Types And Application Fields of Fluorocarbon Surfactants

Fluorocarbon surfactants refer to surfactants with hydrophobic and oleophobic carbon-fluorine segments formed by replacing all or part of the oxygen atoms in the carbon-oxygen chain of non-polar groups with fluorine atoms. They are currently the most active surfactants.

The excellent properties of fluorocarbon surfactants can be summarized as "three highs" and "two hates", namely high chemical activity, high thermal stability, high chemical stability, and hydrophobic and oleophobic properties. Due to its special properties, it has been widely used in many fields such as detergents, food, cosmetics, petrochemicals, coatings, plastics, rubber, fire protection, photosensitive materials, and medical devices.

Generally speaking, fluorocarbon surfactants are divided into two categories: ionic and non-ionic. Among them, ionic surfactants are divided into anionic, cationic and di-carbon surfactants. This article will introduce them one by one:

Anionic fluorocarbon surfactants

Anionic fluorocarbon surfactants are a type of ionic surfactant that is widely used and used earlier. The polar part of the surfactant molecule is negatively charged after dissociation in water. According to the structural classification of anionic polar groups, they can be divided into carboxylate type (RfCOOM), sulfonate type (RfSO3M), phosphate type (RfOPO3M) and sulfate type (RfOSO3M), etc. The first three are mainly used in industry.

Carboxylate fluorocarbon surfactants generally have low solubility in strong acid or high-valent cation aqueous solution, but high thermal stability;

Sulfonate fluorocarbon surfactants have relatively better oxidation resistance and low sensitivity to strong acid and electrolyte;

Phosphate fluorocarbon surfactants have relatively poor foaming properties and are generally used as defoamers.

Cationic fluorocarbon surfactants

Most cationic fluorocarbon surfactants are derivatives of organic amines, which are directly or indirectly connected to quaternary ammonium groups, protonated amino groups or heterocyclic bases by fluorocarbon non-polar chains. This type of fluorocarbon surfactant dissociates into positively charged surface active ions and negatively charged common ions in water, and is sensitive to electrolytes and the pH value of the medium.

Since most surface particles of substances are negatively charged, cationic surfactants are easily adsorbed. This feature makes them often used in wastewater treatment. Because the cationic fluorinated surfactant neutralizes the charge on the surface of the sludge particles after being adsorbed, it makes it easier for the sludge to collide with each other, thereby aggregating to form sediments, achieving the purpose of treating wastewater.

Zwitterionic fluorocarbon surfactants

The presence of alkaline (or cationic) groups and acidic (anionic) groups is a distinct feature of amphoteric fluorocarbon surfactant molecules. The alkaline groups are mainly amino or quaternary ammonium groups, and the acidic groups are mainly sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, etc. Amphoteric fluorocarbon surfactants show the characteristics of anionic surfactants or cationic surfactants at the same time depending on the pH of the medium.

Zwitterionic fluorocarbon surfactants are particularly widely used in the chemical industry and are one of the main ingredients of foam fire extinguishing agents. In addition, due to their excellent emulsifying properties, they are often used as emulsifiers in the manufacturing process of fluorocarbon materials, paper, leather and other products.

Nonionic fluorocarbon surfactants

Nonionic fluorocarbon surfactants can be mainly divided into four categories: polyethylene glycol type, sulfoxide type, polyol type and polyether type, among which polyethylene glycol type is the most used and studied. Nonionic fluorocarbon surfactants are more soluble in water and organic solvents than other types of surfactants, and have better compatibility with other types of surfactants. In addition, since they are not ionized in aqueous solution, they are basically not affected by the pH value of the medium and inorganic salts. However, because the polar group of nonionic fluorocarbon surfactants is composed of a certain number of oxygen-containing ether bonds/hydroxyl groups, they cannot be used in strong oxidizing media to avoid ether bond breakage.