Category and mechanism of dispersant

Dispersant is widely used in the preparation process of ceramic slurry, which can effectively improve the performance of slurry and increase the stable dispersion effect. 

At present, there are traditional and new dispersants commonly used in ceramic production. The traditional dispersants for ceramics include water glass, sodium humate, 

sodium hexametaphosphate, sodium tripolyphosphate, CMC, sodium citrate and ammonium salt.

For the same raw material, different kinds of dispersants have different effects, and the dispersants can be divided into water-based and non-water-based dispersants according to the different media used. According to the different charge properties of the dispersant, it can be divided into ionic dispersants (anionic and cationic) and non-ionic dispersants. According to the different chemical composition, it can be divided into inorganic dispersant, organic small molecule dispersant and polymer dispersant. Among them, 

the action mechanism of the dispersant is mainly based on the following three kinds:

1, electrostatic stability mechanism

The inorganic dispersant (sodium tripolyphosphate, sodium pyrophosphate, etc.) is ionized into ions and adsorbed on the surface of the particles. 

The surface of the particles forms a double electric layer structure, which increases the surface charge density.

2. Steric hindrance stability mechanism

Steric hindrance mechanism is also known as stereoscopic effect or entropy effect, steric hindrance mechanism is mainly for polymer dispersants, and its superior performance depends on the special anchoring groups and solvation chains in its structure. Common solvation chains (polyether, polyester, polyolefin and polyacrylate), etc., in polar-matched media, the solvation chain extends to the dispersion medium, making the polymers on adjacent particles repulsion due to volume effects, effectively maintaining the suspension stability of the system.

3, static steric stability mechanism.

Static steric stability refers to the stability of electrostatic repulsion and steric hindrance between particles. Static steric stabilization mechanism can prevent the dispersed particles from flocculating and maintain the stability of suspension, and is also the main dispersion mechanism of dispersants with good performance. Static steric stabilization is one of the most effective ways to prepare suspension with high solid content.

There are many types of dispersants, and not all dispersants are suitable for ceramic powders, nor are new dispersants adapted to this material suitable for all ceramic powders. Because the physical and chemical characteristics of different dispersion systems are very different, the role of dispersants is also very complex, it is necessary to verify the effect of various dispersants on a certain raw material through experiments, and determine the various parameters of the dispersant on the slurry viscosity, settlement, PH value to analyze and adjust various factors to select the appropriate dispersant.