Hydrophobic fumed silica is a specially treated form of silicon dioxide that exhibits exceptional hydrophobicity and a range of other beneficial properties. This material is primarily prepared by reacting general hydrophilic silicon dioxide with silane coupling agents and other treatment agents under controlled conditions. The resulting product is a solid powder silicon dioxide with polysiloxane grafted onto its surface, imparting it with a hydrophobic contact angle that can reach between 70 and 150 degrees.
Properties and Characteristics
Hydrophobic fumed silica is characterized by its high hydrophobicity, high bulk density, and good operability. These properties make it easy to mix into resins and other matrices in a short period and achieve a high degree of dispersion. The powder's high porosity and surface treatment further enhance its performance in various applications.
The material also demonstrates good defoaming, thickening, leveling, and anti-sedimentation properties. These characteristics make it suitable for use in a wide range of industries, including textile dyeing and finishing, defoamers, lubricating oils, unsaturated polyester resins, powder fire extinguishing agents, and silicone rubber.
Applications
In the textile industry, hydrophobic fumed silica can be used as a defoamer and to improve the leveling and anti-sedimentation properties of dyes and finishes. In lubricating oils, it enhances the oil's performance by providing thickening and anti-wear properties.
The material's use in unsaturated polyester resins and silicone rubber is particularly noteworthy. In these applications, hydrophobic fumed silica acts as a reinforcing filler, improving the physical strength and tensile strength of the final product. It also helps to control the rheology of the resin or rubber during processing.
Additionally, hydrophobic fumed silica has found applications in powder fire extinguishing agents, where its high porosity and hydrophobicity contribute to improved fire-suppressing performance. In battery partitions and polishing materials, the material's unique properties enable it to enhance the durability and performance of these products.
Preparation and Production
The preparation of hydrophobic fumed silica involves reacting hydrophilic silicon dioxide with silane coupling agents and other treatment agents. This reaction takes place under controlled conditions to ensure the grafting of polysiloxane onto the silicon dioxide surface. The resulting powder is then carefully processed to achieve the desired particle size and porosity.
Research and Development
Ongoing research and development efforts are focused on improving the properties and performance of hydrophobic fumed silica. One area of interest is the use of cyclic dimethylsiloxane to hydrophobize fumed silica, which can result in materials with higher oleophilic degrees and tapping bulk densities.
Another area of research is the application of hydrophobic fumed silica in 3D printing. Studies have shown that fumed silica nanoparticle-based yield-stress suspensions can be used as hydrophobic support baths to enable 3D extrusion printing of various hydrophobic ink materials. This technology has the potential to revolutionize the manufacturing of complex 3D structures in fields such as soft robotics and microfluidics.
Conclusion
Hydrophobic fumed silica is a versatile material with a wide range of applications in various industries. Its high hydrophobicity, high bulk density, and good operability make it an ideal choice for use in textile dyeing and finishing, defoamers, lubricating oils, unsaturated polyester resins, powder fire extinguishing agents, and silicone rubber. With ongoing research and development efforts, the properties and performance of hydrophobic fumed silica are expected to continue to improve, further expanding its potential applications.