Vapor−Liquid Equilibrium for Polymer−Diluent Systems from Melting Point Depression

A novel approach for determining vapor−liquid equilibrium (VLE) for polymer−diluent systems is described. The concentration- and temperature-dependence of diluent−polymer Flory−Huggins interaction parameter χij is first estimated from depression in polymer melting point as a function of monomer (diluent) concentration. VLE for the polymer−diluent binary system is then obtained using an activity coefficient model and equation of state model with Aspen Polymer Plus. The technique is validated for the syndiotactic polystyrene−toluene and syndiotactic polystyrene−methyl ethyl ketone and is extended to polybutylene terephthalate − with various diluents such as butanediol, tetrahydrofuran, isophorone, 1-methylnaphthalene, and benzonitrile, systems hitherto not reported in the literature.