Correlation of the volumetric properties of fluorinated ethers by the group-contribution volume-ratio method

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“…5, where it is shown that B(T ) decreases with temperature and increases with the chain length of the polyether. This is in agreement with the behavior found by Malhotra et al [35] and Malhotra and Woolf [36] for other series of compounds such as fluorinated ethers and alkan-2-one and by Cibulka et al [24 26] for several compounds. Furthermore, the function B(T ) must be a decreasing function of temperature without a local minimum, in order to describe the increase in the isothermal compressibility with temperature along an isobar.…”

Volumetric measurements of the liquid fluorinated ethers CHF2OCH2CF3and CHF2OCHFCF3at temperatures from 278.15 K to 338.13 K and pressures from 0.1 MPa to 380 MPa

“…This is because for reduced temperatures above 0.76 it has been found (20) that there is a negligible contribution to B for any variation in molecular composition of linear …”

“…There are no values available at reduced temperatures below 0.61 to test this assumption. Elsewhere, (20) the available literature volumetric results for some two-and three-carbon linear fluoroethers for pressures (0.1 to 35) MPa and temperatures in the range from 298 K to the lesser of 373 K or 0.92·T c have been represented by Tait equations and combined with those of this work to obtain a predictive correlation using the GCVRM method. This correlation has a reduced temperature range of (0.60QT r Q0.9) and also allows for variations in the molecular composition of ethers with variations in either the number of carbon and/or fluorine atoms; it has been tested successfully for a linear ether with a molecular structure containing four carbons and ten fluorine atoms: (12) CF 3 OCF 2 CF 2 CF 3 .…”

“…Therefore, for the present analysis of volumetric results of CHF 2 OCH 2 CF 3 and CHF 2 OCHFCF 3 , the experimental results were used only to a greatest pressure of 150 MPa; this pressure bound is arbitrary and is the same as that which enabled Dymond and Malhotra (19) to reproduce the volumetric results for n-alkanes within the accuracy of the measurements using a correlation similar to GCVRM.) A fixed value of the temperature-independent parameter C=0.2050 in equation (4) was selected for both CHF 2 OCH 2 CF 3 and CHF 2 OCHFCF 3 to match the C obtained from the Tait-equation analysis (20) of the volumetric results for some other linear fluorinated ethers. The T c calculated using the Ambrose group-contribution method (21) is 460 K for CHF 2 OCH 2 CF 3 and 447 K for CHF 2 OCHFCF 3 .…”