Definition of surfactant:
In the dyeing and finishing additives there are most varieties belong to surfactants, they play a role in refining, emulsifying, wetting, dispersing, foaming and other roles, the role of the entire dyeing and finishing process is very important and has an irreplaceable position. So today we will take you a brief understanding of what is a surfactant and its characteristics.
Simple definition: when it is dissolved in water (or solution system), it can be adsorbed at the interface of heterogeneous phases, thus reducing or improving the surface tension of water and air or the interfacial tension of other substances.
Surfactant in the dyeing and finishing process generally do not participate in the reaction, mainly through its physicochemical and colloidal chemical properties, so that the dyes or fibers or the main chemicals to play a better role.
Structural properties of surfactants:
The nature of surfactant is determined by its structure, no matter what type of surfactant, in its molecule is always non-polar, lipophilic hydrocarbon chain part and polar hydrophilic group composed of two parts.
These two parts are often located on both sides, forming an asymmetric structure, such a structure so that the molecule has a part of the water molecules have an affinity for water differentiation, while the other part of the tendency to break away from the water surroundings, this tendency determines the surfactant can be oriented on the surface of the solution arrangement, affecting the surface tension of the water, but also determines the hydrophobic groups close to each other and aggregation, the formation of gel groups in solution. Hydrophilic groups can be differentiated by water to make them soluble in water, and the strength of water differentiation is determined by the strength of hydrophilic groups and the ratio of hydrophilic and lipophilic groups in its molecular structure. So all the properties presented by surfactants depend on its hydrophilic and lipophilic group structure.
Classification of surfactants:
Surfactants are categorized in various ways, generally according to their ionic type.
Anionic surfactants: generally there are two types, acid salts and ester salts. They can be dissociated in water, and the part that plays a role in surface activity is the anionic group. Anionic surfactants have good dispersing, dirt-carrying and solubilizing functions, and are generally used as washing, refining, penetrating and emulsifying auxiliaries.
Nonionic surfactants: These surfactants do not dissociate in water and do not carry an electric charge. Generally there are ether-type, amide-type, polyether-type polyoxyethylene polyoxypropylene ether type, alkyl polyglycoside type. The hydrophilic part is mostly composed of polyoxyethylene, and its hydrophilicity is controlled by the number of oxyethylene contained. Nonionic surfactants have good emulsification, penetration and washing effects, and are generally used as washing, emulsification, refining, soaping and other additives.
Cationic surfactants: These surfactants can be dissociated in water, and after ionization, they play a role in surface activity partly with cationic groups. Generally, there are fatty amine salts, alkyl imidazoline salts, pyridine salts and polyethylene polyamine salts. Cationic surfactants are mainly used in dyeing and finishing auxiliaries as softening, dye-blocking, anti-bacterial and anti-mildew, color-fixing, anti-static and other auxiliaries.
Amphoteric surfactants: They can also be ionized in water, and after ionization, the surface-active part carries two kinds of charge groups at the same time, so they become amphoteric surfactants. Generally, there are betaine type, amino acid type and other types. In dyeing and finishing auxiliaries, they are generally used as fabric leveling agents, softeners, antistatic and other auxiliaries.
5. Special surfactants: here generally refers to polymer surfactants. Characterized by high molecular weight and different charges, they are generally anionic, cationic, nonionic and amphoteric. Commonly used water-soluble macromolecules are sodium alginate, polyacrylamide, polyethylene glycol and so on. There are also some special active agents, such as fluorine-containing and silicone surfactants. In dyeing and finishing auxiliaries are generally used as thickening, flocculating, anti-staining, waterproofing, oil-proofing and other auxiliaries.
