Miscibility, Phase Separation, and Phase Settlement Dynamics in Solutions of Ethylene–Propylene–Diene Monomer Elastomer in Propane +n-Octane Binary Fluid Mixtures at High Pressures

Abstract

Miscibility and phase separation of ethylene–propylene–diene monomer (EPDM) elastomer at a polymer concentration of 11.7 wt % in n-octane (61.9 wt %) + propane (26.4 wt %) have been explored over a wide range of temperatures up to 187 °C and pressures up to 200 bar. Experiments were carried out using a new system that allows assessment of volumetric properties, thermodynamic phase boundaries, phase settlement times, and the mechanistic details of phase separation all in the same instrument. The system involves a novel, dual-piston variable-volume cell with two pairs of sapphire windows. One pair of the windows is used for the measurement of the transmitted light intensities, while the other pair is used for the measurement of scattered light intensities from a He–Ne laser source. Piston positions are continuously recorded with two dedicated linear variable differential transformers, which allow continuous determination of the solution densities as a function of pressure at a given temperature. The solutio...