The structure of silica is characterized by the size of the voids between the morphology of the primary structural monomer (aggregate) and the aggregate of the secondary structure.
The change of the properties of the silica structure has a great influence on the vulcanizate. The tensile stress increases remarkably with the increase of the structure, and the permanent compression deformation increases. This is because the structural improvement reduces the rubber size to a greater extent. The volume fraction of the molecule, in order to achieve the same deformation, the deformation of the rubber portion is greater than the unfilled compound. The change in structure of silica is less affected by wear than the change in specific surface area, and its effect is only apparent under harsh conditions. However, structural changes have a great influence on the modulus and permanent compression set of the vulcanizate.
The higher the structure of silica, the more the internal pores of aggregates and aggregates, the stronger the surface activity, and the stronger the adsorption of the promoter. The concentration of the accelerator in the vulcanized rubber is lowered, and the vulcanization rate is slowed down. The size of the silica black (floccule) is mainly determined by the final step of the production of silica, namely drying, compaction, ultrafine and the like. The structure of silica can be determined by various methods such as DBP oil absorption. Due to the porosity of the silica (BET-CTAB), it is easier to adsorb rubber auxiliaries, especially accelerators. At the same time, the interaction between the fillers is enhanced, and the interaction between the rubber and the silica is also weakened due to the hydrophilicity of the silica, so it is necessary to add a surfactant in the compound formulation. The size of the voids can be determined by a mercury pore volume.