Inert : Stabilizes systems and extends storage life (bacterial, enzymatic and chemically inert)
Inorganic : Improves color strength, coverage and water repellency
Hydrophilic : easy dispersion in polar systems
Compatibility : Applicable to different ranges of local recipesPowdered : Easy to combine with other systems, easy to disperse
Moderate price : Reduces overall cost
Practice has proved that the dispersant with the best steric hindrance should have a pigment anchoring group, which is firmly laid on the surface of the pigment particles by chemical adsorption or physical adsorption to ensure that the particles will not produce polymer compounds during Brownian motion.
For desorption, it should also have a free-stretching chain part compatible with the dispersion medium (resin solution) to form an adsorption layer with a certain thickness, which can keep a certain distance between particles. Once the adsorption layer overlaps, the particles can be repelled by the free energy generated in the overlapping area to achieve remote repulsion.
When two particles with an adsorption layer are close to each other and have not overlapped, they will not interact with each other. Overlapping adsorption layers
There will be the following two phenomena:
①Osmotic pressure effect or desolvation effect (AGM);
②The entropy repulsion (AGv) that hinders the movement of the high-score chain in the adsorption layer.
It is a value obtained from measuring the viscosity of the polymer. It is a positive value in a good solvent and a negative value in a poor solvent. Therefore, in a good solvent, AGM>0 is a positive value. The adsorption layer shows a repulsive effect, and this effect increases with the increase of C. If 8 becomes larger, it constitutes a long-distance repulsion.
Regarding AGy, there is no analytical formula like (2-21). Its main principle of action is pp wax uk entropy repulsion. When two particles with an adsorption layer overlap, in the overlapping area, the freedom of movement of the polymer chain link in the liquid phase is reduced due to steric hindrance, and the entropy of the adsorbed molecule is reduced, because a system always faces The direction of entropy increase spontaneously changes, so the particles at this time have a tendency to separate again, which is the result of entropy repulsion. According to calculations, its value is roughly the same as AGM.
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