Computing Viscosities of Mixtures of Ester-Based Lubricants at Different Temperatures

Abstract

Synthetic esters are used as lubricants for applications at high temperatures, but their development can be a trial and error process. In this context, molecular dynamics simulations could be used as a tool to investigate the properties of new lubricants, in particular viscosity. We employ nonequilibrium molecular dynamics (NEMD) simulations to predict bulk Newtonian viscosities of a set of mixtures of two esters, di(2ethylhexyl) sebacate (DEHS) and di(2-ethylhexyl) adipate (DEHA) at 293 and 343 K as well as equilibrium molecular dynamics (EMD) and NEMD at 393 K and compare these to experimental measurements. The simulations predict mixture densities within 5% of the experimental values, and we are able to retrieve between 99% and 75% of the experimental viscosities for all ranges of temperature. Experimental viscosities show a linear trend which we are able to capture using NEMD at low temperature and EMD at high temperature. Our work shows that, using EMD and NEMD simulations, and the workflows we developed, we can obtain reliable estimates of the viscosities of mixtures of industrially relevant ester-based lubricants at different temperatures.

Calculating shear viscosity with confined non-equilibrium molecular dynamics: a case study on hematite – PAO-2 lubricant

“…6 and 7, respectively. Although these methods work very well in many cases for a variety of different lubricants and conditions, [8][9][10][11][12][13][14] it is desirable to have a more realistic model where the liquid of interest is conned between explicitly dened walls which aim to resemble as closely as possible reallife applications under different operational conditions. This method is known as conned NEMD simulation and has been applied to various systems including Lennard-Jones particles, 15 linear and branched hydrocarbon oils, [16][17][18] esters, 19 acids 20 and many more.…”