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Biobased poly(hexamethylene 2,5-furan dicarboxylate) (PHF) was synthesized by the two-stage melt polycondensation method (transesterification and polycondensation) in a glass batch reactor. The nonisothermal crystallization from the melt and from the glass was studied by means of Differential Scanning Calorimetry, Fast Scanning Calorimetry and advanced kinetic analysis. It is shown that changes in the crystallization regime occurs at certain temperatures and that the end of the crystallization presents some deviation from what is predicted by the Hoffman-Lauritzen's theory of growth rate. A method is presented that allows the determination of the equilibrium melting temperature, the infinite glass transition temperature, the temperature at maximum of the growth rate, and accurate simulation of crystallization rate curves. An equation is proposed for modelling the crystallization process using a methodology that avoid the problem of local minima occurring when too many parameters must be determined simultaneously. [Display omitted] • Nonisothermal crystallization of a new biobased polyester. • Changes in the crystallization regime occurs at certain temperatures. • A new method allows the determination of key parameters of crystallization processes. • Accurate simulation of crystallization rate curves are obtained. • The method can be extended to modelling crystallization of polymers in processing applications. [ABSTRACT FROM AUTHOR]

Abstract: The biaxial orientation behavior of poly(ethylene 2,5‐furandicarboxylate) (PEF) is studied in comparison to poly(ethylene terephthalate) (PET). PEF is a polyester that can be produced through similar steps as PET but using 100% biobased 2,5‐furandicarboxylic acid instead of terephthalic acid. This work highlights the stress–strain behavior of PEF during biaxial orientation at various temperatures. Strain hardening and strain‐induced crystallization in the oriented PEF samples generally appeared at higher stretch ratios for PEF than for PET at comparable molecular weight, while somewhat lower degrees of crystallinity are reached in PEF. Shrinkage in oriented PEF is found to be on par with PET in the region of the glass transition. Higher modulus and improved barrier properties, compared to PET, are found in the oriented materials when sufficiently high stretch ratios are applied in biaxial orientation. [ABSTRACT FROM AUTHOR]

The effect of nanocrystalline cellulose dispersion on the nonisothermal crystallization of poly(ethylene 2,5-furandicarboxylate) (PEF) has been investigated by means of solvent casting. The cellulose dispersion plays a significant role on the crystallization temperature, thus dispersive equipments of increasing energies were employed to improve the cellulose particles disaggregation. Therefore, ultra-sonic bath, ultra-sonication, and ultra-turrax were used to disperse cellulose nanocrystals in 1,1,1,3,3,3-hexafluoro-2-propanol. Dissolved separately in the same solvent, PEF was then poured into the cellulose suspension before casting. The cellulose whiskers were inspected by transmission electron microscopy. Differential scanning calorimetry was used to measure the crystallization temperature, while scanning electron microscopy visualized the cellulose dispersion at the fracture surface. After investigation on the interaction of cellulose/PEF via Fourier transform infrared spectroscopy, the thermal stability of the blends was measured by means of thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Poly(ethylene 2,5-furandicarboxylate) (PEF), an emerging biobased polyester, was compounded with cellulose via twin-screw extrusion. Different extrusion parameters such as mixing time, screw speed and temperature were employed. Composite thin films containing 1, 2 and 4% cellulose w/w were prepared and compared with neat PEF films. The morphology of PEF/cellulose composites was examined by scanning electron microscopy (SEM) and the molecular weight after extrusion was controlled by means of size exclusion chromatography (SEC). The influence of the cellulose on both isothermal and non-isothermal crystallizations of PEF was investigated by differential scanning calorimetry (DSC). Crystallization is faster in presence of cellulose and the nucleating effect increases with the cellulose concentration. [ABSTRACT FROM AUTHOR]

The present work focuses on the influence of nucleation processes on the crystallization of bio-based poly(ethylene 2,5-furandicarboxylate) (PEF). Nuclei formation has been studied by means of fast scanning calorimetry (FSC) both when cooling from the melt (nonisothermal conditions) and when annealing at either low- or high-temperatures (isothermal conditions). FSC results show that nucleation on cooling can be prevented by using fast rates allowing to keep the polymer in its amorphous state; whereas cooling at moderate rates results in sample nucleation with a subsequent increase of the crystallization rate. Isothermal pretreatment just above the PEF glass transition temperature ( Tg) results in nuclei formation whose rate decreases when the nucleation temperature approaches PEF Tg. On the other hand, annealing below the PEF melting point allows determination of the sample self-nucleation behavior which occurs in a very narrow temperature range, i.e., between 195 and 198 °C. [ABSTRACT FROM AUTHOR]

Poly(ethylene 2,5-furandicarboxylate) (PEF) is a polyester from ethylene glycol and 2,5-Furandicarboxylic acid which has gained increasing interest due to its excellent properties compared to chemically similar PET. This paper presents an estimation of the crystallization enthalpy, the crystalline and amorphous density and the crystallization kinetics of PEF. Using Avrami and the Hoffman-Lauritzen theory, Hoffman-Lauritzen parameters are proposed that relate crystal growth rate of catalyst-free PEF to temperature and molecular weight. Characteristic is a higher activation energy for chain diffusion (U*) for PEF compared PET, which can be attributed to more restricted chain conformational changes. Finally, the crystallization rate of PEF is shown to be significantly affected by catalyst type. [ABSTRACT FROM AUTHOR]

Compared to other semicrystallinepolymers, PTFE demonstrates a very fast crystallization process oncooling. This study explores for the first time the nonisothermalPTFE ultrafast crystallization under tremendously fast cooling rates(up to 800 000 K·s–1) achieved by usingfast scanning calorimetry (FSC) and ultra-fast scanning calorimetry(UFSC). Regular DSC was also used to get crystallization at slowerrates. The data obtained on a wide range of cooling rates (over 8orders of magnitudes) help to get new knowledge about crystallizationkinetics of PTFE. Both FSC and UFSC data show that it is impossibleto bypass the crystallization and thus to reach a metastable glassystate even for the fastest cooling rate employed (800 000 K·s–1). The crystals formed under such conditions are slightlyless stable than those produced under slower cooling rates, as reflectedby a shift of the melting peak to lower temperature. The differencein crystal morphologies was confirmed by SEM observations. The variationof the effective activation energy (Eα) with the relative extent of crystallization reveals that PTFE crystallizationfollows a transition from regime II to regime III around 315–312°C. Corroborated temperature dependences of Eαobtained respectively for crystallizations underslow and fast cooling rates were combined and fitted to the theoreticaldependence of the growth rate derived from the Hoffman–Lauritzentheory. [ABSTRACT FROM AUTHOR]

Humins is a biomass-derived material, co-product of the acid-catalyzed conversion of cellulose and hemicellulose to platform chemicals. This work presents a thorough study concerning the crosslinking kinetics of humins by chemorheological analysis and model-free kinetics under isothermal and non-isothermal curing. Humins can auto-crosslink under the effect of temperature, and the reaction can be fastener when adding an acidic initiator. Thus, the effect of P-Toluenesulfonic acid monohydrate (pTSA) on the crosslinking kinetics was also studied. The dependencies of the effective activation energy (Eα-dependencies) were determined by an advanced isoconversional method and correlated with the variation of complex viscosity during curing. It is shown that humins curing involves multi-step complex reactions and that the use of an acidic initiator allows faster crosslinking at lower temperatures, involving lower Eα. The shift from chemical to diffusion control was also estimated. [ABSTRACT FROM AUTHOR]