Ultrasonic and Viscoelastic Studies on Liquids at Different Pressures

Ellis, J

Abstract

This thesis describes experimental researches in ultrasonic
and viscoelastic relaxation in pure liquids, mixtures and a polymer
solution. The measurements were made over a range of temperatures and
pressures in the frequency range 5 to 78 MHz.
Density, steady flow viscosity, real part and imaginary part
of the shear impedance were measured on five liquids. Four of the
liquids obeyed the Time-Temperature Superposition principle and could
be described by the Barlow, Erginsav and Lamb (B. E. L, ) model. The
fifth liquid did not obey the Time-Temperature Superposition principle
and deviated from the model. This was attributed to the distribution
of relaxation times wideningas the temperature is decreased.
The shear compliance for all five liquids varied
linearly with temperature at atmospheric pressure. At higher pressures
it was the shear modulus that varied linearly with pressure.
Both low and high frequency longitudinal velocities were
found to vary linearly with temperature at atmospheric pressure, while
at higher pressures only the low frequency velocity varied linearly
with pressure, the high frequency velocity results were too scattered.
Values of the bulk moduli obtained from the longitudinal
moduli and shear moduli were normalised and the variation with reduced
I
frequency was found to be of the same shape as for the shear moduli but
displaced along the reduced frequency axis. Therefore the shear and
bulk relaxation properties have a common origin. From this displacement
and the values of G(w) and the relaxing part of the bulk modulus
K(O)) the ratio of volume to shear viscosity was calculated for
three liquids at atmospheric pressure and two liquids at higher
pressures. The ratio Tlv/T), varied from 2.7 to 4.2 at atmospheric
pressure with slightly lower values at higher pressures but the
difference was notstatistically significant.
Measurements of density and velocity were made on solutions
of a surfactant at elevated pressures. The density measurements were
fitted to the linear secant modulus equation. Investigation of the
shear properties of a gel-soap solution showed that it was thixotropic. '
Finally, a conformati onal analysis at pressures above
atmospheric pressure showed that the relaxation frequency was not
significantly changed by increasing the pressure.

Citation

Ellis, J. Ultrasonic and Viscoelastic Studies on Liquids at Different Pressures. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Jul 22, 2011
• Publicly Available Date: Jul 22, 2011
• Award Date: Jan 1, 1976