Stretch blow moulding of PET; structure development and constitutive model
Résumé
Microstructure 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.