Five surface modification methods and characteristics of silica

At present, the industrial production of white carbon black is mainly based on the precipitation method. The surface of the produced white carbon black contains a large number of polar groups such as hydroxyl groups, which lead to problems such as easy adsorption of water molecules, poor dispersibility, and easy occurrence of secondary aggregation. , thereby affecting the industrial application effect of silica. Therefore, most of silica needs surface modification treatment before industrial application to improve its application performance.

At this stage, the chemical surface modification of silica mainly includes surface grafting modification, coupling agent modification, ionic liquid modification, macromolecular interface modification and combined modification, etc. Although each modification process has its own advantages and characteristics, but the current industrial application is mainly based on coupling agent modification.

1. Surface graft modification of silica

The principle of the surface grafting modification method is to graft the macromolecular polymer with the same properties as the matrix polymer (such as rubber) on the surface of silica by chemical grafting method. On the one hand, it can enhance the force between the particles and the matrix. And change the polarity of the particle surface, on the other hand, it can also improve the dispersibility of silica itself.

At present, the widely used coupling agents include silane coupling agents, siloxane coupling agents and silazane coupling agents. In practical application, the main process of coupling agent modification is divided into four steps: mixing reaction, cooling separation, repeated washing and precipitation.

3. Silica ionic liquid modification

Ionic liquids, also known as room temperature ionic liquids, are molten salts that are composed of organic cations and organic or inorganic anions and are liquid at temperatures below 100°C. Ionic liquid modification is to use ionic liquid modifier instead of traditional organic phase modifier to modify silica. Compared with traditional organic phase modifier, ionic liquid has the advantages of liquid state at room temperature, strong conductivity and high stability. It has the advantages of good solubility and non-volatile, and it is not easy to cause pollution, which is more in line with the requirements of green production, but the modification effect is poor.

The ionic liquid modification process is relatively simple. A certain amount of absolute ethanol is added to the mixed system of silica and ionic liquid, and then put into a constant temperature water bath for reaction. After the reaction is sufficient, the modified silica can be obtained by drying. .

4. Interfacial modification of silica macromolecules

The modifier used in macromolecular interface modification is a macromolecular polymer containing polar groups. During the modification reaction with silica particles, the molecular backbone of the macromolecular interface modifier can be introduced into the polymer. More polar epoxy groups are maintained while maintaining the basic main chain structure, so as to improve the compatibility between the silica particles and the matrix, and achieve a better interface modification effect.

5. Modified with white carbon black

Combination modification is to modify the combination of silica and other materials to improve the overall performance of rubber products by combining their respective advantages. This method can combine the advantages of the two modifiers to enhance the comprehensive properties of the matrix, but the modification effect is closely related to the modifier ratio.

For example, both carbon black and white carbon black are good reinforcing agents in the rubber industry, among which carbon black is one of the commonly used reinforcing agents in the rubber industry. The special structure of carbon black can enhance the tensile and tear strength of rubber materials and improve Its wear resistance, cold resistance and other properties; and white carbon black as a reinforcing agent can significantly improve the rolling resistance and wet skid resistance of rubber products, but its effect alone is not as good as carbon black. A large number of studies have shown that the combination of carbon black and silica as a reinforcing agent can combine the advantages of the two to improve the overall performance of rubber products.

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