TY - CONF A1 - Geburtig, Anja A1 - Kömmling, Anja A1 - Wachtendorf, Volker ED - Reichert, T. T1 - UV-LEDs - a new tool to determine the spectral response T2 - 5th European weathering symposium - Natural and artificial ageing of polymers N2 - To determine a polymer’s spectral response of photo degradation, two main methods have been established. The so-called “filter technique” uses polychromatic radiation, which is filtered by a set of various sharp cut-on filters. This procedure provides separated reading points of an activation spectrum of the investigated material. With the "spectrographic technique” a specimen is irradiated with pectrally dispersed radiation, locally quasi monochromatically, and the local property changes.are related to the radiant exposure at the respective wavelengths. A third method, the irradiation of specimens with quasi monochromatic radiation behind interference filters, is rarely used. These methods have advantages and disadvantages and therefore, there are limits for conclusions from these spectral data. Concerning the quasi monochromatic Irradiation of specimens the development of new UV radiation sources looks promising. With the rapid development of inexpensive UV Light-emitting diodes (LEDs), new : sources of nearly monochromatic radiation in the UV ränge are available, even down to about 250 nm. To determine the spectral response, the use of such UV-LEDs in TO-18 ) and TO-39 metal cases combines the advantages of low cost and energy efficiency, stable spectral irradiance, temperature.and humidity control, larger specimen areas, and an easy and stable analysis. Combinations of different UV LEDs are also discussed as replacement for xenon arc ' radiation sources, see patent application EP01528388A1. T2 - 5th European weathering symposium - Natural and artificial ageing of polymers CY - Lisbon, Portugal DA - 21.09.2011 KW - UV resistance KW - Weathering KW - Spectral sensitivity KW - Action spectrum KW - UV-LEDs PY - 2011 SN - 978-3-9813136-2-8 N1 - Serientitel: CEEES Publication – Series title: CEEES Publication IS - 15 SP - 77 EP - 86 PB - GUS (Gesellschaft für Umweltsimulation) CY - Pfinztal AN - OPUS4-24396 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 Study on Elastomeric O-ring Seals T2 - Kautschuk Herbst Kolliquium / Rubber Fall Colloquium N2 - At BAM Federal Institute for Materials Research and Testing in Germany, it is our responsibility to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes the investigation of elastomeric seals applied in the containers. Besides examining the low-temperature behavior 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. Furthermore, we deem it necessary to exceed the requirements given in the ageing standard DIN 53508 and take into account diffusion-limited oxidation (DLO) effects [1] and non-Arrhenius behavior [2] when making lifetime predictions. Therefore, we started an ageing programme with selected rubbers (HNBR, FKM and EPDM) which are oven-aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) in order to extrapolate the data to service temperature using different models and check which one is appropriate. Samples are examined at different times up to 5 years. In order to be able to compare between compressed and relaxed rubber, they are aged in two conditions: the undeformed O-ring state as well as compressed between plates with a compression of 25 % corresponding to the actual compression during service. Additionally, we are ageing samples in flanges that allow leakage rate measurements which is the central performance criterion. Analysis methods include hardness as a quick indicator, compression set and compression stress relaxation as measures reflecting the actual properties of a compressed seal. Additionally, we are applying classical polymer analysis methods like dynamic mechanic analysis and thermogravimetric analysis which show changes in the polymeric structure due to chain scission and crosslinking. Furthermore, we are testing the leakage rate of the O-rings in order to correlate the changes in physical properties to the actual performance of the seal. First results of samples aged up to 100 days show a strong increase in hardness for HNBR, a moderate increase for EPDM and hardly a change for FKM. A similar result is seen in the compression set of samples aged 100 d at 100 °C in compression as HNBR has reached 60 %, EPDM 25 % and FKM 15 % compression set. However, after ageing at 150 °C, EPDM shows a worse performance with 95 % compression set compared to HNBR with only 80 %. This is probably due to DLO effects in HNBR that appear because of the fast ageing and low oxygen permeability in HNBR. This leads to a deficit of oxygen in the center of the sample which is thus protected from ageing and can retain elastic properties. The full paper shall discuss the changes in material properties observed to date and the impact on the performance of elastomeric seals. References: 1. Wise, J., K.T. Gillen, and R.L. Clough, Quantitative model for the time development of diffusion-limited oxidation profiles. Polymer, 1997. 38(8): p. 1929-1944. 2. Gillen, K., et al., Evidence that Arrhenius high-temperature aging behavior for an EPDM o-ring does not extrapolate to lower temperatures, 1997, Sandia National Labs., Albuquerque, NM (United States). T2 - Kautschuk Herbst Kolliquium / Rubber Fall Colloquium CY - Hannover DA - 2014-11-26 PY - 2014 AN - OPUS4-32200 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Aging of Elastomer Seals for Storage Casks T2 - Waste Management Symposia 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 - Waste Management Symposia CY - Phoenix, AZ, USA DA - 2015-03-15 PY - 2015 AN - OPUS4-32921 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - von der Ehe, Kerstin A1 - Wolff, Dietmar T1 - Neutron Radiation Shielding Material Polyethylene - Consequences of Gamma Irradiation T2 - Waste Management Symposia T2 - Waste Management Symposia CY - Phoenix, AZ, USA DA - 2015-03-15 PY - 2015 AN - OPUS4-32922 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Alterung von Dichtungen für Behälter mit radioaktivem Abfall T2 - Deutsche Kautschuk-Gesellschaft - Tagung Bezirksgruppe Ost T2 - Deutsche Kautschuk-Gesellschaft - Tagung Bezirksgruppe Ost CY - Berlin, Deutschland DA - 2015-05-27 PY - 2015 AN - OPUS4-33397 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Effects of Adapted Ageing Methodology for Elastomeric O-ring Seals T2 - Polymer Degradation Discussion Group N2 - At BAM Federal Institute for Materials Research and Testing in Germany, it is our responsibility to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes investigating the elastomer seals used in the containers. Our current goal is a deeper understanding of ageing processes and examination of service lifetime of compressed O-ring seals with regard to interim storage periods which might be longer than the currently licensed 40 years in Germany. For this reason, we started an ageing programme with selected rubbers (HNBR, EPDM, FKM) for investigating the change of properties during accelerated ageing over long periods of time (up to five years). In contrast to standard procedure which recommends the ageing of standard test pieces, we are ageing O-rings, both uncompressed and compressed [1]. This approach takes into account the specific geometry and stress state of compressed O-rings. Additionally, it allows leakage rate measurements as the most important property of the sealing system under conditions relevant to the application. Other investigated properties and applied methods include hardness, dynamic mechanic analysis (DMA), thermogravimetric analysis (TGA), compression stress relaxation (CSR, loss of sealing force over time), compression set (CS, increases if resilience decreases), density and tensile tests. The aim is to correlate leakage rate with common material properties in order to identify a suitable and easily measurable end-of-lifetime criterion for elastomer O-ring seals. Furthermore, the appearance of diffusion-limited oxidation (DLO) effects is investigated, as these effects can lead to heterogeneous ageing and thus distorted bulk properties, resulting in overestimated lifetimes [2]. Extrapolations are made using time-temperature shifts and Arrhenius graphs. For hardness and compression set data the extrapolation leads to different lifetimes. This is because crosslinking and chain scission reactions influence hardness in opposite directions [3], whereas both effects add up to increase compression set [4]. After 0.5 years of ageing, EPDM exhibits only slight hardness increase except at 150 °C, while CS increases substantially at all ageing temperatures. On the other hand, for HNBR, both hardness and CS increase strongly. This confirms that crosslinking is the major degradation mechanism in HNBR [5], while in EPDM both crosslinking and chain scission are apparent [6]. Consequently, hardness is not a suitable measure for extrapolation, as a slight hardness increase can be accompanied by significant chain scission, resulting in severe degradation in other properties, such as CS. NMR, TGA, DMA and density measurements can give further information about the contribution of crosslinking or chain scission in the materials at different ageing stages. The experiments are in progress and results will be presented at the conference. References [1] Kömmling A, Waste Management Symposia 2015. [2] Gillen KT, Polym. Eng. Sci. 1989:29:1. [3] Snijders EA, Polym. Degrad. Stab. 2005:89:2. [4] Andrews RD, J. Appl. Phys. 1946:17:5. [5] Bhattacharjee S, Polym. Degrad. Stab. 1991:31:1. [6] Bender H, Kautsch. Gummi Kunststoffe 2001:54. T2 - Polymer Degradation Discussion Group CY - Stockholm, Sweden DA - 2015-08-30 PY - 2015 AN - OPUS4-34094 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 Casks T2 - Annual Meeting on Nuclear Technology 2015 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 PY - 2015 AN - OPUS4-33200 LA - eng 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 T2 - Deutsche Kautschuk-Tagung/International Rubber Conference 2015 N2 - At BAM Federal Institute for Materials Research and Testing in Germany, it is our responsibility to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes the investigation of elastomeric seals applied in the containers. Besides examining the low-temperature behavior 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. Furthermore, we deem it necessary to exceed the requirements given in the ageing standard DIN 53508 and take into account diffusion-limited oxidation (DLO) effects [1] and non-Arrhenius behavior [2] when making lifetime predictions. Therefore, we started an ageing programme with selected rubbers (HNBR, FKM and EPDM) which are oven-aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) in order to extrapolate the data to service temperature using different models and check which one is appropriate. Samples are examined at different times up to 5 years. In order to be able to compare between compressed and relaxed rubber, they are aged in two conditions: the undeformed O-ring state as well as compressed between plates with a compression of 25 % corresponding to the actual compression during service. Additionally, we are ageing samples in flanges that allow leakage rate measurements which is the central performance criterion. Analysis methods include hardness as a quick indicator, compression set and compression stress relaxation as measures reflecting the actual properties of a compressed seal. Additionally, we are applying classical polymer analysis methods like dynamic mechanic analysis and thermogravimetric analysis which show changes in the polymeric structure due to chain scission and crosslinking. Furthermore, we are testing the leakage rate of the O-rings in order to correlate the changes in physical properties to the actual performance of the seal. First results of samples aged up to 100 days show a strong increase in hardness for HNBR, a moderate increase for EPDM and hardly a change for FKM. A similar result is seen in the compression set of samples aged 100 d at 100 °C in compression as HNBR has reached 60 %, EPDM 25 % and FKM 15 % compression set. However, after ageing at 150 °C, EPDM shows a worse performance with 95 % compression set compared to HNBR with only 80 %. This is probably due to DLO effects in HNBR that appear because of the fast ageing and low oxygen permeability in HNBR. This leads to a deficit of oxygen in the center of the sample which is thus protected from ageing and can retain elastic properties. The full paper shall discuss the changes in material properties observed to date and the impact on the performance of elastomeric seals. T2 - Deutsche Kautschuk-Tagung/International Rubber Conference 2015 CY - Nürnberg, Germany DA - 2015-06-29 PY - 2015 AN - OPUS4-33594 LA - deu 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 T2 - WM2015 Conference (Proceedings) 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 - von der Ehe, Kerstin A1 - Kömmling, Anja A1 - Wolff, Dietmar T1 - Neutron radiation shielding material polyethylene: consequences of gamma irradiation T2 - WM2015 Conference (Proceedings) N2 - High and ultra-high molecular weight polyethylenes are high performance materials, which are predestined for a wide range of applications due to characteristics like high density, low weight, good dimensional stability, high chemical resistance, and high hydrogen content. These polymers are used in two demanding areas: as implant material in medical technology (only ultra-high molecular weight polyethylenes) and as a component for neutron shielding purposes in casks for storage and transport of radioactive waste. In the medical field (joint replacements) as well as during neutron radiation shielding application, high and ultra-high molecular weight polyethylenes are exposed to gamma irradiation: in the first case requested as sterilization process and for surface-crosslinking and in the second case existing as a side effect of inserting the radioactive material in the cask. Given that polyethylene as shielding material has to withstand any type of degradation affecting safety relevant aspects to be applicable for long-term radiation shielding purposes for instance over a period of 40 years, the durability of the material is of special interest. High molecular weight polyethylene (HMW-PE; LUPOLEN 5261Z; Lyondell Basell) and ultra-high molecular weight polyethylene (UHMW-PE; GUR 4120; Ticona) were subjected to gamma radiation and afterwards thermally treated. The gamma doses used are in the range of 50 to 600 kGy and irradiation takes place at RT using a Co-60 source. The planned thermal treatment will take place at a temperature of 125 °C for periods of minimum 30 days and maximum of five years. With the applied conventional analytical techniques it is possible to detect structural changes of both types of polyethylene induced by gamma irradiation and certainly of thermal treatment. Through gamma irradiation melting temperature, crystallinity, and density, respectively increased. Furthermore both polyethylenes get oxidized and cross-linked. With regard to the special application as neutron radiation shielding material in casks for storage and transport of radioactive materials, the impact of irradiation lead to changes of material properties. A consolidated view indicates that the detected changes of the irradiated (U)HMW-PE are not safety relevant for long-term neutron radiation shielding purposes over a period of 40 years in Germany. T2 - WM2015 Conference CY - Phoenix, Arizona, USA DA - 15.03.2015 KW - Gamma radiation KW - Polyehtylene KW - HMW KW - DSC KW - IR KW - Crosslinking PY - 2015 SN - 978-0-9828171-4-8 SP - 15062, 1 EP - 10 AN - OPUS4-33254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -