GAS PLASTICIZATION EFFECT OF CARBON-DIOXIDE FOR POLYMERIC LIQUID

The low-shear-rate viscosities of poly(ethylene glycol)(PEG)/CO2 solut ions were measured over a range of pressures (1-8 MPa) and temperature s (30-60 degrees C). Photon correlation spectroscopy (PCS) was used to determine the viscosities based on measuring diffusivities of suspend ed colloidal particles. Assuming spherical particles and knowing the s ize of particles, the Stokes-Einstein relation was employed to find th e medium viscosity. The interesting results were observed as follows: in the high range of the volume fraction of polymer phi(p), the plasti cization effect is stronger than that of the compressibility, the solu tion viscosity decreases as more CO2 dissolves in the polymer, while a t the low range of phi(p) the viscosity reduction reverses and the vis cosity of solution increases due to the compressibility effect. The Ke lley-Bueche (KB) free volume treatment of the viscosities of polymer s olutions was modified to account for gas solvent and applied to interp ret our data on PEG/CO2 systems. It was shown that the theoretical equ ation, based on the assumption of the additivity of free volumes of th e components, wits capable of predicting with excellent accuracy the c oncentration, temperature, and pressure dependence of the viscosities of the investigated polymeric solutions. Copyright (C) 1996 Elsevier S cience Ltd.