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. Several analytical techniques were employed, in order to evaluate the correlation between chemical modifications, morphology and mechanical properties of PA 6,6 films irradiated at lambda > 300 nm, 90 degrees C, and 50% relative humidity. Infrared 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. The morphology 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. Tensile 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. This study evidenced that the mixture Of CuCl2 and KI has a far better long-term stabilizing efficiency in comparison with the HALS stabilizer. (c) 2005 Elsevier Ltd. All rights reserved.