TY - JOUR A1 - Kömmling, Anja A1 - von der Ehe, Kerstin A1 - Wolff, Dietmar A1 - Jaunich, Matthias T1 - Effect of high-dose gamma irradiation on (U)HMWPE neutron shielding materials N2 - High and ultra-high molecular weight polyethylenes were gamma-irradiated with doses up to 600 kGy. The changes in the material properties were analysed using DSC, DMA, IR spectroscopy, as well as measurements of density and insoluble content. The irradiation led to an increase of the degree of crystallinity because of chain scissions during irradiation, leading to shorter and thus more mobile chains. Both the plateau value of the shear modulus G′ and the insoluble content increased with Irradiation dose, indicating the formation of additional crosslinks. Furthermore, IR spectroscopy revealed irradiation induced oxidation and the formation of double bonds, indicating that some of the hydrogen atoms responsible for the neutron shielding capability have been released. KW - Ultra high molecular weight KW - Polyethylene KW - Gamma irradiation KW - Crosslinking KW - Oxidation PY - 2018 DO - https://doi.org/10.1016/j.radphyschem.2017.02.014 SN - 0969-806X VL - 142 SP - 29 EP - 33 PB - Elsevier AN - OPUS4-42941 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von der Ehe, Kerstin A1 - Jaunich, Matthias A1 - Wolff, Dietmar A1 - Böhning, Martin A1 - Goering, Harald T1 - Radiation induced structural changes of (U)HMW polyethylene with regard to its application for radiation shielding N2 - The special properties of high molecular weight polyethylene (HMW-PE) and ultra high molecular weight polyethylene (UHMW-PE) result basically from their extreme chain lengths and their high degree of crystallinity. As high-performance polymers, they are used for a variety of applications. UHMW-PE in particular is often utilized for endoprothesis (due to its excellent slip and wear properties) and due to its high hydrogen content as a neutron moderator in casks for storage and transport of radioactive materials. To prepare the material for instance for its use as a total joint replacement, it is exposed to radiation for several reasons, such as sterilization and crosslinking, leading to partial improvement of the mechanical properties (e.g. fracture toughness, crack propagation resistance, wear resistance) and better chemical stability. To be applicable for long term radiation shielding purposes for instance over a period of 40 years, PE has to withstand any type of degradation affecting safety relevant aspects. The scope of our investigation comprises an estimation of the radiation impact on the molecular and supra molecular structure of two types of PE and to what extent these changes are detectable by thermo-analytical (TA) methods, such as Differential Scanning Calorimetry (DSC), Thermo Mechanical Analysis (TMA), Dynamic Mechanical Analysis (DMA) and Thermo Gravimetric Analysis (TGA). Additionally FT-IR spectroscopy as well as density and gas sorption measurements were carried out. Due to the poor solubility of HMW-PE and UHMW-PE, some classical analytical techniques are not applicable. But TA-methods represent a feasible approach to detect structural and morphological features of these materials as well as changes caused by external influences, such as thermal treatment and/or irradiation. With the combination of the applied TA-techniques it is possible to distinguish between crosslinking and degradation. T2 - PATRAM 2010 - 16th International symposium on the packaging and transport of radioactive materials CY - London, UK DA - 2010-10-03 PY - 2010 SP - 1 EP - 8 (T25/Paper 173) AN - OPUS4-24621 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wolff, Dietmar A1 - von der Ehe, Kerstin A1 - Jaunich, Matthias A1 - Böhning, Martin T1 - Performance of neutron radiation shielding material (U)HMW-PE influenced by gamma radiation N2 - Due to their extreme high hydrogen contents high molecular weight (HMW-) and ultra-high molecular weight (UHMW-) polyethylene (PE) are a comprehensible choice as neutron radiation shielding material in thick walled metallic casks for storage and transport of radioactive materials. For this application it has to be taken into consideration that gamma radiation – that is a direct consequence of inserting radioactive material in such casks – has a high influence on the molecular structure of polyethylene. In order to be applicable for long-term neutron radiation shielding purposes during the whole storage period (in Germany for instance up to 40 years) PE has to withstand any type of degradation affecting safety relevant aspects. The scope of our work comprises an estimation of the influence of gamma radiation and temperature on the molecular and supra molecular structure of (U)HMW-PE used as cask components for neutron radiation shielding. Therefore it was investigated to what extent these changes are detectable by a combination of conventional polymer characterization techniques such as Differential Scanning Calorimetry (DSC), Thermo Mechanical Analysis (TMA), Dynamic Mechanical Analysis (DMA), and Thermo Gravimetric Analysis (TGA). Additionally optical (FTIR) and weighing methods were applied. For UHMWPE the results are compared with those published for similar UHMW-PE material that is used in medical technology. For this application, gamma irradiation is applied deliberately for purposes such as sterilization and crosslinking, the latter leading to partial improvement of mechanical properties and better chemical stability. As a result the so far observed structural changes of the irradiated material are not safety relevant for the application of polyethylene as neutron shielding material; moreover, some properties actually improve via irradiation. T2 - PSAM 11 ESREL 2012 - 11th International probabilistic safety assessment and management conference & The annual european safety and reliability conference CY - Helsinki, Finland DA - 25.06.2012 KW - (U)HMW-PE KW - Gamma irradiation KW - Shielding material KW - Cask for storage and transport of radioactive materials PY - 2012 SP - 1 EP - 8 AN - OPUS4-26176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von der Ehe, Kerstin T1 - UHMW-PE - A shielding material with special properties influenced by radiation T2 - Jahrestagung Kerntechnik 2011 CY - Berlin, Germany DA - 2011-05-17 PY - 2011 AN - OPUS4-23700 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von der Ehe, Kerstin A1 - Goering, Harald T1 - Radiation induced structural changes of HMW-PE and UHMW-PE as detected by thermo-analytical methods T2 - GEFTA Jahrestagung zum Rahmenthema "Lebenswissenschaften" CY - Giessen, Germany DA - 2009-10-07 PY - 2009 AN - OPUS4-20021 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von der Ehe, Kerstin T1 - Detection of structural changes of (U)HMW-PE induced by gamma irradiation T2 - Polymeric Materials 2010, 14th International Scientific Conference CY - Halle (Saale), Germany DA - 2010-09-15 PY - 2010 AN - OPUS4-21319 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von der Ehe, Kerstin T1 - UHMW-PE Study of structural differences induced by exposure to gamma radiation T2 - 25th Symposium on Effects of Radiation on Nuclear Materials CY - Anaheim, CA, USA DA - 2011-06-15 PY - 2011 AN - OPUS4-23980 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Chatzigiannakis, E. A1 - Beckmann, Jörg A1 - Wachtendorf, Volker A1 - von der Ehe, Kerstin A1 - Braun, Ulrike A1 - Jaunich, Matthias A1 - Schade, U. A1 - Wolff, Dietmar T1 - Discoloration Effects of High-Dose gamma-Irradiation and Long-Term Thermal Aging of (U) HMW-PE N2 - Two polyethylene types with ultra-high (UHMWPE) and high molecular weight (HMW-PE) used as neutron radiation shielding materials in casks for radioactive waste were irradiated with doses up to 600 kGy using a 60Co gammasource. Subsequently, thermal aging at 125∘C was applied for up to one year. Degradation effects in the materials were characterized using colorimetry, UV-Visspectroscopy, IR spectroscopy, and DSC. Both materials exhibited a yellowing upon irradiation.The discoloration of UHMW-PE disappeared again after thermal aging.Therefore, the yellowing is assumed to originate fromannealable color centers in the formof free radicals that are trapped in the crystalline regions of the polymer and recombine at elevated temperatures. For the antioxidantcontaining HMWPE, yellowing was observed after both irradiation and thermal aging. The color change was correlated mainly to decomposition products of the antioxidant in addition to trapped radicals as in UHMW-PE. Additionally, black spots appeared after thermal aging of HMW-PE. KW - Irradiation KW - UHMWPE KW - Colour center KW - Yellowness index PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-423992 DO - https://doi.org/10.1155/2017/1362491 SN - 1687-9422 VL - 2017 IS - Article ID 1362491 SP - 1 EP - 10 PB - Hindawi AN - OPUS4-42399 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - von der Ehe, Kerstin A1 - Wolff, Dietmar A1 - Völzke, Holger A1 - Stark, Wolfgang T1 - Understanding the low temperature properties of rubber seals N2 - Rubbers are widely used as main sealing materials for containers for low and intermediate level radioactive waste and as additional component to metal seals in spent fuel and high active waste containers. The save encapsulation of the radioactive container inventory has to be guaranteed according to legislation and appropriate guidelines for long term storage periods as well as down to temperatures of -40 °C during transport. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. It is known that the material properties of rubbers are strongly temperature dependent. At low temperatures this is caused by the rubber-glass transition (abbr. glass transition). During continuous cooling the material changes from rubber-like entropy-elastic to stiff energy-elastic behaviour, that allows nearly no strain or retraction, due to the glass transition. Hence rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely, what can cause problems during application. 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 the results of standardized measurements as the compression set according to ISO 815. To reduce the test time of the standard tests a faster technique was developed. Additionally, the breakdown temperature of the sealing function of complete O-ring seals is measured in a component test setup to compare it with the results of the other tests. The experimental setup is capable of measuring the leakage rate at low temperatures by the pressure rise method. A fluorocarbon rubber (FKM) was selected for this investigation as it is often used for radioactive waste containers. Some materials (seals and test sheets) were purchased from a commercial seal producer and some materials were compounded and cured at BAM in form of rubber sheets. T2 - PATRAM 2010 - 16th International symposium on the packaging and transport of radioactive materials CY - London, UK DA - 2010-10-03 KW - Dichtungen KW - Elastomere KW - Tieftemperaturverhalten PY - 2010 SP - 1 EP - 7 (Session T41 / Paper 169) AN - OPUS4-23887 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von der Ehe, Kerstin A1 - Jaunich, Matthias A1 - Böhning, Martin A1 - Goering, Harald A1 - Wolff, Dietmar T1 - Detection of structural changes of (U)HMW-PE induced by gamma irradiation T2 - 14th International conference "Polymeric materials" CY - Halle (Saale), Germany DA - 2010-09-15 PY - 2010 SN - 978-3-86829-282-4 SP - 1 EP - 6 PB - Druck-Zuck GmbH CY - Halle / Saale AN - OPUS4-21997 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -