Silica sol: Nano black technology that transforms wood

Silica sol is a high-performance nanomaterial widely used in various fields. The main synthesis methods include ion exchange method, electrolytic electrodialysis method, dispersion method, etc. The properties of silica sol synthesized by different methods have their own characteristics. In order to improve their shortcomings, it is often necessary to modify the silica sol. This article summarizes the synthesis methods, modification methods, and properties of silica sol after modification, and examines its application in the field of wood, with a focus on related research on improving the mechanical properties and flame retardancy of wood.

1. Preparation method of silica sol

1.1 One step dissolution method of elemental silicon

The one-step dissolution method of elemental silicon refers to the chemical reaction between silicon powder and water under alkaline conditions to prepare silica sol. This method has the characteristics of stable sol structure, low impurities, and uniform particle morphology. Research has shown that elemental silica sol has the advantages of low impurity content, uniform particle size, easy quality control, and excellent performance.

1.2 Ion exchange method

Ion exchange method is a product made by promoting the growth, concentration, and purification of seed particles through ion exchange reaction of silica sol. This method can significantly increase the content of SiO2, and is easy to control in the preparation process, not easy to gel.

1.3 Electrolytic electrodialysis method

Electrolytic electrodialysis is a method of preparing silica sol using electrochemistry. By adjusting the reaction conditions such as pH value, current density, and temperature of the electrolyte solution, monosilicic acid is generated and forms crystal nuclei in the polymerization reaction, ultimately resulting in the formation of silica sol products.

1.4 Dispersion method

The dispersion method is to use mechanical agitation to disperse SiO2 particles in an aqueous solution and prepare SiO2 sol. The SiO2 hydrogel particles prepared by the method are uniform, well dispersed, high in purity and low in viscosity.

2. Silica sol modification method

2.1 Physical Modification

The physical modification method mainly forms a protective film on the surface of SiO2 molecules through intermolecular forces, reducing agglomeration and improving dispersibility. Research has shown that by regulating the hydrolysis process of silicon seeds, size controllable silica sol can be prepared.

2.2 Chemical Modification

Chemical modification can form different chemical bonds between SiO2 molecules, improving the hydrophobicity and stability of silica sol. Common chemical modification methods include metal ion modification, graft modification, and silane coupling agent modification.

2.2.1 Metal ion modification

By introducing metal ions for surface modification of silica sol, its stability can be significantly improved. For example, aluminum based modified silica sol and boron based modified silica sol have good antioxidant capacity and stability.

2.2.2 Grafting modification

Grafting different silanol groups onto nano-SiO2 can expand its surface functional groups for use in the field of biomedicine.

2.2.3 Silane coupling agent method modification

The use of silane coupling agents to modify silica sol can give it both organic and inorganic advantages, improving product performance. Research has shown that silane coupling agents can significantly reduce cracks in thin films and enhance the corrosion resistance of coatings.

3. Application of silica sol in the field of wood

3.1 Enhance mechanical properties

Silica sol impregnation of wood can significantly improve its mechanical properties. Research has shown that using a composite process of silica sol impregnation and heat treatment to modify rubber wood can further improve its dimensional stability. Silica sol/phenolic resin composite modifier can effectively fill the pores, cell walls, and grooves of wood, improving its mechanical properties.

3.2 Enhanced flame retardancy

Silica sol modified wood can significantly improve its flame retardant properties. Research has shown that the dosage and impregnation method of silica sol have a significant impact on the mechanical properties of modified materials. Increasing the soaking pressure and time can both increase the weight gain rate of wood, and the modification effect is significant.

4. Conclusion

After modification, the silica sol showed significant improvements in stability, anti gelation, hydrophobicity, surface activity, and other aspects. When used for wood modification, it can not only improve the poor toughness of wood, but also endow wood with flame retardant properties. In the future, further exploration is needed on the formulation of silica sol for different wood materials and products, optimizing preparation and modification processes, reducing production costs, and expanding application areas.