Influence of phytic acid on flame retardancy and adhesion performance enhancement of poly (vinyl alcohol) hydrogel coating to wood substrate

Traditional fireproof strategies for wood mainly involve using organic flame retardants that may affect human health and environment, there is a need to explore a greener and nontoxic method. Herein, we proposed an easy-to-process, environmentally friendly and highly efficient polyvinyl alcohol (PVA)/phytic acid (PA) hydrogel coating to improve flame retardancy of wood by freeze-thaw cycles. PA can promote the gelatinization of PVA and further enhance mechanical properties and flame retardancy of PVA coating. The obtained PVA/PA hydrogel coating shows better adhesion and fire-safety performance compared to pure PVA hydrogel coating, including achieving 151.68 kPa of adhesion strength, reaching V0 rating in UL-94 test, a significant enhancement of time to ignition (TTI, from 63 s to 130 s), and 51.47% and 55.47% decrease in the mean heat release rate (HRR) and total release rate (THR), respectively. The PVA/PA coating with enhanced superior adhesion and flame-retardant properties ensures the fire-safety of wood for its wide applications as structural materials in architecture and furniture fields.