The Research On Synthesis And Properties Of Two Novel Benzoxazine Monomers

Recently, the demand for high performance materials has increased tremendously due to the rapid development of microelectronics and aerospace industries. Benzoxazine, as a new type of phenolic resin, has attracted much attention owing to its outstanding characteristics such as good thermal properties, electrionic properties, and flame retardant.By taking advantage of the molecular design flexibility of benzoxazine, some special performance polybenzoxazines have been synthesized through altering the functional groups on the amines and/or phenols. In this thesis, we described the synthesis, characterization and cuing kinetics of two kinds of benzoxazine monomers NTAF and P-BZ, which are obtained from the incorporation of carboxyl and DOPO group into benzoxazine structure, respectively.The brief contents are shown as follows:Firstly, the carboxyl based benzoxazine NTAF was synthesized from trimellitil anhydride(TMA) and its curing kinetics were investigated by non-isothermal differential scanning calorimetry (DSC) at different heating rates. Three different methods (Ozawa, Kissinger and Flynn-Wall-Ozawa) were employed to research the activation energy (Ea) of NTAF. The Flynn-Wall-Ozawa method provided the change of activation energy Ea values as a function of the degree of conversion. The autocatalytic kinetic model was found to be the best description of the investigated curing reactions. Non-isothermal DSC curves obtained from the experimental data showed a good agreement with that theoretically calculated.Secondly, the curing behavior and thermal properties of cured NTAF were studied. DSC curves showed that the curing temperature is188℃, decreasing obviously, compared to some common benzoxazine monomers. Thermogravimetric analysis (TGA) result shows the10%weight loss temperatures is450.5℃and char yield is49.2%at800℃.TGA result shows the prepared benzoxazine have the excellent thermal stability. Thirdly, novel benzoxazine containing organophosphorus (P-BZ) was prepared using DOPO and p-phenylene diamine as raw materials, and the chemical structure was characterized. The curing reaction was also investigated under non-isothermal differential scanning calorimetry (DSC) at different heating rates. The average activation energy of the curing reaction was determined according to Kissinger and Ozawa method. The curing mechanism was given by the Friedman methods. The autocatalytic kinetic model was found to be the best description of the investigated curing reactions. In addition, the predicted curves from our kinetic models fit well with the non-isothermal DSC thermograms.Fourthly, thermal properties of P-BZ improved significantly, and char yield at800oC is proportional to the phosphorus content. The introduction of DOPO significantly increased the flame retardant performance of cured resins. Compared with the pure PAF cured material, the introduction of the phosphorus make material’s LOI enhance from26to38.