The combination effect of hindered amine light stabilizers with UV absorbers on the radiation resistance of polypropylene

The UV absorber 2-(2′-hydroxy-3′,5′-dipentyl-phenyl) benzotriazole (Tinuvin 328) shows excellent stabilizing effectiveness in the γ-ray-induced degradation of polypropylene (PP). Antagonism was observed when hindered amine light stabilizers were used with benzotriazole type UV absorbers. The carbonyl index and hydroxyl index, the hydroperoxide concentration, the mass change and the relative concentration of alkyl free radicals of irradiated samples were measured. Tinuvin 328 could effectively inhibit the formation of alkyl free radicals in PP under γ-irradiation, and it is possibly the fundamental reason for its high stabilizing efficiency. A mechanism of dissipating radiation energy for Tinuvin 328 was proposed. Some reactions yet unknown between the two stabilizers decreased their stabilizing effectiveness.