Biobased poly(butylene 2,5-furandicarboxylate) and poly(butylene adipate-co-butylene 2,5-furandicarboxylate)s: From synthesis using highly purified 2,5-furandicarboxylic acid to thermo-mechanical properties

- An new method was proposed to effectively purify 2,5-furandicarboxylic acid.
- High MW PBF and PBAFs were successfully synthesized from highly purified FA.
- PBF behaves as a high-performance thermoplastic with balanced tensile properties.
- PBAF shows thermo-mechanical properties tunable from thermoplastics to elastomers.
- Using purified FA seems necessary and effective for high performance polyesters.

To synthesize high quality (co)polyesters derived from 2,5-furandicarboxylic acid (FA), an acetic acid refluxing/pH-swing method was proposed to purify FA. 2-Carboxyl furfural and other impurities were removed completely from FA with this method. Using highly purified FA, biobased polyester poly(butylene furnadicarboxylate) (PBF) and aliphatic-aromatic copolyesters poly(butylene adipate-co-butylene 2,5-furandicarboxy-late)s (PBAFs) were synthesized via melt (co)polycondensation. The (co)polyesters were characterized with GPC, FTIR, 1H NMR, DSC and TGA, and their tensile mechanical properties were also assessed. The copolyesters possess random chain structure, monomer feed ratio-controlled copolymer composition and excellent thermal stability (Td,5% > 340 °C) in full composition range. Both BA-rich and BF-rich PBAFs are crystalline polymers. The crystallizability decreases with composition, up to nearly amorphous at moderate ϕBF (40-60%). PBAFs with ϕBF no more than 50% exhibit obvious high-elastic deformation and rebound resilience, and possess tensile properties (E 18-160 MPa, σb 9-17 MPa, εb 370-910%) comparable to poly(butylene adipate). PBAFs with higher ϕBF behave like nonrigid plastics with low tensile moduli (42-110 MPa), moderate strength (30-42 MPa) and high elongation at break (310-470%). In comparison, PBF is a strong and tough thermoplastic having balanced mechanical properties, namely, much higher tensile modulus (1.9 GPa) and strength (56 MPa) and high elongation at break (260%). It seems necessary and effective to use highly purified FA for synthesizing high performance FA-derived (co)polyesters.

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