tel
+86-21-6420 0566
There are many kinds of dispersants. According to preliminary estimates, there are more than 1.000 kinds of dispersants in the world. According to their structure, they can be divided into: anionic; cationic; nonionic; amphoteric; electrically neutral; polymer (including high, medium and low molecular weight) dispersants. Commonly used dispersants include inorganic dispersants, such as sodium hexametaphosphate, sodium pyrophosphate, and metal soaps; organic small molecule dispersants, such as various surfactants (including detergents), polyethylene, polypropylene, polystyrene, etc.; polymer dispersants, such as sodium polyacrylate, polyvinyl alcohol, polyethylene glycol, paraffin, etc.
1. The wetting process of solid particles, the dispersant is adsorbed on the surface of the solid particles, reducing the surface tension between the solid and the liquid, making the surface of the condensed solid particles easy to wet.
2. Dispersion or rupture of particle clusters. Dispersants act on particle clusters through static electricity, van der Waals forces or hydrogen bonds, so that particle clusters can penetrate water to generate osmotic pressure, reduce the adhesion between particle clusters and the mechanical work required for rupture, and gradually play the role of dispersants in dispersing particle clusters.
3. Prevent the reaggregation of solid particles, form a double-layer structure on the surface of solid particles, and the polar end of the outer dispersant has a strong affinity with water, which increases the degree of wetting of solid particles by water, and the solid particles are separated by electrostatic repulsion.
1. Dispersion of non-polar solid particles. After the surfactant is added to the suspension, the surfactant can reduce the surface tension of water, and the hydrophobic bonds of the surfactant can be adsorbed on the surface of non-polar solid particles through van der Waals forces. The hydrophilic group extends into the water to increase the hydrophilicity of its surface. Improve the wettability of non-polar solid particles
2. Dispersing and stabilizing effect on charged particles: The particle surface of ionic surfactant carries the same charge. When the charge of ionic surfactant is the same as that of the particle surface, it is difficult for ionic surfactant to be adsorbed on the charged particle surface due to electrostatic repulsion. However, if the van der Waals force between ionic surfactant and particle is strong and can overcome electrostatic repulsion, ionic surfactant can be adsorbed on the particle surface through characteristic adsorption. At this time, the absolute value of zeta potential on the particle surface will increase, making the charged particle more stable in water. Ionic surfactant and particle surface carry opposite charges. If the ionic surfactant used has opposite charges to the particle, when the surfactant concentration is low, the particle surface charge will be neutralized, eliminating electrostatic repulsion, and flocculation may occur; but when the surfactant concentration is high, after the second layer of surfactant ions is adsorbed on the neutralized particles, the solid particles will be charged again, and the solid particles will be dispersed again due to electrostatic repulsion.
The dispersion of particles in organic media is mainly achieved by generating entropy repulsion through steric hindrance. For non-polar particles, the van der Waals force between particles is overcome and the particles are stably dispersed in the organic medium. The surface treatment of organic pigments can be achieved in the following ways:
1. Surface treatment of organic pigments using organic amines
2. Surface treatment of organic pigments using pigment derivatives.
After so much theoretical introduction, the world of dispersants seems to be far away from us. In fact, both our daily life and the scientific research career of materials people are full of various dispersants!
The detergent used for washing clothes and dishes in daily life is a typical dispersant. Detergents disperse stains in water by stripping and coating them, thereby achieving the purpose of washing.
In scientific research, the help of dispersants is indispensable, from adding dispersants before the reaction to evenly disperse the reactants and then generate products of uniform morphology through related chemical reactions, to adding dispersants after the reaction to extract the generated products through related separation methods, and then to adding dispersants in subsequent functional tests to make the product performance more stable.
