Phase equilibrium of PVAc + CO2 binary systems and PVAc + CO2 + ethanol ternary systems

Abstract

The cloud point and bubble point isopleths were measured for poly(vinyl acetate) (PVAc) + CO2 binary systems and PVAc + CO2 + ethanol ternary systems using a supercritical CO2 phase equilibrium apparatus. A transition point measurement device was designed to accurately determine the cloud point pressures by measuring the resistance variation of a photoresistor. The effects of the temperature, pressure, components, and polymer molecular weight on the phase behavior of these binary and ternary systems were investigated. We found that the transition point pressure increased with increasing temperature and molecular weight of PVAc, the cloud point isopleths for the PVAc + CO2 binary systems are upper critical solution pressure (UCSP) type, the cloud point pressures moved downwards with the addition of ethanol to PVAc + CO2, and the cloud point pressures decreased with increasing PVAc + ethanol concentration at a fixed mass ratio of 1:7. The perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS) was used to investigate the phase behavior of these binary and ternary systems by adjusting the binary interaction parameter, kij. The modeling shows a very good agreement with the experimental data.