Polyphenol-based fire-resistant coatings: a bio-inspired solution for forest fire prevention

The bark of hardwood trees contains abundant polyphenols, which can rapidly transform into a graphite layer that acts as a thermal barrier, minimizing fire damage. Inspired by this natural fire resistance mechanism, we developed an eco-friendly, cost-effective fire-retardant coating system for forest fire prevention. Comprising only pyrogallol (PG) and polyethyleneimine (PEI), the system forms a polyphenolic layer through oxygen-mediated oxidative crosslinking when exposed to air. This method uses water as the sole solvent and requires no additional catalysts, allowing easy, material-independent application via spray-coating. Heat resistance tests showed that the PG-PEI coating improved the wood's inherent fire resistance by approximately threefold, attributed to the rapid coating conversion into a graphite layer at high temperatures, as confirmed by X-ray photoelectron and Raman spectroscopies. Furthermore, a 70-day colorimetric analysis under simulated weathering conditions exposure demonstrated the coating's durability against environmental stresses. The PG-PEI coating also preserved wood's natural functionality, supporting tree health, as evidenced by the high survival rates of the treated trees. These findings suggest the PG-PEI coating is a promising solution for mitigating forest fire damage while maintaining eco-friendliness and practicality.