Development of intrinsically flame-retardant bio-thermosets with further enhanced thermal stability through a photo-thermal dual polymerization strategy

In response to safety and environmental concerns, there has been a significant increase in research focused on developing high-performance thermoset materials from sustainable sources. In this study, a sophisticated chemical design approach integrates coumarin and furan moieties into a bio-based UV-dimerizable benzoxazine resin. The newly obtained bio-benzoxazine exhibits a reduced curing temperature along with improvements in both thermal stability and flame-retardant properties compared to conventional thermosetting counterparts. Extensive characterization of the chemical structure of the UV-dimerizable bio-based benzoxazine is conducted through nuclear magnetic resonance, Fourier transform infrared spectroscopy, elemental analysis, and high-resolution mass spectrometry. The photo-dimerization processes are monitored using UV–Vis and NMR techniques. Additionally, the thermally activated curing behavior is scrutinized via differential scanning calorimetry and in situ FT-IR techniques. Remarkably, the fully polymerized bio-thermoset demonstrates exceptional thermal stability, possessing a T d10 of 410 °C and a T g of 283 °C. Moreover, the resulting thermosets also shows very low flammability, as evidenced by a heat release capacity of 14.6 J·g -1 ·K -1 and a total heat release of 2.97 kJ·g -1 . This study not only outlines a method to enhance the overall performance of bio-polybenzoxazines but also provides a direct and sustainable synthesis route for bio-derived, intrinsically non-flammable thermosetting materials.