1.White carbon black manufacturing

White carbon black is prepared by two methods, namely calcination and precipitation.

White carbon black prepared by calcination method is also known as gas phase white or dry white, it is based on multi-silicon halide (SiClx) as raw materials in high temperature thermal decomposition, gas reaction.

The particle size of dry silica is very small, about 15~25nm, with great floatability. Gas phase silica has few impurities and good reinforcing property, but the preparation is complicated and the cost is high. It is mainly used in silicone rubber. The product obtained is transparent and translucent, with good physical and mechanical properties and dielectric properties, and excellent water resistance.
Precipitated silica is generally prepared by neutralizing precipitation reaction of silicate (usually sodium silicate) and inorganic acid (usually sulfuric acid).

Precipitation method of silica particle size is larger, about 20~40nm, low purity, poor reinforcement than calcination method, the dielectric properties of rubber material is especially poor after damp, but the price is cheap, good process performance. It can be used only in NR, SBR and other general rubber, and can also be used with carbon black to improve the flexure and cracking resistance of rubber material and slow down the growth of crack.
two Structure of silica

1. Chemical structure of silica

Silica is 95~99% of the composition of silica, confirmed by X-ray diffraction, because of the different preparation method of silica, its structure is different. The internal structure of gas phase silica is almost completely a three-dimensional network structure of tightly arranged silicic acid, which makes the particle hygroscopicity is small, the surface adsorption is strong, and the reinforcing effect is strong. In addition to the silicic acid with three-dimensional structure, there are still more two-dimensional silicic acid in the structure of precipitated silica, resulting in loose structure and many capillary structures, which are easy to absorb moisture, so as to reduce its reinforcing activity.
2. Structure of silica
White carbon black is structured like carbon black, and its elementary particles are spherical. During production, these elementary particles collide with each other at high temperatures to form chain dendrimers linked by chemical bonds, called elementary aggregates. The chain dendritic structures adsorb each other by hydrogen bond and form secondary aggregate structure, which is easy to be destroyed during processing and mixing.