Ultrasonic relaxation study in gelatin sols and gels

Ultrasonic absorption was measured in gelatin sols and gels in the frequenc y range of 0.2-35 MHz. Two techniques, a plano-concave resonator method and optical beam deflection by ultrasonic waves, were used to cover the wide f requency range. The absorption spectra observed both in the sets and gels w ere well fitted to the relaxation curves, assuming the Cole-Cole-type distr ibution of relaxation times. A change in relaxation parameters upon gelatio n was obtained: the relaxation frequency decreased, the relaxation strength increased and the distribution became wider The relaxation mechanism is di scussed in the light of the hydration equilibrium ui gelatin polymers.