Phosphaphenanthrene-modified zirconium phosphate nanosheets for improving fire resistance, smoke suppression and water tolerance of intumescent coatings

Developing intumescent fire-retardant coatings (IFRCs) combining superior smoke suppression and water resistance is crucial for their industrial applications. Herein, novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-decorated zirconium phosphate (ZrP-D) nanosheets are synthesized and employed in the IFRCs. The ZrP-D nanosheets feature multifunctionality, which simultaneously improve the fire resistance, smoke suppression, thermal stability and water tolerance of IFRCs. Notably, introducing 3wt% ZrP-D decreases the backside temperature of IFRC from 293.9 to 166.3°C by ~ 43.4% in fire resistance test, followed by 47.9%, 33.5% and 89.4% reductions in peak heat release rate, total heat release and total smoke release. Moreover, this IFRC exhibits improved thermal stability and water tolerance, of which char yield and water contact angle reach up to 64% and 82.7°, respectively. When exposed to high-temperature flame, the ZrP-D nanoplatelets mainly function in condensed phase, which significantly increases the expansion and compactness of residual char due to the barrier and catalytic charring effects, thus suppressing the heat release and smoke diffusion. This work provides a rational design for creating intumescent fire-retardant coatings combining smoke suppression and water resistance, thus possessing broad prospects in industry. Graphical Abstract