Fumed silica aggregates have a three-dimensional branch structure, which can form an interactive network in the dispersion system. With this characteristic, fumed silica in the sealant field can increase viscosity as a thickener and thixotropic agent. To ensure the free flow of the rubber, it has the effect of preventing agglomeration, sagging, and collapse. The thickening and thixotropic mechanism of fumed silica is mainly achieved by the hydrogen bonding interaction of the surface silicon hydroxyl groups. When dispersed in polysiloxane, different particles generate hydrogen bonding through the surface silicon hydroxyl groups. , Forming a silica network, which limits the fluidity of the system, increases the viscosity, and plays a role of thickening; when subjected to the shear force, the silica network is damaged, resulting in a decrease in system viscosity and contact. The effect is conducive to construction. Once the shear force disappears, hydrogen bonds re-form, the silicon dioxide network recovers again, and the viscosity of the RTV silicone rubber compound system gradually increases, which effectively prevents the compound from sagging during the vulcanization process. The anti-sagging property of the system is closely related to the yield value and network reduction rate after shearing of the material during use. In practical applications, the higher the yield value, the better the anti-sagging performance of the compound. The ideal compound should have a high yield value, a high shear dilution index, and a fast reduction rate.

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