Synergistic Fire Hazard Effect of a Multifunctional Flame Retardant in Building Insulation Expandable Polystyrene through a Simple Surface-Coating Method

[Image: see text] This work reports a strategy based on γ-aminopropyltriethoxysilane (KH550) and graphene oxide (GO)-functionalized 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to fabricate P–N–Si integrated flame retardant [KDOPO-modified GO (DGO)] through mild Mannich and Silanization reactions to overcome the challenge of single gas-phase fire retardancy of DOPO. DGO-based phenolic epoxy resin (DGO/PER) is manufactured and coated on the surface of expandable polystyrene (EPS) foam plates to achieve fire safety, which is used as the thermally insulating external wall in buildings and constructions. The DGO/PER paintcoat imparts high fire safety to the EPS foam plate, exhibiting a high limiting oxygen index value of 29%, and a UL-94 V-0 classification is achieved with only 300 μm of layer thickness compared with the DOPO/PER paintcoat. Meanwhile, all combustion parameters such as peak heat release rate, heat release rate, total heat release, smoke release rate, total smoke rate, and ignition time present excellent promotions for EPS@DGO compared with EPS@DOPO. These dramatically reduced fire hazards are mainly attributed to the synergistic effects of DGO. Meanwhile, the DGO/PER flame-retardant paintcoat cannot deteriorate the thermal insulation performance of the EPS foam plate.