1. Oil-Leakage-Proof Mechanism
Physical Adsorption: Fumed silica possesses a rich microporous structure and a high specific surface area (200-500 m²/g), enabling it to adsorb oil molecules through surface tension, similar to a sponge absorbing water, effectively preventing oil penetration.

Chemical Adsorption: Its surface silanol groups can form chemical bonds with oil molecules, enhancing adsorption stability, especially providing long-lasting barrier effects against automotive oils such as engine oil and gasoline.

Three-Dimensional Network Structure: Forms a hydrogen-bonded network structure within the rubber matrix, increasing system viscosity and reducing oil migration rates.

2. Aging-Resistant Mechanism
UV Protection: Fumed silica absorbs ultraviolet light and converts it into heat energy, reducing the direct damage of UV rays to rubber molecules and delaying the photo-aging process.

Environmental Isolation: Adsorbs moisture and harmful gases (such as ozone), preventing their chemical corrosion of rubber materials and extending the service life of the sealing strip. Thermal Stability: Wide temperature range (-60℃~150℃), not easily decomposed at high temperatures, maintaining the performance stability of the sealing strip in extreme environments.

3. Synergistic Effects in the Formulation
Reinforcing Effect: As a reinforcing agent, it improves the tensile strength (e.g., replacing carbon black in EPDM compounds) and abrasion resistance of the sealing strip, while also improving tear resistance.

Thixotropic Regulation: Achieves shear thinning properties through a hydrogen bond network, optimizing the processing performance and application thickness of the sealing strip.

Hardness Adjustment: Higher surface activity results in a more significant hardening effect (approximately 1 degree of hardness increase for every 2.5 parts of precipitated silica), requiring a balance between resilience and compression set.

4. Typical Application Cases
EPDM Sealing Strips: In light-colored automotive door and window sealing strips, fumed silica is used instead of carbon black, balancing abrasion resistance and appearance requirements. The dosage is typically 20%-70% of the raw rubber. High weather-resistant formula: When combined with antioxidants and UV absorbers, it is used on long-term exposed components such as sunroof sealing strips to significantly improve weather resistance.