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.