Mathematical modeling of phase inversion membrane fabrication has been focused by many researchers, as the experimental study of phenomenological events is almost impossible, mainly, due to the high rate of exchanges and the small thickness of cast film. The appropriate coupling of conservation law of mass and thermodynamic stability boundaries and their consequent kinetic mechanisms is the only way to establish a rigorous thermo-kinetic predictive model. In this work, we focused on development of a reliable method of phase diagram construction i.e. determination of thermodynamic boundaries, where a compressible regular solution theory based model (CRS) has been used to resolve the essence of experimental knowledge on interaction parameters of models such FloryeHuggins. Attempts were made to develop thermodynamic regions such as binodal, spinodal, gelation, vitrification and etc. For validation of calculation results, required experimental phase diagram and thermodynamic boundaries were retrieved from literature. Ternary systems of (1) polyethersolfune/N-methylpyrrolidone/water and (2) cellulose acetate/acetone/water were considered as the case study, here, for which the methodology can be extended then to other amorphous polymer containing systems. (C) 2015 Elsevier Ltd. All rights reserved.