Dual-crosslinking network and pre-anchorage effect enable high-performance, low-cost, and eco-friendly geopolymer adhesive for the wood industry

Alkali-activated geopolymers have shown unique advantages in applying adhesive materials because of their low cost, flame retardancy, and environmental friendliness. However, the high brittleness of the single aluminosilicate network and the weak interfacial compatibility of the geopolymer system result in poor bonding performance, which severely limits their application in the adhesives industry. Herein, a geopolymer-PF resin adhesive (GPA) with excellent comprehensive performance was successfully prepared by crosslinking geopolymer and PF resin with numerous reactive sites for the strong hybrid dual network under hot-pressing. In addition, the introduction of PF resin can achieve an effective pre-anchorage effect on wood for strong mechanical locking due to the excellent wettability, water resistance, and dimensional stability of PF resin. The produced GPA exhibits high initial wet shear strength (0.94 MPa) and adhesion toughness (0.271 J), 236% and 450% higher than pure geopolymer. The GPA also demonstrated remarkable age-strengthen performance, with bonding strength increasing to 1.27 MPa after 28 d, exceeding the majority of reported inorganic, biomass, and PF adhesives. In addition, the GPA displayed desirable eco-friendly and flame-retardant properties with a low-cost and sustainable approach. The pre-anchorage and double network structure design provide a general strategy for strengthening and toughening geopolymers, a key step forward in today's high-performance, low-cost, and sustainable production of inorganic adhesives from industrial solid wastes and geological resources.