Synthesis of novel calixarene‐based intumescent flame retardant and application of flame retardant epoxy resin

Abstract A new intumescent flame retardant containing APP, MEL and p‐tert‐Butylcalix[4]arene was synthesized and added to epoxy (EP) resin in different proportions with aluminum hydroxide (ATH). The flame retardancy, thermal stability and smoke suppression of flame retardant EP composites were studied. When adding 20% APP to EP matrix, the limiting oxygen index can reach 30.5%. After adding synergist ATH, the amount of char residue in air at 700°C increased significantly from 0.83% to 15.80%, indicating that its heat resistance and oxidation resistance were improved. In terms of peak heat release rate (pHRR), the pHRR of ATH synergistic flame‐retardant EP composites can be reduced to 128.53 kW/m 2 (EP3), which is much lower than pure EP and FR/EP composites, indicating that FR and ATH has a good synergistic flame retardant effect. For the stable carbon layer produced, on the one hand, it can block the release of combustible gas, and on the other hand, it can function as heat insulation and oxygen barrier inside the matrix.