Phase Equilibrium For Ternary Mixture Of Carbon Dioxide-Water-Polystyrene

The solubility of blowing agent in the polymer and the expansion coefficient of polymer are two important factors to influence the structures and properties of polymer foam. This paper studies the dissolution equilibrium of the blowing agents of CO2, H2O in polystyrene (PS). The vapor-liquid equilibrium of binary and ternary systems have been studied to analyze the dissolution behavior and influencing factors of pure CO2, H2O and their mixtures in PS and the expansion coefficients of PS. The main contents include:In the framework of density functional theory, the homogeneous equilibrium properties and inhomogeneous interfacial properties are predicted simultaneously. The Helmholtz free-energy functional has been constructed in consideration of hard-sphere repulsion, dispersive attraction, and hydrogen association. The contribution of hard-sphere repulsion is represented by the improved fundamental measure theory; the attraction term is given by the direct correlation function interactions including dispersive and electrostatic interactions. The equilibrium and interface density of CO2-PS and H2O-PS have been predicted. The solubilities of CO2 and H2O in PS at different temperatures and pressures and the expansion coefficient of PS have been given. Comparing with the corresponding experimental data, the theoretical predictions have an average deviation of less than 5%, which means the predictions is reliable.The basic theoretical calculation method has been established, which has been used to solve the heterogeneous ternary system equilibrium. Comparing with experimental values simple alkane ternary system, the prediction accuracy of the proposed model to calculate heterogeneous ternary system phase equilibrium is less than 5%. It shows that this method can be used for analyzing and prediction of phase equilibrium of the ternary system.The equilibrium of CO2 (1)-H2O(2)-PS (3) system has been studied to analyze the solubilities of mixed blowing agent CO2 and H2O in PS and the solubility properties of CO2 as the presence of H2O role. On this basis, the expansion coefficient of PS has been assessed to analyze the effect of H2O on the expansion properties of PS, which provided important physical parameters calculation and analysis methods for mixed polymer foam blowing agents using in polymer foam.