Modelling the nonlinear viscoelastic behavior of amorphous glassy polymers

Constitutive equations are derived for the nonlinear viscoelastic response of glassy polymers at isothermal loading with small strains. The model is based on the concept of temporary networks, where the rates of breakage and reformation for active chains depend on the specific entropy production. It is demonstrated that the stress-strain relations with a dissipation-driven internal clock adequately predict an apparent aging of polycarbonate observed in dynamic tests on stretched specimens.