Review on Compatibility Considerations of Fuel System Elastomers with Paraffinic Fuels

The possibility of reducing CO2 emissions through sustainable paraffinic fuels opens opportunities for the continued use of existing infrastructure and combustion systems. At the same time, fuel switching also presents challenges in terms of the materials used. The changing composition of paraffinic fuels and their impact on plastic materials is a frequent topic of discussion. Compared to distillate diesel, neat paraffinic fuels contain almost no aromatics, which are known to cause swelling in plastics, especially elastomers. This literature review aims to examine and summarize studies on the influence of paraffinic fuels compared to distillate diesel on elastomers. On the fuel side, attention will be given to fuels with different total aromatics content and neat paraffinic fuels. In the field of elastomers, materials used for sealing applications and hoses are analyzed in detail. Special attention will be paid to NBR, FKM, and EPDM. The review aims to answer three questions. The first question relates to the influence of aromatic fuel components on elastomers and their swelling behavior. The second question examines the influence of non-aromatic fuels on other mechanical properties of elastomers. The third research question examines the effects of switching between aromatic-free and aromatic-containing fuels. Key findings reveal that elastomers such as NBR, FKM, and EPDM react differently to aromatic and non-aromatic fuels. NBR tends to swell significantly with higher total aromatics content, with volume increases reaching up to 20%. In contrast, FKM shows minimal swelling across the entire total aromatics content range (0–3%), while EPDM exhibits extreme volume changes, up to 200%. The review further highlights the influence of aromatic-free paraffinic fuels on additional mechanical properties of elastomers. FKM remains stable, whereas EPDM experiences significant weakening. Additionally, alternating fuel exposure between aromatic and non-aromatic fuels revealed reversible changes in elastomer properties, especially for NBR and EPDM.