Dispersants can be divided into the following categories according to their chemical structure and functional characteristics, which are summarized as follows in combination with authoritative sources:
1. Classification by ionic properties Anionic type
The most common type, the hydrophilic groups with negative charges in the molecule (such as sulfonic acid groups, carboxylic acid groups) disperse particles through electrostatic repulsion.
Representative substances: sodium dodecylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate (AES), sodium oleate, etc.
Features: Suitable for neutral or alkaline environments, and have significant dispersing effects on inorganic pigments and fillers.
Cationic type
The molecule is positively charged and is suitable for negatively charged particles (such as clay, carbon black).
Representative substances: hexadecyltrimethylammonium bromide (CTAB), amine salts, quaternary ammonium salts, etc.
Note: It may react with anionic substances to form precipitation, so it needs to be used with caution.
Nonionic type
It is not charged, and dispersion is achieved through steric hindrance and reduced surface tension. It is insensitive to pH and electrolytes.
Representative substances: fatty alcohol polyoxyethylene ether (AEO), nonylphenol polyoxyethylene ether (NPEO) (gradually eliminated due to environmental issues).
Amphoteric type
Contains both anionic and cationic groups (such as phosphate polymers), adapts to a wide pH range, but may affect material adhesion.
2. Classification by molecular weight
Polymer type
Includes synthetic polymers (such as sodium polyacrylate, polyvinyl alcohol) and natural polymer derivatives (such as cellulose, starch).
Advantages: It forms steric hindrance through long chain structure and has high dispersion stability. It is the main type of superdispersant.
Low molecular type
Such as fatty acids (stearic acid) and alcohols (ethanol), reduce interfacial tension through adsorption, but the stability is weak.
3. Special functional type
Metal soaps
Higher fatty acid metal salts (such as calcium stearate, zinc stearate) have both lubrication and dispersion effects, and the dosage is usually 0.2%-1.5%.
Paraffin
Including liquid paraffin, microcrystalline paraffin, etc., which need to be used in conjunction with other lubricants, and the dosage needs to be strictly controlled (such as microcrystalline paraffin only 0.1%-0.2%).