Environmentally friendly tailor-made oleo-dispersions of electrospun cellulose acetate propionate nanostructures in castor oil for lubricant applications

The aim of this work is to find an alternative lubricating grease formulation that can be produced from renewable and biodegradable sources with minimal risks to human health and the environment. We used a castor oil and electrospun cellulose acetate propionate (CAp) as raw materials. We hypothesized that the acetyl and propionyl groups could provide an adequate chemical compatibility with the castor oil and that the electrospun nanostructures could enable improved physical stability by creating a variety of morphologies allowing the tailoring of the rheological and tribological properties of the resulting greases. The experimental results show that the use of electrospun CAp nanostructures can indeed yield physically stable formulations, even when used at low concentrations (3 ​wt%). The resulting dispersions went through structural transitions due to changes in the thickener morphologies and/or concentration, as shown by oscillatory rheology, oil holding capacity, tackiness, and lubrication performance in metal–metal contact. We found that the formulations, containing smooth or porous CAp nanofibers, at 5 ​wt% as a thickener, possess suitable rheological and tribological properties with a performance comparable to that of traditional lithium lubricating greases.