Cr. Novenario et al., VAPOR-LIQUID-EQUILIBRIUM OF POLYMER PLUS SOLVENT MIXTURES BY THE CHAIN-OF-ROTATORS EQUATION OF STATE, Industrial & engineering chemistry research, 37(8), 1998, pp. 3142-3150
Vapor-Liquid equilibrium (VLE) of polymer + solvent mixtures is descri
bed by the chain-of-rotators (COR) equation of state (EOS) using segme
nt parameters that are applicable to polymers of varying molecular wei
ght. Segment parameters a and b are obtained from small molecules of t
he same chemical structure as the polymer segment. The segment paramet
er c is then obtained by fitting polymer pressure-volume-temperature (
PVT) data. van der Waals and free energy matching mixing rules are inv
estigated to describe mixtures of various types. Excellent correlation
of VLE data is obtained for all mixtures studied by using only one co
nstant interaction coefficient for a, k(12), in the van der Waals mixi
ng rule independent of temperature or polymer molecular weight. VLE pr
edictions from the COR EOS by using van der Waals mixing rules with ze
ro k(12) as well as by using UNIFAC free energy matched mixing rules a
re presented. For the majority of systems studied, both predictive met
hods gave better or equal results compared to the UNIFAC-FV model (FV
= free volume).