Hexafunctional N/P‐Containing Monomer Enabled Epoxy Thermosets With Superior Flame Retardancy and Low Smoke Emission

ABSTRACT

Epoxy resin (EP) is one of the most widely used thermosetting materials; however, its high inherent flammability severely restricts its practical applications. To address this issue, a novel nitrogen/phosphorus (N/P)‐containing hexafunctional monomer (HCPB) was synthesized and employed to partially substitute diglycidyl ether of bisphenol A (DGEBA) in the preparation of flame‐retardant epoxy thermosets (EP/HCPB), using polyetheramine (D230) as the curing agent. The effects of HCPB content on the thermal stability, mechanical strength, and flame retardancy of EP were systematically investigated. Specifically, the EP‐HCPB ₁₅ composite with 15.00 mol% HCPB achieved a tensile strength of 48.87 MPa, a limiting oxygen index (LOI) of 30.5%, a UL‐94 V‐0 classification, and a glass transition temperature ( T _g ) of 58.11°C. Furthermore, the flame‐retardant mechanism of HCPB in the epoxy matrix was systematically elucidated, involving both gas‐phase free‐radical quenching and condensed‐phase charring effects. This work provides a facile and effective strategy for the design and preparation of high‐performance flame‐retardant epoxy thermosets.