Analytical evaluation of the performance of stabilization systems for polyolefinic materials. Part I: Interactions between hindered amine light stabilizers and phenolic antioxidants

Degradation pathways and interactions between the phenolic antioxidant Irganox 1330 and three commercially used hindered amine light stabilizers (HALS) were successfully studied by accelerated aging of model formulations in the polymer-mimicking solvent squalane. Methods based on high-performance liquid chromatography hyphenated with mass spectrometric detection (HPLC-MS) were developed for structural elucidation of transformation products and monitoring of interactions between the two chemical groups. The developed method was able to differentiate and chromatographically separate transformation products originating from the HALS including the active aminoxyl radicals. The investigations showed a strong antagonism between HALS and phenols, leading to useless consumption of both stabilizer groups, whereby tertiary amines showed less effect compared to secondary HALS. By monitoring the degradation behavior of unstabilized squalane it was possible to perform a rating of stabilization efficiencies of the different systems.