Preparation Of Bio-based Benzoxazine Monomer And Its Polymer Properties

Benzoxazine resins are a series of phenolic redins having excellent properties.With the increasing of global energy crisis and human's awareness of environmental protection,many researchers are committed to develop bio-based benzoxazine polymer materials based on sustainable biomass raw materials.Bio-based benzoxazine not only has the characteristics of flexible molecular design,acid and alkali resistance,easy curing and strong thermal stability,but also can greatly reduce people's dependence on petrochemical resources.Therefore,it is of great practical significance to develop bio-based benzoxazine polymer materials as the green and sustainable polymer materials.In this paper,the biomass raw materials cardanol and eugenol were used as phenol sources,and 2-aminofluorene which was obtained by nitrification and reduction of fluorene,was used as the amine source to react with paraformaldehyde to synthesize cardanol-based benzoxazine(FBOZ-Ca)and eugenol-based benzoxazine(FBOZ-Eu).The monomers were thermally cured to obtain two polymers,PFBOZ-Ca and PFBOZ-Eu,and the properties of the monomers and their polymers were carefully studied.The structure of the monomer is characterized by infrared spectroscopy(FT-IR),nuclear magnetic resonance spectrum(~1H NMR)and nuclear magnetic resonance carbon spectroscopy(¹³C NMR).The thermal performance of the monomer is carried out by DSC and TG tests.The non-isothermal temperature by DSC method is adopted to study the solidification kinetics of the monomer,the apparent activation energy E of FBOZ-Ca and FBOZ-Eu was 112.8 k J/mol,121.6 k J/mol,the precursor A is 2.944×10¹⁰and 2.568×10¹²,respectively,and the reaction fraction N is 0.92 and0.93,respectively.The optimum cure temperature of the two monomers is determined by the T-?extraction.The open loop temperature(T_i)of the monomer FBOZ-Ca is 222.62°C,and the hot peak temperature(T_p)is 240.79°C,the exothermic termination temperature(T_f)was 251.85°C;while these values for the monomer FBOZ-Eu was 158.32°C(T_i),205.94°C(T_p)and 248.91°C(T_f).Programming temperature method was used to cure the monomers FBOZ-Ca and FBOZ-Eu,cardanol-based benzoxazine Resin(PFBOZ-Ca)and eugenol-based benzoxazine Resin(PFBOZ-Eu)were prepared,the thermal stability and flame retardancy of the two benzoxazine resins were analyzed by TG,at 800?,the residual charcoal ratio of polymer PFBOZ-Ca and PFBOZ-Eu were 25.0%and50.5%,respectively,and the ultimate oxygen index LOI value were 27.5%and37.7%,respectively,the results show that the flame retardant effect of polymer PFBOZ-Eu is better.The SEM electron microscope was observed to observe the cross-sectional morphology of the two polymers,the polymer PFBOZ-Ca was tough fracture and the polymer PFBOZ-Eu was brittle fracture.The two monomers FBOZ-Ca and FBOZ-Eu were mixed with the epoxy soybean oil(ESO)with different mass ratios,respectively.The DMA test shows that the toughness of the polymer can be enhanced with a slightly increase of the proportion of ESO.In addition,the two monomers were blended and copolymerized with ESO,eugenol and cardanol at a mass ratio of 1:1,respectively,and a series of composite polymer materials were prepared.Using TG test,all have good thermal stability and flame retardancy.