Experimental cloud-point data to 250 degrees C and 2000 bar are presen
ted to demonstrate the impact of dimethyl ether (DME) and ethanol on t
he phase behavior of poly(ethylene-co-acrylic acid) (3.9 mol % acrylic
acid) (EAA(3.9))-butane mixtures. The addition of 6.4 wt % DME to the
EAA-butane system decreases the cloud-point pressure from 2000 to 650
bar at 165 degrees C due to the cross-association of dimethyl ether a
nd acrylic acid in EAA(3.9). At high DME concentrations, its impact is
reduced as the amount of DME increases since polar interactions betwe
en excess DME increase after the acrylic acid sites are saturated with
DME. Ethanol is a better cosolvent than DME at low ethanol concentrat
ions. The addition of 2.2 wt % ethanol decreases the cloud-point press
ure from 2000 to 650 bar at 165 degrees C due to the cross-association
of ethanol and acrylic acid in EAA(3.9). Ethanol becomes an ''antisol
vent'' at concentrations greater than 16 wt % as excess ethanol self-a
ssociates, forming multimers that increase the polarity of the mixture
. The cloud-point data are modeled with statistical associating fluid
theory (SAFT). The ternary calculations use temperature-independent, b
inary mixture parameters whose values are obtained by fitting the phas
e behavior of the three binary pairs that form the ternary system. SAF
T correctly predicts the trends observed in the cloud-point curves fro
m zero to 100 wt % DME, although quantitatively it overestimates the e
ffect of DME. SAFT underestimates the effect of ethanol, as the calcul
ated one-phase region is smaller than that observed. However, SAFT cor
rectly predicts the decreasing impact of ethanol with increasing ethan
ol concentration and that ethanol becomes an antisolvent at high ethan
ol concentrations.