Effect of nitrogen-phosphorus fire retardant blended with Mg(OH)_2/Al(OH)_3 and nano-SiO_2 on fire-retardant behavior and hygroscopicity of poplar

摘要

The aim of the study was to screen any possible synergistic effects related to the combination of nitrogen-phosphorus fire retardant and Mg(OH)_2/Al(OH)_3. This combination is used to improve fire performance, especially smoke suppression of poplar through ultrasonic wave impregnation after microwave treatment. In this study, nano-SiO_2 was used to impregnate poplar treated with nitrogen-phosphorus fire retardant and form a hydrophobic layer on wood cells in order to improve hygroscopicity and reduce water uptake. Cone tests and thermal analysis showed that poplar treated with blended fire retardant had improved behavior. Results show that a 20% and 25% nitrogen-phosphorus fire-retardant solution (blended by adding 10% Mg(OH)_2/Al(OH)_3 based on the dry weight of nitrogen-phosphorus fire retardant) was more effective for smoke suppression. The heat release rate, total heat release, and total smoke production of a 25% nitrogen-phosphorus fire-retardant solution blended by adding 10% Mg(OH)_2/Al(OH)_3 showed significant reduction. The char residual yield showed a marked increase to 35.5%. Fourier transform infrared analysis suggested a -CH_2-Si-CH_2- and Si-O-C stretching vibration in nano-SiO_2 treated poplar, which greatly decreased the hygroscopicity of fire-retardant-treated poplar.