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

Abstract

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.