Study on the modification mechanism of modifiers on the properties of sawdust-magnesium oxychloride cement composite

Physicochemical properties and in vitro activity of SrHPO4 modified magnesium oxychloride bone cement

“…MOC is usually used in the construction material industry because of its good mechanical properties and flameretardant performance, but its poor water resistance restricts its large-scale application [40][41][42]. However, on the other hand, MOC is an easy reaction with water which can be used as a biodegradable bone repair material, and by improving the water resistance of MOC and controlling its leaching rate, it can be used as a bone repair material that can control the rate of degradation.…”

High-Bond-Strength, Water-Resistant Magnesium Oxychloride Cement-Based Inorganic Adhesive Inspired by Adsorbed Heavy Metal Ions

“…Unlike calcium silicate hydrate (C–S–H) or calcium aluminum silicate hydrate (C-A–S-H) of silicate cement, , the main physical structures of MOC are 3-phase, 5-phase, 2-phase, and 9-phase, , where the main phases present at room temperature are 3-phase and 5-phase, and they improve the mechanical strength of MOC composites in the form of needle rods and short rods. However, MOC composites are unstable in aqueous environments, where the 5-phase crystal structure is converted to a 3-phase crystal structure, which decomposes into Mg (OH) 2 , thus providing no mechanical strength, leading to volume expansion of the MOC composites, resulting in cracks and loss of mechanical strength, consequently limiting the application of MOC composites as wood adhesives. , At present, a number of studies have shown that certain acids have a positive effect on the stability of MOC composites in water; Deng Dehua first found that phosphoric acid and its phosphate can be coordinated with magnesium ions to form complex ions during hydration, which leads to the formation of more multinuclear hydroxylated magnesium ions and then forms a stable 5-phase crystal structure, improving the ability of MOC composites to resist water decomposition. , Tartaric acid, , citric acid, , and hydroxyacetic acid also have been used to modify MOC composites, mainly due to the chelating effect of −COOH on Mg 2+ , which causes them to adsorb on the surface of the 5-phase crystals, thus preventing the 5-phase crystals from being hydrolyzed, which serves to prevent water molecules from intruding and damaging the MOC composites. However, introducing some acids will cause the MOC composites to show internal defects such as microcracks and large pores, reducing their mechanical strength and affecting their internal bond strength as a wood adhesive .…”