Pressure Dependence of the Elastic Moduli of Liquid Glycerol

Abstract

Ultrasonic measurements were made of the longitudinal sound velocity, the absorption coefficient, and the shear impedance of liquid glycerol at constant temperatures over the pressure range 1 − 4000 kg/cm². Low‐ and high‐frequency limiting compressional moduli and the high‐frequency shear modulus were obtained from the measurements. The relaxational moduli were found to increase linearly with pressure. A reduction of the data showed that the width of the distribution of acoustic relaxation times, shear and compressional, is independent of pressure and temperature over the region studied. Low‐frequency absorption measurements made at 26°C as a function of pressure showed the ratio of the bulk to the shear viscosity to be pressure independent. It was observed that the ratio of the acoustic compressional relaxation time to the dielectric relaxation time was independent of pressure. However, it is noted that the width of the distribution of relaxation times for the two processes behaved differently as a function of pressure.