Photochemical stability and photostabilizing efficiency of anthracene/hindered amine stabilizers in polymer matrices

Abstract

Adducts of chromophore (anthracene substituted in position 9) and hindered amine stabilizers (HAS) such as 2,2,6,6-tetramethylpiperidine-4-yl 3-(9-anthracene)propanoate, 1-oxo-2,2,6,6-tetrametylpiperidine-4-yl 3-(9-anthracene)propanoate, [2,2,6,6-tetramethyl-piperidine-4-yl 3-(9-anthracene)propanoate]ium chloride as well as model compounds 3-(9-anthracene) propanoic acid and methyl 3-(9-anthracene)propanoate were investigated. The photochemical stability of the adducts was determined in photo-decomposition in polystyrene, poly(methyl methacrylate), poly(vinyl chloride), isotactic polypropylene (iPP) and low density polyethylene (LDPE). Their photo-stabilizing efficiency was determined in iPP and in LDPE. The rate of decomposition of adducts on irradiation λ> 310 nm was very fast in all matrices. Intramolecularly combined chromophore/HAS are more effective stabilizers than 1:1 mixtures of the separated components. The decomposition of anthracene produces free radicals containing HAS. These radicals are able to graft to the polymer chain of iPP and LDPE.