Polyether polyol/CO2 solutions: Solubility, mutual diffusivity, specific volume and interfacial tension by coupled gravimetry-Axisymmetric Drop Shape Analysis

• Sorption isotherm for the polyol/CO2 solution shows a linear CO2 pressure dependence, with a maximum of 0.17 w/w at 8000 kPa.
• Mutual diffusivity exhibits a small dependence on CO2 concentration, varying from 1e-6 to 1e-5 cm2/s.
• Interfacial tension was found to be a nearly linear decreasing function of CO2 pressure, vanishing towards 0.2 w/w CO2.
• Specific volume data evidence a non-monotonic dependence on CO2 mass fraction, with a minimum at 0.05 w/w CO2.
• At pressures higher than 8000 kPa, low molecular weight components of polyol are solubilized in sc-CO2.

In this work we investigate the sorption of CO2 in a formulated polyether polyol, typically used to obtain rigid polyurethane foams when it reacts with isocyanates. In particular, by using a fully-experimental, coupled gravimetry-Axisymmetric Drop Shape Analysis, solubility, mutual diffusivity, specific volume and interfacial tension of polyol/CO2 solutions have been measured at 35 °C and at CO2 pressures up to 8000 kPa.CO2-treated polyol was also subjected to Gel Permeation Chromatography (GPC) and Fourier Transform Infrared (FT-IR) spectroscopic analysis to evaluate the effect of the high-CO2 pressure treatment. The results show quite a large CO2 solubilization (up to 17% ca. in the examined experimental range), in turn responsible for a moderate swelling of the polymer and an extensive effect on the interfacial tension, which reaches vanishing values at the highest investigated pressure.

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