A high effective P/N-containing flame retardant additive CDD was triumphantly synthesized with nitrogen-rich 3,5-Diamino-1,2,4-triazole, DOPO and cinnamaldehyde. With the help of 4 wt% CDD, Epoxy resin (EP) sample succeeded in UL-94 V-0 test, and improved its LOI value to 33.5%. EP/4 wt%CDD sample also performed very well in cone calorimeter (CC) test. For example, the peak of heat release rate of EP/4 wt%CDD decreased to 603 kW/m2, which was 56.8% of EP sample without flame retardants. All these details showed that CDD was highly effective in fire resistance. Besides, the addition of CDD also drastically improved mechanical strength of EP. Tensile strength, flexural strength and izod iMPact strength of EP/4 wt%CDD sample was increased to 102 MPa, 124 MPa and 38 kJ m−2, which was 118.6%, 129.2% and 126.7% of control group. At last, the flame-retardant mechanism of CDD was studied by FTIR, XPS, Raman spectra, and SEM. The results showed that CDD’s perfect performance in fire resistance was ascribed to the generation of phosphorus-rich char layer in condensed phase.

Two effective flame retardant additives hsalaminopyridine phosphaphenanthrene (HAD) and methoaminopyridine phosphaphenanthrene (MAD) were respectively prepared with DOPO, aminopyridine, salicylaldehyde and 3-Methoxysalicylaldehyde. Subsequently, HAD and MAD was added into epoxy resin (EP) respectively, and flame retardancy of EP/HAD and EP/MAD thermosets were dramatically enhanced. The result of cone calorimeter (CC) test revealed that both HAD and MAD showed perfect smoke suppression performance. In respect of transmittance and mechanical properties, there was a huge difference between HAD and MAD. The introduction of HAD dramatically harmed transmittance and mechanical properties of EP, while, EP/10%MAD was transparent and nearly possessed the same mechanical properties with pure EP.