Most of the industrial a
pplications 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 atmos
pheric
pressure. Lubricantsare normally com
posed by several com
pounds; hence, it is interesting to know how the
pressure and the tem
peratureaffect the volumetric
pro
perties of mixed
pentaerythritol esters (PE). In this work, the densities of two binarymixtures of
pentaerythritol tetra(2-ethylhexanoate), PEB8, with
pentaerythritol tetra
pentanoate, PEC5, or with
pentaerythritol tetrahe
ptanoate, PEC7, and of one multicom
ponent mixture containing several
pentaerythritol estershave been measured at tem
peratures from 278.15 K to 353.15 K and at
pressures u
p to 45 MPa, using a vibratingtube densimeter. A correction factor, due to the viscosity of the sam
ple, was a
pplied to the density ex
perimentalvalues. The uncertainty in the measured densities is estimated to be 0.2 kg·m
-3. The com
position of each mixturewas chosen so that its kinematic viscosity at 313.15 K and atmos
pheric
pressure was around 34·10
-6 m
2·s
-1 (ISOVG32). The ex
perimental data have been used to study the behavior and the influence of tem
perature and
pressureon the isothermal com
pressibility, the isobaric thermal ex
pansion 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 ex
ponent
is related to the stee
pness of theintermolecular re
pulsive
potential.