1、 Characteristics of fluorinated surfactants
Fluorinated surfactant (simple FS) is a kind of surfactant with special properties gradually commercialized in recent years. Different from common surfactants, fluorinated surfactants mainly use perfluoroalkyl or perfluoroenyl or partially fluorinated alkyl as the hydrophobic group in the surfactant, and then introduce appropriate linker and hydrophilic group according to the needs. According to the different properties of hydrophilic groups, different series of anionic, cationic, nonionic and amphoteric surfactants are prepared respectively Fluorinated surfactant products.
Due to the special structure of fluorocarbon surfactants, fluorine atoms are substituted for hydrogen atoms on hydrophobic groups in common surfactants, and the structure of C-H bond is changed into the form of C-F bond. Therefore, it shows some unique excellent properties of fluorocarbons. At the same time, it is hydrophobic to both water and oil. The high surface activity of fluorinated surfactants depends on their strong hydrophobicity and low molecular cohesion. It can reduce the surface tension of water to a very low value, but the concentration used is very small. In addition, fluorinated surfactants also show good surface activity, thermal stability and chemical inertness in organic solvents,.
Some studies have shown that the high surface activity of fluorine-containing surfactants is due to the low van der Waals force between the molecules. The small tension required for the surfactant molecules to move from the aqueous solution to the solution surface leads to the aggregation of surfactant molecules on the surface of the solution, forming a strong surface adsorption. These compounds not only have low affinity for water, but also have affinity for hydrocarbons For example, the fluorine-containing surfactant can selectively adsorb on the water surface and reduce the surface tension; however, the hydrocarbon surfactant can be adsorbed on the oil / water interface and the interfacial tension can be reduced In this way, the wettability of aqueous solution will be improved.
2、 Application of fluorinated surfactants
In view of the characteristics of fluorinated surfactant, it has strong application in some fields, especially in industrial field. Its main applications are as follows:
(1) . dispersion
Fluorinated surfactants can be used as dispersants in dispersion polymerization of various fluororesins. Fluorinated surfactants are used as dispersants in the emulsion dispersion polymerization of tetrafluoroethylene, trifluorochloroethylene and vinylidene fluoride. It can be used in electroplating additives, cleaning agents and other surface treatment agents.
(2) . dehydration, release agent
The fluorinated surfactant has good dehydration property, which is helpful for the surface dehydration treatment of some decorative seed plating. Fluorinated surfactant can also be used as release agent, which not only has good demoulding performance for thermoplastic polymers, but also has excellent demoulding performance for thermosetting polymers and silicone rubber. It has no pollution on the parts after demoulding. It can be directly processed (such as printing, painting, pasting, etc.) and can be demoulded several times after using once. The release agent prepared by fluorine-containing surfactant has gradually formed a series of products, including solvent type and water type. It can be used not only in the processing industry of organic polymer elastomer, but also in the processing industry of steel body (such as drawing of copper and steel pipe, pressing needle, stamping of die casting parts, etc.). At present, fluorine-containing (high-efficiency) release agent has been highly appraised by users in plastics, rubber and other processing industries.
(3) . antistatic agent
The antistatic agent, which is made up of fluorine-containing surfactant and integrates cleaning and dust prevention, has been tested by relevant departments: after surface treatment of PVC sheet, its surface resistance decreases from 1012 Ω to 108 Ω. As a result, the phenomenon that the surface of the substrate is easy to dust due to static electricity is greatly reduced. This kind of antistatic agent can be used to clean the surface of magnetic drum and magnetic switch in video recorder. The effect is far superior to that of general cleaning agent or cleaning tape, and the service life of magnetic drum and magnetic switch can be prolonged. The volume of the film or compact disc after cleaning can be increased by 3dB when playing. This kind of antistatic agent can also be used to clean the surface of household appliances, plastic products, TV screens and other high-grade furniture and precision instruments without any side effects.
(4) . leveling agent
When a small amount of surfactant is added into pigment, coating and other products, the phenomenon of solidification can be prevented and the dispersibility can be improved. The surface tension of the coating and ink can be reduced, the wettability can be improved, and the bubbles can be prevented, and the color can be more uniform.
(5) . other applications
Adding fluorine-containing surfactant into floor rainbow wax can improve the luster of floor, increase its wear resistance and pollution resistance. Fluorinated surfactants can also be used as additives for oil recovery, oil collecting agents on the sea, metal preservatives and metal gloss treatment agents.
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