Metal complexes with ligands—organic phosphites as polyolefin antioxidants. III. Kinetics and mechanism of the inhibiting action of individual stable Cu(i)‐complexes with phosphites

Abstract

The general features of behavior of kinetically labile complexes (metal phosphite) revealed earlier 1,2 provide the basis for the prediction of the activity of a new class of oxidation inhibitors. These are individual, stable metal complexes with organic phosphites as main ligands. The remarkable feature of these complexes, as shown as in this article on Cu(I) complexes, is the significant increase in the stoichiometric coefficient of inhibition f due to the suppression of the additional chain consumption of phosphite in the complex. The study of the initiated oxidation of styrene and solid isotactic polypropylene has proved that the phosphite complexes with Cu(I) ion are more effective than free, noncoordinated phosphites; quantitative characteristics of the inhibiting action of these complexes have been calculated. It is proved that termination of oxidation kinetic chains on the inhibitor molecules includes oxidation of coordinated phosphite without changing the oxidation degree of the central ion of metal. During inhibition of the oxidation of the substrate with mixtures of phosphite complexes of Cu(I) and phosphites (in styrene) or with aromatic amines (in polypropylene), the phenomenon of nonadditive strengthening (synergism) was discovered and the mechanism and kinetic regularities of synergism were revealed. This investigation of the phosphite complexes of the ions of Cu(I) presents new opportunities for controlled stabilization of polymers in uncontrolled conditions.