Synthesis of bio-based tetrafunctional benzoxazines derived from furfurylamine: excellent heat resistance and flame retardant properties

Abstract

Tetrafuran tetramine (TFTA) was synthesized from biomass feedstock furfurylamine, and two bio-based tetrafunctional benzoxazines (BZ-satfta and BZ-mosatfta) were subsequently prepared in a three-step process with salicylaldehyde and 4-methoxysalicylaldehyde, respectively, by Mannich condensation reaction. The chemical structure was characterized with fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy, which showed the successful preparation of tetrafunctional benzoxazines containing a furan ring. Differential scanning calorimetry (DSC) tests and cure kinetics studies revealed that BZ-mosatfta has higher curing temperatures (234 °C) and apparent activation energies (E_k: 109.10 kJ/mol and E_o: 111.53 kJ/mol) compared to BZ-satfta due to the electron-donating effect of methoxyl. Meanwhile, the thermal properties were analyzed by the dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA), which indicated that poly(BZ-satfta) had more excellent thermal properties and thermal stability, with glass transition temperatures (T_g) and residual carbon rates (Y_c) as high as 376 °C and 58.6%. In addition, limiting oxygen index (LOI) and microscale combustion calorimetry (MCC) tests demonstrate the outstanding flame retardant properties of both materials, which meets the standard for non-flammable materials. Furthermore, it can be extinguished within 0.5 s in the UL-94 vertical burning test. At the same time, both resins have good mechanical properties, with poly(BZ-satfta) having a flexural strength of 80 MPa. Both resins could be applied as resin matrices for high-performance heat-resistant and flame-retardant composites.