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)-triyetribenzonic acid (P-paba)). Their structures and curing reactions had been characterized by Fourier transform infrared spectroscopy (FTIR), proton and carbon nuclear magnetic spectroscopy (H-1 NMR and C-13 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 degrees 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.