A study of viscoelastic properties of butanediol-1,3 using optical digital correlation spectroscopy

Abstract

A temperature study of viscoelastic relaxation in butanediol‐1,3 was made using digital correlation and Brillouin scattering spectroscopic methods. The digital correlator provided measurement of the relaxation function from which average relaxation times were calculated. The Brillouin scattering method allows a more accurate determination of the high frequency longitudinal modulus than older ultrasonic methods that require extrapolation of data over a large temperature range for the determination of this modulus. From the light scattering data, it has been concluded that, contrary to previous studies, the relaxations observed in the real and imaginary parts of the complex longitudinal modulus are the same. Under these circumstances the use of a ’’hysteresis’’ effect to interpret the nature of the relaxation at high frequencies is unnecessary. A theoretical derivation has been given that allows the average relaxation time obtained via correlator studies to be compared directly to the measured shear viscosity.