Synthesis, Curing Mechanism And Flame Retardantcy Of Intrinsically Flame Retarded Biobased Benzoxazine

Using biobased platform compounds diphenolic acid to synthesize diphenolic acid pentaerythritol phosphate benzoxazine (DPA-PEPA-boz), as well as new method to synthesize bisphenol acidbenzoxazine (DPA-boz) and bisphenol acid methyl benzoxazine(MDP-boz).The purity and structure of reaction intermediate and monomer were confirmed by FT-IR,’H-NMR, and 13C-NMR spectra.Benzoxazine monomers can form polybenzoxazines by ring-opening curing reaction under heat or catalyst. Under the circumstance without catalyst,the activations energy of DPA-boz, MDP-boz, DPA-PEPA-boz are11.95 kJ/mol,15.58 kJ/mol and 21.23 kJ/mol respectively according to the model of chemical reaction kinetics in the case of Kissinger model calculation equation.The activation energy of DPA-boz is the lowest because carboxyl functional groups in the molecular structure can act as the catalyst. However, theactivation energy of DPA-PEPA-boz is the highest because steric hindrance of PEPA group is the biggest among PEPA,CH3 and H.the catalysis of Al2O3. PTSA, AlCl3, PC15, adipic acid were investigated qualitatively and it was concluded that AlCl3, PCl5 and adipic acid had a relatively good catalytic effect compared with Al2O3, PTSA. So AlCl3, PCl5 and adipic acid were chosento make systematic DSC tests to demonstrate their catalytic efficiency according to the model of chemical reaction kinetics in the case of Kissinger model calculation equation.Through experiment and analysis, AlCl3 and PCl5 have no catalyst action aimed at DPA-boz,MDP-boz and DPA-PEPA-boz. The activations energy of DPA-boz, MDP-boz, DPA-PEPA-boz are 6.7 kJ/mol,10.30 kJ/mol,7.48 kJ/mol respectively.Thus adipic acidcan significantly reduce the activation energy of benzoxazine monomer because adipic acid is an organic weak acidand it has two carboxyl groups in the result of excellent catalysis aimed at benzoxazine monomers.The best curing process of novel biomass benzoxazine monomers was established by the DSC test results.Three kinds of polybenzoxazines were obtained from DPA-boz, MDP-boz and DPA-PEPA-boz and named as P-DPA-boz, P-MDP-boz and P-DPA-PEPA-boz respectively. Thermal and flammability properties of theirresins were evaluated by TG,MCC, limit oxygen indexand vertical combustion tests. In the condition of nitrogen atmosphere tests, the carbon residue of P-DPA-PEPA-boz is 55.36%at 800℃,but the carbon residue of P-DPA-boz and P-MDP-boz were 37.39% and 34.07% respectively. From the DTG, the rate of maximum quality of P-DPA-PEPA-boz wasabout 3.78%/min and that of P-DPA-boz and P-MDP-boz were 6.51%/min and 6.84%/minrespectively. MCC tests showed that the heat capacity of P-DPA-boz and P-MDP-boz were 138.5 J/g·K and 145.5 J/g-K,the heat capacity of P-DPA-boz and P-MDP-boz were138.5 J/g·K and 145.5 J/g-K,the total heat release rate of P-DPA-boz and P-MDP-boz were 18.25 kJ/g and 19.4kJ/g.Compared to P-DPA-PEPA-boz,the heat capacity was 68 J/g-K, the peak heat release rate was 55.415 w/g and the total heat release rate was 8.6 kJ/g. Vertical burning tests showed flame retardant properties of P-DPA-PEPA-boz reached V-0 but P-DPA-boz and P-MDP-boz did not pass the tests. Limited oxygen index tests showed the LOI of P-DPA-PEPA-boz was 33.5%, and P-DPA-boz and P-MDP-boz were only 26.1% and 25.7% respectively. The results showed that P-DPA-PEPA-boz owned very excellent flame retardant properties.