Synthesis and Investigation of the Flame Retardancy, Mechanism, and Comprehensive Properties of a Reactive Flame‐Retardant UV ‐Curable Acrylate Monomer

A reactive flame‐retardant acrylate monomer (PEDP) with a high phosphorus content has been synthesized through a straightforward process to improve the fire safety of UV‐curable materials. In comparison to the traditional monomer PETA, the UV‐cured PEDP (UV‐PEDP) enhances the limiting oxygen index (LOI) from 28.7% to 31.9% and achieves a UL‐94 V0 rating without any melt dripping. Meanwhile, UV‐PEDP exhibits a 42.7% reduction in peak heat release rate (PHRR) and a 30.6% decrease in total heat release (THR) compared to UV‐PETA in the cone calorimetry test (CCT). Mechanistic analysis attributes the improved flame retardancy to gas‐phase quenching and dilution effects from phosphorus‐containing decomposition products, as well as the formation of char in the condensed phase. The UV‐PEDP demonstrates high transparency (exceeding 80% at 800 nm) and excellent hardness (above 93 Shore‐D). Although there is a decrease of 27% in tensile strength and 30% in elongation, these trade‐offs remain acceptable for many coating applications. This study presents an effective strategy to expand the safe use of UV‐curable materials.