Comparison of photo-oxidative degradation of polyamide 6,6 films stabilized with HALS and CuCl2+KI mixtures

The photo-oxidative stability of polyamide 6,6 (PA 6,6) doped with a hindered amine light stabilizer (HALS) and a mixture of cupric chloride and potassium iodide was examined. l analytical techniques were employed, in order to evaluate the correlation between chemical modifications, morphology and mechanical properties of PA 6,6 films irradiated at λ>300 nm, 90 °C, and 50% relative humidity. ed spectroscopy showed a build-up of carbonyl absorption in the range 1700–1780 cm−1 due to primary and secondary photo-oxidation products. The increase in content of carbonyl groups was greatest in the case of the pure polymer, and it was also appreciable in the case of PA 6,6 stabilized with copper/KI system. On the other hand, the use of the HALS additive brought about a substantial increase in the amount of carboxylic acids formed. rphology of the samples was found to have an effect on the kinetics of the accumulation of carbonyls, and it was observed that at a later stage of exposure the crystalline phase was also involved in the oxidation process. e tests on films revealed a large reduction in ductility as a result of ageing for both neat polymer and HALS-doped polymer. Only a slight reduction in ductility was found for the polymer stabilized with the inorganic mixture. tudy evidenced that the mixture of CuCl2 and KI has a far better long-term stabilizing efficiency in comparison with the HALS stabilizer.