Viscoelastic Properties of Network Structure

We investigate the statistical mechanics of modified rubber-like network structure in order to make a molecular theoretical explanation of viscoelastic behaviors displayed by amorphous high-polymeric substances. In the former part of this paper we discuss a theory in which the relaxation mechanism is ascribed by the breakage and reformation of junctions, and in the latter part another theory is treated making use of the concept of slipping of chains for the relaxation mechanisms. It is shown that the above two theories have the similar results. Owing to this fact, we can conclude that the concept of slipping of chains is essentially equivalent to that of the rearrangement of chains caused by the breakage and reformation of junctions. Furthermore, the stress-strain-time relations of our models are essentially equivalent to that of the so-called generalized Maxwell model in the phenomenological theory of viscoelasticity.