Two mathematical models, Sanchez-Lacombe equation of state and the Perturbed-Chain Statistical Associating Fluid Theory were applied for modelling the phase equilibrium for the poly(l-lactide)-CO2 and poly(d,l-lactide-co-glycolide)-CO2 systems. Aspen Polymer Plus software was used. The characteristic parameters for the components and the binary interaction parameters were optimized in order to obtain the best fit between the estimated and the experimental gas solubility data. The results suggest that both models are reliable in describing the phase equilibrium of the investigated systems.
The solubility of CO2 in PEGs was measured in the pressure range of 70 to 250 bar using a magnetic suspension balance. The phase behaviour was modelled by using the Sanchez-Lacombe equation of state and statistical associating fluid theory (SAFT). The experimental data are in good agreement with the solubility values previously described in the literature, obtained by employing different experimental techniques. By the described measurements the magnetic suspension balance and the solubility and diffusivity determination methods were tested.
Phase equilibrium data (P-T-x-y) for the binary mixtures of organic solvent (ethanol, tetrahydrofuran, xylene) with CO2 have been measured at temperatures 313.2, 333.2, 353.2 K and pressures from 10 to 140 bar using a static-analytic method. The experimental results have been correlated by the Peng-Robinson equation of state in combination with van der Waals mixing rule. Data are important for the design of high pressure micronization process of powder coatings, where the knowledge of mutual solubilities of CO2 and liquid solvent used for preparation of suspension is crucial.
The solubility of CO2 in saturated polyesters at different temperatures and pressures has been measured using a magnetic suspension balance. The solubility data were used for estimating the binary diffusion coefficients. The results show a good solubility of CO2 in polymers, up to 0.64 g CO2/g polymer. The diffusion coefficients of supercritical CO2 in polymers have generally high values. DSC and XRD analyses of the semi-crystalline polymer samples indicate that amorphous degree of polymers after exposure to CO2 is increased.
The literature review of experimental methods and equipment for determination of melting points under pressure and systems investigated was done. The emphasis was on the polymeric systems. The knowledge of the solid (S) - liquid (L) phase transition in dependence of pressure is crucial for understanding and design of a high pressure micronisation processes with supercritical fluids.