The designation of highly efficient intrinsic fame-retarding epoxy materials via the regulation of the phosphorus and nitrogen content for the curing agents

Epoxy resin (EP) is one kind of widely applicated thermosetting resin with excellent manufacturability, mechanical performance and chemical resistance, but its flammability seriously limited its widely application. In this work, the flame-retarding curing agent (BIPD) with was prepared by a simple one-step substitution reaction between benzimidazole (BI) and phenylphosphonyl dichloride (PD). When the mass fraction of BIPD is 10 %, the flexural strength and impact strength are 174.7 MPa and 14.9 KJ/m2, respectively, which are 15.5 % and 69 % higher than those of EP/BI10. The EP/BIPD10 passed the UL-94 V-0 rating with a limiting oxygen index (LOI) reaching to 33 %. Meanwhile, the peak of heat release rate (PHRR) and total heat release rate (THR) of EP/BIPD10 decreased by 50.2 % and 37.8 %, the total smoke production (TSP) and the mass percentage of residues increased by 10.4% and 204.1 % than that of EP/BI10 in the cone calorimeter (CC) measurement, showing a jointly flame-retarding process in the condensed and gas phase. Furthermore, the results of Raman spectrum, the thermogravimetric infrared spectroscopy (TG-FTIR) and pyrolysis-gas chromatography/mass spectrometry (PY-GC/MS) confirmed the conclusion.