The Deborah number, relaxation phenomena and thermally stimulated currents

Abstract

In the field of the science of flow and deformation of matter (rheology), the so-called Deborah number plays an important role, since it describes the influence of time on the observed flow properties. The technique of thermally stimulated depolarisation currents (TSDC) constitutes a dielectric technique whose experimental result is an electric current flow that is the manifestation of a dipole relaxation. In the present work we use the concept of the Deborah number to describe and interpret a TSDC experiment. We show that, in the linear heating ramp of a TSDC experiment, the Deborah number decreases as the temperature increases, in such a way that it reaches a value of unity at the temperature of maximum intensity of the experimental peak. This particular feature is the origin of a new procedure, proposed here, for evaluating the fragility of a glass-forming liquid.