Fluorinated surfactants have high chemical stability

2020-09-21 16:06:31

The unique properties of fluorinated surfactants are often summarized as "three high" and "two hydrophobic", that is, high surface activity, high thermal stability and high chemical stability; its fluoroalkyl groups are both hydrophobic and oleophobic.

The low surface tension of fluorinated surfactant aqueous solution can reach below 20 mN / m, even to about 15 Mn / m. Generally, the application concentration of hydrocarbon chain surfactant should be between 0.1% and 1%, and the surface tension of aqueous solution can only be reduced to 30 ~ 35MN / m, while the surface tension of aqueous solution can be reduced to less than 20Mn / m when the dosage of fluorocarbon surfactant is 0,005% ~ 0,1%. Fluorinated surfactants are so highly active that their aqueous solution can be spread on the surface of hydrocarbon oil.

Fluorinated surfactants have high heat resistance, such as solid potassium perfluoroalkyl sulfonate, which can be used at temperatures above 300 ℃ after being heated to above 420 ℃. Fluorinated surfactants have high chemical stability, which can resist the action of strong oxidants, strong acids and strong bases, and can still maintain good surface activity in this solution. If it is made into oil soluble surfactant, the surface tension of organic solvent can also be reduced.

The results show that the high surface activity of fluorinated surfactants is due to the low van der Waals gravitation 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 the surfactant molecules on the surface of the solution, resulting in the formation of strong surface adsorption. This kind of compounds not only have low affinity for water, but also have low affinity for hydrocarbons, Therefore, it is hydrophobic to both water and oil, but its ability to act on the interfacial tension of oil / water interface is not strong. For example, when the fluorine-containing surfactant is combined with the hydrocarbon surfactant, the fluorine-containing surfactant can selectively adsorb on the surface of water, thus reducing the surface tension; while the hydrocarbon surfactant can be adsorbed on the oil / water interface to reduce the interfacial tension, This will certainly improve the wettability of the aqueous solution.

Fluorinated surfactant is an important variety of special surfactants, which has many irreplaceable uses. Fluorinated surfactants mainly use perfluoroalkyl or perfluoroenyl or partially fluorinated alkyl as hydrophobic groups, and then introduce appropriate linkers and hydrophilic groups as required. According to the different properties of hydrophilic groups, different series of fluorinated surfactants, such as anionic, cationic, nonionic and amphoteric, are prepared.