Photostabilising action of a p-hydroxybenzoate light stabiliser in polyolefins: Part IV—Catalyst effects and additive interactions in linear low density polyethylene

• Published in: Polymer degradation and stability 1985, Vol.12 (4), p.363-372
• Main Authors: Allen, Norman S., Parkinson, Alan, Loffelman, Frank F., MacDonald, Patrick, Rauhut, Michael M., Susi, Peter V.
• Format: Article
• Language: English
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/0141-3910(85)90126-0

The photostabilising action of a p-hydroxybenzoate light stabiliser (Cyasorb® UV2908) is examined in linear low density polyethylene (LLDPE). The efficiency of this light stabiliser is shown to be significantly influenced by levels of residual catalyst such as Ti and Al. Deactivation of the catalysts with phosphoric acid in 2-propanol markedly improves both the performance and light stability of the stabiliser. Processing history reduces the efficiency of the stabiliser whereas its light stability increases linearly with processing time and is associated with the ability of the residual catalyst to destroy hydroperoxides during processing. Stabilising efficiency, however, is reduced by a corresponding reduction in stabiliser concentration during processing. The stabiliser synergises effectively during both oven ageing and photo-oxidation with a hindered piperidine light stabiliser due to the complementary function of each additive. Thus, whilst the former terminates primarily alkoxy/hydroxy radicals produced from the decomposition of hydroperoxides, the latter destroys hydroperoxides in a stoichiometric reaction and through the nitroxyl radical intermediate which selectively reacts with macroalkyl (P •) radicals and through the hydroxylamine which reacts with peroxy radicals (PO 2 •). Strong synergism is also observed with TiO 2 (rutile).