Synthesis of a novel phosphorus-containing benzoxazine-monomer and its polymer alloys based on bismaleimides

To improve the flame resistance properties and thermal properties of bismaleimides (BMI) resin, a reactive phosphorus-contained benzoxazine monomer (PBOZ) was synthesized based on a phosphorus-containing compound 10-(2, 5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(ODOPB), and its chemical structure was characterized by infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). The novel PBOZ monomer was then used to blend with BMI (PBOZ-BMI), and the flame resistance of PBOZ-BMI resin was evaluated by the vertical flame test and the limited oxygen index (LOI) test. The results showed that the PBOZ-BMI exhibits better flame resistance. The thermal properties of cured PBOZ-BMI resins were investigated by differential scanning calorimeter (DSC) and thermogravimetry (TG). DSC results showed that the curing temperatures of PBOZ-BMI resins decreased with suitable content of PBOZ in comparison with BMI. The TGA result showed that the onset decomposition temperatures and the char yields also increased with the suitable addition of PBOZ. These conclusions can further confirms that the flame resistance of PBOZ-BMI enhanced as its thermal properties increase.