Application of fluoro surfactant and surface treatment agent

Characteristics and application fields of fluorinated surfactants

1、 The characteristics of fluorinated surfactants

Fluorine containing surfactants (simple FS) are a special type of surfactant with special properties that have been gradually commercialized in recent years. Unlike ordinary surfactants, fluorinated surfactants mainly use perfluoroalkyl, perfluoroalkyl, or partially fluorinated alkyl groups as hydrophobic groups in the surfactant, and then introduce appropriate connecting and hydrophilic groups as needed. Based on the different properties of the hydrophilic groups, different series of fluorinated surfactant products are prepared, including anionic, cationic, non-ionic, and amphoteric types.

Due to the unique structure of fluorinated surfactants, hydrogen atoms on hydrophobic groups in ordinary surfactants are replaced by fluorine atoms, transforming the structure of C-H bonds into C-F bonds. Therefore, it exhibits some excellent properties unique to fluorocarbons, while also possessing both hydrophobic and oil repellent properties. The high surface activity of fluorinated surfactants depends on the strong hydrophobicity and low molecular cohesion of their carbon fluorine bonds. It can reduce the surface tension of water to a very low value, but the concentration used is very small. The application concentration of surfactants for general hydrocarbon chains needs to be between 0.1% and 1%. At this time, the surface tension of the aqueous solution can only be reduced to 30-35 dyn/cm (1 dyn=10-3N/m). When the amount of carbon fluorine bond surfactants is between 0.005% and 0.1%, the surface tension of the aqueous solution can be reduced to below 20 dyn/cm. In addition, fluorinated surfactants also exhibit good surface activity in organic solvents, especially with the introduction of N-substituted perfluorooctamides, which can reduce the surface tension of hydrocarbon solvents by 5-15 dyn/cm. The excellent thermal stability and chemical inertness exhibited by fluorinated surfactants are mainly due to the substitution of hydrophobic groups of hydrocarbon chains by hydrophobic groups of fluorocarbon chains. As the bond energy of C-F bonds (116 kcal/mol) is greater than that of C-H bonds (99.5 kcal/mol), C-F bonds are more stable and less prone to breakage than C-H bonds. Furthermore, due to the larger volume of fluorine atoms replacing hydrogen atoms, the C-C bond is protected by the shielding effect of fluorine atoms, which stabilizes the previously low energy C-C bond. This also stabilizes the C-C bond, giving fluorinated surfactants chemical and thermal stability that hydrocarbon surfactants do not have. For example, the usage temperature of C9F17OC6H4SO3K can be around 300 ℃, and the intermediate C9H17OC6H5 of this compound will not decompose even after being treated at 80 ℃ for 48 hours in 50% sulfuric acid or 25% sodium hydroxide aqueous solution.

Studies have shown that the high surface activity of fluorinated surfactants is caused by the small van der Waals forces between their molecules. The tension required for surfactant molecules to move from aqueous solutions to the surface of the solution is small, resulting in a large number of surfactant molecules aggregating on the surface of the solution, forming strong surface adsorption. These types of compounds not only have a low affinity for water, but also for hydrocarbons, resulting in both water and oil repellent properties. However, their interfacial tension force on the oil/water interface is not strong. For example, when fluorinated surfactants are combined with hydrocarbon surfactants, they can selectively adsorb on the surface of water, reducing surface tension; And hydrocarbon surfactants can adsorb at the oil/water interface, reducing the interfacial tension, which will inevitably improve the wetting performance of the aqueous solution.

2、 The application of fluorinated surfactants

Due to the characteristics of fluorinated surfactants, they have strong applicability in certain fields, especially in industrial fields with multiple applications. Its main applications are as follows:

(1) Dispersant

Fluorine containing surfactants can be used as dispersants in the dispersion polymerization of various fluorine resins. Fluorinated surfactants are used as dispersants in the emulsion dispersion polymerization of fluorinated monomers such as tetrafluoroethylene, trifluoroethylene, and vinylidene fluoride. Its high dispersibility can be utilized in surface treatment agents such as electroplating additives and cleaning agents.

(2) Aqueous film forming foam additive

As the core additive of aqueous film-forming foam extinguishing agent, fluorine-containing surfactant can reduce the surface tension of water to about 20 due to its extremely low surface activity, so that it can spread on the oil surface and achieve the function of extinguishing fire. It can be used in Class B fires, such as aqueous film-forming foam, fluoroprotein foam extinguishing agent, polar resistant solvent extinguishing agent and other foam extinguishing agents.

(3) Coating wetting leveling agent

After adding fluorine surfactants to the coating system, the surface tension of the system can be quickly reduced, thereby improving the wetting and leveling functions of the coating, reducing orange peel, fisheye, and enhancing gloss.

(4) Agricultural film defogger

Fluorine surfactants can be applied to plastic greenhouse films, playing a very good defogging function. When combined with droplets, it can prevent the generation of fog inside the greenhouse in winter.

(5) Solf flux

Fluorine surface activity can be applied in soldering formulas to improve the wetting expansion of the flux and enhance the quality of soldering.

(6) Oil assisted drainage agent

Fluorine surface activity can be applied as a drainage aid in acidizing and fracturing operations during oilfield development, improving the backflow rate of fracturing fluid.