Fire Resistance Improvement of Fast-Growing Poplar Wood Based on Combined Modification Using Resin Impregnation and Compression

Fast-growing poplar with low wood density has been generally regarded as a low-grade wood species and cannot be used as a building material due to its poor fire resistance. As the fire resistance of wood materials is positively correlated with density, combined treatment using resin impregnation, which imparts thermal resistance, and compression, which improves density, appeared to be a route toward improved combustion performance. Fast-growing poplar wood was modified with a combination of borate-containing phenol–formaldehyde resin impregnation and compression in a transverse direction at varying intensities. The effects of the combined treatment on fire resistance were then examined and discussed. Char residue morphology analysis and microscopic observations were conducted to reveal the effects and mechanism of the combined treatment on fire resistance improvement. The test results showed that fire resistance was greatly improved, including the static and dynamic bending performance at elevated and high temperatures, as well as the combustion performance. The higher the compression ratio was, the better the fire resistance of the modified wood.