Fumed silica (commonly known as fumed white carbon black in China, hereinafter referred to as fumed SiO2) is a fine, special amorphous silica product obtained by high-temperature hydrolysis of halogen silane in a hydrogen-oxygen flame. The original particle size of the product is between 7-40nm, the specific surface area is generally in the range of 100m2/g to 400m2/g, the product is of high purity, and the SiO2 content is not less than 99.8%. It is an extremely important inorganic nanopowder material. Due to its excellent stability, reinforcement, thickening and thixotropy, it is widely used in rubber, plastics, electronics, coatings, medicine, agriculture and CMP. Fumed SiO2 generally has two types of products: hydrophilic and hydrophobic. The hydrophobic product is obtained by surface chemical treatment of the hydrophilic product.

Product usage

Rheological Additive

Rheological properties are important properties of coatings. They directly affect the appearance, construction performance and storage stability of coatings. Different coating systems also have different requirements for rheological additives.

Anti-settling agent

Fumed silica is an ideal anti-settling agent. The hydrogen bond structure it forms is very uniform and stable, and it is a three-dimensional network structure. Therefore, it is very effective in preventing the precipitation of pigments in the coating system.

Dispersant

In the powder system, when the dry (low moisture content) particles are less than 75μm, the force between the particles causes the powder to usually stick together (especially particles below 25μm in size), making it difficult to achieve fluidization. At this time, fumed silica can be added to solve this problem.

In the same coating system, adding fumed silica can significantly shorten the dispersion time and improve production efficiency. However, it is worth noting that it is better to disperse the silica completely first. The amount of silica added as a dispersant should not be too much, generally not more than 1%, because too much addition will cause the system to have too strong thixotropy, resulting in insufficient edge shear force during dispersion and a frozen state, affecting the dispersion efficiency. In special cases such as zinc-rich paint, when 2% needs to be added, it can be used together with other rheological additives, and the rheological properties of fumed silica can be adjusted using alcohol solvents.