63011 2025 eng 1 17 147 article Elsevier BV Amsterdam 1 -- -- -- To support the development of solar reactor technologies for hydrogen production, this study investigates the thermo-oxidative degradation mechanisms of fluorinated elastomers and predicts their lifetimes at high temperatures (200–300 ◦C) consistent with the application requirements. An accelerated ageing programme is conducted with FKM and FFKM O-rings and flat samples for up to 21 days. Optical microscopy is used to analyse the exposed seals’ morphological changes, while IR microscopy is utilised to investigate the underlying chemical degradation mechanisms of both elastomers. Findings suggest that FKM’s degradation arises from dehydrofluorination of the polymer, followed by chain scission and backbone cleavage as a result of the oxidation of newly formed C=C double bonds. FFKM’s degradation is primarily associated with chain scission, but there is also indication that post-curing processes may occur during material ageing. Furthermore, hardness, equilibrium compression set (CS), continuous compression stress relaxation (CSR) and leakage rate tests are used to evaluate changes in the mechanical properties and sealing performance of the elastomers. Equilibrium CS data is extrapolated using time-temperature shifts (TTS) and used to derive an end-of-life criterion of 75 % equilibrium CS, which correlates to leakage rates higher than a predetermined threshold. Service lifetime predictions of FKM and FFKM O-rings at several temperatures are performed and a seal operating temperature of 200 ◦C is suggested, which ensures reasonable O-ring replacement intervals of more than half a year in the solar reactor for both considered materials. Polymer Testing 10.1016/j.polymertesting.2025.108820 1873-2348 urn:nbn:de:kobv:b43-630112 true journal-article publish 12.05.2025 1 Creative Commons - CC BY-NC-ND - Namensnennung - Nicht kommerziell - Keine Bearbeitungen 4.0 International E. Vega Puga Volker Wachtendorf Anja Kömmling S. Brendelberger Matthias Jaunich C. Sattler eng uncontrolled Fluoroelastomer eng uncontrolled Perfluoroelastomer eng uncontrolled Thermo-oxidative ageing eng uncontrolled Lifetime prediction eng uncontrolled Compression set Ingenieurwissenschaften und zugeordnete Tätigkeiten 3 Gefahrgutumschließungen; Energiespeicher 3.4 Sicherheit von Lagerbehältern 7 Bauwerkssicherheit 7.5 Technische Eigenschaften von Polymerwerkstoffen Energie Material Degradationsmechanismen Verlagsliteratur Datei für die Öffentlichkeit verfügbar ("Open Access") Wissenschaftliche Artikel der BAM Wasserstoff Bundesanstalt für Materialforschung und -prüfung (BAM) https://opus4.kobv.de/opus4-bam/files/63011/Puga_2025_lifetime prediction and degr assessment of FKM and FFKM orings_PoTE.pdf