• Treffer 37 von 27
Zurück zur Trefferliste

Effects of Adapted Ageing Methodology for Elastomeric O-ring Seals

  • At BAM Federal Institute for Materials Research and Testing in Germany, it is our responsibility to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes investigating the elastomer seals used in the containers. Our current goal is a deeper understanding of ageing processes and examination of service lifetime of compressed O-ring seals with regard to interim storage periods which might be longer than the currently licensed 40 years in Germany. For this reason, we started an ageing programme with selected rubbers (HNBR, EPDM, FKM) for investigating the change of properties during accelerated ageing over long periods of time (up to five years). In contrast to standard procedure which recommends the ageing of standard test pieces, we are ageing O-rings, both uncompressed and compressed [1]. This approach takes into account the specific geometry and stress state of compressed O-rings. Additionally, it allows leakage rate measurements asAt BAM Federal Institute for Materials Research and Testing in Germany, it is our responsibility to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes investigating the elastomer seals used in the containers. Our current goal is a deeper understanding of ageing processes and examination of service lifetime of compressed O-ring seals with regard to interim storage periods which might be longer than the currently licensed 40 years in Germany. For this reason, we started an ageing programme with selected rubbers (HNBR, EPDM, FKM) for investigating the change of properties during accelerated ageing over long periods of time (up to five years). In contrast to standard procedure which recommends the ageing of standard test pieces, we are ageing O-rings, both uncompressed and compressed [1]. This approach takes into account the specific geometry and stress state of compressed O-rings. Additionally, it allows leakage rate measurements as the most important property of the sealing system under conditions relevant to the application. Other investigated properties and applied methods include hardness, dynamic mechanic analysis (DMA), thermogravimetric analysis (TGA), compression stress relaxation (CSR, loss of sealing force over time), compression set (CS, increases if resilience decreases), density and tensile tests. The aim is to correlate leakage rate with common material properties in order to identify a suitable and easily measurable end-of-lifetime criterion for elastomer O-ring seals. Furthermore, the appearance of diffusion-limited oxidation (DLO) effects is investigated, as these effects can lead to heterogeneous ageing and thus distorted bulk properties, resulting in overestimated lifetimes [2]. Extrapolations are made using time-temperature shifts and Arrhenius graphs. For hardness and compression set data the extrapolation leads to different lifetimes. This is because crosslinking and chain scission reactions influence hardness in opposite directions [3], whereas both effects add up to increase compression set [4]. After 0.5 years of ageing, EPDM exhibits only slight hardness increase except at 150 °C, while CS increases substantially at all ageing temperatures. On the other hand, for HNBR, both hardness and CS increase strongly. This confirms that crosslinking is the major degradation mechanism in HNBR [5], while in EPDM both crosslinking and chain scission are apparent [6]. Consequently, hardness is not a suitable measure for extrapolation, as a slight hardness increase can be accompanied by significant chain scission, resulting in severe degradation in other properties, such as CS. NMR, TGA, DMA and density measurements can give further information about the contribution of crosslinking or chain scission in the materials at different ageing stages. The experiments are in progress and results will be presented at the conference. References [1] Kömmling A, Waste Management Symposia 2015. [2] Gillen KT, Polym. Eng. Sci. 1989:29:1. [3] Snijders EA, Polym. Degrad. Stab. 2005:89:2. [4] Andrews RD, J. Appl. Phys. 1946:17:5. [5] Bhattacharjee S, Polym. Degrad. Stab. 1991:31:1. [6] Bender H, Kautsch. Gummi Kunststoffe 2001:54.zeige mehrzeige weniger

Metadaten exportieren

Weitere Dienste

Teilen auf Twitter Suche bei Google Scholar Anzahl der Zugriffe auf dieses Dokument
Metadaten
Autor*innen:Anja KömmlingORCiD
Koautor*innen:Matthias Jaunich, Dietmar Wolff
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Deutsch
Titel des übergeordneten Werkes (Deutsch):Polymer Degradation Discussion Group
Jahr der Erstveröffentlichung:2015
Veranstaltung:Polymer Degradation Discussion Group
Veranstaltungsort:Stockholm, Sweden
Beginndatum der Veranstaltung:2015-08-30
Enddatum der Veranstaltung:2015-09-03
Verfügbarkeit des Dokuments:Weder Datei noch physisches Exemplar vorhanden ("No Access")
Datum der Freischaltung:20.02.2016
Referierte Publikation:Nein
Eingeladener Vortrag:Nein
Einverstanden
Diese Webseite verwendet technisch erforderliche Session-Cookies. Durch die weitere Nutzung der Webseite stimmen Sie diesem zu. Unsere Datenschutzerklärung finden Sie hier.