Molecular Place Changes and Mechanical Damping Spectra

Abstract

The loosely packed structure of amorphous polymers makes it possible that, for small segments or side groups, two (or more) neighboring potential minima exist which are separated by a small potential barrier ΔΦ. Place changes between two potential minima take time, the so-called relaxation time τ. It is a function of the potential distribution and the temperature. By external mechanical or dielectric loading the populations of the double well minima are disturbed (see Fig.6.10). The equilibrium is restored by place changes. As the relaxation time of place changes is finite, there is a delay between loading and deformation of a material, which causes dissipation of the loading energy. For cyclic loading a loss-angleδ occurs between stress and strain, which is a function of the temperature and of the load frequency. It determines the damping behavior.

The erratum of this chapter is available at http://dx.doi.org/10.1007/978-1-4757-6213-6_12