Investigation of nonelastic response of semicrystalline polymers at high strain levels

The nonelastic behavior at high strains of three semicrystalline polymers [i.e., nylon-6, poly(ethylene terephthalate), and poly(ethylene 2,6-naphthalenedicarboxylate] was investigated. For all materials, room temperature tensile strain recovery tests revealed the existence of two components of nonelastic deformation: a fast-relaxing component (called anelastic) and a slow-relaxing component (usually called plastic). A strain recovery master curve could be constructed for each material from the strain recovery data obtained at various temperatures. The shift factors versus temperature relationship for the strain recovery master curves allowed us to evaluate an activation energy for the nonelastic strain recovery process. These data were then compared with the activation energy for the glass-transition process evaluated by dynamic mechanical measurements at low strain. The aim of this comparison was to investigate the influence of viscoelasticity on the nonelastic deformation recovery.