Simple Apparatus for the Measurement of Total Pressure of Polymer-Solvent Mixtures

A new apparatus for determining the total pressure in binary systems with one nonvolatile component, such as polymer-solvent mixtures, was designed. In contrast to the ebulliometric method, it enables measurement of the pressure above solutions across wider concentration ranges. The apparatus was tested on mixtures of water and poly(ethylene glycol). The tested polymers had three nominal molar weights. The measurements were correlated with the UNIQUAC-free volume model described earlier and compared with the published data. The applicability of known predictive models on the measurements was also tested and it was found that the entropic free-volume model yielded the best prediction of vapor-liquid equilibria for the studied systems.