The dispersion and reinforcement of fumed silica in low-hardness silicone rubber is a process requiring precise control, involving several key factors. The following are the core points summarized based on available data:

Dispersion Control
Due to its large specific surface area and numerous surface hydroxyl groups, fumed silica is prone to agglomeration and is difficult to mix. To improve dispersibility, the following should be noted:

**Batch Addition:** Adding fumed silica in small batches reduces heat generation and avoids gel formation.
**Mixing Process:** Maintaining high shear force during initial mixing and appropriately increasing the temperature to remove surface-adsorbed moisture.
**Surface Modification:** Using silane coupling agents (such as hexamethyldisilazane) to convert hydrophilicity to hydrophobicity improves compatibility with silicone rubber. For example, the reinforcing effect of fumed silica is optimal when the treatment agent dosage is 35 parts.

Optimization of Reinforcing Effect
Silica can significantly improve the mechanical properties of silicone rubber, but a balance between dosage and performance is necessary:
Optimal Dosage: Experiments show that adding 40 parts of silica results in the best elongation at break; 50 parts achieves peak tensile strength (9.43 MPa), but excessive addition can lead to agglomeration.

Structure Inhibition: Silica easily induces hardening of the compound (structural effect), which can be mitigated by adding substances such as hydroxyl silicone oil or diphenylsilanediol, or by pre-modifying the surface hydroxyl groups.

Performance Balancing: While silica improves tear strength, it may reduce abrasion resistance. A balance between Mooney viscosity and processability needs to be achieved through formulation adjustments (such as adding softeners).

Role of Additives
Treatment Additives: For example, dimethyldiethoxysilane can improve tear strength, but excessive addition will reduce tensile strength. The optimal dosage is 5 parts.

Water Dosage: An appropriate amount of water is required during treatment (e.g., a mass ratio of hexamethyldisilazane to water of 5:1). Insufficient or excessive water will affect the treatment effect.

Summary: The application of fumed silica in low-hardness silicone rubber requires achieving a balance between dispersion and reinforcement through surface modification, process optimization, and formulation adjustment. Key control points include the dosage of the treatment agent, mixing conditions, and the ratio of auxiliary agents to balance mechanical properties and processability.