There are many special ceramic forming methods. In the production, the forming method should be selected according to the shape of the product, and different forming methods require different binders.
Binders can be divided into lubricants, plasticizers, dispersants, surfactants (with dispersant and lubricating functions), etc. In order to meet the needs of forming, a combination of multiple organic materials is usually used. When selecting a binder, consider the following:
1) It is a necessary condition that the binder can be wetted by the powder. When the critical surface tension (yoc) or surface free energy (yos) of the powder is greater than the surface tension (yoc) of the binder, it can be well wetted.
2) A good binder is easy to be fully wetted by the powder and has a large cohesive force. When the binder is wetted by the powder, a gravitational effect occurs between the molecules, and a red bond (one-time binding) occurs between the binder and the powder. At the same time, cohesion occurs in the binder molecule due to the orientation, induction, and dispersion effects. (Secondary combination). Although water can also fully wet poplar, but water is volatile, molecular weight is small, cohesion is small, it is not a good binder.
3) The molecular weight of the binding agent should be moderate. In order to fully wet, it is desirable that the molecular weight is small, but the cohesion is weak. As the molecular weight increases, the binding capacity increases. However, when the molecular weight is too large, the cohesion is too large to be easily wetted, and the green body is liable to deform. In order to help the intra-molecular chain segment to move, a plasticizer should be appropriately added at this time. While it is easy to wet, the binding agent is softer and easier to form.
4) In order to ensure product quality, it is also necessary to prevent impurities from being mixed in from the binding agent, raw materials and preparation process, which will cause harmful defects in the product.