TY - JOUR A1 - Hoster, B. A1 - Jaunich, Matthias A1 - Stark, Wolfgang T1 - Monitoring of the vulcanisation process by ultrasound during injection moulding N2 - Today rubber is due to its unique property profile one of the most important materials for the production of bearings, dampers or also tires and tubes. In the production of rubber goods a chemical cross-linking reaction (vulcanisation) generates the final material properties. This process takes place during the shape giving of the rubber compound in the mould and can proceed for several minutes. The cross-linking process is influenced by the mixture of the basic polymer, the cross-linking agent, the influence of catalysts and inhibitors and especially the processing conditions. The quality of every ingredient, the reproducibility of the mixing ratio, the homogeneity of the mixture and the accurateness in temperature control can have a direct influence on the cross linking reaction. To control the quality of a rubber compound and verify the processing conditions in industry moving die rheometers, named curemeter, are involved in the production process. Starting from our experience in cure monitoring of thermosetting materials by measuring ultrasound velocity in the mould we extended the measuring principle to rubber vulcanisation monitoring. After first investigations using a compression mould we dealt here with on-line monitoring of vulcanisation in an injection moulding process which is one of the most used techniques in rubber industry. KW - Ultrasonic KW - Sound velocity KW - Vulcanisation KW - On-line monitoring KW - Injection moulding PY - 2009 UR - https://www.ndt.net/search/docs.php3?id=8042 SN - 1435-4934 VL - 14 IS - 9 SP - 1 EP - 9 PB - NDT.net CY - Kirchwald AN - OPUS4-19858 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Stark, Wolfgang A1 - Hoster, B. T1 - Monitoring the vulcanization of elastomers: Comparison of curemeter and ultrasonic online control N2 - The vulcanization of elastomeric materials has a high impact on the properties of the final product. Therefore, it is important to monitor and control this crosslinking process. A common technique to attain the necessary curing time is the use of a curemeter in accordance with ISO 6502 in order to determine the time for full cure of a sample with a standardized geometry. Based on this result and a lot of practical experience, the required curing time for a given product geometry is estimated. Within the scope of this work, a new analysis technique will be compared with the standard procedure. The ultrasonic online control employs ultrasound waves to measure the changes in material properties caused by vulcanization. For this study, a natural rubber compound with a conventional curing system was investigated by both techniques. It was found that the results of the ultrasonic technique show good agreement with the results of the curemeter. KW - Cure process KW - Ultrasound KW - Curemeter KW - Elastomer KW - Vulcanization KW - Online control PY - 2009 U6 - https://doi.org/10.1016/j.polymertesting.2008.11.005 SN - 0142-9418 VL - 28 IS - 1 SP - 84 EP - 88 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-18674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Stark, Wolfgang T1 - Monitoring the vulcanization of rubber with ultrasound: Influence of material thickness and temperature N2 - In consideration of the influence of the curing reaction on the material properties of elastomers, it is very important to control the vulcanization process properly. As shown previously [1], the effects of the vulcanization reaction of an elastomer can be monitored by use of ultrasonic sound waves. This technique has to a certain degree a high similarity to the standard curemeter test according to ISO 6502 but can be applied also inside a production tool. So far, the method was only applied to the vulcanization of one compound at a given temperature and sample thickness. This is now complemented with measurements on another compound system at different temperatures and sample thicknesses. The expected effects of temperature and thickness on the curing behaviour were found by use of the ultrasound online control. KW - Vulcanization KW - Cure process KW - Ultrasound KW - Curemeter KW - Elastomer KW - Natural rubber PY - 2009 U6 - https://doi.org/10.1016/j.polymertesting.2009.08.006 SN - 0142-9418 VL - 28 IS - 8 SP - 901 EP - 906 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-19959 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Stark, Wolfgang T1 - Einfluss der Härtung auf die Materialeigenschaften eines Harnstoffharzes N2 - Über die in der Technik weit verbreitete typisierte Harnstoffformmasse UF 131.5, ein Aminoplast, wird berichtet, dass sie im Zuge der thermisch aktivierten Vernetzungsreaktion wegen "Überhärtung" mangelhafte Eigenschaften annimmt. Zur Verifizierung dieses Effektes werden mithilfe der Ultraschall-Prozesskontrolle gezielt Proben unterschiedlicher Aushärtegrade hergestellt. Sie werden mit verschiedenen Methoden, wie der "Kochprobe" und der Thermoanalyse, charakterisiert und auf ihre Materialeigenschaften untersucht. Dabei zeigt sich ein deutlicher Einfluss der Härtezeit auf die Glasübergangstemperatur der Formmasse. In den mechanischen Eigenschaften ist eine Veränderung allerdings nur in der Schlagzähigkeit festzustellen, die sich mit steigender Härtezeit sogar wesentlich verbessert. PY - 2009 SN - 0025-5300 VL - 51 IS - 11-12 SP - 828 EP - 834 PB - Hanser CY - München AN - OPUS4-20566 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Stark, Wolfgang A1 - Wolff, Dietmar T1 - A new method to evaluate the low temperature function of rubber sealing materials N2 - A new method for the evaluation of the low temperature properties of rubber materials is presented. The method emulates the standardized compression set measurement, which is frequently used for sealing materials, but can be performed within a considerably shorter time. The results are compared with the standard test and found to be qualitatively the same. Slight differences are discussed on the basis of the differences in the measurement procedures. Further data evaluation is done by fitting functions to describe the material behaviour. KW - Sealing material KW - Elastomer KW - Compression set KW - Dynamic mechanical analysis KW - Low temperature behaviour PY - 2010 U6 - https://doi.org/10.1016/j.polymertesting.2010.07.006 SN - 0142-9418 VL - 29 IS - 7 SP - 815 EP - 823 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-21914 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Jaunich, Matthias T1 - Investigation of ethylene/vinyl acetate copolymer (EVA) by thermal analysis DSC and DMA N2 - Two types of commercially applied Ethylene/Vinyl Acetate Copolymers (EVA) for encapsulation of photovoltaic modules were investigated by the thermal analysis methods of Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) in the temperature range from -150 °C to 200 °C. Glass transition, crystal melting and cross-linking were analyzed. The aims of the investigations were to gain more information for incoming goods control and to get information about the whole temperature dependent material properties in the investigated temperature range, starting at very low temperatures up to the crosslinking temperature region. KW - EVA KW - Thermal analysis KW - DSC KW - DMA KW - Glass transition KW - Crystal melting KW - Cross-linking PY - 2011 U6 - https://doi.org/10.1016/j.polymertesting.2010.12.003 SN - 0142-9418 VL - 30 IS - 2 SP - 236 EP - 242 PB - Elsevier Ltd. CY - Amsterdam [u.a.] AN - OPUS4-23206 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Jaunich, Matthias T1 - Thermoanalytische Charakterisierung von Ethylen-Vinylacetat-Copolymer (EVA) für Photovoltaikmodule N2 - Das Ziel der Untersuchungen war mit Hilfe von DSC und DMA EVA-Folien im Anlieferungszustand hinsichtlich der Lage der Glasübergangstemperatur, des Schmelzverhaltens und der Temperaturabhängigkeit der Vernetzungsreaktion zu charakterisieren. Auf dieser Basis sollte die Lieferstabilität im Sinne einer Wareneingangskontrolle auf eine messtechnische Basis gestellt werden. In einem 2. Schritt sollte die vernetzte Folie dahingehend charakterisiert werden, ob infolge der Vernetzung eine Änderung der KW - Photovoltaik KW - Klebfolie KW - EVA KW - DSC KW - DMA PY - 2011 VL - 8 SP - 3 EP - 5 AN - OPUS4-24168 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Stark, Wolfgang A1 - Wolff, Dietmar T1 - Low temperature properties of rubber seals N2 - Rubber is widely used as sealing material in various applications. In many fields the sealing function at low temperatures is necessary. Therefore the understanding of failure mechanisms is of high importance. Rubbers are normally used above their glass-rubber transition region but the minimum working temperature limit is not defined precisely. 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 the standardized compression set according to ISO 815 respectively a modified test using the DMA equipment. N2 - Tiefentemperaturverhalten von Elastomerdichtungen Elastomere werden vielfach als Dichtungsmaterial für verschiedene Anwendungen eingesetzt. In vielen Bereichen ist die Funktion der Dichtung auch bei tiefen Temperaturen erforderlich. Daher ist das Verständnis des Versagensmechanismus von großer Bedeutung. Normalerweise werden Elastomere oberhalb ihres Glass-Gummi Übergangsbereiches eingesetzt aber die minimale Einsatztemperatur ist nicht exakt definiert. Daher ist es sinnvoll diese untere Temperatureinsatzgrenze in Abhängigkeit von den Materialeigenschaften zu bestimmen. Die Ergebnisse der DSC und der DMA werden mit den Ergebnissen des standardisierten Druckverformungsrestes nach ISO 815 und einer abgewandelten Messung mit der DMA kombiniert. KW - Sealing material KW - Elastomer KW - Compression set KW - Dynamic mechanical analysis KW - Low temperature behaviour PY - 2011 SN - 0948-3276 SN - 0022-9520 IS - 03 SP - 52 EP - 55 PB - Hüthig CY - Heidelberg AN - OPUS4-23422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - von der Ehe, Kerstin A1 - Wolff, Dietmar A1 - Völzke, Holger A1 - Stark, Wolfgang T1 - Understanding low temperature properties of elastomer seals N2 - Elastomers are widely used as the main sealing materials for containers for low and intermediate level radioactive waste and as an additional component to metal seals in spent fuel and high active waste containers. The safe encapsulation of the radioactive container inventory has to be guaranteed according to regulation and appropriate guidelines for long term storage periods as well as for temperatures as low as -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 elastomers are strongly temperature dependent. At low temperatures, this is caused by the rubber-glass transition (abbreviated: glass transition). During continuous cooling, the material changes from a rubber-like entropy elastic to a stiff energy elastic behaviour, which allows nearly no strain or retraction. Hence, rubbers are normally used above their glass transition, but the minimum working temperature limit is not defined precisely; this can cause problems during the above noted applications. Therefore, the lower operation temperature limit of elastomer seals must be determined in dependence of the material properties. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are combined with standardised measurements to determine the compression set according to ISO 815. To reduce the test time of the standard tests, a faster technique than normally used was developed. Additionally, the breakdown temperature of the sealing function of complete O ring seals was measured in a component test set-up to compare it with the results of the other tests. The experimental set-up 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. The materials (seals and test sheets) were purchased from a commercial seal producer. KW - Sealing material KW - Elastomer KW - Compression set KW - Dynamic mechanical analysis KW - Low temperature behaviour PY - 2011 U6 - https://doi.org/10.1179/1746510911Y.0000000004 SN - 1746-5095 SN - 1746-5109 SN - 0957-476X VL - 22 IS - 2 SP - 83 EP - 88 PB - Ramtrans Publ. CY - Ashford AN - OPUS4-24015 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Jaunich, Matthias A1 - Bohmeyer, W. A1 - Lange, K. T1 - Investigation of the crosslinking behaviour of ehtylene vinyl acetate (EVA) for solar cell encapsulation by rheology and ultrasound N2 - EVA is a widely used material for the encapsulation of photovoltaic modules. It melts at elevated temperatures, and seals the module before it is crosslinked at temperatures above 130 °C by a peroxide-initiated crosslinking reaction. EVA has good optical properties necessary for application in solar modules. For process optimization and quality management, a method for the quick and reliable characterization of EVA crosslinking behaviour is of great value. Here, the practicability of ultrasound for online crosslinking monitoring is demonstrated. A sound velocity increase of about 8 m/s during the crosslinking reaction is found. The ultrasound results are compared with rheometer measurements performed with a curemeter typically used for the investigation of rubber crosslinking. KW - Ethylene vinyl acetate KW - EVA KW - Crosslinking KW - Ultrasound KW - Rheology KW - Curemeter KW - DSC PY - 2012 U6 - https://doi.org/10.1016/j.polymertesting.2012.07.004 SN - 0142-9418 VL - 31 IS - 7 SP - 904 EP - 908 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-26291 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Stark, Wolfgang A1 - Wolff, Dietmar T1 - Comparison of low temperature properties of different elastomer materials investigated by a new method for compression set measurement N2 - The method for the determination of compression set values with a Dynamic Mechanical Analysis (DMA) setup at low temperatures, which was presented previously, allows a much faster and readily automated procedure than the standardized compression set test according to ISO 815-2. This method is applied to a series of different elastomeric materials that are commonly used for sealing applications. The results of the compression set test are compared with results from thermal analysis to allow an in depth comparison of the material behaviour at low temperatures. Furthermore, a comparison between two EPDM materials is presented. These materials show very similar properties determined by thermo analytical methods such as Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) but differ clearly in their compression set behaviour. This comparison shows the importance and value of information of the compression set test in addition to thermal analysis to judge the behaviour of sealing materials and confirms the relevance of the new compression set test method for the investigation of low temperature properties of elastomers. KW - Sealing material KW - Elastomer KW - Compression set KW - Dynamic mechanical analysis KW - Low temperature behaviour PY - 2012 U6 - https://doi.org/10.1016/j.polymertesting.2012.07.016 SN - 0142-9418 VL - 31 IS - 8 SP - 987 EP - 992 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-26538 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Trappe, Volker A1 - Günzel, Stephan A1 - Jaunich, Matthias T1 - Correlation between crack propagation rate and cure process of epoxy resins N2 - Fracture mechanics approaches are increasingly applied for the characterization of epoxy resin and adhesive mechanical properties. Therefore, the fracture toughness and crack resistance under static load ISO 13586 [1] are often regarded as state of the art to analyse material improvements. However, experimental investigations on fatigue behaviour, thus the crack propagation according to ISO 15850 [2], seem to be much more sensitive to characterize the materials for in service loading conditions. Firstly, an efficient testing concept was developed at BAM. In this framework, the geometry for a modified single edge notched tensile specimen (SET) was developed in order to assure appropriate resolution in measuring the crack length via a CCD-camera [3]. In the next step, the influence of the cure temperature on the fracture-mechanical properties was investigated. KW - Fracture toughness KW - Crack resistance KW - Fracture mechanics KW - Plastics KW - Crack propagation PY - 2012 U6 - https://doi.org/10.1016/j.polymertesting.2012.03.007 SN - 0142-9418 VL - 31 IS - 5 SP - 654 EP - 659 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-26937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Buchholz, Uwe A1 - Jaunich, Matthias A1 - Stark, Wolfgang A1 - Habel, Wolfgang A1 - Petersson, B.A.T. T1 - Acoustic data of cross linked polyethylene (XLPE) and cured liquid silicone rubber (LSR) by means of ultrasonic and low frequency DMTA N2 - Partial discharges may cause damage to electrical insulation of high voltage equipment. They initiate elastic waves in the insulating material, e.g. in the stress cone of an outdoor termination. Localisation of the origin of such elastic waves can help to predict serious damaging processes in the electrical insulation. In order to measure and evaluate the wave propagation effects in typical multilayered elastomeric structures, knowledge of the material properties is required. The propagating velocity and the attenuation of longitudinal waves are important parameters. Values for these quantities found in the literature were not appropriate. Therefore, for cross-linked polyethylene (XLPE) and cured liquid silicone rubber (LSR), the longitudinal wave velocity and the attenuation were evaluated in the temperature interval from -20°C to 50°C and in the frequency range from 200 kHz to 600 kHz using a two-sample ultrasound technique. The loss factor was determined from these measured quantities. Additionally, low frequency Dynamic Mechanical Thermal Analysis (DMTA) was applied to investigate LSR and XLPE in a temperature interval between -100 and 50°C and to check qualitatively the ultrasound data. KW - Acoustic propagation KW - Cross linked polyethylene insulation KW - Mechanical variables measurement KW - Silicone rubber PY - 2012 U6 - https://doi.org/10.1109/TDEI.2012.6180250 SN - 1070-9878 SN - 0018-9367 SN - 1558-4135 VL - 19 IS - 2 SP - 558 EP - 566 PB - Institute of Electrical and Electronics Engineers CY - New York, NY AN - OPUS4-26106 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Jaunich, Matthias A1 - McHugh, J. T1 - Cure state detection for pre-cured carbon-fibre epoxy prepreg (CFC) using temperature-modulated differential scanning calorimetry (TMDSC) N2 - Carbon-fibre prepregs have found widespread use in lightweight applications. They are based on a carbon-fibre fabric impregnated with reactive epoxy resin. Prepreg materials are generally pre-cured so that they have a higher molecular weight than typical resins in order to reduce resin flow, which facilitates storage and later processing properties. The measurements were carried out using commercially available materials and follow the published DMA investigations of the same material. TMDSC was used to find the correlation between curing conditions, the degree of cure and glass transition temperature. TMDSC has the advantage over standard DSC that it enables better determination of the glass transition temperature, which is often accompanied by an exothermic curing reaction, and thus overshadowed. The influence of the amplitude of temperature modulation was tested in preliminary experiments. For non-cured material a glass transition temperature of approximately 0 °C was determined; whereas for the totally cured material it was approximately 230 °C. The changes in degree of cure, temperature of actual glass transition and post-reaction are given as a function of curing time at 180 °C. The correlation between actual glass transition temperature and degree of cure is derived. KW - Prepreg KW - Carbon fibre KW - Glass transition KW - Degree of curing KW - DSC KW - TMDSC PY - 2013 U6 - https://doi.org/10.1016/j.polymertesting.2013.07.007 SN - 0142-9418 VL - 32 IS - 7 SP - 1261 EP - 1272 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-29067 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - Stark, Wolfgang A1 - Jaunich, Matthias A1 - McHugh, J. T1 - Carbon-fibre epoxy prepreg (CFC) curing in an autoclave analogue process controlled by dynamic mechanical analysis (DMA) N2 - Carbon fibre prepregs have found widespread application in lightweight constructions. They are based on a carbon-fibre fabric impregnated with reactive epoxy resin. DMA measurements under temperature conditions similar to an autoclave programme were carried out using commercially available prepreg material with a high glass transition temperature. The characteristic of the temperature programme was a dynamic heating segment at 1.5 K/min followed by a longer isothermal segment at 180 °C. The courses of the storage modulus E', loss modulus E'' and tanδ were recorded. The measuring frequency was varied between 1 Hz and 33.3 Hz. Gelation and vitrification are assigned. The influence of the measuring frequency on the time to vitrification and the correlation with DSC are discussed. The reaction does not end even after 10 h curing at 180 °C, which is interpreted as the slow cessation of the reaction caused by vitrification. KW - Prepreg KW - CFC KW - Curing KW - DMA KW - DSC KW - Autoclave KW - Gelation KW - Vitrification KW - Glass transition PY - 2013 U6 - https://doi.org/10.1016/j.polymertesting.2013.09.014 SN - 0142-9418 VL - 32 IS - 8 SP - 1487 EP - 1494 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-29479 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Stark, Wolfgang A1 - Wolff, Dietmar T1 - Druckverformungsrest bei tiefen Temperaturen N2 - Der Druckverformungsrest (DVR) stellt insbesondere für Dichtungsanwendungen eine wichtige Kenngröße zur Beurteilung der Eignung eines Elastomers dar. Er ermöglicht die Einschätzung des zeitabhängigen Rückstellverhaltens eines Werkstoffs nach Deformation. Neben der Prüfung bei erhöhten Temperaturen, zur Beurteilung des Alterungsverhaltens, lässt sich bei der Durchführung bei tiefen Temperaturen die limitierende Einsatztemperatur bestimmen. Die Versuchsdurchführung unterscheidet sich je nach angewandter Norm und kann einen deutlichen Einfluss auf den DVR-Wert haben. Um bei tiefen Temperaturen eine schnelle Aussage zu gestatten, ist eine im Vergleich zu genormten Methoden deutlich schneller durchzuführende, automatisierte Methode entwickelt und mit Standardmethoden verglichen worden. Durch kontinuierliche Messung des Druckverformungsrests kann die Kinetik der Materialrückstellung betrachtet und dadurch ein effizienter Materialvergleich und eine effiziente Materialauswahl ermöglicht werden. Compression set (CS) is especially for sealing applications an important parameter for material selection. It allows an assessment of the time dependent recovery after deformation. In addition to testing at elevated temperatures which aims at the evaluation of the ageing behaviour, testing at low temperatures permits the determination of the low working temperature limit. The test procedure varies depending on the applied standard and can show a significant effect on the CS value. In order to allow a quick statement regarding low temperatures an automated procedure being significantly faster realisable in relation to the standardised methods has been developed and compared with standard procedures. Continuous measurement of the compression set allows evaluating the recovery kinetics and therefore an efficient comparison and selection of materials. KW - Druckverformungsrest KW - Elastomere KW - Dichtung KW - O-Ring PY - 2014 SN - 0176-1625 VL - 67 IS - 8 SP - 487 EP - 491 PB - Gupta CY - Ratingen AN - OPUS4-31572 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Jaunich, Matthias A1 - Mc Hugh, Jarlath T1 - Dynamic mechanical analysis (DMA) of epoxy carbon-fibre prepregs partially cured in a discontinued autoclave analogue process N2 - Epoxy carbon-fibre prepreg, Hexcel Type 6376 HTS, was investigated using Dynamic Mechanical Analysis (DMA). The DMA characteristic parameters are storage modulus E', loss modulus E' and loss factor tanδ. These parameters are ideally suited to observe the vitrification, referred to as glass transition, resulting from the cross-linking reaction. Detection of the cure state may also be achieved by determining the momentary glass transition temperature of partially cured samples. The consequent use of a multi-frequency measuring regime was used to derive the apparent activation energy for the glass transition process. Different temperature programs were also applied to monitor the curing process directly, as well as to investigate the different states of incomplete cure reached in preceding curing steps. The intention was to provide better understanding of the consequences of an interrupted autoclave curing process and to use DMA to detect the cure state achieved. With DMA, the continuation of an incomplete curing process also can be monitored. DMA measurements up to 300 °C showed, furthermore, that the final glass transition temperature was reduced by thermal degradation at high temperatures. KW - Composites KW - Epoxy KW - Cross-linking KW - Prepreg KW - Degree of cure KW - Glass transition PY - 2015 U6 - https://doi.org/10.1016/j.polymertesting.2014.11.004 SN - 0142-9418 VL - 41 SP - 140 EP - 148 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-32325 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 - JOUR A1 - Grelle, Tobias A1 - Wolff, Dietmar A1 - Jaunich, Matthias T1 - Temperature-dependent leak tightness of elastomer seals after partial and rapid release of compression N2 - A device has been designed, built and tested that allows the investigation of effects of dynamic loads on the leak tightness of elastomer seals at low temperatures. With the test setup, the compression of the tested seal can be reduced by a defined degree in a time period of less than 1 s. For the evaluation of the leak tightness, leakage rates can be determined. It was shown that the rapid partial release of an elastomer seal leads to its failure already at the beginning of the rubber–glass transition and, therefore, at significantly higher temperatures than the loss of leak tightness observed under static conditions. KW - Sealing material KW - Elastomer KW - Dynamic loading KW - Low temperature behaviour KW - Leakage rate PY - 2015 U6 - https://doi.org/10.1016/j.polymertesting.2015.09.009 SN - 0142-9418 VL - 48 SP - 44 EP - 49 PB - Elsevier Ltd. CY - Amsterdam [u.a.] AN - OPUS4-34445 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias ED - Brown, R. ED - Gedde, U. ED - Jaunich, Matthias T1 - Polymer Testing - Editorial N2 - Conferences and trade fairs as meeting points for technical people concerned with testing of polymers. KW - conferences KW - editorial KW - trade fair PY - 2016 U6 - https://doi.org/10.1016/j.polymertesting.2016.06.020 SN - 0142-9418 VL - 2016/53 IS - 1 SP - A1 PB - Elsevier Sci Ltd. CY - Oxford, UK AN - OPUS4-37361 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias T1 - Polymer Testing - Editorial N2 - Thoughts about getting started as Associate Editor for Polymer Testing. KW - Editorial KW - Getting started KW - Polymer Testing PY - 2016 U6 - https://doi.org/10.1016/S0142-9418(16)30279-3 SN - 0142-9418 VL - 2016/51 IS - 1 SP - III PB - Elsevier Sci. Ltd. CY - Oxford, UK AN - OPUS4-37362 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 - JOUR A1 - Agroui, K. A1 - Jaunich, Matthias A1 - Hadj Arab, A. T1 - Analysis techniques of polymeric encapsulant materials for photovoltaic modules: situation and perspectives N2 - The properties of the encapsulant are critical to the long-term performance of photovoltaic (PV) modules under the influence of sunlight including UV, elevated temperature, humidity and diffusion of oxygen. Encapsulation process represents a bout 40% of the whole PV module cost. The introduction of new non-EVA encapsulant material type "Low-Cost, High-Performance" should provide a solution to outdoor yellowing degradation problems. The emerging encapsulant materials exhibit a good compatibility with emerging PV solar cells for long term durability. This new generation of encapsulant materials has the advantage to improve e the PV module performances and long term durability for specific climate like desert regions. This scientific contribution presents an overview of the different encapsulant materials currently on the market, the general requirements of the emerging encapsulant materials and characterizations techniques for degradation, diagnostic and reliability lifetime estimation in the framework of Algerian renewable energy strategy. T2 - Africa-EU Renewable Energy Re search and Innovation Symposium, RERIS 2016 CY - Tlemcen, Algeria DA - 08.03.2016 KW - Solar cell KW - Polymer encapsulant KW - PV module KW - Encapsulation process KW - Analysis technique PY - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-377186 SN - 1876-6102 VL - 2016 IS - 93 SP - 203 EP - 210 PB - Elsevier Ltd. AN - OPUS4-37718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Revealing effects of chain scission during ageing of EPDM rubber using relaxation and recovery experiment N2 - Both chain scission and crosslinking reactions occur during ageing of EPDM rubber. However, with many conventional polymer analysis methods such as hardness and DMA, it is hardly possible to obtain information about the contribution of each reaction type to the measured data. For example, hardness and Tg both increase during ageing of EPDM, indicating crosslinking during ageing, but it is not clear whether this is partly counterbalanced by chain scission reactions which would lower hardness and Tg. An indication that chain scission reactions probably counteract the hardness or Tg increase by crosslinking is given by Compression Set (CS) measurements. CS exhibits a higher change than hardness or Tg, as CS increases additively through both chain scission and crosslinking reactions. In order to elucidate the share of chain scission reactions in the total degradation, a method testing relaxation and recovery behaviour using DMA equipment was applied. The method revealed the strong influence of chain scissions, leading to more pronounced relaxation and higher residual strain after compression. KW - Compression set KW - DMA KW - Nnetwork KW - Crosslinking PY - 2016 U6 - https://doi.org/10.1016/j.polymertesting.2016.10.026 SN - 0142-9418 SN - 1873-2348 IS - 56 SP - 261 EP - 268 PB - Elsevier Ltd. AN - OPUS4-38012 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Effects of heterogeneous aging in compressed HNBR and EPDM O-ring seals N2 - Seals used in containers for dangerous goods need to maintain leak tightness for several decades. For investigating the change in seal material properties during aging, a comprehensive aging program on both uncompressed and compressed EPDM and HNBR seals was started. In order to obtain results closely related to practical conditions, O-rings with a full-scale cord diameter of 10 mm were aged. However, this set-up can lead to heterogeneous aging caused by diffusion-limited oxidation (DLO) effects. These effects depend on material, dimensions, time and temperature. Heterogeneous aging results in distorted bulk properties such as compression stress relaxation and compression set (CS) suggesting that HNBR has better performance than EPDM at 150 °C but which is not the case at 100 °C. The presence of heterogeneous material properties was shown by hardness measurements across the seal cross-section. If DLO-affected data is excluded, extrapolations of CS data are possible using time-temperature shifts and Arrhenius graphs. Exemplary CS values of 50 % and 80 % would be reached after approx. 10 years and 29 years, respectively for HNBR and after approx. 400 years and 1100 years, respectively for EPDM. KW - Ageing KW - Rubber KW - Compression KW - DLO KW - Extrapolation KW - Lifetime prediction PY - 2016 U6 - https://doi.org/10.1016/j.polymdegradstab.2016.01.012 VL - 126 SP - 39 EP - 46 PB - Elsevier Science CY - Oxford AN - OPUS4-35775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Böhning, Martin A1 - Braun, Ulrike A1 - Teteris, G. A1 - Stark, W. T1 - Investigation of the curing state of ethylene/vinyl acetate copolymer (EVA) for photovoltaic applications by gel content determination, rheology, DSC and FTIR N2 - The cure behaviour of a specific ethylene vinyl acetate material as used for encapsulation of photovoltaic modules was analysed by rheometer, differential scanning calorimetry and Fourier transform infrared spectroscopy to test for a suitable replacement for the laborious determination of gel content. The results show that all applied methods are capable of describing the effects of the cross-linking process. Some provide results very similar to those yielded by analysis of the insoluble content, but the question remains as to whether indirect methods should be preferred over the direct measurement of physical properties, e.g. as performed by the curemeter. A material stored for one year was also tested to demonstrate the effect of extended storage on cure behaviour and how this is detected by different methods. This complements the other methods, which were clearly able to detect the different cure behaviour of the aged EVA, whereas determination of the gel content could not. KW - Photovoltaic cell encapsulation KW - EVA KW - Incoming goods control KW - Insoluble content KW - Rheometer PY - 2016 U6 - https://doi.org/10.1016/j.polymertesting.2016.03.013 SN - 0142-9418 VL - 52 IS - 1 SP - 133 EP - 140 PB - Elsevier Ltd. CY - Oxford, UK AN - OPUS4-35918 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grelle, Tobias A1 - Wolff, Dietmar A1 - Jaunich, Matthias T1 - Leakage behaviour of elastomer seals under dynamic unloading conditions at low temperatures N2 - In technical applications, static seals are sometimes also subjected to dynamic loadings. Therefore, the leakage behaviour under dynamic conditions has to be evaluated as well. For this purpose, FKM elastomer seals have been tested by using newly designed equipment that allows for rapid partial release of the seal and simultaneous leakage rate measurement at a wide range of test temperatures. Furthermore, material characterisation was done by using Dynamic Mechanical Analysis, Differential Scanning Calorimetry and Compression Set. It was shown that, under static conditions, the leakage rate increased significantly during cooling at temperatures around 18 K lower than the glass transition range. On reheating, the seal’s functionality was restored in the high temperature region of the glass rubber transition. In the subsequent dynamic release tests, that comprised a reduction of the seal compression within 1 s from 25 % to 23 %, increased leakage rates were observed in the high temperature region of the glass transition range. It was shown that the temperature that is critical for increased leakage is significantly lower under static conditions compared to dynamic conditions. The obtained leakage rates for static tests and dynamic release tests at different temperatures were analysed with reference to results of the material characterisation. KW - Sealing material KW - Rubber KW - Partial release KW - Low temperature behaviour KW - Leakage rate PY - 2017 U6 - https://doi.org/10.1016/j.polymertesting.2016.12.018 SN - 0142-9418 SN - 1873-2348 VL - 58 SP - 219 EP - 226 PB - Elsevier Ltd. CY - Oxford, UK AN - OPUS4-38911 LA - eng 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-423992 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 - JOUR A1 - Jaunich, Matthias T1 - Editorial: Shape memory polymers N2 - In this editorial the focus lies on the testing of shape memory materials. KW - Shape memory polymer KW - Testing PY - 2017 U6 - https://doi.org/10.1016/j.polymertesting.2017.08.019 SN - 0142-9418 VL - 62 SP - A1 PB - Elsevier CY - Oxford AN - OPUS4-41714 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Pourmand, P. A1 - Wolff, Dietmar A1 - Gedde, U.W. T1 - Influence of ageing on sealability of elastomeric 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 the assessment of the service lifetime of elastomeric seals that are part of the container lid system 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 1.5 years. 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 relatively constant or even decreases until shrinkage combined with the loss of resilience of the aged seal leads to leakage. This demonstrates that static leakage rate, which is the only available direct seal performance criterion, has only limited sensitivity towards the degradation of the seal material. CS data is extrapolated using time-temperature shifts and Arrhenius graphs. An exemplary CS of 50 % would be reached after approx. 1.2, 17 and 29 years at 60 °C for HNBR, EPDM and FKM respectively. T2 - PolymerTec 2016 CY - Merseburg, Germany DA - 15.06.2016 KW - Compression KW - Leakage KW - Degradation KW - Rubber KW - Lifetime PY - 2017 U6 - https://doi.org/10.1002/masy.201600157 SN - 1022-1360 SN - 1521-3900 VL - 373 IS - 1 SP - UNSP 1600157, 1 EP - 10 PB - WILEY-V C H VERLAG GMBH CY - Weinheim AN - OPUS4-40958 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias T1 - The average number of references per article published in Polymer Testing over the years N2 - This Editorial is focussed on the changes in the number of references per article published in Polymer Testing from 1980 until today. To set in into context with other changes a comparison with the impact factor of Polymer Testing is presented. KW - Reference KW - Editorial KW - Impact factor KW - Changes with time PY - 2018 U6 - https://doi.org/10.1016/j.polymertesting.2018.05.034 SN - 0142-9418 VL - 68 SP - A1 EP - A2 PB - Elsevier AN - OPUS4-45212 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Trajkovski, B. A1 - Jaunich, Matthias A1 - Müller, W. A1 - Beuer, F. A1 - Zafiropoulos, G. A1 - Houshmand, A. ED - Eppel, S.J. T1 - Hydrophilicity, viscoelastic, and physicochemical properties variations in dental bone grafting substitutes N2 - The indication-oriented Dental Bone Graft Substitutes (DBGS) selection, the correct bone defects classification, and appropriate treatment planning are very crucial for obtaining successful clinical results. However, hydrophilic, viscoelastic, and physicochemical properties’ influence on the DBGS regenerative potential has poorly been studied. For that reason, we investigated the dimensional changes and molecular mobility by Dynamic Mechanical Analysis (DMA) of xenograft (cerabone®), synthetic (maxresorb®), and allograft (maxgraft®, Puros®) blocks in a wet and dry state. While no significant differences could be seen in dry state, cerabone® and maxresorb® blocks showed a slight height decrease in wet state, whereas both maxgraft® and Puros® had an almost identical height increase. In addition, cerabone® and maxresorb® blocks remained highly rigid and their damping behaviour was not influenced by the water. On the other hand, both maxgraft® and Puros® had a strong increase in their molecular mobility with different damping behaviour profiles during the wet state. A high-speed microscopical imaging system was used to analyze the hydrophilicity in several naturally derived (cerabone®, Bio-Oss®, NuOss®, SIC® nature graft) and synthetic DBGS granules (maxresorb®, BoneCeramic®, NanoBone®, Ceros®). The highest level of hydrophilicity was detected in cerabone® and maxresorb®, while Bio-Oss® and BoneCeramic® had the lowest level of hydrophilicity among both naturally derived and synthetic DBGS groups. Deviations among the DBGS were also addressed via physicochemical differences recorded by Micro Computed Tomography, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, X-ray powder Diffractometry, and Thermogravimetric Analysis. Such DBGS variations could influence the volume stability at the grafting site, handling as well as the speed of vascularization and bone regeneration. Therefore, this study initiates a new insight into the DBGS differences and their importance for successful clinical results. KW - Biomaterials KW - Bone grafting KW - Bone substitutes KW - Hydrophilicity KW - Mechanical analysis PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-439890 SN - 1996-1944 VL - 11 IS - 2 SP - Article 215, 1 EP - 19 PB - MDPI AG CY - Basel, Switzerland AN - OPUS4-43989 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 U6 - 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 - JOUR A1 - Grelle, Tobias A1 - Wolff, Dietmar A1 - Probst, Ulrich A1 - Jaunich, Matthias A1 - Völzke, Holger T1 - Component and material investigations on metal seals for high level radioactive waste containers N2 - Long-term investigations performed at BAM look to extend the state of knowledge on safety-related components of interim storage containers. Metal seals act as the primary sealing barrier in the bolted double lid closure system of the containers. The behaviour of metal seals has been investigated for ageing times up to 8.5 years and for various temperatures. The main cause for reduction in useable resilience overtime was due to creep deformation of the outer jacket of the seal. KW - Metal seal KW - Radioactive waste containers KW - Creep KW - Long-term behaviour PY - 2018 SN - 1745-2058 SP - 32 EP - 34 PB - Nuclear Institute CY - London AN - OPUS4-48206 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 - Scission, cross-linking, and physical relaxation during thermal degradation of elastomers N2 - Elastomers are susceptible to chemical ageing, i.e., scission and cross-linking, at high temperatures. This thermally driven ageing process affects their mechanical properties and leads to limited operating time. Continuous and intermittent stress Relaxation measurements were conducted on ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) samples for different ageing times and an ageing temperature of 125 °C. The contributions of chain scission and cross-linking were analysed for both materials at different ageing states, elucidating the respective ageing mechanisms. Furthermore, compression set experiments were performed under various test conditions. Adopting the two-network model, compression set values were calculated and compared to the measured data. The additional effect of physical processes to scission and cross-linking during a long-term thermal exposure is quantified through the compression set analysis. The characteristic times relative to the degradation processes are also determined. KW - Ageing KW - Scission KW - Cross-linking KW - Compression set KW - Physical relaxation PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-486091 SN - 2073-4360 VL - 11 IS - 8 SP - 1280, 1 EP - 12 PB - MDPI AN - OPUS4-48609 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Pourmand, P. A1 - Wolff, Dietmar A1 - Hedenqvist, M. T1 - Analysis of O-ring seal failure under static conditions and determination of end-of-lifetime criterion N2 - Determining a suitable and reliable end-of-lifetime criterion for O-ring seals is an important issue for long-term seal applications. Therefore, seal failure of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) O-rings aged in the compressed state at 125 °C and at 150 °C for up to 1.5 years was analyzed and investigated under static conditions, using both non-lubricated and lubricated seals. Changes of the material properties were analyzed with dynamic-mechanical analysis and permeability experiments. Indenter modulus measurements were used to investigate DLO effects. It became clear that O-rings can remain leak-tight under static conditions even when material properties have already degraded considerably, especially when adhesion effects are encountered. As a feasible and reliable end-of-lifetime criterion for O-ring seals under static conditions should include a safety margin for slight dimensional changes, a modified leakage test involving a small and rapid partial decompression of the seal was introduced that enabled determining a more realistic but still conservative end-of-lifetime criterion for an EPDM seal. KW - EPDM KW - HNBR KW - Seal failure KW - Leak-tightness KW - DLO KW - Oxygen permability KW - DMA KW - Indenter modulus PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-486125 SN - 2073-4360 VL - 11 IS - 8 SP - 1251, 1 EP - 19 PB - MDPI CY - Basel, CH AN - OPUS4-48612 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias T1 - Editorial N2 - Dear Readers, a new year started for all of us (as I write these lines, possibly it was already some time ago when these lines are finally available) and this is the time for the so-called New Year’s resolutions. Setting goals and changing our behavior as well in a private as in a professional context. For Scientists the resolutions may comprise tasks like finalizing a longago started publication, picking up the loose ends of an application for funding or just bringing the running projects in a greater structure. KW - Editorial KW - Polymer Testing PY - 2019 U6 - https://doi.org/10.1016/j.polymertesting.2019.01.010 SN - 0142-9418 VL - 74 SP - A1 PB - Elsevier AN - OPUS4-47406 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 - Erroneous or Arrhenius: A Degradation Rate-Based Model for EPDM during Homogeneous Ageing N2 - To improve the predictive capability of long-term stress relaxation of elastomers during thermo-oxidative ageing, a method to separate reversible and irreversible processes was adopted. The separation is performed through the analysis of compression set after tempering. On the Basis of this separation, a numerical model for long-term stress relaxation during homogeneous ageing is proposed. The model consists of an additive contribution of physical and chemical relaxation. Computer simulations of compression stress relaxation were performed for long ageing times and the results were validated with the Arrhenius treatment, the kinetic study and the time-temperature superposition technique based on experimental data. For chemical relaxation, two decay functions are introduced each with an activation energy and a degradative process. The first process with the lower activation energy dominates at lower ageing times, while the second one with the higher activation energy at longer ageing times. A degradation-rate based model for the evolution of each process and ist contribution to the total system during homogeneous ageing is proposed. The main advantage of the model is the possibility to quickly validate the interpolation at lower temperatures within the range of slower chemical processes without forcing a straight-line extrapolation. KW - Kinetic study KW - Arrhenius KW - TTS KW - Modeling KW - Chemical processes KW - Stress relaxation PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-512931 SN - 2073-4360 VL - 12 IS - 9 SP - 1 EP - 21 AN - OPUS4-51293 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Wolff, Dietmar T1 - Insights for lifetime predictions of O-ring seals from five-year long-term aging tests N2 - O-rings made of HNBR, EPDM and FKM were aged in the compressed and uncompressed state at 150 °C, 125 °C, 100 °C, 75 °C, 60 °C and 23 °C for aging times of up to five years. Hardness was measured and increased with aging time and temperature for HNBR and EPDM, but it remained practically constant for FKM. Indenter modulus measurements were performed on the lateral O-ring surface (that was free of DLO effects) to assess an influence of the compression during aging, but none was detected. The equilibrium compression set (CS) exhibited faster and stronger degradation than hardness and was used for lifetime predictions using the time-temperature superposition (TTS) principle. With an end-of-lifetime criterion of 70 % CS, lifetimes of 4.5 years, 50 years and 526 years at 75 °C were estimated for HNBR, EPDM and FKM, respectively. The activation energies derived from an Arrhenius plot of the shift factors from the TTS were 85 kJ/mol, 99 kJ/mol and 78 kJ/mol for HNBR, EPDM and FKM, respectively, revealing that a higher activation energy does not necessarily mean that the material has a higher lifetime at lower temperatures. Furthermore, the measured lifetime of EPDM O-rings at 100 °C (5 years) was compared to that predicted on the basis of the lifetime at 150 °C as well as 125 °C using the corresponding shift factors. The error of the prediction was only ± 4 %. However, this precise prediction could only be achieved using the five-year long-term aging data. When using only data from aging times up to 0.5 years and 2 years, the lifetime of EPDM O-rings at 100 °C was underestimated by 31 % and 22 %, respectively. KW - HNBR KW - EPDM KW - FKM KW - DLO KW - Hardness KW - Compression set KW - Rubber KW - Elastomer KW - Degradation PY - 2020 U6 - https://doi.org/10.1016/j.polymdegradstab.2020.109278 VL - 179 SP - 109278 PB - Elsevier Ltd. AN - OPUS4-51060 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 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Übersicht über laufende Untersuchungen zur Langzeitalterung von Elastomerdichtungen N2 - Eine Aufgabe des Fachbereichs 3.4 Sicherheit von Lagerbehältern der Bundesanstalt für Materialforschung und -prüfung (BAM) ist es, die Sicherheit von Behältern zur Lagerung von radioaktivem Abfall mit vernachlässigbarer Wärmeentwicklung zu bewerten. Da solche Behälter vor der Entsorgung transportiert und gelagert werden, ist während dieser Zeit ein sicherer Einschluss des radioaktiven Inhalts von größter Bedeutung. Zur Abdichtung dieser Behälter sind Elastomer-O-Ringe weit verbreitet. Um für solche, wie auch für viele andere Anwendungen, eine Voraussage über die Lebensdauer dieser Komponenten treffen zu können, ist es unerlässlich zu verstehen, welchen Einfluss der durch Alterung hervorgerufene Abbau auf Dauer auf die Elastomerdichtungen hat. In einem Langzeittest wurden drei Kautschukarten (EPDM und FKM, die für die Anwendung relevant sind, und HNBR als Vergleich) über mehrere Jahre untersucht. Dabei wurden die Veränderungen der mechanischen Eigenschaften (z. B. Härte und Bruchdehnung) bei vier verschiedenen Alterungstemperaturen (75 °C, 100 °C, 125 °C und 150 °C) sowie das Dichtungsverhalten betrachtet. Um den Einfluss von Vernetzung und Kettenspaltung auf die beobachteten Alterungseffekte zu bestimmen, wurden Messungen zur kontinuierlichen und intermittierenden Druckspannungsrelaxation durchgeführt. Dadurch konnten Erkenntnisse über Kinetik und Mechanismus der Abbaureaktionen gewonnen werden. Zur Einschätzung des Dichtungsverhaltens wurden Durckverformungsrest und Leckagerate gemessen. Die Ergebnisse zeigen, dass die O-Ringe unter statischen Bedingungen auch dann dicht halten, wenn die Werte für Druckverformungsrest, Druckspannungsrelaxation und mechanische Eigenschaften schon auf einen fortgeschrittenen Alterungsabbau hindeuten. Aus diesem Grund wurde ein modifizierter Dichtigkeitsversuch mit einer geringen und schnellen teilweisen Entlastung der Dichtung entwickelt, mit dessen Hilfe sich ein Lebensdauerkriterium bestimmen lässt, das eine Sicherheitsspanne für thermische Schrumpfung und Vibrationen beinhaltet. KW - Alterung KW - O-ring KW - Elastomer Dichtung PY - 2020 SN - 0176-1625 VL - 73 IS - 07-08 SP - 326 EP - 332 PB - Gupta CY - Ratingen AN - OPUS4-51207 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Wolff, Dietmar A1 - Völzke, Holger ED - Krüssenberg, A. T1 - Overview of metal seal tests performed at BAM and implications for extended interim storage N2 - The investigation of the long-term performance of sealing systems employed in containers of 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. The behaviour of metallic seals, which are employed in interim storage casks for spent nuclear fuel and high active waste, over time 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. Our aim is to understand the longterm behaviour of the sealing systems for evaluation of their performance during possible extended interim storage and subsequent transportation. In this contribution an overview of the performed tests and their respective results is given. A focus lies on a comparison between seals with large torus diameter in comparison to small diameters. T2 - Safety of Extended Dry Storage of Spent Nuclear Fuel SEDS2020: International online-workshop CY - Online meeting DA - 03.06.2020 KW - Metal seal KW - Seal performance KW - Long-term investigation KW - Ageing PY - 2020 U6 - https://doi.org/10.3139/124.200071 SN - 0932-3902 VL - 85 IS - 6 SP - 440 EP - 443 PB - Carl Hanser Verlag CY - München AN - OPUS4-51833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Grelle, Tobias A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Wolff, Dietmar T1 - Three-dimensional thermal expansion of neat and irradiated (U)HMWPE materials at elevated temperatures N2 - The thermal expansion of polymeric parts can be an issue in many applications where the available space is limited, or exact dimensions of the part are required. For this study, a device was designed and built that allowed measuring the thermal expansion simultaneously in all three spatial directions on cubic samples with real-scale dimensions (78 mm edge length). The results are shown between 25 °C and 125 °C for two PE materials, one HMWPE and one tempered UHMWPE, for non-irradiated samples as well as cubes that have been irradiated with 100 and 400 kGy. The results measured with the new device were very similar to those measured with conventional thermo-mechanical analysis equipment and to literature data of UHMWPE. The HMWPE material shows a much larger thermal expansion coefficient in one direction compared to the other two directions during the first heating due to frozen stresses from the pressing step during material manufacturing. These stresses are mostly released by the expansion during the first heating, so that the expansion during the second heating is more uniform. The overall volumetric expansion is the same for both heating runs. By contrast, the tempered UHMWPE material shows no significant difference between first and second heating run, as the stresses from processing could already relax in the tempering step. The irradiation treatment does not affect the values significantly for the given test set-up. KW - Lupolen KW - Ultra high molecular weight polyethylene KW - GUR KW - Coefficient of thermal expansion KW - High temperature PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-563987 SN - 0142-9418 VL - 117 SP - 1 EP - 8 PB - Elsevier Ltd. AN - OPUS4-56398 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 - Oxidative ageing of elastomers: Experiment and modelling N2 - During an extensive test programme at the Bundesanstalt für Materialforschung und prüfung, material property changes of EPDM O-rings were investigated at different ageing times and two ageing temperatures of 125∘C and 150∘C. To exclude possible diffusion-limited oxidation (DLO) effects that can distort the data, IRHD microhardness measurements were taken over the cross section of compressed O-rings. Continuous stress relaxation measurements were taken on samples free of DLO effects. The additional effect of physical processes to irreversible chemical ones during a long-term thermal exposure is quantified by the analysis of compression set measurements under various test conditions. By combining the different experimental methods, characteristic times relative to the degradation processes were determined. On the basis of experimental data, a microphysically motivated model that takes into account reversible and irreversible processes was developed. The parameter identification strategy of the material model is based on our experimental investigations on homogeneously aged elastomer O-rings. The simulated results are in good agreement with the experiments. KW - Compression stress relaxation KW - Compression set KW - IRHD microhardness KW - Modelling PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-545910 SN - 1432-0959 SP - 1 EP - 9 PB - Springer CY - Berlin AN - OPUS4-54591 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 - Understanding the recovery behaviour and the degradative processes of EPDM during ageing N2 - Recovery is an important measure for seal applications representing to which extent the elastomer regains its initial shape after deformation and release of an applied force. Compression set (CS) indicates the degree of recovery. Ethylene propylene diene rubber (EPDM) was aged at 75 ◦C, 100 ◦C, 125 ◦C and 150 ◦C for different ageing times up to five years and compression set measurements were performed at different times after disassembly and after additional tempering. Short- and long-term recovery up to one year after release for samples aged at 125 ◦C and 150 ◦C was also studied. To assess the curvature in the Arrhenius diagram that may occur due to non-sufficiently aged specimens, a degradation-rate based model was fitted to the CS data after tempering. For each ageing temperature, two decay fit functions were proposed, each with an activation energy and a corresponding degradative process. The influence of ageing on the leak-tightness after fast small partial release is investigated and estimated through the analysis of the shift factors from time temperature superposition (TTS) of CS measurements at different times after disassembly. Shift factors of CS measurement after 1 s and after additional tempering are in good agreement. KW - Compression set KW - Ageing KW - Recovery KW - Degradative processes KW - Leakage rate PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-573699 SN - 0142-9418 VL - 121 SP - 107987 PB - Elsevier Ltd. AN - OPUS4-57369 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-597417 SN - 0360-3199 VL - 63 SP - 207 EP - 216 PB - Elsevier B.V. AN - OPUS4-59741 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -