TY - JOUR A1 - Jaunich, Matthias A1 - Wolff, Dietmar A1 - Stark, Wolfgang T1 - Low temperature properties of rubber seals - Results of component tests - N2 - Rubbers are widely used as sealing material in various applications. In many fieldsthefunction of seal materials at lowtemperatures is required. Therefore the understanding of faiiure mechanisms that lead to leakage at low temperatures is of high importance. Therefore the lower Operation temperature limit of rubber seals should be determined in dependence of the material properties. The results of Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) are combined with results of standardized measurements as the compression set according to ISO 815. To reduce the test time of the Standard tests a faster and more efficient technique was developed and applied. In addition the breakdown temperature of the sealing function of O-ring seals at lowtemperatures is measured in a component test Setup in dependence of the material and the degree of compression. KW - Seal KW - O-ring KW - Low temperature KW - Component test KW - Compression set KW - Dichtungen KW - O-Ringe KW - Tiefe Temperatur KW - Bauteilversuche KW - Druckverformungsrest PY - 2013 SN - 0948-3276 SN - 0022-9520 VL - 66 IS - 7-8 SP - 26 EP - 30 PB - Hüthig CY - Heidelberg AN - OPUS4-28894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Ageing of HNBR, EPDM and FKM O-rings N2 - HNBR, EPDM and FKM O-rings were aged uncompressed and compressed at 75 °C, 100 °C, 125 °C and 150 °C for up to 1 year. HNBR exhibited the strongest ageing effects with high increases of hardness and glass transition temperature. Furthermore, heterogeneous ageing caused by diffusion-limited oxidation effects had a significant influence for HNBR at ageing temperatures of 125 °C and 150 °C. EPDM showed similar property changes as HNBR, but less pronounced. FKM displayed only minor ageing effects. O-rings aged in compression exhibited considerable compression set (CS). CS data was used for a time-temperature shift and resulting master curve construction. Leakage rate measurements showed that O-rings can remain leak tight under static conditions even if material properties have already deteriorated strongly. N2 - HNBR-, EPDM- und FKM-O-Ringe wurden unverpresst und verpresst für bis zu 1 Jahr bei 75 °C, 100 °C, 125 °C und 150 °C gealtert. HNBR wies mit hohen Anstiegen von Härte und Glasübergangstemperatur die stärksten Alterungseffekte auf. Weiterhin hatte heterogene Alterung aufgrund von diffusionsbegrenzten Oxidationseffekten einen wesentlichen Einfluss auf HNBR bei Alterungstemperaturen von 125 °C und 150 °C. EPDM zeigte ähnliche Eigenschaftsänderungen wie HNBR, allerdings schwächer ausgeprägt. FKM wies nur geringfügige Alterungseffekte auf. O-Ringe, die verpresst gealtert wurden, hatten eine starke bleibende Verformung (DVR). Die gemessenen DVRWerte wurden für eine Zeit-Temperatur-Verschiebung und die Konstruktion einer Masterkurve genutzt. Leckageratenmessungen zeigten, dass O-Ringe unter statischen Bedingungen dicht bleiben können, auch wenn die Materialeigenschaften schon stark degradiert sind. KW - Aging KW - Degradation KW - Leakage KW - Compression KW - Seal PY - 2016 SN - 0022-9520 SN - 0948-3276 VL - 69 IS - 4 SP - 36 EP - 42 PB - Hüthig CY - Heidelberg, Germany AN - OPUS4-36336 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Influence of Ageing on Sealability of HNBR, EPDM and FKM O-rings N2 - At BAM, which is the federal institute for materials research and testing in Germany, it is one of our tasks to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes assessment of elastomeric seals applied in the containers. Besides examining the low-temperature behaviour and irradiation effects of elastomeric seals, it is our goal to evaluate the service lifetime of the seals with regard to the requirements for long-term safety (40 years and more) of the containers. Therefore, we started an accelerated ageing programme with selected rubbers often used for seals (HNBR, EPDM and FKM) which are aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) up to 1 year. In order to assess sealability, O-rings are aged in compression by 25 % (corresponding to the compression during service) between plates as well as in flanges that allow leakage rate measurements. For comparison, uncompressed O-rings are aged as well. Further methods characterising seal performance are compression stress relaxation (CSR) reflecting the loss of sealing force of a compressed seal over time, and compression set (CS) which represents the recovery behaviour of a seal after release from compression. Additionally, hardness is measured for information about the change of mechanical properties. The experimental results indicate that while hardness, CSR and CS show considerable degradation effects, the leakage rate stays constant or even decreases until shrinkage and the loss of resilience of the aged seal leads to the formation of a leakage path. This indicates that static leakage rate, which is the only available direct seal performance criterion, has only limited sensitivity for the degradation of the seal material. T2 - International Sealing Conference CY - Stuttgart, Germany DA - 12.10.2016 KW - Rubber KW - Seal KW - Degradation PY - 2016 SN - 978-3-8163-0674-9 VL - 2016 SP - 551 EP - 563 PB - VDMA AN - OPUS4-38014 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Aging of elastomeric seals for storage casks N2 - Elastomeric seals are used in many containers, including casks for radioactive waste. However, like all polymers, elastomers are prone to aging, which leads to a loss of sealing force and the ability for recovery which can ultimately result in leakage. Therefore it is important to be able to define an end-of-lifetime criterion and to judge the lifetime of elastomeric seals. For this reason, we started an aging program on three kinds of rubbers (HNBR, EPDM, FKM), monitoring the change of properties at four different aging temperatures over extended periods up to five years. The measured data is used for lifetime prediction by applying a suitable model. T2 - WM2015 Conference CY - Phoenix, Arizona, USA DA - 15.03.2015 KW - Aging KW - Elastomer KW - Seal KW - Leakage KW - Compression PY - 2015 SN - 978-0-9828171-4-8 SP - 15080, 1 EP - 12 AN - OPUS4-33253 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Low temperature properties of rubber seals - influence of gamma irradiation N2 - Rubbers are widely used as sealing material in various applications. In many fields, the function of seal materials at low temperatures is required. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. KW - Compression set KW - Irradiation KW - O-ring KW - Seal PY - 2014 SN - 978-3981407624 SP - 1 EP - 7 AN - OPUS4-32326 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Investigation of the low-temperature performance of rubber seals N2 - For many sealing applications rubbers are applied due to their special material properties and easy use. In many applications as e.g. in aviation, traffic or process technology the material can be exposed to low temperatures during operation. Therefore, it is important to know the material behaviour at those low temperatures to determine the temperature range that allows a safe operation of the seal. In this work, we focus on the behaviour of elastomer seals at low temperatures with regard to potential decrease of leak-tightness or catastrophic seal failure of O-ring rubber seals. This is required as material properties of rubbers are strongly temperature dependent but their temperature application range is not always clearly defined. Based on previous investigations which considered the physical material properties and the seal behaviour under purely static conditions we widen the focus on the sealing performance after a fast partial relief of compressed seals and additional materials. For the investigations, different typical rubber seal materials were used as e.g. fluorocarbon (FKM), ethylene propylene diene (EPDM) and hydrogenated acrylonitrile-butadiene (HNBR) rubber. The correlation of the physical material properties with seal performance is studied. This includes as well purely static sealing applications as the performance during/after fast partial relief of seals at low temperatures. T2 - Polymertec 2018 CY - Merseburg, Germany DA - 13.06.2018 KW - Seal KW - Low temperature KW - Leakage PY - 2018 AN - OPUS4-45214 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Overview of ongoing long-term ageing investigations on elastomer seals N2 - At the Bundesanstalt für Materialforschung und -prüfung (BAM) in Division 3.4 Safety of Storage Containers, one of our tasks is to evaluate the safety of containers designed for disposal of low and intermediate radioactive waste. As such containers might be transported before and stored until disposal, safe enclosure of the radioactive inventory is important for this time span. Elastomer O-rings are widely used as barrier seals in these containers. Thus, as for many other applications, an understanding of the practical effects of ageing degradation on elastomer seals during long-term exposure is mandatory for predicting the lifetime of such components. According to a long-term test programme on three kinds of rubbers (EPDM and FKM (relevant for application), HNBR (for comparison)), over several years we have studied the degradation and the change of mechanical properties (e.g. hardness, strain at break) at four different ageing temperatures (75 °C, 100 °C, 125 °C and 150 °C) as well as the change of sealing properties. Continuous and intermittent compression stress relaxation (CSR) measurements were performed in order to investigate the respective contribution of crosslinking and chain scission to the observed degradation effects. Thus, the degradation kinetics and mechanisms could be resolved more clearly. For assessing the seal performance, compression set (CS) and leakage rate measurements were conducted. The experimental results showed that the O-rings remained leak-tight under purely static conditions even when CSR, CS and mechanical properties already indicated far advanced degradation. For this reason, a modified leakage test involving a small and rapid partial decompression of the seal was developed that enabled determining an end-of-lifetime criterion for O-rings with a safety margin for thermal shrinkage and vibrations. KW - Seal KW - O-Ring KW - Ageing KW - Component tests PY - 2020 SN - 1863-7116 VL - 15 IS - 3 SP - 146 EP - 151 PB - Gupta CY - Ratingen AN - OPUS4-51161 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Influence of gamma irradiation on low temperature properties of rubber seal materials N2 - In many fields the function of seal materials is required at low temperatures. Therefore the understanding of failure mechanisms at low temperatures is of high importance. In some applications elastomeric seals are used in environments with increased irradiation backgrounds, as e.g. in containers for radioactive waste. This paper reports on the influence of gamma irradiation on the low temperature properties of different fluorocarbon rubber (FKM) materials. The samples were irradiated with gamma doses of up to 600 kGy and the induced changes of material properties were tested by methods sensitive to the rubber-glass transition, like DSC and DMA. Additionally, compression set measurements were performed to give information about recovery behaviour at low temperatures. KW - Seal KW - O-ring KW - Low temperature KW - Gamma irradiation KW - Compression set KW - Dichtungen KW - O-Ringe KW - Tiefe Temperatur KW - Gamma-Bestrahlung KW - Druckverformungsrest PY - 2015 SN - 0948-3276 SN - 0022-9520 VL - 68 IS - 6 SP - 85 EP - 89 PB - Hüthig CY - Heidelberg AN - OPUS4-33552 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Alterung von Elastomerdichtungen für Lagerbehälter N2 - Unsere Aufgabe im Fachbereich 3.4 der Bundesanstalt für Materialforschung und prüfung (BAM) ist die sicherheitstechnische Begutachtung von Transport- und Lagerbehältern für radioaktiven Abfall, die für langfristige Zwischenlagerung ausgelegt sind. Ein Arbeitsschwerpunkt ist die Bewertung der Lebensdauer von Metall- und Elastomerdichtungen in den Behältern im Hinblick auf die Anforderungen für langfristige Behältersicherheit (min. 40 Jahre in Deutschland). Um die Eigenschaftsänderungen der Elastomerdichtungen während einer beschleunigten Alterung über lange Zeiträume (bis zu fünf Jahre) untersuchen zu können, wurde ein Alterungsprogramm an ausgewählten Elastomeren (HNBR, EPDM, FKM) begonnen. Im Gegensatz zu Normalterungsverfahren altern wir keine Normteile, sondern O-Ringe im unverpressten sowie verpressten Zustand. Diese Vorgehensweise ermöglicht die Bewertung des Einflusses der Verpressung auf die Alterung sowie die Untersuchung des Bauteilversagens mittels Leckageratenmessungen unter anwendungsnahen Bedingungen. Weitere Charakterisierungsmethoden sind Härtemessung, dynamisch-mechanische Analyse (DMA), Thermogravimetrie (TGA), Druckspannungsrelaxation, Druckverformungsrest (DVR), Dichtebestimmung und Zugversuch. Das Ziel ist, die Leckagerate mit anderen Eigenschaften bzw. Methoden zu korrelieren, um so ein aussagekräftiges und leichter zu bestimmendes Lebensdauerkriterium für elastomere O-Ringe abzuleiten. Während der Alterung können in Abhängigkeit von Material sowie Alterungsdauer und –temperatur Inhomogenitäten aufgrund von diffusionsbegrenzter Oxidation auftreten, durch die sich unterschiedliche Eigenschaften an der Oberfläche und im Volumen der Dichtung ergeben, was zu falschen Lebensdauerabschätzungen führen kann. Mittels Mikrohärtemessung über den Querschnitt werden diese Effekte charakterisiert und bei der Extrapolation mittels Zeit-Temperatur-Verschiebung und Arrheniusgraph berücksichtigt. Bisher liegen Daten von bis zu einem Jahr bei vier verschiedenen Temperaturen (75 °C, 100 °C, 125 °C und 150 °C) gealterten Proben vor. Nach 100 Tagen bei 150 °C weisen HNBR und EPDM schon einen DVR von über 80 % auf, aber noch keinen signifikanten Anstieg der Leckagerate. Diese sinkt zunächst während der Alterung, da die Permeabilität aufgrund von Vernetzungsreaktionen sinkt. Bei HNBR ist dies aufgrund der dominanteren Vernetzungsreaktionen während der Alterung noch stärker ausgeprägt als bei EPDM. T2 - Technomer 2015 - 24. Fachtagung über Verarbeitung und Anwendung von Polymeren CY - Chemnitz, Germany DA - 12.11.2015 KW - Aging KW - Elastomer KW - Seal KW - Leakage KW - Compression PY - 2015 SN - 978-3-939382-12-6 SP - 43 CY - Chemnitz AN - OPUS4-35050 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Ageing of elastomeric seals for storage containers N2 - At BAM Federal Institute for Materials Research and Testing in Germany, it is our responsibility to audit the safety of casks designed for transport and/or storage of radioactive material. With regard to the requirements on long-term safety of the containers, it is necessary to evaluate the service lifetime of the elastomeric seals used in the containers. With ageing, the elastomers will gradually lose their elasticity and their ability for recovery, which might result in a leakage above the allowed level or in a release of radioactivity during an incident. It is important to know the rate of degradation and which property can be used as an practical and easily measurable end-of-lifetime criterion. For this reason, we devised ageing experiments on different kinds of elastomers, namely FKM, EPDM and HNBR. The former two are actually used in containers for radioactive wastes – either as auxiliary seal in casks containing high activity waste, or as main seal in casks for medium or low activity waste. The latter is an often used seal material that is tested for comparative reasons. In our ageing program, these three materials are aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) in order to extrapolate the data to service temperature using a suitable model. They are examined at logarithmic time intervals of several days up to 5 years. The samples are aged in their undeformed O-ring state as well as compressed between flanges with a deformation corresponding to the actual compression during service. Thus we can compare the ageing between relaxed and stressed sample. Additionally, we are ageing samples in flanges that allow leakage rate measurements. Other measurements include monitoring of the recovery force of the seal and the compression set. Furthermore, the samples are examined by thermal and dynamic-mechanical analysis for detecting changes in the glass transition temperature due to crosslinking or chain scission in the material. Besides, hardness is measured as a practical macroscopic indicator. Until now, we have analyzed samples aged up to 100 days. At the highest ageing temperature of 150 °C, the compressed EPDM has already reached a compression set of 95 %, while HNBR and FKM have reached 80 % and 30 %, respectively. Furthermore, HNBR has reached a Shore D hardness of 85, which is an immense increase after the initial value of 80 Shore A. However, when looking at the cross-section of the sample, it was obvious that only a layer of about 1 mm thickness has become so hard, while the inner part remained rubbery. This shows that there has been intense crosslinking mostly near the surface of the HNBR which forms a kind of oxygen diffusion barrier, inhibiting the thermooxidation of the inner part of sample which can retain elastic properties. In EPDM, the oxygen permeability is much greater, which leads to a more homogeneous degradation across the whole sample and thus resulted in a higher compression set. The low compression set of FKM shows the outstanding high-temperature properties of this material. T2 - Annual Meeting on Nuclear Technology 2015 CY - Berlin, Germany DA - 2015-05-05 KW - Elastomer KW - Rubber KW - Aging KW - Lifetime KW - Seal KW - Cask KW - Compression PY - 2015 SN - 978-3-926956-98-9 SP - 1 EP - 10(?) PB - INFORUM-Verl. u. Verwaltungsges. AN - OPUS4-33782 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -