Long-term viscoelastic response in physically aging amorphous polymers

Based on the concept of transient networks, a constitutive model is derived for the long-term viscoelastic response in physically aging amorphous polymers. Breakage and reformation rates for active chains of various kinds are assumed to depend on a sum of free-volume fractions, which are governed by kinetic equations. Comparison of numerical results with experimental data demonstrates fair agreement between observations and their prediction