Phase Equilibria of Polypropylene with Compressed Propane and Related Systems. 2. Fluid-Phase Equilibria of Polypropylene with Propane Containing Alcohols as Cosolvents and of Some Other Branched Polyolefins with Propane

Abstract

The phase equilibrium measurements for the pseudobinary supercritical polypropylene−propane system reported in the previous paper are extended to include pseudoternary systems where a polar cosolvent, in this case a low molecular weight alcohol, has been added. The cloud-point isopleths near the critical composition show the range of behavior to be expected as the type V pseudobinary system, polypropylene−propane, described in the previous paper, is transformed into the type IV pseudobinary system polypropylene−alcohol. This type of system contains an additional critical locus with upper critical solution temperatures (UCSTs) emanating from an upper critical end point (UCEP). The pseudoternary systems polypropylene−propane−alcohol possess in most cases a merged critical locus which contains a set of UCSTs and lower critical solution temperatures (LCSTs) and which does not touch the vapor pressure curve of the solvent. The phase equilibrium measurements of the system polypropylene−propane were also extended to include some polymers and copolymers which vary in branch length and frequency. The cloud-point pressures of these systems correlate with the wt % carbon in the branches but not with the branch frequency.