Thermodynamic properties of aqueous polyacrylamide solutions as a function of pressure and temperature

Abstract

The viscosities of dilute aqueous solutions of polyacrylamide were measured at temperatures from 20 to 60.4° and pressures up to 150 MPa using a falling-body viscometer. The viscosity coefficient, ν, increases exponentially with increasing pressure at a given temperature and concentration. The rate of increase of the apparent energy of activation. E≠, with pressure becomes more rapid as the concentration of the solutions increases. Intrinsic viscosity, [ν], increases with increasing pressure at a given temperature but almost levels off at pressures above 100 MPa while the Huggins constant, k H, decreases. The Flory-Huggins interaction parameter, X1 , decreases at a greater rate with increasing pressure as the temperature decreases indicating that the effect of pressure on improving the compatability between the polymer and solvent is greater near the θ-temperature. The second virial coefficient, A 2, was calculated from the intrinsic viscosity data and compared with the results obtained by light scattering technique.