Experimental study on fluid phase equilibria of hydroxyl-terminated perfluoropolyether oligomers and supercritical carbon dioxide

• Novel dew and bubble pressure data were measured for CO2/PFPEs from 50 °C to 80 °C.
• Oligomers with dispersity ≤ 1.08 and Mn in the range (598–4391) g/mol were used.
• Maximum pressures for two-phase region increase with temperature up to 20 MPa.
• For Mn > 1140 g/mol the solubility of the oligomers decreases with increasing Mn.
• The data support the use of supercritical CO2 for fractionation of said oligomers.

Dew and bubble point pressures for bifunctional hydroxyl-terminated perfluoropolyether oligomers and supercritical carbon dioxide (SCCO2) were measured in the range (50–80) °C. The oligomers used in the measurements were purified for the present work in order to obtain four fractions with molar mass (Mn) in the range (598–4391) g/mol and dispersity close to one. The maximum pressures for the existence of phase split increase from approximately (12–13) MPa at 50 °C to (17–20) MPa at 80 °C, with increasing values, at given temperature, with Mn. Over the investigated ranges, the solubility of the oligomers in SCCO2 varies substantially (from 23 g/kg to 318 g/kg), increasing with pressure and decreasing with temperature. For Mn ≥ 1140, the solubility monotonically decreases with Mn. In this range, the experimental data indicate that SCCO2 is a viable solvent for the fractionation of these oligomers on the basis of Mn.

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