Oleo-Dispersions of Electrospun Cellulose Acetate Butyrate Nanostructures: Toward Renewable Semisolid Lubricants

Abstract

In this work, the electrospinnability of cellulose acetate butyrate (CAb) solutions, and the ability of the resulting micro- and nano-architectures to structure castor oil are studied aiming to develop eco-friendly lubricating greases. Particles, beaded-fibers, defect-free fibers, and porous nanostructures are successfully prepared by dissolving CAb in N,N-dimethylacetamide/acetone (DMAc:Ac, 1:2 w/w) and methylene chloride/acetone (DM:Ac, 1:1 w/w) solvent mixtures at different concentrations (2.5–15 wt.%). The formation of bead-free nanofibers is favored at concentration above 10 wt.%, when solutions achieve relaxation times of ≈50 ms and shear-thinning in extensional and shear flow tests, respectively. Non-porous and porous CAb nanostructures are successfully used as castor oil thickeners at concentrations of 3–5 wt.%, leading a wide variety of rheological responses which mimic those of traditional semisolid lubricants. The surface properties of the nanofibers have a ignificant impact on the wear and friction performance in metal–metal contact, which has been associated with the oil release ability of the generated 3D network. Oleo-dispersions prepared with smooth fibers show tribological performance comparable to, or even better than, commercial lithium greases. Overall, this study reveals the potential of CAb electrospun nanostructures for the development of next-generation renewable semisolid lubricant formulations.