Structural and Chemical Modification of Cellular Wood Composite for Enhanced Strength, Fire, and Biological Resistance

High-performance cellular wood composites with enhanced strength, flame retardancy, and termite resistance were developed through delignification, densification, and impregnation with amino-functionalized polyglycerol phosphate (APGP) and disodium octaborate tetrahydrate (DOT). Compared with the performance of control samples, the flexural strength of treated wood samples increased by 56%. Flame resistance was enhanced with increased char yield (from <1 to 42.6%), improved limiting oxygen index value (from 23 to 56%), and a reduction in peak heat release rate (127 to 48 W/g). Termite resistance was also enhanced, with the sample weight loss reduced from 83.75 to 30.45% and termite mortality increased from less than 20 to 100% after 56 day testing. These improvements were attributed to a dual-phase flame-retardant mechanism involving gas-phase intumescent char formation by APGP and solid-phase B₂O₃ barrier formation from DOT, along with the borate-induced enzymatic disruption of termite digestion. These findings demonstrate that optimized chemical impregnation and densification strategies can yield multifunctional wood composites with superior mechanical durability, fire resistance, and biological protection, suitable for demanding structural and outdoor applications.