Enhancing the efficiency of organic phosphites as inhibitors of the oxidation of solid polypropylene by transition metal ions

Abstract

By reacting with peroxide radicals organic phosphites inhibit the oxidation of solid polypropylene (PP). A quantitative evaluation of the efficiency of two phosphites was carried out; the inhibiting efficiency of the phosphite containing masked phenoxyl fragments in its molecule is higher by one order than that of the unsubstituted triphenylphosphite (as in the liquid phase). The efficiency of organic phosphites is greatly enhanced by additions of acetylacetonates of transition metals to a solid polymer. The observed critical effects are explained in terms of concepts of rapid kinetic chain termination by molecules of a phosphite coordinated in a complex with a metal chelate. It is demonstrated that the synergetic system phosphite+metal is most efficient when the ability of the metal to catalyze the oxidation of solid PP is lowest.