In‐situ formation of macromolecule P/N/Si flame retardant for epoxy resin with low smoke toxicity and excellent flame‐retardancy

Epoxy resins (EP) have great chemical and physical properties, but their poor flame retardant properties have prevented their widespread use. To improve the flame retardancy properties of EP, an active P/N/Si flame retardant (KDC) containing a double bond was successfully synthesized in this work by using a typical aldehyde amine condensation reaction. This flame retardant not only can form a large molecule flame retardant in situ by double bond reaction and increase the tightness with EP matrix, but also has the advantage of P/N/Si three elements synergistic flame retardant, and at the same time play the flame retardant performance of each element, can achieve excellent flame retardant performance and low smoke and toxicity with low addition amount. Subsequently, the performance of the flame retardants was tested. When 7 wt% of KDC was added, the pHRR and TSR of the EP composites were reduced by 51.7% and 29.8%, respectively. More importantly, the addition of KDC inhibited the release of toxic fuels and smoke from EP, where the TSP values of EP/3‐KDC were 18.14% below those of neat EP and increased the residual amount of charcoal, while the inhibition of CO and CO2 release was particularly pronounced with the presence of KDC. A multielement flame retardant containing P/N/Si was prepared and applied to the flame and smoke suppression of epoxy resins, and the smoke toxicity of the burning EP matrix could be reduced.