An emulsifier is a stabilizer for emulsions and is a surfactant. The function of the emulsifier is to form a film or an electric double layer when it is dispersed on the surface of the dispersoid, so that the dispersed phase can be charged, so that the droplets of the dispersed phase can be prevented from coagulating with each other, so that the formed emulsion relatively stable. For example, a certain amount of emulsifier is added to the original drug (solid) or crude oil (liquid) of the pesticide, and then dissolved in an organic solvent, and evenly mixed to form a transparent liquid, called emulsifiable concentrate. Commonly used emulsifiers are: surfactants, oil-water balance coefficient is higher, suitable for the preparation of water-in-oil emulsion; oil-water balance coefficient is lower, suitable for the preparation of oil-in-water emulsion; natural emulsifier is mostly hydrophilic glue, It can improve the viscosity of the continuous phase and increase the stability of the emulsion. It is suitable for formulating oil-in-water emulsions, solid particulate emulsifiers, and auxiliary emulsifiers.
Emulsifiers can be divided into two categories, natural and synthetic. According to the properties of the emulsion system formed in the two phases, it can be divided into two types: oil-in-water (O/W) type and water-in-oil (W/O) type.
The most commonly used measure of emulsification performance is the hydrophilic-lipophilic balance (HLB value). A low HLB value indicates that the emulsifier has strong lipophilicity and is easy to form a water-in-oil (W/O) type system; a high HLB value indicates that the hydrophilicity is strong, and an oil-in-water (O/W) type system is easily formed. Therefore, the HLB value has a certain degree of additivity. With this property, emulsions of different HLB value series can be prepared.
