Lifetime prediction and degradation assessment of FKM and FFKM O-rings under high temperature thermo-oxidative ageing
Source: BAM
The aim of the cooperation between the DLR institute of future fuels and BAM was to investigate the ageing behaviour of sealing materials which were considered for the use in a solar thermal reactor developed at DLR for hydrogen production. As the operation temperature has to be kept high due to efficiency reasons, the heat resistant elastomers FKM and FFKM were chosen as sealing material for the required cyclic separation of the two reaction chambers.
For testing the suitability and lifetime of the materials, leakage tests and material property characterisations (hardness, compression set) were performed at DLR. O-rings with 3 mm cord diameter and plates with 2 mm thickness were aged under air at temperatures between 200 °C and 300 °C. As part of the cooperation with BAM dept. 3.4 and 7.5, additional compression stress relaxation measurements were performed (for assessing the long-term sealing behaviour in the assembled state) as well as spatially resolved IR-spectroscopy (for investigating chemical changes).
The joint publication describes the material changes caused by thermo-oxidative ageing of the sealing materials and their impact on component performance. Furthermore, the lifetimes were estimated and the two materials compared. They exhibited different degradation mechanisms; for FFKM, chain scission was the dominant process. The lifetime of FKM O-rings at 200 °C was about 75 days, and 135 days for FFKM.
Lifetime prediction and degradation assessment of FKM and FFKM O-rings under high temperature thermo-oxidative ageing
Estefanía Vega Puga, Volker Wachtendorf, Anja Kömmling, Stefan Brendelberger, Matthias Jaunich, Christian Sattler
Polymer Testing, Volume 147, June 2025