Features of Fluorosurfactants
fluorosurfactant is a surfactant with special properties that has been gradually commercialized in recent years. Fluorosurfactants mainly use perfluoroalkyl or perfluoroalkenyl or partially fluorinated alkyl groups as the hydrophobic part of the surfactant, and then introduce appropriate linking groups and hydrophilic groups. Different series of fluorine-containing surfactants can be prepared according to the different properties of the groups, such as anionic, cationic, nonionic and amphoteric.
Due to the special structure of fluorine-containing surfactants, the hydrogen atoms on the hydrophobic groups in ordinary surfactants are replaced by fluorine atoms, so it shows some excellent properties unique to fluorocarbons, and it has both hydrophobicity. And oil repellent properties. The high surface activity of fluorosurfactants depends on the extremely strong hydrophobicity and low molecular cohesion of their molecular carbon-fluorine bonds. It can reduce the surface tension of water to very low values while using very small concentrations. When the dosage is 0.005% to 0.1%, the surface tension of the aqueous solution can be reduced to below 20 dyn/cm. In addition, fluorine-containing surfactants also show good surface activity in organic solvents, especially the introduction of N-substituted perfluorooctamides, which can reduce the surface tension of hydrocarbon alkyne solvents by 5-15 dyn/cm, and contain N-substituted perfluorooctamides. The excellent thermal stability and chemical inertness exhibited by fluorosurfactants are mainly due to the fact that after the hydrophobic group of the fluorocarbon chain replaces the hydrophobic group of the hydrocarbon chain, the bond energy of the CF bond (116kcal/mol) is greater than that of the CH bond. The bond energy (99.5kcal/mol), so the CF bond is more stable than the CH bond, and it is not easy to break. And because the fluorine atom replaces the hydrogen atom, the volume of the fluorine atom is larger than that of the hydrogen atom, so that the CC bond is protected by the shielding effect of the fluorine atom, so the CC bond with the original bond energy is not too high. The CC bond is also stabilized, which gives fluorosurfactants chemical and thermal stability that hydrocarbon surfactants do not have. For example: C9F17OC6H4SO3K can be used at a temperature of about 300 ℃, and the intermediate C9H17OC6H5 of this compound will not decompose in 50% sulfuric acid or 25% sodium hydroxide aqueous solution at 80 ℃ for 48 hours.
Studies have shown that the high surface activity of fluorosurfactants is caused by the small van der Waals forces between the molecules, and the small tension required for the active agent molecules to move from the aqueous solution to the surface of the solution, resulting in the surfactant molecules on the surface of the solution. Aggregate in large quantities to form strong surface adsorption, and this type of compound not only has a small affinity for water, but also has a small affinity for hydrocarbons, so it forms both hydrophobic and oleophobic properties, but it has a low affinity for oil/water. The interfacial tension force of the interface is not strong. For example, if a fluorosurfactant is used in combination with a hydrocarbon surfactant, the fluorosurfactant can be selectively adsorbed on the surface of the water to reduce the surface tension; Surfactants can be adsorbed on the oil/water interface and reduce the interfacial tension, which will definitely improve the wetting performance of the aqueous solution.
Application of Fluorosurfactants
In view of the characteristics of fluorine-containing surfactants, it has strong applicability in some fields, especially in the industrial field. Its main applications are as follows:
(1). Dispersion
Fluorosurfactants can be used as dispersants in the dispersion polymerization of various fluororesins. Fluorine-containing surfactants are used as dispersants in the emulsion dispersion polymerization of fluorine-containing monomers such as tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride. Its high dispersion properties can be utilized in surface treatment agents such as electroplating additives and cleaning agents.
(2). Dehydration and release agent
Fluorosurfactant has good dehydration, which is very helpful for the surface dehydration treatment of some decorative plating seeds. Fluorine-containing surfactants can also be used as mold release agents, which not only have good mold release properties for thermoplastic polymers, but also have excellent mold release properties for thermosetting polymers and elastomers containing silicone rubber. There is no pollution to the workpiece after demoulding, and it can be directly processed for secondary processing (such as printing, painting, pasting, etc.), and can be demolded multiple times after one use. The release agent prepared from fluorine-containing surfactant has gradually formed a series of products, including solvent-based and water-based, which can not only be used in the processing industry of organic polymer elastomers, but also in the processing industry of steel bodies. (such as drawing of copper, steel pipe, pressing needle, stamping of die-casting parts, etc.) can also be used. At present, fluorine-containing (high-efficiency) mold release agents have been highly praised by users in plastics, rubber and other processing industries.
(3).Antistatic agent
The antistatic agent, which is made up of fluorine-containing surfactant, integrates cleaning and dust-proofing has been tested by relevant departments: after the surface treatment of the PVC film base, its surface resistance is reduced from the original 1012Ω to 108Ω. As a result, the phenomenon that the surface of the film base is easy to be vacuumed due to static electricity is greatly reduced. Using this kind of antistatic agent to clean the surface of the magnetic drum and the magnetic switch in the video recorder is far superior to the general cleaning agent or cleaning tape, and can prolong the service life of the magnetic drum and the magnetic switch. After cleaning, the volume of the film or LP can be increased by 3dB during playback. This antistatic agent can also be used to clean the surface of household appliances, plastic products, TV screens and other high-end furniture, precision instruments, etc. Use with dust without any side effects.
(4). Leveling agent
After adding a small amount of surfactant in pigments, coatings and other products, it can prevent the solidification phenomenon and improve the dispersion. Adding it to coatings and inks can reduce its surface tension, improve wettability, prevent bubbles, and make the color more uniform.
(5). Other applications
Adding fluorine-containing surfactants to floor rainbow wax can improve the gloss of the floor, increase its wear resistance and anti-pollution. Fluorosurfactants can also be used as auxiliary agents for petroleum recovery, oil collectors on the sea surface, metal preservatives and metal luster treatment agents, etc.
