Room-temperature curing high-strength, water-resistant, flame-retardant adhesive based on aluminum dihydrogen phosphate and gelatinized starch cross-linking.

Aluminum dihydrogen phosphate (ADP) adhesives, known for their non-toxicity, simple preparation, low cost, and exceptional thermal stability, are considered a promising alternative to formaldehyde-based adhesives. However, their industrial application is limited by the need for a high curing temperature. This study introduces a novel adhesive based on the ADP modified by gelatinized starch (GS), with alumina (Al₂O₃) as a filler, which can be prepared through simple solid-liquid mixing. GS and ADP form covalent cross-links at room temperature, and the incorporation of Al₂O₃ significantly reduces the adhesive's soluble matter rate, thereby enhancing its water resistance. This adhesive is applicable to various materials, demonstrating excellent bonding performance with glass, wood, and metals. With increasing curing temperatures, its bonding performance improves further. Under curing conditions of 120 °C for 2 h, the shear strength on TC4 titanium alloy reached 3.6 MPa, and the wet shear strength on plywood reached 2.18 MPa. Moreover, the inclusion of ADP imparted excellent flame retardancy, with a limiting oxygen index (LOI) of 37.3 % and non-combustibility in cone calorimeter tests, indicating its potential as a flame-retardant coating material. Based on these findings, the GS/AP adhesive demonstrates strong potential for widespread application in wood-based products and related industries.