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

In the present study, the applicability of high-performance liquid chromatography hyphenated with highly sophisticated mass spectrometric detection (HPLC-MS) for analysis of hindered amine light stabilizers (HALS), thiosynergists and their conversion products is demonstrated. Degradation pathways as well as interactions between these stabilizer groups were successfully studied by analytical evaluation of model formulations after accelerated aging in the polymer-mimicking solvent squalane. Binary mixtures including HALS and thiosynergist as well as three component systems additionally including a phenolic antioxidant were investigated. Results showed that transformation pathways of HALS are highly influenced by the presence of sulfur-containing compounds and no aminoxyl radicals (typical reactive intermediates of HALS) were observed in these mixtures. To get an understanding of the effect of this altered stabilization mechanism on the protection of the polymer, rating of stabilization efficacies was performed by comparing the amount of degradation products derived from squalane using different formulations.