FINITE-AMPLITUDE ULTRASONIC MEASUREMENTS OF POLYETHYLENE OXIDE AND POLYACRYLAMIDE SOLUTIONS

Experiments on the propagation of planar acoustic waves in aqueous solutions of high-molecular-weight polyethylene oxide and polyacrylamide are discussed. The acoustic absorption of the solutions was determined at 2.5 and 7.5 MHz, and the growth and decay of the amplitude of the second-harmonic component generated by the 7.5-MHz source was measured. It was found that the absorption and second-harmonic amplitude generally increased with both concentration and molecular weight. However, the absorption was found to be much less than in Newtonian fluids with equal zero-shear-rate properties (i.e., viscosity, density, and small-signal wave speed). Additionally, the frequency dependence of the data indicate that a relaxation process occurs in both polymers at a characteristic frequency in the range 1–10 MHz. At low polymer concentration, the second-harmonic amplitude was less than that found in water under similar experimental conditions. © 1990, Acoustical Society of America. All rights reserved.