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

Abstract

a b s t r a c tIn 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.

Comparison of Crosslinking Kinetics of UV-Transparent Ethylene-Vinyl Acetate Copolymer and Polyolefin Elastomer Encapsulants

“…According to the data sheets, a gel content of more than 75% for EVA and 60% for POE was stated by the supplier. A qualitative stabilizer analysis of EVA and POE was performed using high-pressure liquid chromatography with UV and mass-spectroscopy detection [ 29 , 30 , 31 ]. The EVA and POE films were stabilized with Irgafos 126 (phosphite-based processing antioxidants) and Tinuvin 770 (a hindered amine light stabilizer (HALS)) with secondary amino groups (–NH–), ester ((C=O)–O–) linkage groups and an aliphatic (–C 8 H 16 –) central group.…”

Mechanisms of Uv Stabilization

“…79 The best performance was obtained with the ternary mixture HALS/thiosynergist/phenol with a degree of stabilization higher than the sum of the stabilization effects of the single components. 79 Numerous examples of synergism can be found in PVC thermal and UV stabilization, which is too broad a topic to discuss here, but it is fully disclosed elsewhere. 68,70…”

“…78 HALS, thiosynergist and a phenolic antioxidant systems were investigated in polyolefins. 79 The transformation pathways of HALS were influenced by the presence of thiosynergists (lack of aminoxyl radicals). 79 HALS alone showed only a limited effect in protecting the polymer.…”

“…79 The transformation pathways of HALS were influenced by the presence of thiosynergists (lack of aminoxyl radicals). 79 HALS alone showed only a limited effect in protecting the polymer. 79 The best performance was obtained with the ternary mixture HALS/thiosynergist/phenol with a degree of stabilization higher than the sum of the stabilization effects of the single components.…”

Investigations at the Product, Macromolecular, and Molecular Level of the Physical and Chemical Properties of a γ-Irradiated Multilayer EVA/EVOH/EVA Film: Comprehensive Analysis and Mechanistic Insights

“…The additives seem to be responsible for the change in the color of the multi-layer EVA/EVOH/EVA-film, but yellowing is not directly observed on the individual additive in solid phase (powder state, dark blueish), as illustrated in Figure 2 with the 2,6-di- tert -butyl- p -cresol. When the additive is dissolved in squalene, hydrocarbon good at mimicking the polymer matrix [ 40 ]. γ-irradiation generates yellowing of the solution, as displayed in Figure 3 .…”