APPLICATION OF THE VAN-DER-WAALS-EQUATION OF STATE TO POLYMERS .1. CORRELATION

A reliable methodology for evaluating the energy and co-volume paramet ers of cubic equations of state for polymers is proposed. Only two low -pressure volumetric data points are used. The procedure is applied to the van der Waals equation of state and bubble-point pressure calcula tions are performed for a number of polymer solutions. The usual combi ning and mixing rules are used. It is shown that the van der Waals equ ation can correlate the equilibrium pressures of polymer solutions usi ng one binary interaction parameter. The accuracy of the correlation i s very good; it is comparable to or better than that achieved using th e Flory-Huggins model. It is also shown that the necessary binary inte raction parameters for the van der Waals equation of state can be esti mated using a simple scheme based on the Berthelot combining rule. It is, thus, demonstrated that the van der Waals equation of state can be a simple and successful tool for the description of the vapor-liquid equilibria in polymer solutions.