Experimental and theoretical study of uniaxial deformation of amorphous poly(ethylene terephthalate) above glass transition temperature

Abstract

International audienceUniaxial deformation of amorphous thick and massive poly(ethylene terephthalate) (PET) samples above the glass transition temperature has been studied in the temperature range relevant to the stretch–blow moulding process of PET bottles. A video controlled system coupled to a novel clamping device, together with accurate control of the thermal gradient in the material, make it possible to determine true stress v. true strain data at constant true strain rate up to very high strains of ∼2.5. The mechanical response of PET in these conditions is modelled as a molecular network exhibiting a rubber-like behaviour. Sufficiently far from the alpha transition, it is shown that the Edwards and Vilgis model is able to reproduce experimental data accurately, which also offers a relevant insight into the nature of the molecular networks. Closer to the alpha transition, this purely hyperelastic model needs refining and improving to take into account an additional non-elastic contribution

Strain-induced crystallization of poly(ethylene 2,5-furandicarboxylate). Mechanical and crystallographic analysis

“…In consequence, it was possible to analyze final microstructure as a function of local strain for a given strain rate and a given temperature. In this paper, one example is chosen in the middle of this range, which is associated to an equivalent strain rate of 0.01 s 1 and is representative for injection stretch blow moulding [38]. At this position on the master curve, the material is supposed to be in a certain state which is related to its "distance" from the α transition.…”

Simulation of the Injection Stretch Blow Molding Process: An Anisotropic Visco‐Hyperelastic Model for Polyethylene Terephthalate Behavior

“…Initially researchers ignored the viscous effects and used hyperelastic models [2]. Billon et al [3,4] recognized the need to include viscous effects and altered the hyperelastic model by making some of the parameters dependent on strain rate; however, the model proved to be unstable when implemented in forming simulations. Previous work from Chevalier and Marco [5] based on biaxial experimental data in the strain rate range of 0.02-2 s −1 clearly demonstrated the need to capture the viscous effects and based on these data, a new model known as the G'Sell-Jonas was developed which took into account the effect of strain rate and the typical strain hardening behavior observed in PET.…”

New constitutive modeling for time‐dependent mechanical behavior of polymers close to glass transition: Fundamentals and experimental validation

“…Chains are assumed to have a limited extensibility (that is, this is a non‐Gaussian approach). Sweeney et al,13–15 in parallel to Buckley et al16–18 and further Gorlier et al19 used this model as a component of a standard material. However, EV's potential allows reproducing most of the shapes of experimental tensile curves20 and could be used in another manner. However, nonlinear viscous effects can be introduces through “non‐Newtonian pseudo plastic, Eyring, or Carreau”–like elements.…”