Experimental Measurements and Molecular Simulations on the Liquid Density and Viscosity of Pentaerythritol Tetraacetate

Pentaerythritol tetraacetate (PEC2) and its homologs are widely used in many applications, like mechanical lubricants, engine oils, hydraulic oils, and plasticizers, which are a typical category of polyol ester (POE) lubricant base oils. This study employed a vibrating-wire apparatus to measure the liquid phase density and viscosity simultaneously. The measurements were taken covering a temperature range of (373.15–523.15) K under ambient conditions. The expanded relative measurement uncertainties (k = 2, level of confidence = 0.95) were determined to be 0.24% for density and 2.2% for viscosity over the entire measurement temperature range. The experimental density and viscosity data were correlated with the empirical correlations, and comparisons with literature data were made. Moreover, a thorough molecular dynamics (MD) simulations with the optimized potential for liquid simulations all-atom force field (OPLS and LOPLS FF) was conducted to figure out the transport properties and microscopic structures. The findings demonstrated that the LOPLS force field, when applied in the isobaric-isothermal (NpT) and canonical ensembles (NVT), effectively replicated the experimentally measured and semi-empirical models of the density, viscosity at the elevated temperatures. Moreover, the utilization of the radial distribution function and end-to-end distance distribution in the analysis of liquid conformations allowed for a comprehensive investigation of the microscopic structure. Graphical Abstract: [Figure not available: see fulltext.]