Boron-based polyelectrolyte complex nanocoating for fire protection of engineered wood

Engineered wood products, such as oriented strand board (OSB), are widely used as the primary structural component in both residential and commercial lumber construction, primarily due to their renewability, aesthetic appeal, and excellent mechanical properties. Unfortunately, the inherent flammability of these wood-based composites poses an ongoing risk to society and the environment. In an effort to reduce its flammability, a polyelectrolyte complex (PEC) coating consisting of sodium polyborate (SPB) and polyethylenimine (PEI) was deposited on OSB using a simple two-dip process. This PEC treatment imparts self-extinguishing behavior to OSB and reduces the total heat release by 21% and total smoke release by 79%, while increasing the time to ignition by 18% relative to untreated OSB. Furthermore, the PEI/SPB coating adds little additional weight (5.8 wt%) to the oriented strand board, preserving visual aesthetics and maintaining mechanical properties. The main flame-retardant effect occurs by condensed phase action via a combination of intumescence and thermal barrier mechanisms. Improving the fire protection of OSB and other engineered wood materials through a simple and environmentally benign treatment will increase their potential as a largely renewable building material, promoting a sustainable bioeconomy.