Ambient-cured dolomite-based magnesium oxychloride adhesive for wood bonding: formulation, characterization and performance

Adhesives in wood-based materials are typically made from fossil-based resources and can cause problematic emissions in finished products. Magnesium oxychloride cement (MOC) is a potential alternative to those established adhesives. While MOC is typically made from caustic calcined magnesite, this study used the widely available dolomite, as an alternative resource to magnesite, to develop dolomite-based MOC (DMOC). Due to the inherently high filler content in the form of calcium carbonate in dolomite, strategies were needed to control workability for adhesive application. A multi-technique characterization and mechanical testing of DMOC-bonded wood were used to evaluate the effects of molar water ratio and dispersant content. Although increasing water content and adding dispersant improved viscosity and workability, both adversely affected adhesive curing and consequently mechanical performance. Shear strength decreased from 6.2 MPa to 3.5 MPa, while H2O:MgCl2 increased from 15 to 21, and from 5.9 MPa to 2.5 MPa with dispersant addition from 0% to 15%. In contrast, viscosity decreased by 90% by changing the molar water ratio and by 70% by adding dispersant. Microstructural analysis revealed good penetration of DMOC crystals into the wood surface in mineral-bonded poplar lamellas.