Both silica and carbon black are commonly used fillers and reinforcing agents and are widely used in the rubber industry. Their different shapes, sizes and chemical properties affect the compound differently.

Shape and Size: Silica is generally more regular in shape and smaller in particle size than carbon black. Due to the larger surface area, silica has a larger contact area with the compound and is therefore easier to mix with rubber. In addition, the regular shape and small particle size of silica make it better dispersed in the rubber compound, thereby improving the strength and wear resistance of the rubber compound.

Surface chemistry: The surface chemistry of silica differs from that of carbon black. The surface of silica contains a large number of hydroxyl groups, oxides and hydrophilic groups, making it more compatible with rubber molecules. The surface of carbon black is mainly alkyl and aromatic groups, so the dispersion in rubber is poor. In addition, silica has high reactivity to rubber vulcanization, which can promote the crosslinking reaction of rubber and improve the mechanical properties of the rubber compound.

Dosage: At the same dosage, silica can provide a higher reinforcing effect than carbon black. Due to the better dispersion and surface chemical properties of silica, it makes closer contact with rubber molecules, so it can more effectively enhance the performance of the rubber compound. However, silica may also lead to a decrease in the processability of the compound when used in high amounts.

To sum up, silica and carbon black with different shapes, sizes and chemical properties have different effects on the rubber compound, and the specific application needs to choose the appropriate filler and reinforcing agent according to the required performance.