High molecular weight, amorphous poly(propylene 2,5-furandicarboxylate) has been aged at 135°C for different times. The crystal phase contributes to achieve exceptionally low oxygen transmission rates and also good impermeability to water vapors, making PPF one of the most interesting fully biobased polyesters for packaging applications. † Electronic supplementary information (ESI) available: Synthesis of PPF, film preparation and ageing experiments are provided. 1 H NMR, DSC, WAXD and DMTA characterization, density and permeability measurements are described. See

Poly(ethylene 2,5-furandicarboxylate) (PEF) is considered today as a very promising biobased polymer for packaging applications. Most often, scientific literature describes synthetic procedures based on the transesterification of the dimethylester of the 2,5-furandicarboxylic acid, whereas this paper aims at studying the possibility of a practical and profitable synthetic route for PEF comprising a direct esterification stage of 2,5-furandicarboxylic acid. In that respect two catalysts, zinc acetate and aluminum acetylacetonate, chosen for their compatibility with food contact applications and for featuring a potentially reduced environmental impact, were investigated. The synthesis was performed by using tight reaction conditions: low excess of diol and short reaction time. Interesting results were obtained in terms of final PEF viscosity, color, and diethylene glycol content, that may strongly influence thermal and barrier properties. Furthermore, the obtained amorphous polymers are potentially suitable for the manufacturing of various packaging articles such as oriented films and bottles.

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Summary: Copolyesters of terephthalic acid with bis(hydroxyethyl ether) of bisphenol A (BHEEB) in different molar ratios have been synthesized by reactive blending from terephthalate polyesters and by melt polycondensation from the monomers. By this way, bisphenol A groups were inserted in the polyester chains with the aim to obtain polyesters with improved mechanical properties. The insertion of the BHEEB into the polyester backbone is quantitative and does not give rise to side reactions. These copolyesters can be obtained by the chemical recycling of commercial polymers; indeed BHEEB can be synthesized by chemical recycling of bisphenol A polycarbonate and may be incorporated in the polyester by reactive blending with recycled terephthalate polyesters. A new method for BHEEB synthesis by chemical recycling of PC is also presented.Glass transition temperature (Tg) as function of BHEEB content for copolyesters prepared by reactive blending BHEEB with terephthalate polyesters.magnified imageGlass transition temperature (Tg) as function of BHEEB content for copolyesters prepared by reactive blending BHEEB with terephthalate polyesters.

Furandicarboxylate-based polyesters are considered an interesting class of bio-based polymers due to their improved properties with respect to the petrol-based terephthalate homologs. An in-depth analysis of the crystal structure of poly(propylene 2,5-furandicarboxylate) (PPF), after maximum possible removal of the catalyst, was carried out. The study disclosed that purified PPF presents two different crystalline phases after crystallization from the melt. Crystallizations at temperatures lower than 120 °C lead to growth of a single crystal form (β-form), whereas two different crystal forms (α and β) were found to coexist at higher T c s. This behavior is opposite to that previously observed for unpurified PPF. The possibility that the catalyst nucleates the α-phase, which therefore becomes the kinetically favored modification at low crystallization temperatures in the presence of a higher amount of catalyst residue, has been considered as a feasible explanation. Two concomitantly different spherulitic morphologies were observed and connected to the βand α-phase, respectively. The association between polymorphism and melting behavior was studied. The origin of the peaks that compose the multiple melting endotherm recorded at conventional heating rates was determined by combined wide-angle X-ray scattering, differential scanning calorimetry, fast scanning chip calorimetry, and polarized light optical microscopy measurements. The higher thermal stability of the α-crystals in comparison with the β-form was thus demonstrated.