Some Elastic Properties of Organic Glasses in the Transition Region from Solid to Liquid at Ultrasonic Frequencies

Measurements have been made of the dynamic shear properties of four organic glasses at a frequency of 4 megacycles per second and over a wide temperature range covering the softening region. The behaviour of the shear modulus is in accord with the chemical nature of these materials. Correlation of these results with measurements of the velocity of longitudinal waves at the same frequency suggests that there is a relaxation in the bulk modulus between the solid and liquid state, as has been reported by Kuhn and Vielhauer, but at a somewhat lower temperature than the relaxation in the shear modulus.