International audienceMicrostructure of PET in stretch blow moulding is studied combining controlled tension followed by quenching, free-blow and ISBM. Due to quenching, observed final microstructure is often closer to a mesophase than to crystal. Texture is, for its part, controlled by the loading path. In fact stretching only induces appearance of an oriented precursor-phase that will become a crystal during cooling steps providing that this latter is slow enough. Microstructure evolution does not obey the classical "nucleation -growth" schematic. This enlightens development of constitutive models demonstrating the irrelevance of the crystallinity ratio as parameter and of the Avrami-like approach as part of the model. One, model based on revisited network approach is suggested
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
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