Dielectric and Mechanical Spectroscopy — a Comparison

Abstract

Mechanical spectroscopy is a technique of material characterization in which material deformation and flow behavior is analyzed by means of dynamic mechanical methods. As in dielectric spectroscopy, advantage is taken of the material reaction to periodic variation of the external field, however with the difference that the applied field is mechanical instead of the electrical one. Materials respond to the applied field (stress or strain) by dissipating the input energy in a viscous flow (non-reversible response), by storing the energy elastically (reversible response), or through a combination of both of these two extremes. Dynamic mechanical method makes it possible to detect variation of both contributions as a function of temperature or deformation rate and to determine in this way the spectra of relaxation processes which control the viscoelastic behavior of a given material. The mechanical behavior is often a key criterion for a possibility of application of the materials even if some other properties (e.g., optical or electrical) are effectively used. As a result mechanical spectroscopy is a widely used experimental technique both as a material testing method and as a tool for analysis of the dynamics in complex polymer systems.