25. Martin, Todd M.; Gupta, Ram B.;
Roberts, Christopher B. Measurements and
modeling of cloud point behavior for poly(propylene
glycol) in ethane and in ethane + cosolvent mixtures at high pressure.
Abstract
The phase behavior of polypropylene glycol (PPG) in ethane and ethane + cosolvent mixts. was studied using a high-pressure, variable-vol. view cell. The cosolvents studied were chloroform and carbon tetrachloride. Cloud point pressures for PPG in ethane were measured for three different wt.-av. mol. wt. (Mw) PPG samples (450; 830; 2160) at several different polymer concns. (ranging from 0.5 to 4 mass %). Cloud point pressures for PPG (Mw = 830, 4%) in ethane + cosolvent mixts. were measured for several different cosolvent concns. (ranging from 9 to 42 solvent mass %). The phase behavior of the PPG + ethane system transitioned from lower crit. soln. temp. (LCST)-like to a merged U-LCST-like behavior as the polymer concn. or the polymer mol. wt. was increased. In general, the addn. of the cosolvents reduced the cloud point pressure. The addn. of chloroform cosolvent reduced the cloud point pressure more than carbon tetrachloride due to hydrogen bonding between PPG and chloroform. The lattice fluid hydrogen bonding equation of state was used to model the exptl. data.
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