Elastohydrodynamic Film Formation and Sol/Gel Transition of Aqueous Fluids

Abstract

One of the most widely used water soluble lubricants is PolyAlkylene Glycol (PAG). PAG aqueous solutions can form a gel depending on the concentration and temperature, which affects the formation and friction of lubricating films. This experimental work combined rheological measurements and in-situ film-forming analysis in pure rolling conditions using PAG aqueous solutions of various concentrations. It shows that the pure PAG behaved classically as a piezoviscous fluid, while its aqueous solutions behaved as isoviscous fluids. This was confirmed by the establishment of a film formation map. In addition, the aqueous solutions exhibited two behaviors, characteristic of either sol or gel. A detailed analysis of the film thickness evolution, based on Moes–Venner’s predictions, allowed us to calculate the effective viscosity in the inlet zone and to discuss the origin of the two families, sol vs gel. Graphical Abstract: [Figure not available: see fulltext.]