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 mixt. of cupric chloride and potassium iodide was examd. Several anal. techniques were employed, in order to evaluate the correlation between chem. modifications, morphol. and mech. properties of PA 6,6 films irradiated at ƒÜ>300 nm, 90 „aC, and 50% relative humidity. IR spectroscopy showed a build-up of carbonyl absorption in the range 1700-1780 cm-1 due to primary and secondary photo-oxidn. 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 amt. of carboxylic acids formed. The morphol. of the samples was found to have an effect on the kinetics of the accumulation of carbonyls, and it was obsd. that at a later stage of exposure the cryst. phase was also involved in the oxidn. process. Tensile tests on films revealed a large redn. in ductility as a result of aging for both neat polymer and HALS-doped polymer. Only a slight redn. in ductility was found for the polymer stabilized with the inorg. mixt. This study evidenced that the mixt. of CuCl2 and KI has a far better long-term stabilizing efficiency in comparison with the HALS stabilizer.