Thermally induced low-temperature relaxation of plastic deformation in glassy organic polymers and silicate glasses

A deep analogy between the processes of low-temperature thermally induced relaxation of plastic deformation in amorphous polymers and inorganic glasses is observed. The results of the calculation of the activation energy and activation volume of this relaxation process in terms of the excited state model satisfactorily agree with the experimental data obtained for both epoxy polymer systems and sheet silicate glasses. This evidence allows us to conclude that the initial stage of macroscopic plastic deformation in glassy systems involves small critical displacements of excited atoms (groups of atoms) that are provided by local rearrangements of neighboring particles (entropy fluctuations). In the vicinity of the yield point, the number of excited atoms per unit volume induced by the action of mechanical stresses appears to be quite sufficient (10²⁶–10²⁷ m^?3) for promotion of a marked plastic deformation of glasses and preservation of appreciable amounts of internal energy.