The preparation methods of silica mainly include calcination method (Fumed Silica) and precipitation method. The following is a detailed introduction of these two methods and their respective advantages and disadvantages:

1. Calcination method (Fumed Silica)

Preparation process:

Using polyhalide silicon (such as SiClx) as raw material, thermal decomposition at high temperature, and gas phase reaction to obtain it.

Product characteristics:

The particle size is extremely small, about 15~25nm, and the flying property is extremely large.

Few impurities and good reinforcement.

The internal structure is almost completely a three-dimensional network structure of closely arranged silicate, with low hygroscopicity and strong surface adsorption.

Advantages:

The product has high purity, good dispersion, fine and spherical particles.

It has strong reinforcement effect and is mainly used in silicone rubber. The obtained product is transparent and translucent, with good physical and mechanical properties and dielectric properties, and excellent water resistance.

Disadvantages:

The preparation process is complicated and the cost is high.

2. Precipitation method

Preparation process:

The method of neutralization precipitation reaction of silicate (usually sodium silicate) and inorganic acid (usually sulfuric acid) is generally used to prepare hydrated silica.

Product characteristics:

The particle size is large, about 20~40nm.

The purity is low, and the reinforcement is worse than the calcination method.

In addition to the three-dimensional silicate structure, there are also more two-dimensional silicate structures remaining in the structure, which makes the structure loose, has many capillary structures, is easy to absorb moisture, and reduces the reinforcement activity.

Advantages:

Early start, mature technology, simple preparation process.

Low cost and cheap price.

Good process performance, can be used alone in general rubbers such as NR and SBR, and can also be used with carbon black to improve the flex crack resistance of the rubber and slow down the growth of the crack.

Disadvantages:

The product particle size distribution is uneven and the quality is different.

The dielectric properties of the rubber, especially the dielectric properties after being damp, are poor.

In addition, there are some other preparation methods, such as non-metallic mineral method, cellulose method, by-product recovery method, etc. These methods have their own characteristics, and the appropriate method can be selected to prepare silica according to specific needs and conditions.

In general, the calcination method (Fumed Silica) and the precipitation method have their own advantages and disadvantages. The choice of which method to prepare silica needs to be comprehensively considered according to the specific application scenario and cost-effectiveness.