Hydrophobic silica: Injecting new vitality into the rubber industry
In the field of materials science, silica is an important nanomaterial, and hydrophobic silica, as its modified product, is emerging in many industries with its unique properties, especially triggering a wave of transformation in the rubber industry.

1.Outstanding performance ensures the excellent quality of rubber
Hydrophobic silica has strong hydrophobicity and low hygroscopicity (moisture content ≤0.5%), which enables it to effectively resist the interference of environmental humidity and enhance the stability of rubber in damp environments. The nanoscale particle size (10-20 nanometers) and high specific surface area (80-300 m²/g) ensure its uniform dispersion in rubber, greatly enhancing the interinterface bonding force with rubber molecules.
In tire manufacturing, the addition of hydrophobic silica can significantly improve the wear resistance of rubber. Due to its high specific surface area and hydrophobicity, it can endow rubber with excellent surface toughness, significantly enhancing the tire's resistance to wear under various complex road conditions and extending the tire's service life. Meanwhile, the addition of hydrophobic silica can also enhance the strength and tensile properties of rubber. Its particles interact closely with the rubber chain, enhancing the overall strength of the rubber and endowing rubber products with higher breaking strength and toughness. This is crucial for tires to withstand the tremendous pressure and tension during vehicle operation.

2. Process optimization to solve the problems of mixing and dispersion
Due to its large specific surface area, traditional silica is prone to absorbing water from the air. The hydroxyl groups between particles can easily form strong hydrogen bonds, leading to secondary aggregation. This makes it extremely difficult to mix and disperse in rubber. When mixed in large quantities, it is also prone to gel formation, hardening the rubber and generating a large amount of heat during the mixing process. Hydrophobic silica, through surface modification, has alleviated this problem to a certain extent.
During the mixing process, to ensure the good dispersion of hydrophobic silica, it is necessary to maintain as high a shear force as possible at the initial mixing stage to break down its aggregated particles, while also avoiding excessive mechanical degradation of the rubber molecular chains. Hydrophobic silica is usually added in small amounts and batches to reduce heat generation. Appropriately increasing the mixing temperature can help remove part of the moisture adsorbed on its surface, reduce the cohesion between particles, and promote the dispersion in the rubber compound.

3. Structural regulation ensures the stable quality of rubber
In silicone rubber, hydrophobic silica, especially fumed hydrophobic silica, is an excellent reinforcing agent, but it has a "structural effect" that causes the rubber compound to harden. As the storage time of rubber extends, its structure will continuously increase, and it may even lead to the inability to be recycled or scrapped. One explanation holds that the end groups of silicone rubber undergo condensation with the hydroxyl groups on the surface of hydrophobic silica. Another viewpoint holds that the siloxane chains of silicone rubber form hydrogen bonds with the hydroxyl groups on the surface of hydrophobic silica.
To prevent structuring, one approach is to add substances that can react with the hydroxyl groups on the surface of hydrophobic silica during the mixing process, such as hydroxyl silicone oil, diphenylsilanediol, silanazane, etc. Take diphenylsilanediol as an example. After mixing, it needs to be treated at 160-200 ℃ for 0.5-1 hour, which can effectively prevent the structuring of silicone rubber. Second, the surface of hydrophobic silica is modified in advance to remove some surface hydroxyl groups, fundamentally eliminating the structural root cause.

4. Broad prospects, promoting the upgrading of the rubber industry
At present, hydrophobic silica has been applied in many fields of the rubber industry, ranging from daily rubber shoe soles to industrial rubber conveyor belts and seals. In the future, as research deepens, on the one hand, the production process of hydrophobic silica can be further optimized to reduce costs and improve the stability and consistency of product quality. On the other hand, expand its application in high-end rubber products such as rubber components for aerospace and high-performance special tires. It is believed that with the joint efforts of scientific researchers and the industrial sector, hydrophobic silica will continue to drive the rubber industry towards higher performance and greater innovation.