Polymorphism and Multiple Melting Behavior of Bio-Based Poly(propylene 2,5-furandicarboxylate)

Abstract

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.

The Blending of Poly(glycolic acid) with Polycaprolactone and Poly(l-lactide): Promising Combinations

“…45%) prevents the observation of a distinct glass transition, which should anyhow be present at 35–40 °C [ 33 ]. A double melting peak is observed for PGA, and it is tentatively ascribed to melting–recrystallization phenomena, which is typical of many polyesters (see [ 43 ] and reference therein).…”

Poly(Ethylene Furanoate) along Its Life-Cycle from a Polycondensation Approach to High-Performance Yarn and Its Recyclate

“…Degrees of crystallinity of 25 and 33% for annealing and melt crystallization, respectively, have been reported [9,36,38,42], reaching 50% after solid state polycondensation (SSP) [13]. The coexistence of α-and β-crystal form (multiple melting endotherms), comparable to PET, was demonstrated for purified PEF by Righetti et al [34], as well as by Zheng and Pan [43], and was found to be correlated to catalysts acting as nucleation agents for the α-form.…”

“…The crystallization behavior and, especially, the investigation of the crystal structure of PEF by XRD have already been studied [8][9][10][11][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Three different crystal polymorphs have been reported, i.e., α (triclinic), α', and β (monoclinic) structures [27,29,32,34].…”

“…The crystallization behavior and, especially, the investigation of the crystal structure of PEF by XRD have already been studied [8][9][10][11][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Three different crystal polymorphs have been reported, i.e., α (triclinic), α', and β (monoclinic) structures [27,29,32,34]. In contrast to PET, which preferably crystallizes in the α-form [35,40], the β-form is the most common one for PEF [9,27,29,32,34] [8,10,11,31,36,37], respectively.…”

“…Three different crystal polymorphs have been reported, i.e., α (triclinic), α', and β (monoclinic) structures [27,29,32,34]. In contrast to PET, which preferably crystallizes in the α-form [35,40], the β-form is the most common one for PEF [9,27,29,32,34] [8,10,11,31,36,37], respectively. Bulk crystallization was reported to result in α-crystallization [32]; melt-quenched PEF was reported to yield α'-PEF, while the βform was obtained from slow solvent crystallization [27,39].…”