Construction of durable biomass-based flame retardant with high phosphorus and nitrogen contents for wood coatings

As a commonly used material, wood's inherent flammability poses a significant fire safety hazard to people, and it is necessary to improve the flame-retardant performance of wood. This study prepared a novel lignin-based intumescent flame-retardant (PGL) using phosphorus-rich phytic acid, nitrogen-rich guanazole, and carbon-rich lignin as raw materials. Subsequently, PGL was infiltrated into the urea-formaldehyde resin as a flame-retardant component, and a series of PGL-modified urea-formaldehyde resin wood coatings (PGLUF) were prepared. The wood coated with PGLUF exhibited high flame retardancy and passed the UL-94 V-0 level test with a limit of oxygen index (LOI) of 36.5 %. The total heat release (THR) and peak heat release rate (PHRR) were reduced by 92.73 % and 93.58 %, respectively, compared to pure wood. Moreover, when the PGL content was 3 wt.%, the PGLUF could achieve comparable flame retardancy to the coating containing 5 wt.% commercial flame-retardant (triphenyl phosphate, TPP). PGL also exhibited a plasticizing effect on the coatings. The impact strength of PGLUF-coated wood increased with the increase of PGL content. PGL can simultaneously enhance the flame retardancy and mechanical properties of materials, and the preparation process is green and safe. Therefore, the PGL shows excellent potential in practical applications.