The silica particles have a strong adsorption effect on the vulcanization accelerator in the rubber compound, and the vulcanization is delayed. The smaller the particle size, the larger the specific surface area, and the more the adsorbing agent is adsorbed, the longer the vulcanization time. After adding the coupling agent, the t10 and t90 of the composite with the same particle size of silica decreased, indicating that the addition of the coupling agent would effectively reduce the amount of hydroxyl groups on the surface of the silica particles and promote the adsorption of the promoter on the surface. The reduction and the dispersibility are improved, so that the torque of the composite material is lowered and the MH-ML is lowered.

With the addition of coupling agent, the tensile strength and elongation at break of the composites increased to some extent, and the tensile strength and elongation at break of the 15 nm silica composite increased the most. The tensile strength and elongation at break of the composite of nm are not increased much. This indicates that the coupling agent strongly binds the silica to the rubber macromolecule, and the tensile fracture of the composite does not occur at the interface between the white carbon black particles and the rubber macromolecule.

However, the 100% and 300% modulus of the silica composite without the coupling agent added was higher than that of the composite to which the coupling agent was added. This indicates that under low and medium deformation, the white carbon black particles without the coupling agent are easy to form a filler network, which plays a good reinforcing role. It can be seen from the microscopic image of the rubber cross section shown in the following figure that after the addition of the coupling agent, the distribution of the white carbon black in the rubber material is significantly more uniform, and the combination with the rubber material is more compact.

In the case of large deformation, the interface between the white carbon black particles and the rubber macromolecule without the coupling agent system is easily broken, resulting in lower tensile strength and elongation at break. The more the particle size of silica, the more obvious the effect of the coupling agent, the more favorable the vulcanization characteristics and mechanical properties of the composite.