Thermal Crystallization Kinetics of PET, RPET and PEF for Sustainable Packaging

Poly (ethylene 2,5-furandicarboxylate) (PEF) is a bio-based polyester that is the subject of growing interest as a potential alternative to Poly (ethylene terephthalate) (PET) for sustainable packaging. Its excellent gas-barrier properties and reduced carbon footprint make it a promising candidate, but its use at industrial scale requires a solid understanding of how temperature and thermal history affect its mechanical and viscoelastic behavior. In this study, Differential Scanning Calorimetry (DSC), Dynamic Mechanical Thermal Analysis (DMA), and optical microscopy were used to characterize the thermal transitions and crystallization behavior of PEF, compared with PET and recycled PET (rPET). DSC results show that thermal crystallization of PEF proceeds very slowly, a result confirmed by in-situ microscopy. DMA measurements provide complementary information on the evolution of both storage and loss moduli with temperature, highlighting its dependence on crystallinity and thermal history. Together, these thermal and mechanical analyses clarify how PEF’s crystallization behavior affects its thermo-mechanical response. From a processing perspective, the very slow thermal crystallization of PEF is advantageous for stretch blow molding (SBM) process of bottles, as the polymer remains essentially amorphous during heating and crystallizes predominantly under deformation during the fast forming stage.