The fluorosurfactant is a surfactant having a special property in which part or all of hydrogen in the hydrophobic group of the hydrocarbon surfactant is replaced by fluorine. Since its hydrophobic base is a perfluorinated or polyfluoroalkyl group, its surface tension is lower than that of hydrocarbons, and therefore the fluorocarbon hydrophobic base is subjected to a greater repulsive force in an aqueous solution, so the fluorosurfactant is water and organic. Solvents exhibit very high surface activity with very low levels of surface activity.
The surface tension (γ) and critical micelle concentration (CMC) of common surfactants and fluorosurfactants are shown in Table 1 .
It can be seen that the hydrophobic group has 8 carbon atoms, but the CMC value of the n-C8H17SO3Na hydrocarbon surfactant is 15 times larger than the CMC value of the n-C8F17SO3Na fluorosurfactant, which is higher than that of the partially fluorinated n-C3F7 (CH2)5SO3Na Fluorosurfactant is 3 times larger.
Fluorine-containing surfactants, like common surfactants, are also classified into four types: anionic, nonionic, cationic, and amphoteric, due to their special structure (fluorine-containing atoms), extremely low surface tension, and resistance to oxidation and corrosion. Such excellent characteristics are mainly used in fields where ordinary surfactants cannot be used or where a large amount of usual surfactants are not effective. The products include C10F19OC6H4SO3Na and 7-trifluoromethyl perfluorooctanoic acid (C8F17COOH). Perfluoroalkoxy carboxylic acids (C9F17O4H), C8F17SO3Na, etc.; foreign companies are mainly based on products supplied by American 3M (such as FC-4430), DuPont, Japan Asahi Glass and other manufacturers. In the synthesis of water-based fluororesin, it is necessary to add fluorine-containing monomers (fluon content of 10% to 20%), and the monomer is gaseous at normal temperature and pressure, so the emulsification is relatively difficult, and the selection of emulsifiers is limited; The dosage is also increasing, which will bring a series of problems to the product application, such as long discharging time, more bubbles, decreased water resistance of the coating, influence of gloss and decorativeness, and the like. Therefore, when various fluororesins and fluoroelastomers are subjected to emulsion polymerization, fluorosurfactants can be considered as emulsifiers. Fluorine-based fluororesins can be synthesized by utilizing the structural similarity of fluorosurfactants and fluoromonomers, and the characteristics of small amount and high surface activity, so as to obtain better emulsification effect, improve the application performance of water-based fluororesins, and reduce the residual in the coatings. Effect of Emulsifier on Performance in Coatings.