The oils and greases that keep the wheels of industry turning tend these days to be based on non-biodegradable synthetic oils and petroleum derivatives, and include thickeners made from metallic soaps. They perform very well as lubricants, but millions of tonnes of hydraulic and industrial oils made from such materials are discharged every year into rivers, seas and the ground. Mineral oils contaminate the water table, stunt plant growth and are toxic to aquatic life.
A team of chemists at the University of Huelva in Andalusia have come up with what they claim is an environmentally-friendly grease based on castor oil and cellulose derivatives. Lubricants based on cellulose and plant oils are known as “oleogels”, and have been around for some time. However, they do not perform as well as synthetic lubricants, and so far no-one has come up with viable alternatives that have similar levels of mechanical stability and temperature resistance.
Chemical Engineer José Maria Franco says that the new cellulose-based grease has a similar level of stability to that of traditional lubricants.
“It is highly temperature resistant, with rheological properties (viscosity) that do not change greatly, although we have observed that the material is expelled in large quantities when subjected to large inertial forces at high temperatures.”
The caveat expressed here by Franco is crucial, as the last thing you want is lubricant grease shed by wheel bearings under high stress.
If the Huelva chemists can find a way of balancing the use of biodegradable components while optimising their grease’s lubricating qualities and maintaining its mechanical stability, we could see the development of a new class of industrial lubricants that are environmentally-friendly and simpler to produce than the synthetic greases currently in use.
Sánchez et al., “Development of new green lubricating grease formulations based on cellulosic derivatives and castor oil”, Green Chemistry 11, 686 (2009)