A model of adaptive links in finite viscoelastoplasticity of glassy polymers

Constitutive equations are derived for the viscoelastoplastic response of glassy polymers at finite strains. The model combines the theory of temporary polymeric networks (in the version of a model of adaptive links) with the concept of semiaffine junctions. Viscoelasticity of polymers is modeled by breakage and reformation of adaptive links (physical crosslinks and entanglements), whereas the viscoplastic phenomena are described by sliding of junctions with respect to a bulk medium. Thermodynamic potentials are proposed for nonaffine networks, and constitutive equations are developed using of the laws of thermodynamics. For uniaxial compression of a bar, fair agreement is demonstrated between results of numerical simulation and experimental data for polyethylene and poly(methyl methacrylate) during nonmonotonic loading.