Synthesis And Fire Performance Evaluation Of Methylolated Guanylurea Phosphate/Boric Acid Fire Retardant Complex

Lignocellulosic materials are more widely used along with the progress of the social material civilization. The fire disaster may occur frequently because of the use of this flammable material. The requirement of fire-retardant lignocellulosic materials'research and application is increasing.This paper combined the previous scientific research and our research accumulates about wood fire retardant based on phosphorus-nitrogen-boron fire retardant composites. A phosphorus-nitrogen-boron fire retardant complex G21BA was synthesized, which is mainly composed of methylolated guanylurea phosphate G21 and boric acid as fire retardant active substances. Systematic evaluation of its fire performance was performed by thermogravimetric analysis (TGA) of plywood treated with methylolated guanylurea phosphate and G21BA, the controlled atmosphere cone calorimeter analysis, and the fire retardant mechanism was discussed.By using the complete reaction of high pure guanylurea phosphate (GUP), formaldehyde and water at a controlled reaction condition, methylolated guanylurea phosphates were synthesized with different hydroxymethyl content. The characteristics of methylolated GUP are that the colorless clear solution, the enhanced solubility, the mild acidity, the low hygroscopicity and better leachability. The FTIR analysis results of methylolated GUP showed that the intensity of the primary amide absorption peak decreased compared to GUP and the hydroxyl methyl peak appeared, explaining the hydroxyl methyl group being grafted successfully on to GUP. Along with the increasing methylolated degree, the primary amide infrared absorption peak gradually disappeared. The X-Ray Diffraction (XRD) result showed the amorphous state structure of methylolated GUP is more apparent. TGA results showed that the initial decomposition temperature of methylolated GUP is lower than GUP, but eventually the residue mass fraction is slightly more than GUP. CONE testing results showed that the heat release, smoke release and fire growth index were increasing slightly along with the increasing methylolated degree. G21, which was synthesized from 2 mole GUP and 1 mole formaldehyde, was basically the same with GUP on fire-retardant and smoke inhibiting effect.Plywood was impregnated with G21BA aqueous solution. Tiny particles were found on the cell wall in dry plywood treated with G21BA, which were arranged very closely and scattered evenly. The fire-retardant and smoke inhibition performances were very strong and the plywood's mechanical properties had been improved by G21BA. The open fire environment and the relative close indoor fire environment were simulated by controlled atmosphere cone calorimeter. At the open fire environment, the cone results showed that the heat release, mass loss ratio, fire growth index, smoke product and toxicity of G21BA fire-retardant plywood were obviously lower than untreated plywood. In the relative close indoor fire environment, the smoke product and CO release under low oxygen concentration of G21BA fire-retardant plywood were obviously higher than that under high oxygen concentration. Meanwhile, the smoke product and heat release under high oxygen concentration of untreated plywood increased greatly compared with low oxygen concentration. When the oxygen concentration in the air was higher than 18%, the fire-retardant and smoke inhibition properties of G21BA fire-retardant plywood were lower greatly than untreated plywood, and the usage safety of G21BA fire-retardant plywood was improved significantly. In the relative close indoor, the G21BA fire-retardant plywood may be ignited by the fire caused by stacked much more inflammables. It would release much CO and heavy smoke if oxygen concentration in the air was very low. Therefore, we suggest that do not pile up too many flammable materials in the public places where much amount of G21BA treated plywood was used and human activities are frequent.G21BA fire-retardant mechanism on plywood mainly is condensed-phase fire-retardant mechanism. When plywood was heated to high temperature, dehydration, decomposition, condensation, polymerization, aromatization reaction was took place and formed charcoal rapidly. In addition, the non-flammable gas (such as water vapor and ammonia) formed during the decomposition of G21BA could play a role of fire-retardant effectively through diluting the oxygen concentration. The pyrolysis products from G21 and boric acid at high temperature may form boron phosphate which plays a certain physical cover and heat shielding effect to inhibit red-hot combustion.