As an important inorganic chemical raw material, the moisture-proof performance of Sodium Metasilicate Nonahydrate directly affects the storage stability and application effect. The moisture-proof system is designed by simulating the natural deliquescence process. The core of the deliquescence chemical method is to build a synergistic mechanism of directional moisture absorption barrier and lattice stability structure. This method breaks through the limitations of traditional physical isolation methods and shows significant advantages in the fields of chemical industry and building materials.
During the preparation process, the raw material ratio plays a decisive role in the pore structure and surface activity of the product. Experimental data show that when the modulus of sodium silicate solution is controlled in the range of 3.2-3.4, the three-dimensional network structure formed has the best capillary effect. The temperature gradient of the reactor needs to be controlled in stages. The initial 65±2℃ promotes the polymerization of silicon-oxygen tetrahedrons, the middle 82℃ accelerates the migration of sodium ions, and the temperature is lowered to 45℃ in the later stage to achieve directional growth of crystals. The pH value is adjusted by the dynamic balance method. The hydrochloric acid addition rate is accurately controlled by the metering pump to maintain the system in a weak alkaline environment of 8.6-9.0.
The introduction of organosilicon modifiers in the crystallization process is the key to the technology. Studies have shown that adding 0.3wt% of γ-aminopropyltriethoxysilane can increase the contact angle of the product to 112°, while keeping the water vapor permeability below 0.15g/(m²·h). The program temperature control curve is used in the vacuum drying stage: in the initial stage, the temperature is raised to 80℃ at a rate of 5℃/min, and the temperature is kept constant for 2h to remove free water; in the second stage, the temperature is slowly raised to 105℃ at 0.5℃/min, and the crystal water is removed for 4h. Under this process, the moisture content of the product is stable at 8.7±0.2%.
Microstructure analysis shows that a nano-scale siloxane protective layer is formed on the surface of the optimized product, and the half-peak width of the characteristic peak in the XRD spectrum is reduced by 32%, indicating that the crystal integrity is significantly improved. BET test data confirms that the specific surface area is reduced from 25m²/g of conventional products to 12m²/g, and the pore size distribution is concentrated in the range of 2-5nm. This densified structure effectively blocks the penetration of water molecules. The weight loss rate of the thermogravimetric analysis curve in the range of 150-300℃ decreased from 9.8% to 4.2%, proving that the thermal stability of the moisture-proof system has been enhanced.
In the actual application test, the treated Sodium Metasilicate Nonahydrate was exposed to a relative humidity of 85% for 240 hours, and the agglomeration rate dropped from 47% in the control group to below 8%. Application data in the building materials field show that the initial setting time of silicate cement added with 3% modified products is extended by 25min, and the compressive strength at 28 days is increased by 6.2MPa. These performance improvements are due to the precise regulation of the moisture-proof system on the hydration reaction process, which not only delays premature hydration but also ensures the later strength development.