Silica reinforcement is a technique used to enhance the strength of elastomers by incorporating a filler system consisting of silica and a coupling agent. The addition of these reinforcing fillers brings about changes in both the physical and dynamic-mechanical properties of the material, resulting in heightened strength and decreased elasticity. The ability to vary the types and quantities of fillers offers flexibility in tailoring the properties of rubber to specific needs. The widespread utilization of silica in various industries, including automotive, aerospace, construction, and consumer goods, showcases its importance. By incorporating silica reinforcement, manufacturers are able to produce rubber products with exceptional mechanical strength and durability. This makes them well-suited for a range of applications such as tires, seals, gaskets, conveyor belts, and industrial hoses. The enhanced properties achieved through silica reinforcement contribute to the reliability and performance of these rubber products in demanding environments.

The Classification of Silica

Silica can be divided into fumed silica and precipitated silica

Fumed Silica

Fumed silica is a commonly used reinforcing agent for silicone rubber. The properties of fumed silica particles, such as size, specific surface area, surface properties, and structure, are influenced by factors like the feed gas ratio, combustion speed, and residence time of SiO2 in the combustion chamber.

Finer particles of fumed silica have larger specific surface areas, which result in better reinforcement effects. However, their operational performance may be compromised. Conversely, thicker particles have smaller specific surface areas, leading to poorer reinforcement effects but better operability.

When fumed silica is used as a reinforcing agent, the vulcanizates (cured rubber) exhibit high mechanical strength and good electrical properties. Fumed silica can also be combined with other reinforcing agents or weaker reinforcing agents to create rubber materials with different properties.

Precipitated Silica

The properties of precipitated silica are influenced by precipitation conditions, including acidity and temperature. In comparison to silicone rubber compounds reinforced with fumed silica, the compound reinforced with precipitated silica typically exhibits slightly lower mechanical strength. The dielectric properties, especially after dampening, may be poorer. However, precipitated silica offers better heat-resistant aging properties and significantly lower rubber mixing costs. When high mechanical strength is not a critical requirement, a combination of precipitated and fumed silica can be employed.

White carbon black can undergo treatment with suitable compounds to achieve a hydrophobic surface. Two methods for addressing this are the liquid-phase method and the gas-phase method. The liquid-phase method provides better control over conditions, ensures stable product quality, and offers good treatment effects. However, this method involves complex processes and requires solvent recovery. The gas-phase method, on the other hand, is simpler in terms of process but does not provide as stable product quality and exhibits a less desirable treatment effect.