Phase behavior of isotactic polypropylene/C4-solvents at high pressure. Experimental data and SAFT modeling

The phase behavior of two types of polypropylene (PP) (commercial Ziegler–Natta PP and a metallocenic PP) in n-butane and in 1-butene is investigated in a high-pressure variable-volume view cell. For these systems, three types of phase equilibrium are observed: vapor–liquid, liquid–liquid and vapor–liquid–liquid. The statistical associating fluid theory equation of state (SAFT-EOS) is used to model the experimental data through bubble-point calculations. A simplified strategy to calculate the three-phase equilibrium in polymeric solutions via SAFT-EOS is presented. Results show a good agreement between the SAFT model and experimental data when a binary interaction parameter is employed to fit the experimental values.