Biobased Thermoplastic Elastomers: Structure-Property Relationship of Poly(hexamethylene 2,5-furanodicarboxylate)-Block-Poly(tetrahydrofuran) Copolymers Prepared by Melt Polycondensation (original) (raw)
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In this study, the effect of thermal aging on the physical transitions, crystalline structure development and the mechanical performance of furan-ester, multiblock copolymers is reported. The materials were synthesized via polycondensation in a melt using 2,5-furandicarboxylic acid (FDCA), 1,3-propanediol (1,3-PD) and dimerized fatty acid diol (FADD). All reagents were plant-derived. The copolymers were characterized by a multiblock structure with randomly distributed poly(trimethylene 2,5-furandicarboxylate) (PTF) and FADD segments and a phase separation forced by the crystallization of the rigid segment. As a consequence, the copolymers revealed elastomeric behavior and a rubbery plateau over a relatively large temperature range and also good processability. However, due to the specific architecture of FDCA-the most important bio-based monomer-the crystallization of the rigid segment was impeded. Differential scanning calorimetry (DSC), wide-angle (WAXS) and small-angle X-ray scattering (SAXS) analyses confirmed a significant development in the crystalline structure due to the thermal treatment. As a consequence, noticeable changes in the mechanical performance of the copolymer samples were observed, which is interesting for potential applications of these new materials.
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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-cobutylene 2,5-furandicarboxy-late)s (PBAFs) were synthesized via melt (co)polycondensation. The (co) polyesters were characterized with GPC, FTIR, 1 H NMR, DSC and TGA, and their tensile mechanical properties were also assessed. The copolyesters possess random chain structure, monomer feed ratiocontrolled copolymer composition and excellent thermal stability (T d,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 f BF (40e60%). PBAFs with f BF no more than 50% exhibit obvious high-elastic deformation and rebound resilience, and possess tensile properties (E 18 e160 MPa, s b 9e17 MPa, ε b 370e910%) comparable to poly(butylene adipate). PBAFs with higher f BF behave like nonrigid plastics with low tensile moduli (42e110 MPa), moderate strength (30e42 MPa) and high elongation at break (310e470%). 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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