The reinforcement of fumed silica on HTV silicone rubber is affected by its particle size, comparative area and structure, generally the smaller the particle size, the higher the specific surface area, the higher the structure, the better the reinforcement effect, and the higher the strength and hardness of vulcanized rubber. In addition, the amount of fumed silica and its dispersion in the matrix also have a great impact on the properties of vulcanizates. Figure 1 shows the influence of the amount of fumed silica on the tensile strength of vulcanizates. As can be seen from the figure, with the increase of the amount of fumed silica, the strength of the vulcanized rubber increases, and the peak is generally reached when the amount is 35-50 parts. There are also many reinforcing mechanisms and models of fumed silicon dioxide on silicone rubber. The more accepted explanation is that the free hydroxyl group on the surface of fumed silicon dioxide forms a physical or chemical combination with silicone rubber molecules, forming a silicone rubber molecular adsorption layer on the surface of silicon dioxide, forming a three-dimensional network structure of fumed silicon dioxide and silicone rubber molecules. Thus, the deformation of silicone rubber molecular chain is effectively limited and its reinforcement effect is achieved. The change of tear strength of vulcanized rubber is similar to that of tensile strength, which increases with the increase of fumed silica reinforcement, increases first with the increase of the amount of fumed silica, and then decreases slightly after reaching the peak.

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