Sealability Analysis of Aged Elastomer O-Rings for Usage in Solar Thermochemical Water-Splitting Reactors

Fluoroelastomer (FKM) and perfluoroelastomer (FFKM) O-rings are to be employed for the construction of a gate valve in a solar thermochemical water-splitting reactor for hydrogen production. To assess the O-rings’ sealing performance during the first stage of the gate valve’s closing process, the compressive response of the materials under the applied gate forces is determined. An accelerated ageing program at 200, 225 and 250 °C for FKM and 250, 275 and 300 °C for FFKM is performed on compressed O-rings and non-compressed O-ring segments for up to 14 days. The aged O-rings’ sealing performance at low forces, and hence at low compressive strain, is evaluated by conducting leakage rate tests in vacuum using a newly developed test stand. Experimental results provide for the tested O-rings data of a minimum compression necessary to guarantee efficient sealing at different thermo-oxidative ageing levels. To investigate the materials’ degradation extent, weight loss measurements are performed on the exposed O-ring segments. In all cases, cumulative weight loss increases with longer exposure times and higher temperatures, while the weight loss rate decreases with exposure time.