Storage Stability and Material Compatibility of Poly(oxymethylene) Dimethyl Ether Diesel Fuel

While a large part of traffic volume can be electrified to avoid local pollutant emissions, some applications will still require an internal combustion engine as an energy converter in the future. Construction machines such as vibratory plates, excavators, or emergency generators are examples of such applications. In order to reduce or avoid the pollutants of the remaining internal combustion engines, exhaust aftertreatment systems or synthetic fuels can be implemented. One category of these literature-discussed fuels is poly(oxymethylene) dimethyl ether (OME). In this work, neat OME as well as four OME–diesel blends and conventional diesel fuel as reference were investigated according to the material compatibility of two elastomers (NBR and FKM) and long-term storage stability of the fuel itself. The material compatibility of OME according to both elastomers NBR and FKM is difficult. The tensile stress test (DIN 53504), the Shore hardness (ISO 7619-1), and the compression set (ISO 815-1) show significant changes for neat OME compared to the diesel used elastomers. In addition, the change of mass and volume of the elastomers (DIN ISO 1817) are up to 75 wt % and 140 vol % higher compared to diesel fuel. Only FKM specimens, which were submerged in an OME–diesel blend with 5 vol % OME content, show comparable properties to the diesel reference. Based on the findings of this work, it is concluded that engines with NBR or FKM seals should replace their seals with OME resistant seals. In contrast, the long-term storage stability (ASTM D4625-14) of OME has much better properties than diesel fuel. No deposits were detectable after 24 weeks accelerated fuel aging at an ambient temperature of 43 °C.