The combination effects of 1

2

2

6

6-pentamethyl-4-hydroxy-piperidine (PMP) with several UV absorbers and quencher during the photo-oxidation of polypropylene film have been examined. It was found that PMP gives a synergistic effect with 2-hydroxy-4-n-octy loxy-benzophenone (UV-531)

an additive effect with nickel (3

5-di-tertbutyl-4-hydroxy ben-zylphosphonate monoethylate) (Irgastab 2002) and a weak antagonistic effect with 2-(2'-hydroxy-3'

5'-di-tert-butyl-phenyl)-5-chlorobenzotriazole (UV-327). The difference be-bween the combination effects of tetramethyl piperidine derivatives and pentamethyl pipe-ridinol with these UV absorbers and quencher was compared.