Novel full bio-based phloroglucinol benzoxazine resin: Synthesis, curing reaction and thermal stability

The present work demonstrates an approach to develop full bio-based polybenzoxazines with excellent low-temperature curing performance. In order to achieve this goal, biomass-derived phloroglucinol (P) as phenol source, furfurylamine (FA) or P-aminobenzoic acid (PABA) as amine source and paraformaldehyde were selected to synthesize two novel full bio-based benzoxazine resin (3,7,11-tris(furan-2-ylmethyl)-3,4,7,8,11,12-hexahydro-2H,6H,10H-benzol[1,2-e:3,4-e′:5,6-e″]tris([1,3]oxazine) (P-fa) and 4,4′,4″-(2H,6H,10H-benzo[1,2-e:3,4-e′:5,6-e″]tris([1,3]oxazine)-3,7,11(4H,8H,12H)-triyl)tribenzonic acid (P-paba)). Their structures and curing reactions had been characterized by Fourier transform infrared spectroscopy (FTIR), proton and carbon nuclear magnetic spectroscopy (1H NMR and 13C NMR) and differential scanning calorimetry (DSC). Compared with bisphenol A/aniline benzoxazine (BA-a), P-fa and P-paba monomers showed a different curing reaction process and excellent low temperature curing performance, especially P-paba monomer, whose exothermic peak was in a temperature range of 140–170 °C. The obtained full bio-based polybenzoxazines presented a low degradation rate (−3.58 wt%/min), high char yield (53.0%), low heat release capacity (37 J/g·K), and low total heat release (8.3 kJ/g). Meanwhile, P-paba monomer had an excellent promoting effect on the curing reaction of P-fa monomer. These findings have highly significant implications for the design of new full bio-based polybenzoxazines with excellent low-temperature curing performance and high residual char.