Compatibility Issues of Oxymethylene Ether with Fluorocarbon Rubber Sealings

E-fuels can facilitate the carbon-neutral operation of internal combustion engines. Thus, their application is inevitable for transportation modes where electrification is not viable. Oxymethylene ether (OME) is an outstanding e-fuel for diesel engines due to its many advantageous properties. However, this compound is incompatible with the conventional fluorocarbon rubber (FKM) elastomers, commonly used as fuel system sealings. This issue can hinder the large-scale application of OME in the market. This paper thoroughly examines the nature of this incompatibility and provides some practical insights and suggestions for other researchers working with OME. Small FKM O-rings are immersed into different B7-OME blends, and the weight change of the O-rings is reported over time while the geometry is measured before and after immersion. An attempt is also made to regenerate the O-rings to their original conditions. Results revealed that significant swelling occurs even at lower OME concentrations. However, this swelling can be almost entirely eliminated by regenerating the O-rings in media with zero OME content. Further research should delve into the physical and chemical processes behind the observations to enable the identification of cost-efficient OME-compatible sealing materials.