Constructing ultra-strong and water resistance magnesium oxychloride cement-based adhesive for wood industry

Environmentally friendly, aldehyde-free adhesive designs are in high demand in the wood industry, helping to reduce environmental impact and human health concerns. Magnesium oxychloride cement (MOC) is a low-carbon inorganic gel material that can improve the utilization rate of potassium fertilizer and is a potential substitute for aldehyde-based adhesives. However, in practical applications, it is often limited by its poor water resistance and compatibility with wood, resulting in poor bonding performance. In this paper, an organic–inorganic hybrid method is proposed. Sodium hexametaphosphate/soluble polysaccharide (SHP/SP) was introduced to develop a MOC inorganic adhesive with high adhesion, mechanical strength, and water resistance. The abundant functional groups in SHP/SP formed multiple interactions with Mg²⁺, thus creating an internal network with excellent cohesion strength. The addition of SHP/SP enabled stable infiltration of MOC into the wood through electrostatic adsorption and metal chelation. The results showed that the softening coefficient, compressive strength, and wet shear strength of MOC/SHP/SP adhesive were 0.98, 121.14 MPa, and 2.28 MPa, respectively, representing 81.48%, 128%, and 147.83% increase compared to unmodified MOC. Thus, this study provides a promising approach for developing high-performance and environmentally friendly MOC adhesives and composites using agricultural and industrial by-products.