Therification, as well as esterification, may be reversed by HCl which regenerates C4H2; this fact explains the catastrophic character of degradation after the stabilizer has been consumed. The results of the study on model compounds can be applied to the degradation of PVC upon mastication in a Brabender plastograph.