Some questions about the activity and dispersibility of precipitated silica 1 1. How to improve the surface activity of precipitation silica, besides the treatment with silane coupling agent, what other methods are there? (Later improvement)

1.1 Fumed silica production
The pyrohydrolysis of amorphous powders produced by fumed silica, silicon tetrachloride, silicon tetrachloride or trichloromethylsilane in a mixed gas stream of air and hydrogen tends to be spherical particles with a surface of hydroxyl groups and Adsorbed water, particle size is 7~40nm, large specific surface area, high chemical purity, silica > 99.8%. Based on whether fumed silica can be divided into hydrophilic and hydrophobic surface treatments according to the specific surface size, it can be divided into different models.


1.2 Fumed silica Fumed silica is widely used in silicone rubber, cables and unsaturated polyester resins, adhesives, paints and coatings, inks, copier toners, food and cosmetics, and can play a role in reinforcing, thickening, anti-caking The rheology and thixotropy of the control system of the block.
1.2.1
application
In the RTV silicone rubber and high temperature vulcanized silicone rubber used, there is a large amount of fumed silica in the silicone rubber, and they tend to be dispersed in the form of agglomerates on the large contact surface to form a three-dimensional network structure, And silicone rubber matrix material, in the matrix, the cross-linking points are formed during the curing process, so silicone rubber plays a thickening and reinforcing effect. The three-dimensional network structure is formed by fumed silica with relatively stable, "elastic" state, under the action of external force, it will be temporarily destroyed, reducing the viscosity of the system, showing good fluidity when sheared The removal of the force will quickly restore the three-dimensional network structure to the state before the force, so the system has good thixotropy. In addition, because the particle size of the fumed silica is very small, the particles are spherical and dispersed in the binder to form a unified system, which often has good optical properties, and can produce white and transparent silicone rubber products. Room temperature vulcanized acid silicone rubber, produced with fumed silica fillers with a wide range of coating consistency and effective cure, with excellent adhesion to primer or primer substrates, excellent at room temperature storage stability and is widely used in the construction industry.
1.2.2
Plastic and unsaturated polyester resins, in applications
Fumed silica is also often used in plastics and elastomers and unsaturated polyester resins. Plastic mixing, in addition to adding traditional fillers and then adding a small amount of fumed silica, will produce a significant reinforcement effect, greatly improving the hardness and mechanical properties of the material, thereby improving the processing and performance of the product. Adding a small amount of fumed silica to unsaturated polyester resins can impart excellent resin clarity and excellent physical properties, attributes that will help improve the quality of downstream products. Fumed silica has an irreplaceable role in industrial development, but due to its high price, its application range is often limited, such as precipitation silica, which is also widely used in the rubber industry.