Study On The Synthesis And Curing Kinetics Of Bio-based Benzoxazine Based On Eugenol

With the exhaustion of energy and environmental pollution,the extraction of raw materials from biomass to replace traditional petroleum energy has become a research hotspot.Therefore,it is of great significance to study the development of high-performance bio-based benzoxazines.In this paper,bio-based phenolic eugenol was used as the phenol source,and allylamine,propargylamine,and aniline were used as amine sources to synthesize bio-based benzoxazine monomers-allylamine benzoxazine（AP-BZ）,propargylamine benzoxazine（PA-BZ）,aniline benzoxazine（BN-BZ）.The structures of the AP-BZ、PA-BZ、BN-BZ were characterized by ¹H nuclear magnetic resonance（¹H-NMR）spectroscopies and Fourier transform infrared（FTIR）spectroscopies.The thermal stabilities of the obtained polybenzoxazine resins（PAP-BZ,PPA-BZ,PBN-BZ）were analyzed by thermogravimetric analyses（TG）.The T_5%of the three polybenzoxazines were respectively 314.4℃,347.3℃,335.8℃,among which PAP-BZ had the lowest T_5%.This was because the addition reaction of C=C increased the number of flexible alkyl chains and reduced the initial decomposition temperature.The carbon residual rates of the polybenzoxazine at 800℃were 43.4%,49.6%,45.1%,which were all higher than the conventional benzoxazine resins,and the limiting oxygen index formula was used to obtain the limiting oxygen index（LOI）,the values of three resins were respectively 34.8%,37.3%,35.5%,which showed good flame retardant properties.The results showed that the introduction of C=C and C≡C into the molecular structure can increase the cross-linking density of the molecular structure,enhance thermal stabilities,and prepare benzoxazine resins with good thermal stabilities and flame retardancy.The non-isothermal differential scanning calorimetry（DSC）methods were used to study the curing behavior of the three monomers（AP-BZ,PA-BZ,BN-BZ）,the activation energy values of three monomers were obtained by the Ozawa,Kissinger,and Flynn-Wall-Ozawa methods.The activation energy values of AP-BZ、PA-BZ、BN-BZ obtained by the Flynn-Wall-Ozawa methods were respectively 146.0 KJ/mol,118.5 KJ/mol,125.8 KJ/mol.The Friedman methods were used to prove that the mechanism models,the models of three monomers were autocatalytic models,and the kinetic equations were obtained by the Málek methods.The simulated curves fit well with the experimental curves,which proved that the kinetic equations obtained had good applicability.Since the initial decomposition temperature of allylamine benzoxazine monomer（AP-BZ）was relatively low,it was blended with bismaleimide resin（BMI）in a ratio of 1:1,and the blends were studied by DSC and TG,when the heating rate was 10,the polymerization temperature of the blend resin（AP-BZ/BMI）was 212.1℃,which was nearly 30℃lower than the monomer polymerization temperature of 248.3℃,the T_5%of AP-BZ/BMI was 366.3°C,and the carbon residual rate at 800°C was 46.3%.The results indicated that the addition of BMI not only brought down the polymerization temperature,but increased the initial decomposition temperature and carbon residual rate as well,the thermal stability also had been improved.Using the Flynn-Wall-Ozawa method to obatain the activation energy value,the value was 97.8KJ/mol,the Friedman method was used to verify the mechanism model of the blended resin,and the Málek method was used to obtain the kinetic equation.The final simulated curves were in suit with the experimental curves.