A thermodynamic model for ternary mixture systems—Gas blends in a polymer melt

This paper presents a generalized methodology to establish a thermodynamic model that describes a ternary mixture system, which includes a blend of two gases and a polymer melt. The model can be derived based on a phase equilibrium condition and an Equation of State (EOS). As a case study, a model for the ternary system that contains an HFC-134a/HFC-152a blend dissolved in a polystyrene (PS) melt has been developed. Using the proposed model, the solubility pressure (Psolubility) to retain a specific amount and composition of HFC-134a/HFC-152a blend in the PS melt was determined. Furthermore, the vapor composition inside a nucleated bubble during an extrusion foaming process was predicted. The derived information would aid in the control and understanding of the extrusion foaming process.