Dual-functional intumescent fire-retardant/self-healing water-based plywood coatings

Abstract Water-based fire-retardant coatings for wood are non-toxic, aesthetically pleasing, and can provide appreciable fire retardancy properties. However, excessive fire-retardant content and simple fire-retardant function limit their practical application. In this work, a semi-interpenetrating network (SIPN) technique was used to prepare a semi-transparent dual-functional, intumescent fire-retardant/self-healing water-based coating for plywood. The coatings comprised ammonium polyphosphate (APP) as a source of acid source and gas source; poly (vinyl alcohol) (PVA) as the carbon source and self-healing agent; and sodium silicate and sodium fluorosilicate (SS) as precursors for forming an integral inorganic network. Our semi-transparent coatings demonstrated excellent fire retardancy thanks to the interplay between the inorganic silicate network and the intumescent fire-retardant system. Remarkable self-healing properties were provided by the dynamic hydrogen bonding interaction between PVA molecular chains, where significant scratches were healed after exposure to water vapor. The PVA/SSA coating enhanced the fire retardancy of plywood, which was shown to be directly related to the APP content. The combination of semi-transparent, fire-retardant and self-healing capabilities underlines the potential of our PVA/SSA coatings for protecting and safeguarding wooden products.