THE ROLE OF HYDROPEROXIDES IN PHOTO-OXIDATION OF POLYOLEFINS, POLYAMIDES AND POLYURETHANE ELASTOMERS

Special attention is focussed on the various hydroperoxides which appear as primary products in the photooxidation of polypropylene, polyethylene and polyurethanes. Hydrogen-bonded tertiary hydroperoxides accumulate in atactic and isotactic polypropylene. In polyethylene, hydroperoxidation in alpha position to the vinylidene group affords monomeric hydroperoxides. In polyamides, hydroperoxidation alpha to the nitrogen atom is predominant. Four different types of hydroperoxides are observed in four thermoplastic polyurethane elastomers processed from aromatic and aliphatic isocyanate and based on polyester- or polyether-amorphous zones. Large variations in thermal and photochemical stabilities are observed as a function of the structure of hydroperoxides and of the nature of the matrix.