Structure of polyamide 6/poly(ethylene terephthalate) blends under high cooling rate and shear stress and their moisture-sensitive properties

Crystallization of Poly(ethylene terephthalate): A Review

Poly(ethylene terephthalate) (PET) is a thermoplastic polyester with excellent thermal and mechanical properties, widely used in a variety of industrial fields. It is a semicrystalline polymer, and most of the industrial success of PET derives from its easily tunable crystallization kinetics, which allow users to produce the polymer with a high crystal fraction for applications that demand high thermomechanical resistance and barrier properties, or a fully amorphous polymer when high transparency of the product is needed. The main properties of the polymer are presented and discussed in this contribution, together with the literature data on the crystal structure and morphology of PET. This is followed by an in-depth analysis of its crystallization kinetics, including both primary crystal nucleation and crystal growth, as well as secondary crystallization. The effect of molar mass, catalyst residues, chain composition, and thermo-mechanical treatments on the crystallization kinetics, structure, and morphology of PET are also reviewed in this contribution.

Reorganization of Hydrogen Bonding in Biobased Polyamide 5,13 under the Thermo-Mechanical Field: Hierarchical Microstructure Evolution and Achieving Excellent Mechanical Performance

The hierarchical microstructure evolution of an emerging biobased odd-odd polyamide 5,13 (PA5,13) films under the thermo-mechanical field, stepping from hydrogen bond (H-bond) arrangement to the crystalline morphology, has been investigated systematically. It is found that the reorganization of H-bonds under the thermo-mechanical field plays a crucial role in the crystallization of PA5,13. Especially, it is revealed that the crystallization process under the thermo-mechanical field develops along the chain axis direction, while lamellar fragmentation occurs perpendicular to the chain axis. Consequently, a stable and well-organized H-bond arrangement and lengthened lamellae with significant orientation have been constructed. Laudably, an impressive tensile strength of about 500 MPa and modulus of about 4.7 GPa are thus achieved. The present study could provide important guidance for the industrial-scale manufacture of high-performance biobased odd-odd PAs with long polymethylene segment in the dicarboxylic unit combined with a large difference between the polymethylene segments in the dicarboxylic and diamine units.

Shelf Life of Fresh Sliced Sea Bream Pack in PET Nanocomposite Trays

Spoilage of fish due to microbiological activity is one of the biggest problems found by producers to take fresh fish products to customers. It is necessary packaging improvements to be able to increase fish shelf life and, thus, be able to travel further and to keep product freshness longer at customer's houses. In the present work, a new material is developed for fish packaging in modified atmosphere (MAP). This material is poly(ethylene terephathalate) (PET) extruded with a polyamide (PA) nanocomposite containing nanosepiolite. Here, it is shown the production procedure from laboratory to industrial scale. Permeability to oxygen and impact mechanical properties results are shown for different samples, both at laboratory and industrial processes. At the end, a material composition is chosen to produce the finale tray which will contain the sliced sea bream. Microbiological analysis is done over the packed fish, resulting is a lower microbiological count compared to a PET control sample. This means that shelf life of pack sea bream could increase from 2-4 to 7-9 days, which is very important for both producers and customers. On the other hand, trays obtained comply with European regulations in food contact materials (FCM) and, overall, they are suitable for food packaging materials.