Preparation And Properties Of Water Resistant Silicate Wood Adhesive

In recent years, with the development of people’s environmental protection awareness, multifunctional and eco-friendly inorganic adhesives are widely used in various industries and fields. Non-toxic and weather resistant inorganic adhesives re-enter the research field and get attention as a kind of wood adhesive. Silicate adhesive is particular prominent among all common inorganic adhesives. While, when it applies on wood directly, it cannot achieve the inorganic-organic surface fusion and leads to low bonding strength and bad water resistance. Therefore, sodium silicate adhesive applied on wood must be modified.In this study, with sodium silicate as the main raw material, it was explored that different modification methods such as pretreatment by PVA, organic additives, inorganic fillers and organic-inorganic compounds modification have influences on the bonding strength and water resistance. By orthogonal experiment method, the best modification conditions and processes have been determined and high bonding strength and well water resistance sodium silicate adhesive for wood has been made. Through infrared spectroscopy, thermal analysis and scanning electron microscopy analysis, the microstructure has been observed, and on this foundation, the curing kinetic equation was obtained. The main conclusions are as follows:1. The pretreatment by PVA for the adhesive has large influence on bonding strength and water resistance properties of it. The best formula is that the mass ratio of sodium silicate, PVA, OP-10, citrate and phenol is50:12:0.25:1.0:1.15. The best modification process is time for90min,pH of9.5and temperature of85℃.Under this condition, the bonding strength of the adhesive is0.73MPa. Water resistance time is22days and24hour thickness swelling is12.5%。2. On the foundation of modification by PVA, the research of developing the adhesive’s water resistance property has been held. The best formula is that the mass ratio of active MgO, nano-silica is1:1, and this is component A. The mass ration of amino acid, TEOS and sodium dodecyl sulfate is5:3:3, and this is component B. The mass ratio of A and B in this formula is30:1, and their mass is50%of this adhesive system. Under this condition, the bonding strength of the adhesive is0.83MPa. Water resistance time is26days and24hour thickness swelling is8.0%。3. Infrared spectroscopy, thermal analysis and scanning electron microscopy analysis were used to observe the microstructure and curing situation. The result shows that composite modification not only greatly improves the performance of bonding strength and water resistance, but also promotes the curing and formation of cross-linked structure of the adhesive. Then better thermal stability of it achieved.4. The kinetic equation of composite modified adhesive was determined by dynamic DSC method with different heating rates to scan its curing process. Through linear fit, the differential mechanism function of the compostite modified silicate adhesive curing reaction system is f(α)=(1-α)06。...