TY - JOUR A1 - Silbernagl, Dorothee A1 - Kömmling, Anja A1 - Zaghdoudi, Maha A1 - Ghasem Zadeh Khorasani, Media A1 - Jaunich, Matthias T1 - Data-driven nanomechanical study of filled fluoroelastomer aged in air and hydrogen atmosphere N2 - Fluoroelastomer (FKM) composites are typically used as sealing materials in challenging non-ambient environments. Depending on the environment, two main aging mechanisms, chemical aging, and physical aging, can be identified. Chemical aging, the degradation of the elastomer, is present for example in thermal-oxidative conditions and can be directly observed as it affects the bulk. Physical aging, relaxation and rearrangement of the elastomers segmental conformation is commonly observed at elevated temperatures and effects predominantly the elastomer interphase. As a highly localized nanoscopic effect it is usually observed indirectly by phenomological approaches and not systematically understood. In this study, as a typical example for chemical aging, filled FKM was aged in air (150°C, 100 days). Physical aging of FKM was realized by exposure to chemically inert H2 (150°C, 50 bar, 100 days), since temperature and gas-induced swelling is known to promote physical aging. The effects of both conditions are directly compared with the initial unaged material. We use atomic force microscopy (AFM) force spectroscopy as a method to resolve nanoscopic heterogeneous FKM. With this method the effect of aging on the spatially distinguishable material phases was directly observed. In thermal oxidative aged FKM the matrix shows a decrease in van der Waals interactions and stiffness, indicating dehydrofluorination and chain scission. In H2 aged FKM, the development of an immobilized amorphous interphase (IAP) was observed, indicating physical aging. By additionally evaluating a larger data set with supervised machine learning, these observations were validated for a larger, statistically representative sample area, allowing conclusions to be drawn about the macroscopic behaviour of the material. KW - Fluoroelastomer KW - Atomic force microscopy KW - Data-driven KW - Hydrogen KW - Ageing mechanism KW - Physical aging KW - Polymer interphase PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-648154 DO - https://doi.org/10.1016/j.polymdegradstab.2025.111715 SN - 0141-3910 VL - 242 SP - 1 EP - 10 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-64815 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Völzke, Holger T1 - Reproducing and discussion of mechanisms in the contact area between metallic seals and flange during aging by finite element analysis (FEA) N2 - When the first site-specific interim storage licenses for DPCs (dual purpose casks), loaded with spent nuclear fuel or vitrified high-level waste from reprocessing were issued, a duration of 40 years was considered for interim storage license application and the long-term safety assessment of casks. In the meantime, the availability of a final repository is further delayed by several decades and thus interim storage for more than a century becomes a necessity. To assess the long-term performance of the typically used metal seals (e.g. Helicoflex), consisting of a helical spring (Nimonic), an inner stainless steel liner and an outer liner made from silver or aluminum, several experimental programs were conducted and are still ongoing. The investigated metal seals are typically mounted in mock-up flange systems and stored at increased temperatures to accelerate the aging process. In certain intervals the remaining seal force, the useable resilience and the corresponding leakage rate are determined. BAM has accompanied such programs for many years and started independent investigations in 2009. Although the remaining seal force is often used as “…one of the key parameters regarding sealing performances over time…” the presented results so far have shown that the courses of the leakage rate and the remaining seal force do not always correlate as expected. In 2016 BAM firstly published results of seals with aluminum liners where the measured leakage rate started to rise after a quite short time period (< 1 year) at 150 °C, although the seal force decreased only slightly compared to the previous measurement. After exceeding the required leakage rate of 10-8 Pa*m3/s it decreased again to acceptable values in the further course of aging. With reference to already published works, BAM has developed a new detailed ABAQUS finite-element (FE) model to represent the behavior of the seal mounted in the mock-up flange during aging, mainly characterized by the creeping of the outer liner. The main goal of the numerical simulation is to reproduce and understand the changing distribution of contact stresses (outer liner/flange) during aging and to discuss if and how it could be causative for the observed early breach of the leak tightness criteria and its later recovery. T2 - PATRAM 2025, 21st International Symposium on the Packaging and Transportation of Radioactive Materials CY - San Antonio, Texas, USA DA - 27.07.2025 KW - Finite element analysis KW - Metallic seals KW - Aging KW - Contact area PY - 2025 SP - 1 EP - 10 PB - INMM CY - Indianopolis, Indiana, USA AN - OPUS4-63882 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Kömmling, Anja A1 - Böhning, Martin A1 - Silbernagl, Dorothee T1 - Comparison of ageing behavior of O-ring seals under hydrogen and air N2 - Elastomeric seals are essential components in the infrastructure which prevent leakage of gas and ensure proper function of technical devices and are therefore highly safety relevant. For proper function a remaining resilience and tolerance to pressure changes is required. The ageing of elastomers is an undesirable but inevitable process leading to a limited lifetime of rubber products such as seals. Independent of the application, as e.g. automotive, piping or container applications, a long lifetime or at least a timely exchange of a seal before occurrence of critical failure is desired. Hydrogen is a key element for the energy turnaround and therefore the compatibility of seals with hydrogen is essential. In addition to the effect of hydrogen uptake and release, which might also cause destructive effects such as rapid gas decompression, ageing at high temperature under hydrogen atmosphere is of interest too. Most of the existing work is addressing the performance of new materials and comprises only very limited investigations concerning long-term use and the behaviour of aged materials in contact with hydrogen. As ageing can lead to substantial changes of material properties, it must be evaluated whether these changes are beneficial or deteriorating for the component function. In this work we present and compare results of the characterization of three sealing materials (EPDM, HNBR, FKM) after ageing at high temperature under hydrogen and air. Despite the common assumption that ageing under hydrogen atmosphere should be less severe for the material in comparison to air ageing, this is not the case for every material. T2 - ASME PVP2025, Pressure Vessels & Piping Conference CY - Montreal, Quebec, Canada DA - 20.07.2025 KW - Aging KW - Seal KW - Compression set KW - Atomic force microscopy PY - 2025 SP - 1 EP - 7 AN - OPUS4-63889 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vega Puga, E. A1 - Wachtendorf, Volker A1 - Kömmling, Anja A1 - Brendelberger, S. A1 - Jaunich, Matthias A1 - Sattler, C. T1 - Lifetime prediction and degradation assessment of FKM and FFKM O-rings under high temperature thermo-oxidative ageing N2 - 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. KW - Fluoroelastomer KW - Perfluoroelastomer KW - Thermo-oxidative ageing KW - Lifetime prediction KW - Compression set PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630112 DO - https://doi.org/10.1016/j.polymertesting.2025.108820 SN - 1873-2348 VL - 147 SP - 1 EP - 17 PB - Elsevier BV CY - Amsterdam AN - OPUS4-63011 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Comparison of Ageing Behavior of O-Ring Seals Under Hydrogen and Air N2 - Elastomeric seals are essential components in the infrastructure which prevent leakage of gas and ensure proper function of technical devices and are therefore highly safety relevant. For proper function a remaining resilience and tolerance to pressure changes is required. The ageing of elastomers is an undesirable but inevitable process leading to a limited lifetime of rubber products such as seals. Independent of the application, as e.g. automotive, piping or container applications, a long lifetime or at least a timely exchange of a seal before occurrence of critical failure is desired. Hydrogen is a key element for the energy turnaround and therefore the compatibility of seals with hydrogen is essential. In addition to the effect of hydrogen uptake and release, which might also cause destructive effects such as rapid gas decompression, ageing at high temperature under hydrogen atmosphere is of interest too. Most of the existing work is addressing the performance of new materials and comprises only very limited investigations concerning long-term use and the behaviour of aged materials in contact with hydrogen. As ageing can lead to substantial changes of material properties, it must be evaluated whether these changes are beneficial or deteriorating for the component function. In this work we present and compare results of the characterization of three sealing materials (EPDM, HNBR, FKM) after ageing at high temperature under hydrogen and air. Despite the common assumption that ageing under hydrogen atmosphere should be less severe for the material in comparison to air ageing, this is not the case for every material. T2 - ASME PVP2025, Pressure Vessels & Piping Conference CY - Montreal, Canada DA - 20.07.2025 KW - Aging KW - Seal KW - Compression set KW - Atomic force microscopy PY - 2025 AN - OPUS4-63888 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Elastomerdichtungen für Wasserstoffanwendungen - Vergleich des Alterungsverhaltens in Luft und Wasserstoff N2 - In diesem Beitrag soll ein Fokus auf das Alterungsverhalten von Elastomerdichtungen unter Wasserstoff gelegt werden. Hierfür wurden Untersuchungen bei einem mittleren Wasserstoffdruck über Alterungszeiten von bis zu 100 Tagen durchgeführt. Das Alterungsverhalten wird im Vergleich der Alterungseffekte unter thermooxidativen Bedingungen betrachtet und bewertet. Die Annahme, dass der Alterungseffekt unter Wasserstoff stets weniger ausgeprägt ist als an Luft bestätigt sich nicht durch die Ergebnisse. T2 - 4. O-Ring-Forum der Firma ISGATEC CY - Bad Schönborn, Germany DA - 15.05.2025 KW - Wasserstoff KW - Dichtung KW - Thermische Alterung KW - Elastomer PY - 2025 AN - OPUS4-63135 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - An update on metal seal tests performed at BAM and implications for interim storage N2 - The investigation of the long-term performance of sealing systems employed in containers for radioactive waste and spent nuclear fuel is one research focus area for division 3.4 “Safety of Storage Containers” at the Bundesanstalt für Materialforschung und -prüfung. Metallic seals are in use in interim storage casks for used fuel and high active waste. Their change in performance over time is of high importance for maintaining safe enclosure. Therefore, investigations on these systems were started at BAM to get a general understanding of the relevant processes. Our investigations comprise investigations on different parameters which influence the seal performance and the main part is focussed on the time and temperature dependent behaviour. In this contribution an update on the performed tests and their respective results will be given in respect to the overview presented in 2020. The understanding of the long-term behaviour of the sealing systems and the performance evaluation during interim storage and subsequent transportation are our goals. T2 - SEDS-Workshop: Sicherheit der längerfristigen trockenen Zwischenlagerung CY - Garching, Germany DA - 15.05.2024 KW - Metal seals KW - Ageing KW - Leakage rate KW - Creep PY - 2024 AN - OPUS4-60640 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Sagradov, Ilja A1 - Wolff, Dietmar A1 - Völzke, Holger T1 - Aging investigations of metal seals used in containers for interim storage of spent fuel N2 - For bolted casks for used fuel and high level waste the sealing system has an important impact of ensuring safe enclosure of the inventory The used metal seals show some changes over time which have been addressed for nearly 15 years in running experiments at BAM The observed changes are temperature de pendent and therefore it is expected that test s at higher temperature allow for an acceleration of the effects and ideally the proposal of an ageing model covering the expected time of use . Nevertheless, questions concerning the influence of the experimental approach on the results and effects taking place at the initial days of ageing remain. To address these a new project was launched to give a better understanding of the seal behavior. T2 - PVP2024, Pressure Vessels & Piping Conference CY - Bellevue, WA, USA DA - 29.07.2024 KW - Metal seal KW - Aging KW - Interim storage PY - 2024 SN - 978-0-7918-8851-3 SP - 1 EP - 4 PB - ASME AN - OPUS4-61357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Tests of metallic seals at Bam 3.4 performed over more than 15 years N2 - The investigation of the long-term performance of sealing systems employed in containers for radioactive waste and spent nuclear fuel is one research focus area for division 3.4 “Safety of Storage Containers” at the Bundesanstalt für Materialforschung und -prüfung (BAM) in Germany. The time dependant behaviour of metallic seals, which are employed in interim storage casks for used fuel and high active waste, is of high importance for ensuring safe enclosure. Therefore, investigations on these systems were started at BAM to get a general understanding of the relevant processes. Our investigations comprise investigations on different parameters which influence the seal performance and the main part is focussed on the time and temperature dependent behaviour. In this contribution an overview of the performed tests and their respective results will be given. T2 - 5th sealing workshop by Maestral CY - Avignon, France DA - 05.11.2024 KW - Metal seal KW - Aging KW - Interim storage PY - 2024 AN - OPUS4-62048 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, M. A1 - Kömmling, Anja A1 - Böhning, Martin A1 - Jaunich, Matthias T1 - Ageing of elastomers in air and in hydrogen environment - A comparative study N2 - EPDM, HNBR and FKM materials were exposed at 150 ◦C to air under atmospheric pressure and to hydrogen at 50 bar for different ageing times. All measurements after hydrogen exposure were conducted on samples in degassed condition to assess irreversible effects resulting from that exposure and to compare them to those after ageing in air. Density, hardness, tensile properties, compression set, and hydrogen permeability of all samples were analysed. In both ageing environments, HNBR exhibited the most significant changes of material properties. However, for both EPDM and HNBR, considerably less severe ageing effects were observed under hydrogen in comparison to ageing in air. On the other hand, FKM showed about the same low level of deterioration in both ageing environments but exhibited poor resistance against damage due to rapid gas decompression in hydrogen environment that can lead to seal failure. The obtained results may serve as a guidance toward a better understanding for design and utilisation of elastomeric materials in future hydrogen infrastructure components. KW - Rapid gas decompression KW - Condensed matter physics KW - Hydrogen KW - Sustainability and the environment KW - Rubber sealing KW - Renewable energy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597417 DO - https://doi.org/10.1016/j.ijhydene.2024.03.053 SN - 0360-3199 SN - 1879-3487 VL - 63 SP - 207 EP - 216 PB - Elsevier CY - Oxford AN - OPUS4-59741 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -