The flow of dilute aqueous solutions of macromolecules in various geometries: VI. Properties of the solutions

Abstract

For pt.V see ibid., vol.9, p.1967 (1976). The flow of dilute aqueous solutions of polyacrylamide (PAM-P250), of polyethylene oxide (PEO-WSR301), and of 'Kelzan' has been studied in straight pipes of circular cross-section, in bent pipes, between concentric rotating cylinders, and in porous beds. Results and their various speculative interpretations are collated and discussed. Viscosities as determined in an Ostwald viscometer, at 15-35 degrees C, were used to characterise the solutions. Values are consistent with views that PAM and PEO occupy flexible spherical shapes between 15 and 35 degrees C, whereas Kelzan is a semi-rigid elongated molecule which is becoming more flexible as temperature increases. Shear thickening of PAM solutions occurs as the Deborah number approaches unity. Values of the material constants of the second-order and third-order fluids are obtained from the stability of Couette flow and from draft reductions in bent pipes. Molecular processes are discussed.