Synthesis and Properties of Biobased 2,5-Furandicarboxylic Acid Copolyesters: Synergistic Realization of Environmental Friendliness, Ultraviolet Shielding, and Glass Bonding

In this study, biobased raw materials 2,5-furandicarboxylic acid (FDCA) was converted into DMFD. DMFD, 1,9-nonanediol (1,9-ND), and trimethylene carbonate (TMC) were used to prepare a new biobased poly(2,5-furandicarboxylic acid nonanediol-co-trimethylene carbonate) (PNF-co-PTMC) copolyester by transesterification–polycondensation. The structure characterization showed that 1H NMR and Fourier transform infrared spectroscopy confirmed that the TMC unit was successfully embedded in the main chain of the copolymer; X-ray diffraction analysis shows that the material has typical semicrystalline characteristics. Thermal performance analysis shows excellent thermal stability; the initial decomposition temperature (Td, 5%) is 242 °C, and the temperature corresponding to the maximum thermal decomposition rate (Tmax) is 395 °C. Differential scanning calorimetry tests showed that the glass transition temperature (Tg) gradually decreased from −7 to −18 °C with the increase in the TMC content, showing good chain segment motion control ability. When the molar ratio of DMFD/1,9-ND/TMC is 1:1:1, the tensile shear strength of the copolyester to the glass substrate reaches 4.48 MPa, showing an excellent bonding performance. In addition, the material exhibited significant UV shielding properties (transmittance in the 300–400 nm band increased from 0 to about 60%) and good acid and alkali resistance (mass retention rate >98% after pH 3–11 treatment). The comprehensive properties show that the biobased copolyester has an important application potential in the field of environmentally friendly glass adhesives.