Fire protection of wood with an environmentally benign UV-cured polyelectrolyte complex

The use of wood in home and commercial structures has continued to grow in recent years, but its flammability poses a threat to lives and property. Previous attempts to flame retard wood have utilized harmful halogenated chemistries or required complex deposition methods. In this work, a UV-cured flame-retardant treatment is deposited on plywood and natural whitewood through in situ photopolymerization of an anionic phosphate-containing methacrylate, in the presence of cationic polyethylenimine (PEI), to form a polyelectrolyte complex. The influence of PEI molecular weight, PEI and methacrylate concentrations, and deposition time were investigated. The best version of this treatment, deposited in only two steps, renders natural wood and plywood flame retardant without affecting mechanical properties. Cone calorimetry reveals a significant reduction in the total heat release, average heat release rate, and maximum average rate of heat release for both substrates. This environmentally benign and facile system represents a significant advancement for safe and effective flame retardant treatment of wood.