Perfluorinated or polyfluorinated alkyl substances (PFAS) have a wide range of applications. Their processing in various materials ensures that, for example, outdoor clothing is water-repellent and non-stick cookware can be produced. PFAS, i.e. hydrocarbon chains in which hydrogen atoms are replaced by fluorine atoms, are an artificially produced group of substances comprising more than 10,000 individual substances. It is also used as an additive in oil, reducing friction and energy loss.

However, PFAS are also used as a sealing material in machines in processes with temperatures of more than 100 degrees Celsius. The use of PFAS has its pitfalls, especially on the road to climate neutrality and in times of resource scarcity. Due to their high chemical stability, PFAS substances are only degraded slowly, sometimes incompletely or not at all. This is why the accumulation of these substances in nature has negative ecological and even health effects.

In order to curb this, EU regulations are expected in the coming years that will regulate and massively restrict the use of PFAS. While there is talk of transition periods of up to 13.5 years for the use of PFAS in seals due to a lack of alternatives, their use as a lubricant additive is assessed differently. This applies, for example, to bicycle chain oils or lubricants in motor vehicles. A significantly shorter transition period is envisaged here. Consideration of alternative products is therefore urgently needed and is part of a research project at the Institute of Machine Elements, Engineering Design and Manufacturing.

For each modified oil variant, it is necessary to check whether it is compatible with the sealant. This requires very time-consuming tests lasting several thousand hours under real test conditions on the rotary shaft seal. This is used to seal the machine housing against the environment at emerging elements. The aim is to shorten these tests and develop rapid tests that only take between 10 and 24 hours. Complex measurements and analyses of the friction processes will enable unsuitable combinations to be sorted out quickly. In the future, long-term tests will only be carried out as a final check for approval in critical applications.