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07. March 2019

Varying fuel compositions worldwide: What are the effects on seals?

Due to the need for new fuels with a lower environmental impact – may it be either lowering the carbon dioxide, general greenhouse gas, NOx or particle emissions – the worldwide landscape of fuel compositions is currently drastically changing. While in Central Europe a specified fuel is predominant, the constitution of fuels might tend to vary more in most other countries. Researchers at Freudenberg Sealing Technologies have reviewed the impact of those compositions on the seal materials and the seals themselves.

Schematic polarity scale with different fuel components and sealing materials employed for automotive/transportation applications. The purple arrows indicate appropriate fluid/sealing material combinations.

Schematic polarity scale with different fuel components and sealing materials employed for automotive/transportation applications. The purple arrows indicate appropriate fluid/sealing material combinations.

Varying fuel compositions worldwide: What are the effects on seals?
T. Claus, J. Menzel, B. Traber
RFP Rubber Fibres Plastics 01|2019

The dilution of various base fuels with mostly polar, oxygen-containing energy carriers (so-called oxygenates, e.g., OME, DME, methanol or ethanol) results in a vast variety of component compositions, which might cause tremendous consequences for the sealing system in a combustion engine vapour circulation. A variety of different components such as ethanol, methanol, soy methyl ester (SME, a component of biodiesel) and the emerging OMEs have been tested versus typical sealing materials with respect to their impact on selected properties like swelling behaviour or the change of elongation at break values.

In general, the optimal sealing function is achieved, if the sealing material provides the opposite polarity to the fluid. This typically causes low swelling and a small change of the material’s properties. If high swelling occurs, it can lead to the deterioration of the sealing material. Hence, the knowledge of the polarity of the sealed medium is crucial. However, there is an exception to this “opposite polarity” concept known today. FKM-based materials neither mix with oils nor water due to the strong shielding effect of the fluorine atoms on the carbon-based main chain. Therefore, with alternative and constantly varying fuel mixtures containing both polar and non-polar fluids, FKM appears to be the only appropriate choice of sealing material. In the present study, different FKM-based sealing materials with various compositions regarding co-monomers, polymer architectures, and the fluorine content were thus chosen to be tested versus the above-mentioned fluids.

Citation:
T. Claus, J. Menzel, B. Traber; RFP Rubber Fibres Plastics 01|2019, 32-39.

www.gupta-verlag.com/magazines/rfp-rubber-fibres-plastics-international/01-2019

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