TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Influence of ageing on sealability of HNBR, EPDM and FKM O-rings N2 - At BAM, which is a 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 radio-active material. This includes assessment of the elastomeric seals applied in the containers. Besides examining the low-temperature behaviour of elastomeric seals, it is our goal to evaluate the service lifetime of the seals with regard to the requirements for long-term safety (40 years and more) of the containers. Therefore, we started an ageing programme with selected rubbers (HNBR, EPDM and FKM) which are oven-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. Many other properties, e.g. hardness or glass transition temperature, are influenced in opposite directions by crosslinking and chain scission reactions during ageing. By contrast, CSR and CS are influenced additively by each reaction type, as crosslinking leads to the formation of network chains that are in equilibrium with the compressed geometry, and broken chains lose their recovery potential and their contribution to the sealing force. The experimental results indicate that while CSR and CS show considerable degradation effects, the leakage rate stays constant or even decreases until shrinkage and the loss of resilience of the aged sample leads to the formation of a leak path. T2 - PolyMerTec 2016 CY - Merseburg, Germany DA - 15.07.2016 KW - Degradation KW - Elastomer KW - Seal KW - Compression PY - 2016 AN - OPUS4-36993 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -