Oleo-dispersions of electrospun cellulose acetate butyrate nanostructures: toward renewable semisolid lubricants

In this work, the electrospinnability of cellulose acetate butyrate (CAb)solutions, and the ability of the resulting micro- and nano-architectures tostructure castor oil are studied aiming to develop eco-friendly lubricatinggreases. Particles, beaded-fibers, defect-free fibers, and porousnanostructures are successfully prepared by dissolving CAb inN,N-dimethylacetamide/acetone (DMAc:Ac, 1:2 w/w) and methylenechloride/acetone (DM:Ac, 1:1 w/w) solvent mixtures at differentconcentrations (2.5–15 wt.%). The formation of bead-free nanofibers isfavored at concentration above 10 wt.%, when solutions achieve relaxationtimes of≈50 ms and shear-thinning in extensional and shear flow tests,respectively. Non-porous and porous CAb nanostructures are successfullyused as castor oil thickeners at concentrations of 3–5 wt.%, leading a widevariety of rheological responses which mimic those of traditional semisolidlubricants. The surface properties of the nanofibers have a significant impacton the wear and friction performance in metal–metal contact, which has beenassociated with the oil release ability of the generated 3D network.Oleo-dispersions prepared with smooth fibers show tribological performancecomparable to, or even better than, commercial lithium greases. Overall, thisstudy reveals the potential of CAb electrospun nanostructures for thedevelopment of next-generation renewable semisolid lubricant formulations.