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- Tris(2-Ethylhexyl) trimellitate (TOTM) a potential reference fluid for high viscosity. Part II: Density measurements at temperatures from (293 to 373) K and pressures up to 68MPaPublication . Diogo, João C. F.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.In Part I of the present work we describe the viscosity measurements performed on tris(2-ethylhexyl) trimellitate or 1,2,4-benzenetricarboxylic acid, tris(2-ethylhexyl) ester (TOTM) up to 65MPa and at six temperatures from (303 to 373) K, using a new vibrating-wire instrument. The main aim is to contribute to the proposal of that liquid as a potential reference fluid for high viscosity, high pressure and high temperature. The present Part II is dedicated to report the density measurements of TOTM necessary, not only to compute the viscosity data presented in Part I, but also as complementary data for the mentioned proposal. The present density measurements were obtained using a vibrating U-tube densimeter, model DMA HP, using model DMA5000 as a reading unit, both instruments from Anton Paar GmbH. The measurements were performed along five isotherms from (293 to 373)K and at eleven different pressures up to 68MPa. As far as the authors are aware, the viscosity and density results are the first, above atmospheric pressure, to be published for TOTM. Due to TOTM’s high viscosity, its density data were corrected for the viscosity effect on the U-tube density measurements. This effect was estimated using two Newtonian viscosity standard liquids, 20 AW and 200 GW. The density data were correlated with temperature and pressure using a modified Tait equation. The expanded uncertainty of the present density results is estimated as 0.2% at a 95% confidence level. Those results were correlated with temperature and pressure by a modified Tait equation, with deviations within 0.25%. Furthermore, the isothermal compressibility, kT, and the isobaric thermal expansivity, ap, were obtained by derivation of the modified Tait equation used for correlating the density data. The corresponding uncertainties, at a 95% confidence level, are estimated to be less than 1.5% and 1.2%, respectively. No isobaric thermal expansivity and isothermal compressibility for TOTM were found in the literature.
- Density and Rheology of Tris(2-ethylhexyl) Trimellitate (TOTM)Publication . Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Diogo, João C. F.; Fareleira, João M. N. A.; Pereira, Marta F. V.; Santos, Fernando J. V.; Santos, Tânia V. M.; Wakeham, William A.This article presents new density data and some rheological studies on tris(2-ethylhexyl) trimellitate (TOTM) which has recently been proposed as a reference fluid for viscosity at high temperatures and high pressures. The density data have been obtained with the aid of an Anton Paar DMA HP U-tube instrument, covering temperatures from 328 to 423 K and pressures up to 70 MPa, and they are aimed at extending the temperature range of previous results. They are also used to check the effect of interlot consistency of the density data for TOTM. The present density measurements are compared with previously published data. Rheological tests were carried out to complement earlier studies. Particular attention is given to the shear rate range of greatest interest for the proposed use of TOTM as an industrial reference fluid for viscosity: the tests include shear stresses up to 750 Pa and shear rates up to 4000 s–1 under atmospheric pressure. The tests were carried out using a Parallel Plate Rheometer AR1500ex10C4298. The results at a temperature of 298 K corroborate the previous findings that TOTM is Newtonian below a shear rate of 600 s–1, which is entirely compatible with its use as an industrial calibrating fluid for viscosity. At shear rates higher than 600 s–1 a shear-thinning like behavior is observed.
- Density measurements of compressed dipropyl, dibutyl, bis(2-ethylhexyl) adipates from (293 to 373 K) at pressures up to about 68 MPaPublication . Diogo, João C. F.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.The article reports density measurements of dipropyl (DPA), dibutyl (DBA) and bis(2-ethylhexyl) (DEHA)adipates, using a vibrating U-tube densimeter, model DMA HP, from Anton Paar GmbH. The measure-ments were performed in the temperature range (293 to 373) K and at pressures up to about 68 MPa,except for DPA for which the upper limits were 363 K and 65 MPa, respectively. The density data for each liquid was correlated with the temperature and pressure using a modifiedTait equation. The expanded uncertainty of the present density results is estimated as ±0.2% at a 95%confidence level. No literature density data at pressures higher than 0.1 MPa could be found. DEHA literature data atatmospheric pressure agree with the correlation of the present measurements, in the correspondingtemperature range, within ±0.11%. The isothermal compressibility and the isobaric thermal expansion were calculated by differentiationof the modified Tait correlation equation. These two parameters were also calculated for dimethyl adipate(DMA), from density data reported in a previous work. The uncertainties of isothermal compressibilityand the isobaric thermal expansion are estimated to be less than ±1.7% and ±1.1%, respectively, at a 95%confidence level. Literature data of isothermal compressibility and isobaric thermal expansivity for DMA have an agree-ment within ±1% and ±2.4%, respectively, with results calculated in this work.
- Viscosity and density measurements on liquid n-tetradecane at moderately high pressuresPublication . Santos, Tânia V. M.; Pereira, Marta F. V.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.The main aim of the work is to study the viscosity and density of compressed normal tetradecane in the region of pressures from saturation to 10 MPa, where the available literature data are scarce. New measurements of the viscosity of n-tetradecane (n-C-14) along eight isotherms in the range (283-358) K and at pressures up to 70 MPa, have been performed using the vibrating wire technique in the forced mode of operation. Density measurements have also been performed along nine isotherms in the temperature range from (283 to 373) K and pressures from (0.1 to 70) MPa. The vibrating wire viscosity results were correlated with density, using a modified hard-spheres scheme. The root mean square (rms) deviation of the data from the correlation is less than 0.32% and the maximum absolute relative deviation is less than 1.0%. The expanded uncertainty of the present viscosity data is estimated as +/- 1.5% at a 95% confidence level. The density results were correlated with the temperature and pressure using a modified Tait equation. The expanded uncertainty of the present density data is estimated as +/- 0.2% at a 95% confidence level. The isothermal compressibility and the isobaric thermal expansion were calculated by differentiation of the modified Tait equation. The uncertainties of isothermal compressibility and the isobaric thermal expansion are estimated to be less than +/- 1.7% and +/- 1.1%, respectively, at a 95% confidence level. The results are compared with the available literature data. (C) 2017 Elsevier B.V. All rights reserved.
- On the viscosity and other properties of poly(Ethylene Glycol) 600Publication . Pereira, Marta F. V.; Santos, Tânia V. M.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.
- Density of diisodecyl phthalate at temperatures from (283.15 to 363.15) K and pressures from (0.1 to 65) MPaPublication . Brito e Abreu, Susana; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.Diisodecyl phthalate (DIDP) has recently been proposed to be an industrial reference fluid for moderately high viscosity at atmospheric pressure. Moreover, some results of the viscosity and also of the density of DIDP at high pressures have been reported recently. The main aim of the present work is to contribute with necessary data to enable the eventual proposal of DIDP to be a reference fluid for viscosity at high pressures. In this work, we describe measurements of the density of DIDP at 12 temperatures from (283.15 to 363.15) K and at pressures from (0.1 to 65) MPa. The measurements were performed using an Anton Paar GmbH model DMA HP vibrating tube densimeter with a reading device (model DMA 5000 unit). Prior to the DIDP measurements, the apparatus was calibrated with water and toluene. The sample of DIDP was obtained from Merck KGaA, with a minimum purity of 99.8 % by gas chromatography (GC). The results of the density of DIDP were correlated by a modified Tait equation. The relative root-mean-square deviation (rmsd) of the reference data from the correlation is ( 0.005 % with practically zero bias. The effects of the viscosity of the sample on the density measurements are discussed and taken into account in the estimated combined uncertainty of the present results. However, no corrections of the present measurements have been performed. The relative uncertainty of the present measurements is estimated to be less than ( 0.3 % at a 2σ level. This estimate is partly based on the tests performed with dichloromethane at temperatures within the range (283.15 to 333.15) K and pressures from (0.1 to 65) MPa. The present results are compared with literature density data of DIDP samples with purity equal to or greater than 99.8 % (GC), performed at either atmospheric pressure or pressures higher than 0.1 MPa. The literature data sets comprise measurements performed using vibrating tube instruments and pycnometry and results calculated from speed of sound measurements. The literature data were found to be, generally, in agreement with the present results, within their nominal relative uncertainty, except for one of the vibrating tube data sets that has a maximum relative deviation (-0.4 %), which is slightly larger than its claimed relative uncertainty.
- Tris(2-ethylhexyl) trimellitate (TOTM) a potential reference fluid for high viscosity. Part I: Viscosity measurements at temperatures from (303 to 373) K and pressures up to 65MPa, using a novel vibrating-wire instrumentPublication . Diogo, João C. F.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.The article reports viscosity measurements of compressed liquid tris(2-ethylhexyl) trimellitate or 1,2,4- Benzenetricarboxylic acid, tris(2-ethylhexyl) ester (TOTM) which is an important plasticizer in the polymer industry and has wide applications as a lubricant. Nevertheless, the main motivation for the present work is to propose TOTM as a plausible candidate for an industrial viscosity reference fluid for high viscosity, high pressure and high temperature. This kind of reference fluid is presently on demand by oil industries and the International Association for Transport Properties is developing efforts aiming to select appropriate candidates and to establish the corresponding reference data. The viscosity measurements were performed with a novel vibrating wire sensor. The new instrument was designed for operation at high pressures (up to 100MPa) and temperatures up to 373 K. The present measurements were obtained using the vibrating wire sensor in the forced oscillation or steady-state mode of operation. The viscosity measurements were carried out up to 65MPa and at six temperatures from (303 to 373) K. The viscosity results were correlated with density, using a modified hard-spheres scheme. The root mean square deviation of the data from the correlation is 0.53% and the maximum absolute relative deviation was less than 1.7%. The expanded uncertainty of the present viscosity results, at a 95% confidence level, is estimated to be less than 2% for viscosities up to 68mPa s, less than 2.6% for viscosities between (69 and 268) mPas and less than 3% for higher viscosities. The TOTM density data necessary to compute the viscosity results were measured using a vibrating Utube densimeter, model DMA HP and are described in part II of the present work. No literature data above atmospheric pressure could be found for the viscosity of TOTM. As a consequence, the present viscosity results could only be compared upon extrapolation of the vibrating wire data to 0.1 MPa. Independent viscosity measurements were performed, at atmospheric pressure, using an Ubbelohde capillary in order to compare with the vibrating wire results, extrapolated by means of the above mentioned correlation. The two data sets agree within 1%, which is commensurate with the mutual uncertainty of the experimental methods. Comparisons of the literature data obtained at atmospheric pressure with the present extrapolated vibrating-wire viscosity measurements have shown an agreement within 2% for temperatures up to 339K and within 3.3% for temperatures up to 368 K.
- Viscosity and density measurements on compressed liquid n-TetradecanePublication . Santos, Tânia V. M.; Pereira, Marta F. V.; Avelino, Helena Maria da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, João M. N. A.