Improving the Weatherability and Intumescent Effects of Naturally Sourced Wood Flame Retardant Coatings.

Approximately 1 billion acres or half of all the United States is considered wildland. As wildland-urban-interface (WUI) development expands, millions of homes are at risk of ignition and destruction. As a result, these communities must adapt by acquiring fire-resistant materials and protectants for their homes. However, commercially available wood flame retardant coatings (WFRC) are perceived to present harm to both human health and the environment. In addition, commercial fire-resistant paints often leach into the environment, losing their efficacy shortly after application in external applications. To properly address this, it is imperative to explore WFRC which use natural products as feedstocks. Chitosan is an abundant, biodegradable, and nontoxic binding agent that can be easily incorporated as a primary component in water-based WFRC. Prior studies in our laboratory have shown that using reduced valence phosphorus-containing acids in chitosan WFRC can significantly delay or prevent ignition of wood under a 50 kW/m2 heat flux. However, Chitosan's solubility in water threatens the overall weatherability of the coating. Photo crosslinking agents were utilized to allow for on-site application in vulnerable WUI areas. After exposure to sunlight, no chitosan dissolved in artificial acidic rainwater, and coated wood substrates self-extinguished immediately after flame impingement was removed. These findings offer a valuable glimpse into which methods and additives may contribute to an overall optimized, weatherable, and flame-retardant Wood Flame Retardant Coating.