1.Thousand-pressure method Polyvinyl butyral, etc. 1~5,
2.Pouring method Acrylic resin 1~3,
3. Extrusion method Methyl cellulose, etc. 5~15,
4. Injection method Polypropylene, etc. 10~25,
5. Isostatic pressing method Ammonium polycarboxylate, etc. 0~3
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Binders can be divided into: lubricants, plasticizers, dispersants, surfactants (with dispersant and lubrication functions), etc. In order to meet the forming needs, multiple A combination of organic materials. When choosing a binding agent, consider the following factors:
1) It is a necessary condition that the zirconia ceramic bonding agent 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, the zirconia ceramic can be well wetted.
2) A good zirconia ceramic bond is easy to be fully wetted by the powder and has high cohesion. When the zirconia ceramic bond is wetted by the powder, attraction occurs between the molecules.Due to the action of force, red bonding (primary bonding) occurs between the zirconia ceramic bonding agent and the powder. At the same time, cohesion (secondary bonding) occurs within the zirconia ceramic bonding agent molecules due to orientation, induction, and dispersion effects. Although water can also fully wet the poplar material, water is volatile, has a small molecular weight, and has low cohesion, so it is not a good zirconia ceramic bonding agent. According to the order of cohesion of various organic materials, expressed in terms of bases, they can be arranged as follows:
CONH ＞－CONH2＞COOH＞OH＞－NO2＞－COOC2H5＞一COOCH5＞－CHO＞＝CO＞－CH3＞＝CH2＞－CH2< /span>
3) The molecular weight of the zirconia ceramic binder should be moderate. For adequate wetting, you want a small molecular weight but weak cohesion. As the molecular weight increases, the binding ability increases. However, when the molecular weight is too large, the cohesive force is too large and it is not easy to be wetted, and the green body is easily deformed. In order to help the chain segment movement within the molecule, a plasticizer should be added appropriately at this time to make the binder softer and easier to form while making it easy to wet.
4) In order to ensure the quality of zirconia ceramic products, it is also necessary to prevent the mixing of impurities from binders, raw materials and preparation processes to cause harmful defects in zirconia ceramic products. In the preparation of zirconia ceramic raw materials, mechanical methods such as crushing and mixing are used with zirconia ceramic binders and dispersants to achieve dispersion and contain no agglomerated particles as much as possible.
Zirconium oxide ceramic binder is affected by the type and molecular weight, the properties of the surface of the zirconia ceramic particles and the solubility of the solvent. It is adsorbed on the surface of the raw material particles and is stabilized through three-dimensional The effect is to prevent the agglomeration of powder raw materials.
In the molding process, the binder gives plasticity to the raw material, has a water-retaining function, and improves the strength and workability of the molded body. Generally speaking, since the zirconia ceramic binder hinders the sintering of ceramics, it should be heated during the degreasing process. Decompose and volatilize. Therefore, it is necessary to choose organic materials that can be easily dispersed and do not contain harmful inorganic salts and metal ions to ensure the quality of zirconia ceramic products!
