Inhibited oxidation of a polyethylene melt

The oxidation of linear polyethylene inhibited by an effective antioxidant of the phenolic type, viz. 2,2′-methylene-bis (4-methyl-6-tert. butylphenol), has been studied over the temperature range 170–210. There is a critical concentration of antioxidant above which the rate of its consumption is directly proportional to its concentration. Deviations from this dependence are due to chain initiation by direct oxidation of the polymer and to reactions involving the products derived from the antioxidant: these products can also retard the oxidation. Similar results have been obtained using the amine type antioxidant, N-phenyl-N′-cyclohexyl-p-phenylenediamine. Some features of the mechanism of polyolefin oxidation are discussed.