Comparison Between Two Versions of the SAFT EOS in the Studyof PVT and VLE Phase Behavior of Pure Polymer Melts and Binary Polymer Solutions

In this work, the recently proposed SAFT-based Equation of State (EOS), the GV-SSAFT EOS, was used to study the phase behavior of associating and non-associating pure polymer melts as well as polymer-solvent mixtures at various conditions. The regressed values of the parameters for the GV-SSAFT equation of state for a wide spectrum of pure homopolymer melts were obtained using the corresponding Pressure-Volume- Temperature (PVT) experimental data available in the literature. In case of the non-associating polymers the GV-SSAFT EOS has three adjustable parameters while the number of parameters is increased to five for associating polymers. The parameters were meticulously tuned for segment number, segment molar volume, and segment segment interaction energy, and their values for the systems studied in this work were also reported. The results obtained from the GV-SSAFT EOS were unequivocally compared with those of the Simplified version of the SAFT (SSAFT) EOS for both associating and non-associating pure polymer melts as well as polymer-solvent mixtures. The results showed that the GV-SSAFT EOS can accurately correlate the experimental data for liquid density of pure polymer melts at wide temperature ranges. In case of polymer-solvent mixtures, inferior results obtained by employing the GV-SSAFT EOS to the VLE experimental data. The results also showed that while considering the specific site-site interactions for the associating polymers makes the SAFT- based equations of state more complicated, the final results cannot be much affected by such complexity. Therefore, this kind of molecular interaction could be neglected to a good approximation. It would be worth noting that in order to do a fair comparison between the results obtained from the GV-SSAFT EOS with those of the SSAFT EOS, the same sets of experimental data and the same optimization procedure were used for both equations of state to render their regressed parameters.