Silica, like carbon black, can be divided into flocs, aggregates, and aggregates (or monomers). Monomers, also known as primary structures or raw particles, are rarely present in the form of monomers. Primary structures are extremely small solid particles or aggregates. The size, shape and surface activity of these tiny particles are filled and reinforced. Rubber properties play a decisive role. The primary structure, that is, the van der Waals force exists between the original particles, and sometimes there is a hydrogen bond, so that the particles can be agglomerated, and the secondary structure is also called an aggregate. Due to the internal non-chemical bonding, it can be disintegrated under the action of strong mechanical action, but the cohesive force of silica is often stronger than their affinity with rubber, so it is difficult to separate them all by mechanical action during processing. Some of the condensed particles can be further polymerized into flocculents which can be opened with only a small shear force.