Crab-claw inspired high performance and flame-retardant magnesium oxychloride cement based adhesive reinforced by 4-arms EDTA and tartaric acid for wood industry

The high CO2 emissions and instability of silicate cement binders during production and use have encouraged the development of low-carbon materials. In this study, an environmentally friendly and flame-retardant building material was produced from magnesium oxychloride cement (MOC) and wood. In practice, the considerable microcracking that forms during the hardening process makes MOC materials very sensitive to water, which limits their further use. Inspired by the predation of crabs, a simple and effective method was proposed to obtain better water resistance and mechanical strength of MOC composite by co-modifying with ethylenediaminetetraacetic acid (EDTA) or disodium ethylenediaminetetraacetic acid (EDTA-Na) in conjunction with tartaric acid. The four –COOH of EDTA and EDTA-Na coordinated well with the 5-phase structure and tightly aggregated the 5-phase crystals, effectively reducing the formation of microcracks. The synergistic effect between EDTA/EDTA-Na and tartaric acid prevented the disruption of 5-phase crystal structures by water molecules, thus improving the water resistance of the MOC composite. The softening coefficients of the MOC composite modified by EDTA and EDTA-Na in cooperation with tartaric acid after soaking for seven days were 0.97 and 0.98, respectively, which is significantly higher than that of the MOC composite modified by tartaric acid alone (0.54). At the same time, the co-modified MOC composite can be utilised as an inorganic adhesive for plywood, and the wet strength of plywood modified with EDTA in cooperation with tartaric acid being 25% higher than that of the unmodified MOC composite. In addition, the resulting composites showed great potential for application in low-carbon building materials, which can help alleviate the environmental impact of construction industries.