TY - CONF A1 - Wolff, Dietmar A1 - Jaunich, Matthias A1 - Stark, Wolfgang T1 - Investigating the performance of rubber seals at low temperatures 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 enclosure 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 for transportation. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is necessary to ensure a proper material choice which is certainly also influenced by additional factors as e.g. the aging behavior. T2 - 14th International high-level radioactive waste management conference CY - Albuquerque, New Mexico, USA DA - 28.04.2013 KW - Rubber seals KW - Elastomers KW - Compression set KW - Low temperature KW - Leakage rate PY - 2013 SN - 978-1-62748-644-6 SP - 1 EP - 7(Paper # 6888) PB - Omnipress AN - OPUS4-28530 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Sturm, Heinz A1 - Stark, Wolfgang A1 - Bovtun, V. A1 - Schulz, Eckhard ED - Xia, Z. T1 - Methods for simultaneous measurements of topography and local electrical properties using scanning force microscopy N2 - Two different approaches to investigate the local complex conductivity and the surface charge with Scanning Force Microscopy (SFM) techniques are presented. It is shown that the measurement of local electrical properties with SFM leads to interesting information about the composition of electrically heterogeneous surfaces T2 - 9th International Symposium on Electrets (ISE 9) CY - Shanghai, China DA - 1996-09-25 PY - 1996 SN - 0-7803-2695-4 U6 - https://doi.org/10.1109/ISE.1996.578073 SP - 223 EP - 228 PB - IEEE Service Center CY - Piscataway, NJ AN - OPUS4-6851 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Sturm, Heinz A1 - Schulz, Eckhard A1 - Stark, Wolfgang A1 - Bovtun, V. A1 - Friedrich, Jörg Florian ED - Olefjord, I. ED - Nyborg, L. ED - Briggs, D. T1 - Techniques for surface composition analysis with scanning force microscopy (SFM) using electrical surface properties T2 - 7th European Conference on Applications of Surface and Interface Analysis CY - Göteborg, Sweden DA - 1997-06-16 PY - 1997 SN - 0-471-97827-2 SP - 579 EP - 582 PB - Wiley CY - Chichester AN - OPUS4-6854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Straet, T. A1 - Bayerl, H. A1 - Stark, Wolfgang A1 - Döring, Joachim A1 - Kürten, Ch. T1 - Ultrasonic Measurements on Thermoset Moulding Compounds KW - Ultraschall KW - Fertigungskontrolle KW - Schallgeschwindigkeit KW - Vernetzungsreaktion KW - Qualitätssicherung PY - 2005 SN - 0945-0084 VL - 95 IS - 7 SP - 1 EP - 5 PB - Hanser CY - München AN - OPUS4-10304 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stark, Wolfgang A1 - Teteris, Gundars A1 - Braun, Ulrike A1 - Bohmeyer, W. A1 - Lange, K. T1 - Kontrolle der Vernetzungsreaktion bei reaktiven Harzen - DSC, Rheologie, DMA, FTIR und Online-Ultraschall im Vergleich N2 - Faserverbundbauteile werden durch Tränkung von Fasergewebe mit flüssigem Harz, in der Regel Epoxidharzen, und anschließender Härtung des Harzes gefertigt. Dabei kann man das Gewebe im Vorfeld mit reaktivem Harz tränken und als so genanntes Prepreg verarbeiten oder man injiziert das frisch mit dem Härter gemischte Harz in ein Werkzeug, in dem das Gewebe bereits liegt - z. B. beim RTM-Prozess. Ausgehend von der Aufgabenstellung, eine Prepregherstellung mit hohem Qualitätsstandard zu realisieren und Möglichkeiten der Fertigungskontrolle für den Prepreg-Verarbeiter aufzuzeigen, wurde an einem für die Prepregherstellung vorgesehenen Harzsystem eine weitgehende Charakterisierung des Aushärtungsverlaufs vorgenommen. Wegen der Schwierigkeit, schnell konstante Aushärtungstemperaturen zu erreichen, wurden bei allen Methoden mit einer Heizrate von 1 K/min von RT bis 200 °C aufgeheizt. T2 - Technomer 2011 - 22. Fachtagung über Verarbeitung und Anwendung von Polymeren CY - Chemnitz, Deutschland DA - 10.11.2011 KW - Thermoanalyse KW - Lineare Aufheizung KW - Online Prozesskontrolle KW - Epoxidharz KW - Prepreg PY - 2011 SN - 978-3-939382-10-2 IS - Kap. 1.1 SP - 1 EP - 9 AN - OPUS4-24910 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Kürten, Ch. T1 - Prozessüberwachung bei duroplastischen Formmassen N2 - Dielektrische Sensoren überwachen den Vernetzungsprozess beim Spritzgießen direkt im Werkzeug. Der Aushärtungszustand wird kontinuierlich verfolgt, Abweichungen werden erkannt und die Zykluszeit optimiert. KW - Prozesskontrolle KW - Aushärtegrad KW - Kochversuch KW - Harnstoffformasse KW - Dielektrik PY - 2006 SN - 0023-5563 IS - 7 SP - 97 EP - 100 PB - Hanser CY - München AN - OPUS4-13084 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stark, Wolfgang A1 - Kürten, C. T1 - Verarbeitung von Harnstoff-Formmassen - Begleitende Online-Prozesskontrolle N2 - Harnstoff-Formmassen gehören zu den duroplastischen Formmassen, die im Werkzeug chemisch vernetzen und so ihre herausragende Temperaturbeständigkeit erreichen. Im Wettbewerb mit Thermoplasten weisen Formmassen den Nachteil auf, dass die Vernetzungsreaktion eine kritische Zeit bedingt, damit die Glasübergangstemperatur soweit verschoben werden kann, dass die heißen Teile stabil und blasenfrei entformt werden können. Die Zykluszeiten sind bei Formmassen daher deutlich höher als bei Thermoplasten. Eine Möglichkeit, die Zykluszeit zu verringern, wäre die Erhöhung der Werkzeugtemperatur, da bekanntlich eine Erhöhung der Reaktionstemperatur um 10 K zu einer Verdoppelung der Reaktionsgeschwindigkeit führt. Allerdings wird dabei das Zeitfenster für die Entformung optimal gehärteter Teile deutlich kleiner, der Prozess anfälliger gegen Schwankungen im Prozess und in der Formmasse-Zusammensetzung. Mit einer Online-Kontrolle des Vernetzungszustands sollte es aber gelingen, den Prozess auch bei einer höheren Werkzeugtemperatur noch stabil zu beherrschen. In der vorliegenden Arbeit wird die Methode der dielektrischen Prozesskontrolle in der Fertigung von Spritzgieß-Formteilen erprobt und die Möglichkeiten einer Prozesssteuerung werden herausgearbeitet. KW - Harnstoffharz KW - Elektroinstallationsteile KW - Aushärtungsverlauf KW - Kochversuch PY - 2008 SN - 0176-1625 VL - 61 IS - 12 SP - 790 EP - 793 PB - Gupta CY - Ratingen AN - OPUS4-18734 LA - deu 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 - 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 - 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 -