How to Choose Between Hydrophilic and Hydrophobic ...

In the realm of nanomaterials, fumed silica emerges as a versatile substance with properties that can be tailored for various applications. One significant distinction lies in its hydrophilic and hydrophobic attributes. Understanding the factors influencing the selection between these two forms of fumed silica is paramount for optimizing product performance. Let’s delve into the world of fumed silica and explore the key considerations that shape this choice.

The Genesis of Fumed Silica

Fumed silica comes into being through a high-temperature hydrolysis process involving silicon halides in a hydrogen-oxygen flame. The resultant nanoscale amorphous powder exhibits unique characteristics that find utility across diverse industries.

What Are The Materials And Processes Used To Manufacture Fumed Silica?

Fumed silica, or pyrogenic silica, colloidal silicon dioxide, is an amorphous white inorganic powder that has high specific surface area, nano-scale primary particle size and a relatively high (among silica…

Hydrophilic Fumed Silica: Properties and Applications

Hydrophilic fumed silica is characterized by surface hydroxyl groups that readily interact with water molecules, endowing it with water-attracting qualities. This type of fumed silica smoothly wets surfaces and disperses within water-based systems. It’s particularly suited for non-polar or low-polarity products.

Applications of hydrophilic fumed silicahydrophilic fumed silica extend to non-polar systems such as methyl siloxanes, polyvinyl chloride (PVC), and various hydrocarbons. It also finds a place in low-polarity systems like MS Polymers and STP-E, contributing to stability and dispersion.

Hydrophobic Fumed Silica: A Shift in Properties

By treating hydrophilic fumed silica with modifying agents, its surface hydroxyl groups can be either reacted or masked, leading to hydrophobicity. Hydrophobic fumed silica repels water, making it ideal for medium to high-polarity systems.

In contrast to its hydrophilic counterpart, hydrophobic fumed silica suits systems like polyurethanes, polyols, epoxy resins, and other polar environments. Its reduced polarity aligns with higher-polarity product systems.

Why Fumed Silica Need To Be Treated To Be Hydrophobic?

Fumed silica is available in both hydrophilic and hydrophobic forms. However, its hydrophilic nature makes it unsuitable for certain applications. Untreated fumed silica has many silanol groups on its surface,…

Factors Influencing the Choice

Three primary factors govern the selection between hydrophilic and hydrophobic fumed silica:

1. Inherent Properties of Fumed Silica

The polarity of the product system determines the compatibility of fumed silica. Hydrophilic fumed silica aligns with non-polar and low-polarity systems, whereas hydrophobic fumed silica is suited for medium to high-polarity environments. As the polarity of the system increases, the polarity of the fumed silica should decrease.

2. Application System and Scenario

The nature of the application system is a key determinant. Hydrophilic fumed silica finds favor in non-polar systems such as PVC, while hydrophobic fumed silica is fitting for epoxy resins and high-polarity environments. Matching the fumed silica polarity to the application system is crucial for optimal performance.

3. Cost Considerations

Cost plays a significant role in the selection process. Hydrophilic fumed silica is generally more cost-effective than its hydrophobic counterpart. This aspect is vital for applications where cost sensitivity is a primary concern.

conclusion

In conclusion, the choice between hydrophilic and hydrophobic fumed silica rests on a careful analysis of the product’s nature, the application system, cost considerations, and the desired dispersion method. Hydrophilic fumed silica is best suited for products requiring interaction with water molecules, while hydrophobic fumed silica serves well in scenarios where water repellency or specific processing methods are required. Ultimately, the decision should be aligned with the product’s requirements and the overall cost-effectiveness of the chosen fumed silica variant.

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                   The difference and application of hydrophilic silica and hydrophobic silica

Silica itself is hydrophilic, hydrophobic silica is modified by hydrophobic groups. Hydrophilicity is usually added to the aqueous system. In the organic system, the hydrophilic silica can not be well dispersed after being added, and the hydrophobic silica can be well dispersed.

Hydrophilic silica

Hydrophilic silica was prepared by hydrolysis of volatile chlorosilane in oxyhydrogen flame. From a chemical point of view, these loose white powders are composed of high-purity amorphous silica. Hydrophilic silica can be wetted with water and dispersed in water. In addition to the traditional industrial fields, such as polyester, silicone, paint and coating, hydrophilic silica products are more and more successfully used in high-tech fields. The nano particle characteristics and high purity of silica make its application in electronic and optical fiber industry play a leading role. The product of hydrophilic fumed silica has amorphous structure by X-ray analysis. According to different market and application fields, we can provide products with different particle sizes and specific surface areas. Some fumed silica products can be compressed and supplied. Some products are medical grade.

Functions of hydrophilic silica: suitable for processing and adjusting to good rheological property; reinforcement of silicone elastomer; thickening of non-polar liquid; flow aids for food and industrial powder; high chemical purity; excellent insulation performance even under high temperature; transformation of liquid into powder, such as medicine and cosmetics.

Hydrophobic silica

Hydrophobic silica is prepared by the chemical reaction between hydrophilic silica and active silane (such as chlorosilane or hexamethyldisilazane). It is hydrophobic (hydrophobic) and cannot be dispersed in water. In order to solve some special technical problems in the industry, various types of hydrophobic silica were developed. For example, the hydrophobic silica is produced by treating the modified hydrophilic silica with silane or siloxane. In the final product, the chemical treatment agent is combined on the original hydrophilic oxide by chemical bond. In addition to the above advantages of hydrophilic products, hydrophobic silica products are characterized by low moisture absorption, good dispersion, and rheological regulation ability even for polar systems. Some products, after structural modification on the basis of hydrophobic treatment, can provide further help for customers to develop new products and improve product performance. For example, in the liquid system, hydrophobic silica can reach a high content, but has little effect on the viscosity of the system.

Functions of hydrophobic white carbon black: suitable rheology in processing and use; thickening of polar liquid, such as epoxy resin; reinforcement of silicone elastomer; high addition, such as in molded products; good hydrophobicity, improving corrosion resistance; improving dielectric properties, such as in cable composite; powder flow aid, such as in powder coating and fire extinguishing agent; improving resistance in coating and plastic Scratched.

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