Inorganic silica sol mineral coating

Silica hydrosol, also known as silica sol, is not made by dissolving silica in water, but by ion exchange. Coatings made with silica sol as the main adhesive are inorganic silica sol coatings. The solution of silica sol is a colloidal solution.

After scientists discovered colloidal systems in the early 20th century, they gradually discovered the "strange and interesting phenomenon" of colloidal particles, and continuously studied, discovered, and utilized this peculiar characteristic in high-tech. The particle size of colloidal particles is in the nanometer range, between the "marvelous" and "microscopic" particle sizes, and can be referred to as the "mesoscopic" size. It was not until the 1980s that it was uniformly referred to as "nanoscale". Materials with nanoscale properties are called nanomaterials, which have many unique properties that ordinary materials do not possess, and silica sol coatings also utilize these properties.

Q: What are the characteristics of silica sol and silica sol coatings?

Silica sol is a colloid with particle size within the range of nanomaterials, thus possessing the properties of nanomaterials.

The viscosity of silica sol is very low, similar to that of water (8mpa. s), about 8-10mpa. s, so it has strong permeability and can fully penetrate and adhere to the substrate.

Both silica sol adhesive and potassium silicate aqueous solution adhesive systems contain ions of metasilicic acid, orthosilicate, and polysilicic acid. Under normal conditions (pay attention to this point!), they all undergo volume shrinkage when they form films separately. The performance of potassium silicate mineral coatings is similar to that of silica sol coatings, but there are differences between the two.

The coating film formed by silica sol itself under specific conditions and the coating film usually made with it are very dense, weather resistant, and pollution resistant.

The coating of silica sol and its coatings will not deteriorate, age, or deteriorate.

Under specific circumstances, silica sol coatings can form high-density coatings that can pass through all gases (including water molecules).Silicone sol and its coatings have alkali resistance and frost resistance. Potassium silicate coatings are also available.

Silicone sol and coatings made from it are inorganic substances, completely non flammable, and can withstand high temperatures of 800 ℃.

Silicone sol coatings are water-based, single component, non-toxic, odorless, and environmentally friendly; Manufacturing, storage, and construction will not cause fires.

Like potassium silicate, resources are almost infinite.

Potassium silicate mineral building coatings are low-carbon, flame-retardant or non combustible, energy-saving, resource saving, pollution-free, and cost-effective. Combining with inorganic substrates through chemical reactions to form strong siloxane bonds has extremely unique advantages. The Earth's crust, where we live, is almost entirely composed of stones such as silicates and silica, where the combination of oxygen and silicon forms the siloxane bond. Coating our buildings with potassium silicate mineral coatings is like decorating with stones, and it is integrated with the base layer, never falling off. It is also consistent with the natural appearance and harmonious with each other. In today's world where low-carbon, energy-saving, environmental protection, and fire prevention are highly valued, potassium silicate and silica sol mineral coatings undoubtedly have great development prospects.

Calculations show that the acidity of carbonic acid is 2150 times and 1955 times higher than that of metasilicic acid and orthosilicic acid, respectively. It is under the catalysis of carbon dioxide that the generated silica forms a silane bond coating film.

Attachment [II]: Silicate mineral base layer, due to long-term contact with water (or water vapor), forms extended silanol groups (≡ Si-OH). When potassium silicate mineral coating generates silicic acid under the catalysis of carbon dioxide, the following reaction occurs, as illustrated below:

Attachment [III]: Comparison of Bond Energy as follows (at 298K, unit: KJ/mol)

Si-O 466 Si=O 638

C-O 358 C=0 612

C-H 413 C-C 347

The organic adhesive used in architectural coatings is mainly carbon carbon linked between the main chain atoms, and the difference in energy between siloxane bonds and carbon carbon bonds is 466-347=119 (KJ/mol), which is 12 times that of (10KJ/mol).

Attachment [IV]: Reaction Mechanism (Schematic)

Ca (OH) 2+H2SiO3 → CaSiO3+2H2O

(Basic alkali, source of white frost) (Silica sol) (A dense and hard crystalline film that gradually crystallizes and grows, which can block the alkali and then seep out.)

Appendix [V]: "Silicone sol coating" refers to the modification of silica sol with a few feasible lotion, using silica sol as the binder, with a small resin content, so as to achieve the purpose of meeting the requirements of the coating film and being flame retardant or non combustible. While the coating made of silica sol modified lotion adhesive has flammability, it is not called silica sol coating, and it is also called "silica sol modified emulsion paint". So is potassium silicate mineral coating.

Attachment [VI]:

(1) Why do two components require a curing agent to form a film when using potassium silicate as a binder, while a single component can form a film without a curing agent?

Short answer: The curing agent used for two-component mineral coatings is sodium fluorosilicate or specially made aluminum dihydrogen triphosphate. There are the following chemical reactions: (briefly illustrated)

From the reaction, it can be seen that Na2SiF6 and specially made Al (H2PO4) 3 are slightly soluble, so the concentration of acid is extremely low, and the reaction cannot proceed vigorously, otherwise the significance of curing agent will be lost. The released silicic acid slowly forms a film, and the insoluble primary ecological K2SiF6 is embedded in the gaps of the film and forms a complex salt with active silicic acid or primary ecological SiO2, which plays a buffering and filling role, preventing the silicic acid from falling off and cracking during film formation. Na2SiF6 is a curing and modifying agent. Specially made aluminum dihydrogen triphosphate is a complex, and its active ingredient is aluminum dihydrogen triphosphate. It is an acid salt that is slightly soluble in water, and in actual reactions, it is not consumed, only transformed in form. The generated primary basic aluminum phosphate and primary silica or SiO2 form insoluble macromolecular complex salts, which also avoids dehydration shrinkage and cracking during the formation of silica films. So, aluminum dihydrogen triphosphate is both a curing agent and a modifying agent. Note that the generated silicate compounds are all stones and also contain some crystalline water.

From the A.B reaction formula, it can be seen that the conditions under which the reactants and products are located are different. The left side is slightly acidic, while the right side is slightly alkaline. With the participation and absorption of CO2's slightly acidic gas, the pH value continuously decreases, and silicic acid inevitably undergoes aggregation and film formation. So the chemical equilibrium has been shifting to the right until the film-forming process is complete.

(2) Why should one component potassium silicate mineral coatings and silica sol coatings be modified with lotion?

Answer:

1. Increase the wet adhesion of the coating;

2. In normal film-forming conditions, it plays a bridging role to buffer the dehydration shrinkage and brittle cracking caused by silicic acid film-forming

3. Fill the space during coating formation, increase the density of the coating, and reduce the permeability coefficient of the coating. These effects are different from the two-component curing mechanism.

5、 Precautions for inorganic silicate mineral coatings

The most important thing of inorganic silicate mineral coatings is to use inorganic adhesive potassium silicate or silica sol as the main film-forming material, and use a small amount of lotion to adjust its brittleness, so as to increase the crack resistance of the coating film without affecting the hardness. The difficulty in scientific research is how to make potassium silicate or lotion coexist stably. It requires a product that functions like a mild surfactant and has a stable water glass/lotion system to prevent thickening and reunion after the coating, and can complement each other to increase the performance of the coating film during film-forming.