Synthesis and characterization of a phosphorus-containing flame retardant with double bonds and its application in bismaleimide resins

A novel phosphorus-containing flame retardant, bis(4-(allyloxy)phenyl)phenylphosphonate (APP) has been synthesized. The structure of APP has been systemically characterized using Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR and ³¹P NMR). Subsequently, APP was added into bismaleimide (BMI) resin to prepare flame retardant materials, coded as P-DBMI resin. The effects of APP content on the mechanical properties of the P-DBMI resins have been studied. In addition, thermogravimetric kinetics, UL-94 tests, limited oxygen index (LOI), scanning electron microscopy and residual analysis were carried out to reveal the thermal properties and flame retardancy of P-DBMI resin. The results indicate that P-DBMI resin with good mechanical properties, thermal stability and flame retardancy were obtained.