Synthesis of a fire-retardant and high Tg biobased polyester from 2,5-furandicarboxylic acid

A biobased diol (BDBE) is synthesized from vanillin, guaiacol, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to generate a series of fire-retardant polyesters (PECBFs) via melt polymerization with ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), and 2,5-furandicarboxylic acid (FDCA). The chemical structure, sequence distribution, and molecular weights of the obtained polyesters are confirmed by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The results show that BDBE units contribute positively to the high glass transition temperature (Tg) and fire retardancy, while the CHDM moiety provides flexibility and chain propagation activity. As the content of BDBE is increased from 0 to 25%, the Tg of PECBFs increases from 82 to 95 °C, and the limiting oxygen index (LOI) increases from 22.4 to 27.5%. In the UL-94 combustion test, when BDBE units are more than 15%, the samples almost self-extinguish immediately once the flame is moved away. Their mechanical properties are also investigated, and their tensile modulus is stabilized between 1.7 and 1.8 GPa, while the elongation at break ranges from 5 to 56%. Biobased polyesters demonstrating satisfactory properties are reported in this work.