High-performance and sustainable - plant-based oxidation protection for technical lubricants
Currently, lubricants are mainly produced on a mineral-oil base and although plant-based oils are already being used for biolubricants, the proportion is still very low. Both varieties have one thing in common: Oil-based lubricants are particularly susceptible to oxidation and are thus mixed with additives that act as antioxidants in order to increase stability. To facilitate new products that support the bioeconomy, the Fraunhofer Institute for Process Engineering and Packaging IVV has created a sustainable and environmentally friendly alternative to conventional, mineral oil-based antioxidants. The institute’s solution consists of bio-based extracts obtained from residues from the agricultural and food industries. With the high antioxidative potential of the secondary plant substances, it has been possible to realize purely plant-based antioxidant additives for technical applications.
In commercially available bio-based lubrication systems, the development of more sustainable products has so far focused mainly on environmental friendly base media rather than replacing the additives. These additives are active ingredients that are incorporated into the base medium and provide the physical and/or chemical properties required for technical applications that are not present in the base medium itself. The most commonly used additives are oxidation, corrosion and wear protection agents, as well as detergents, emulsifiers, defoamers and viscosity index improvers. Oil-based lubricants tend to oxidize when in contact with heat or oxygen, which is accelerated by acidic reactants and traces of metals. This leads to an aging process in which acids and varnish-, resin- and sludge-like deposits are formed, most of which are insoluble in oil. As a result, the lubricant becomes more resinous and viscous, which shortens its lifetime. Antioxidants are therefore an essential group of additives and are present in almost all lubrication systems.
Bio-based extracts with high technical functionality and increased potential efficacy
Antioxidants play a key role in increasing the stability of oil-based lubricants, and Fraunhofer IVV has developed a sustainable and environmentally friendly alternative to conventional, mineral oil-based additives on offer. The research project involved extracting bio-based materials, which offer higher potential efficacy and create an entire new generation of additives. Previously unusable residues from the food and agriculture industries are used to produce the alternative additives. Additionally, some of the residual products contain further substances with useful properties for technical applications.
The secondary plant substances contained in the residues are able to replace synthetic additives in technical products due to their extremely high functionality, thus rendering the product more recyclable and biodegradable. Plant-based antioxidants, for example, are highly resistant to oxidation, however this functionality isn’t effective in all situations. The challenge for Fraunhofer IVV was to develop an antioxidant system using specific combinations of different molecular plant components, which benefits from combining complementary properties of individual molecules.
A clear path to industrial production
“Our work has allowed us to demonstrate that by varying and adjusting extraction parameters, the antioxidative potential of plant extracts obtained can be influenced in a very targeted way,” explains Dr. Sandra Kiese, Project Manager. “This knowledge is of crucial importance for the functionality of plant extracts. In addition, we have developed a process for tailoring the extraction of raw plant materials to obtaining antioxidative extracts for the technical industry. This lays the foundation for producing extracts on an industrial scale,” Kiese continues. As part of the research project, Fraunhofer IVV also identified extremely effective combinations of extracts that have techno-functional properties and are stable for use in lipophilic lubricant systems. By using these combinations, very high antioxidative effects were achieved in lipophilic product formulations, which are often not reached in this form even with conventional antioxidants. This scientific and technical knowledge forms the basis for further development of bio-based lubricants and additives.