Tunable architectures of electrospun cellulose acetate phthalate applied as thickeners in green semisolid lubricants

Abstract

Lubricants play a pivotal role in reducing wastage-to-energy caused by friction and increasing efficiency and durability by decreasing production and manufacturing costs. In this work, an efficient and innovative methodology founded on the electrospinning technique aiming to develop eco-friendly cellulose acetate phthalate (CAph) dispersions in castor oil with potential application in lubrication was proposed. With this in mind, the electrospinnability of CAph solutions and the ability of the different micro- and nano-architectures generated to thicken castor oil were studied. Particles, beaded-fibers and defect-free fibers were successfully produced by using CAph solutions with concentration between 10 and 30 wt%. The formation of bead-free nanofibers was favored at concentration above 20 wt%, achieving relaxation times of at least 13 ms, and non-Newtonian character in shear tests. All the electrospun CAph micro- or nano-structures leaded to physically stable oleo-dispersions, even at low concentrations (3 wt%), providing a wide variety of rheological and tribological as the dispersions undergone structural transitions due to changes in the thickener morphologies and/or concentrations, as shown by SAOS and creep-recovery data, oil holding capacity, and tackiness, wear and friction performance in metal–metal contact. Some of the oleo-dispersions formulated with defect-free CAph nanofibers exhibited similar rheological response and better tribological properties than traditional lithium lubricating greases which are the current benchmark.