A Perspective on PEF Synthesis, Properties, and End-Life

Abstract

This critical review considers the extensive research and development dedicated, in the last years, to a single polymer, the poly(ethylene 2,5-furandicarboxylate), usually simply referred to as PEF. PEF importance stems from the fact that it is based on renewable resources, typically prepared from C6 sugars present in biomass feedstocks, for its resemblance to the high-performance poly(ethylene terephthalate) (PET) and in terms of barrier properties even outperforming PET. For the first time synthesis, properties, and end-life targeting-a more sustainable PEF-are critically reviewed. The emphasis is placed on how synthetic roots to PEF evolved toward the development of greener processes based on ring open polymerization, enzymatic synthesis, or the use of ionic liquids; together with a broader perspective on PEF end-life, highlighting recycling and (bio)degradation solutions.

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

“…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 ].…”

“…Diffraction peaks have been reported to occur at 2ϴ = 15.8°, 20.2°, 25.2°, and 27.2° [ 9 , 29 , 32 , 35 ] and 2ϴ = 16.2°, 18.0°, 20.8° ([ 10 ]), 23.3°, and 26.7° [ 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 β-form was obtained from slow solvent crystallization [ 27 , 39 ]. An additional XRD-signal was reported to occur at 2ϴ = 19.3 [ 29 ] and was attributable to the α-structure and to the similar α’-structure.…”

“…In order to be suitable for (multi-) filament spinning and, especially, for the production of high-strength yarns, it is mandatory to reach an intrinsic viscosity ( ) of at least 0.6 dL·g −1 , as is the case with fiber-grade PET [ 44 ]. This requires the provision of monomers of sufficient quality and purity for the polycondensation of PEF without by-products, which also avoids colorations [ 39 , 45 , 46 ]. In addition, a high value influences T g [ 47 ].…”

“…The first entails direct synthesis using dimethyl 2,5-furandicarboxylate (FDME), and the second is based on the transesterification of FDCA. While the FDME route results in higher purity PEF, many industrial plants for PET (also usable for PEF) are no longer equipped for the removal of the methanol that is released during the process, restricting synthesis to the more challenging FDCA route [ 39 , 48 ].…”

Enzymatic Synthesis of Poly(alkylene succinate)s: Influence of Reaction Conditions

“…Numerous types of polymers prepared by enzymatic polymerization have been reported, among them polyphenols by enzymatic oxidative polymerization [3], polyaniline by enzymatic catalysis in presence of hydrogen peroxide [4], polysaccharides [5,6], vinyl polymerizates (being typically chain growth polymerizates) [7], a high number of differ-ent polyesters, polythioesters, polythioetheresters, polyphosphates, or polyketoetheresters obtained by ring-opening polymerization [8][9][10][11] or by polycondensation [12][13][14]. Polyesters and polyamides attracted particular attention, reflected by various studies [1,[15][16][17][18][19][20][21][22][23][24]. An advantage of enzymatic polycondensation is the possibility to polymerize monomers with reactive groups (e.g., oxirane and aromatic OH groups, double bonds like in itaconic acid [25][26][27], which would undergo side reactions under standard polycondensation conditions) resulting in polymers opening the opportunity for polymer-analogous reactions [12,15,25].…”