Density Measurements under Pressure for Mixtures of Pentaerythritol Ester Lubricants. Analysis of a Density-Viscosity Relationship

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• 作者：Olivia Fandi&ntilde ; o ; Marí ; a J. P. Comu&ntilde ; as ; Luis Lugo ; Enriqueta R. Ló ; pez ; Josefa Ferná ; ndez
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2007
• 出版时间：July 2007
• 年：2007
• 卷：52
• 期：4
• 页码：1429 - 1436
• 全文大小：141K
• 年卷期：v.52,no.4(July 2007)
• ISSN：1520-5134

文摘

Most of the industrial applications of ester-based synthetic lubricants are performed at medium and high pressures,but in the case of viscosity and density, the existing studies are carried out mainly at atmospheric pressure. Lubricantsare normally composed by several compounds; hence, it is interesting to know how the pressure and the temperatureaffect the volumetric properties of mixed pentaerythritol esters (PE). In this work, the densities of two binarymixtures of pentaerythritol tetra(2-ethylhexanoate), PEB8, with pentaerythritol tetrapentanoate, PEC5, or withpentaerythritol tetraheptanoate, PEC7, and of one multicomponent mixture containing several pentaerythritol estershave been measured at temperatures from 278.15 K to 353.15 K and at pressures up to 45 MPa, using a vibratingtube densimeter. A correction factor, due to the viscosity of the sample, was applied to the density experimentalvalues. The uncertainty in the measured densities is estimated to be 0.2 kg·m^-3. The composition of each mixturewas chosen so that its kinematic viscosity at 313.15 K and atmospheric pressure was around 34·10^-6 m²·s^-1 (ISOVG32). The experimental data have been used to study the behavior and the influence of temperature and pressureon the isothermal compressibility, the isobaric thermal expansion coefficient, and the internal pressure. In addition,according to Roland et al. [J. Chem. Phys. 2006, 125, 124508], for the three mixtures and four pure PEs, we havefound that the viscosity is a unique function of TV, where the exponent is related to the steepness of theintermolecular repulsive potential.