THE EFFECT OF COMBINED FLAME RETARDANTS ON THE PHYSICAL AND MECHANICAL PROPERTIES OF MONGOLIAN PINE

To enhance the flame-retardant properties and physical-mechanical performance of wood, this experiment selected Mongolian pine as the material and employed a vacuum-pressure impregnation method, with different ratios of borax and ammonium polyphosphate (BO:APP) (1:1, 2:1, 1:2) applied and compared with untreated wood (BCW). The treated and untreated Mongolian pine samples were analyzed using scanning electron microscopy (SEM), a universal mechanical testing machine, a limiting oxygen index (LOI) tester, and thermogravimetric analysis (TG) to assess microstructure, weight gain rates, density, physical-mechanical properties, flame retardancy, and thermal stability. Results indicate that the flame retardants were uniformly dispersed within the wood's pores, achieving excellent impregnation. The weight gain rates and density of the treated wood improved when the weight ratio of borax to ammonium polyphosphate was in ratio1:1 (BO-1:APP-1 group).The weight gain rates was 10.36% and a density of 0.632 cm³/g and the MOE and MOR reached 12,076 MPa and 116.3 MPa, respectively, representing increases of 26.5% and 16.7% compared to untreated samples. The oxygen index of the BCW group was 23.1%, while that of the BO-1:APP-1 group was 42.5%, reflecting an 84% improvement over the BCW group. The thermal decomposition temperature of the treated samples decreased by 50°C, with the BCW group's char yield at 11.35%, whereas the char yield for treated samples exceeded 20%, reaching 37.44% for the BO-1:APP-1 group, marking a 230% increase compared to the BCW group.