Study On Synthesis Of A Novel Benzoxazine And Its Curing Behavior

In this paper, the progress of benzoxazine resin was reviewed. Aiming at the disadvantages of benzoxazine resin such as high curing temperature,low crosslink densities and poor toughness, a novel benzoxazine containing maleimide and carboxyl moieties was synthesized. Furthermore, blending modification was used in the research and high performance resin with low processing temperature was obtained.The novel benzoxazine 1-[3-(4-carboxylphenyl)-3,4-dihydro-2H-benzo[e][1,3]-oxazin-6-yl] maleimide (Mal-Bz-Co) was synthesized by solution method with self-made HPM as raw material, and the synthesized condition and purification was researched. By the research, isopropanol was selected to synthesis Mal-Bz-Co, which showed high yield and high purity of the products. And the research showed that main impurity in the primary products was triazine intermediate and un-reacted reagents. A new separation and purification method used isopropanol and dioxane was found by solubility test. The structure of Mal-Bz-Co was characterized with Fourier transform infrared spectra (FTIR) and Proton nuclear magnetic resonance spectra (1H NMR).The curing behavior of Mal-Bz-Co and the cocuring behavior of Mal-Bz-Co with two kind of epoxy resins were researched by Differential scanning calorimetry (DSC). The results showed that the curing temperature of Mal-Bz-Co was still high and the maximum curing temperature (Tp) was 238.3℃. However, the curing temperature of Mal-Bz-Co becomes very low when cocured with o-Cresol formaldehyde epoxy resin (o-CFER) or Diglycidyl ether of bisphenol A (DGEBA). The Tp of Mal-Bz-Co/o-CFER (1:2) and Mal-Bz-Co/DGEBA (1:1) were 148.6℃and 141.3℃respectively, which were not only much lower than that of pure Mal-Bz-Co, but also much lower than that of the reported benzoxazine/epoxy system. The effect of the ratio of Mal-Bz-Co and o-CFER on the curing behavior was researched in this paper. And the results showed that the curing temperature of the blending system was relative low (Tp about 141.5℃) when the ratio of Mal-Bz-Co and o-CFER was 1:1.The thermal properties of pure Mal-Bz-Co resin and Mal-Bz-Co/o-CFER resin was researched by Thermogravimetric analysis (TGA). The results showed that T10 (degradation temperature of loss 10wt%) of pure Mal-Bz-Co resin was 371℃and Yc (char yield at 800) of pure Mal-Bz-Co resin was 45%. And T10 and Yc of Mal-Bz-Co/o-CFER (1:1) resin were 380℃and 43.4% respectively. The TGA results indicated good thermal properties of pure Mal-Bz-Co resin and Mal-Bz-Co/o-CFER resin. Additionally, the higher initial degradation temperature of Mal-Bz-Co/o-CFER than pure Mal-Bz-Co resin indicated that the addition of epoxy could increase the crosslink density and improve the thermal property.The research showed that the curing temperature of the novel benzoxazine/epoxy blend was very low. The low processing temperature and the excellent thermal property indicated its good application prospect.