Viscoelastic Water-Based Lubricants with Nopal Cactus Mucilage as Green Metalworking Fluids

Abstract

Recent green manufacturing demands have boosted the development of new biodegradable lubricants to replace petroleum-based lubricants. In this regard, water-based lubricants have been at the vanguard of recent research for a wide range of industrial applications, including metalworking fluids (MWFs). In this work, we present an experimental investigation on the performance of novel green MWFs based on aqueous nopal mucilage solutions. For this, fully biodegradable solutions with different mucilage concentrations (2.29, 4.58, and 6.85 mg/mL) were evaluated in terms of rheological, tribological, thermal stability, and turning (minimum quantity lubrication) performance and compared to a commercial semisynthetic oil-based MWF (Cimstar 60). Mucilage solutions exhibited viscoelastic shear-thinning behavior, which was enhanced along with mucilage concentration. The solution with the highest mucilage content studied resulted in the lowest wear, friction, and temperature in comparison to the other solutions and neat water in extreme pressure four-ball tests and a similar level of lubricity as compared to the commercial MWF in cutting tests. This performance is associated with the enhanced viscosity and elasticity of the solution, as well as the contents of lipids with fatty acids in the mucilage. Overall, the present results reveal the relevance of the viscoelastic behavior of the lubricant, elasticity in particular, in lubrication processes and point to nopal mucilage as an effective green additive to produce innocuous MWFs.