Hierarchical Lamellar Aluminophosphate Materials with Porosity as Ecofriendly Inorganic Adhesive for Wood-Based Boards

Aluminophosphate inorganic adhesive (APIA), as a binder for wood-based boards (WBB), is synthesized between Al(OH)3 and H3PO4 in solution with hydrothermal treatment in this study. Aluminophosphate compounds with hierarchical lamellar structure are observed on the fibers' surface. The rheological behavior analysis reveals that the viscosity of APIA varied with its P/Al molar ratio [n(P)/n(Al)]. P–O–Al bridges are formed during the hydrothermal treatment of the APIA. The amounts of hydrogen bonds are formed between APIA and wood fibers, which could explain the improvement in mechanical properties of the WBB. In this study, the optimal n(P)/n(Al) in APIA is found to be 2.8, where the bonding strength, together with an acceptable viscosity are found at 1.83 MPa and 31.3 m Pa·s, respectively. Thermogravimetric analysis indicates that the residual weight of plywood is 44.97% greater than pure wood fibers, indicating the fire resistance of the WBB in the study is improved.