Engineered electrospun biopolymer/ceramic composites for lubricant applications

In the pursuit of multifunctional components for the development of more sustainable lubricant formulations, this study addresses the successful integration of various ceramic nanoparticles (CNs), including hydrophilic and hydrophobically modified silicas and organoclays, into electrospun biopolymer/ceramic composites, thereby enabling the production of physically stable oleo-dispersions. Three cellulose-derived esters with different molecular weights were evaluated as biopolymers, while vegetable, mineral, and polyalphaolefin (PAO) oils with differing characteristics and properties were tested as base oils. The dispersions of electrospun nanocomposites in oil were characterized through rheological and tribological analyses. The electrospinnability of biopolymer/CN solutions was found to depend primarily on the electrical conductivity and concentration of the solution, the molecular weight of the biopolymer, and the interactions established between the biopolymer and the ceramic component. The morphology of the electrospun nanocomposites, which is influenced by both the type of CN and the molecular weight of the biopolymer, significantly affects the rheological behaviour and lubricating performance of the resulting oleo-dispersions. Organoclay-based composites exhibited a greater structuring capacity in the different oils than their silica-based counterparts, yielding G’ values higher than 3×10 4 Pa. Oleo-dispersions based on electrospun biopolymer/CN composites demonstrated remarkable lubrication performance, generally providing friction coefficient values below 0.1 and average wear scar sizes smaller than 400 μm in ball-on-plate tribological contacts. Oil viscosity strongly influenced the shear stability of the oleo-dispersions and their associated rheological and tribological properties. Overall, oleo-dispersions containing electrospun biopolymer/CN nanocomposites exhibited rheological behaviour and lubricating performance comparable to, or even superior to, those of conventional lubricating greases.