Isopropanolamine‐modified ammonium polyphosphate for improved flame retardancy of epoxy resin

Abstract In this work, the flame retardant ISA‐APP, obtained by modification of ammonium polyphosphate (APP) with isopropanolamine (ISA), was employed in epoxy resins (EP) in an attempt to enhance the fire resistance of EP. The findings indicate that, with an incorporation of 20 wt% ISA‐APP in the EP, the limiting oxygen index (LOI) of EP/ISA‐APP attains 33.5%, accompanied by a UL‐94 test V‐0 rating. This performance surpasses the flame retardancy observed in EP/APP composites at equivalent content. The outcomes derived from the cone calorimeter test (CCT) demonstrate that EP/ISA‐APP significantly suppresses the release of heat, generation of smoke, and emission of noxious gas during EP/ISA‐APP combustion. The peak‐heat release rate (pHRR) and total heat release (THR) of EP/ISA‐APP are decreased by 74.4% and 63.6%, respectively, compared to pure EP. Further analysis of the char residues of EP/ISA‐APP shows that the POC structure generated during combustion effectively contributes to a high‐quality char layer formation. This investigation presents a viable approach for enhancing flame retardant and economic benefits of APP and advancing the development of highly effective flame retardants.