Recent advances in constructing new type of epoxy resin flame retardant system using ammonium polyphosphate

In recent years, research has focused heavily on the investigation of functionalized ammonium polyphosphate (APP) flame retardants to improve the fire safety of epoxy resins (EP). The reason for this is the dual nature of APP's performance in fire protection of EP. This article provides a comprehensive overview of the advances in the use of functionalized APP flame retardants to improve the fire resistance of EP materials. It then presents the improvement of the modification of the functionalized APP flame retardants in terms of the hydrophobicity, compatibility and catalytic ability of the flame retardants, as well as the effects on the fire resistance, heat resistance, smoke reduction and mechanical properties of the EP composites. After the summary and comparison of the relevant studies, it is clear that the functionalized APP flame retardants can effectively improve the fire safety of EP composites and offset the adverse effects of APP in EP flame retardant applications. In addition, APP flame retardants can obtain various excellent functions through the use of materials with different properties, and the interaction between APP and materials can also lead to more efficient fire protection. However, the current problem is to find ways to streamline the process and minimise the costs associated with functionalized APP flame retardants, as well as to use them effectively in industrial production. We hope that this review can provide valuable hints and insights for the practical application of functionalized APP in EP and perspectives for future research.