FREE-RADICALS FORMED UPON THE PHOTOLYSIS AND RADIOLYSIS OF POLYMERS .2. PHOTOLYSIS AND PHOTOOXIDATION OF POLYETHYLENE IN THE PRESENCE OF FERROCENIC ADDITIVES

The steps of initiation, propagation, and termination of kinetic chain s in photooxidation of polyethylene and its composites with ferrocenic additives were examined. An increase in the stabilizing ability of th e additives with a rise in their concentration was observed in polyeth ylene photolysis at 77 K. Dual behavior was exhibited by 2,2-bis(1,1'- diethylferrocenyl)propane (FEP) additives at 315 K in the presence of oxygen: they act as sensitizers at a low concentration (0.003 mol/kg) and as inhibitors of initiation and photooxidation processes in polyet hylene at 0.010 mol/kg. The inhibiting effect of FEP additives is asso ciated not only with shielding and quenching of excited states of carb onyl groups in polyethylene, but also with their ability to decompose peroxide radicals. The sensitization is due to an increase in the ligh t absorption because of the presence of FEP additives in polyethylene.