The main working principle of the dispersant and the introduction of the three main functions
What is a dispersant?
Dispersants are auxiliaries that improve and improve the dispersion properties of solid or liquid materials. When the solid dye is ground, a dispersing agent is added to help the particles to pulverize and prevent the agglomerated particles from agglomerating to keep the dispersion stable. The water-insoluble oily liquid can be dispersed into a small liquid bead under high shear stirring. After stirring, the layering is quickly layered under the action of interfacial tension. After adding the dispersing agent, stirring can form a stable Emulsion. Its main role is to reduce the interfacial tension between liquid-liquid and solid-liquid. Thus the dispersant is also a surfactant. The types are anionic, cationic, nonionic, amphoteric and polymeric, and anionic is the most used.
Principle of dispersant
There are two functions of the dispersing agent: one is to speed up the deagglomeration speed of the "agglomerate" and shorten the dispersing time; the second is to delay the re-agglomeration of the particles and keep the particles in a dispersed state for a long time. Most dispersants achieve the purpose of dispersing the filler by a process of wetting, grinding and dispersing, coupling and encapsulation.
Role of dispersant
1, the dispersant acts on the solid particle dispersion process
During the wetting process of the solid particles, the dispersing agent is adsorbed on the surface of the solid particles to lower the surface tension between the solid and the liquid, so that the surface of the agglomerated solid particles is easily wetted.
The dispersion or rupture of the particle group, the dispersing agent acts on the particle group by the action of static electricity, van der Waals force or hydrogen bonding, so that the particle group penetrates the water to generate osmotic pressure, and reduces the degree of adhesion between the particle groups and the mechanical mechanism required for cracking. Work, thereby gradually dispersing the dispersing agent on the particle mass.
Preventing the re-aggregation of solid particles, forming a bilayer structure on the surface of the solid particles, the polar end of the outer dispersant has a strong affinity with water, increasing the degree of wetness of the solid particles by water, and the solid particles are separated by electrostatic repulsion .
2. Dispersion stabilization of surfactant in aqueous medium
For the dispersion of non-polar solid particles, after the surfactant is added to the suspension, the surface tension of the water can be lowered by the surfactant, and the hydrophobic bond of the surfactant can be adsorbed on the surface of the non-polar solid particles by van der Waals force, pro The water base extends into the water to increase the hydrophilicity of the surface. Improves the wettability of non-polar solid particles
Dispersion Stabilization of Charged Particles: The surface of the ionic surfactant has the same charge. When the charge of the ionic surfactant is the same as the surface of the particle, the ionic surfactant is not easily adsorbed due to the electrostatic repulsion. Charged particle surface, but if the van der Waals force between the ionic surfactant and the particle is strong, the ionic surfactant can be adsorbed on the surface of the particle by characteristic adsorption when the electrostatic repulsion can be overcome, and the zeta potential of the particle surface will be caused at this time. The absolute value of the rise is such that the dot particles are more stable in water.
The ionic surfactant has an opposite charge to the surface of the particle. If the ionic surfactant used is opposite to the charge between the particles, the surface charge of the particle will be neutralized when the concentration of the surfactant is low, so that the electrostatic repulsion is eliminated. Flocculation may occur; however, when the concentration of the surfactant is high, after the second layer of surfactant ions are adsorbed on the particles which are electrically neutralized, the solid particles are recharged, and the electrostatic repulsion causes The solid particles are redispersed again.
3. Dispersion stabilization of surfactant in organic media
The dispersion of the particles in the organic medium is mainly achieved by the steric hindrance of the steric hindrance. For non-polar particles, it is stably dispersed in the organic medium to overcome the van der Waals force between the particles. Surface treatment of organic pigments can be achieved in several ways:
(1) Surface treatment of an organic pigment using an organic amine.
(2) Surface treatment of an organic pigment using a pigment derivative.
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