Agglutination is a technique based on the in-situ polymerization of organic monomer binder to form a polymer network and agglomerate the powder particles together. The advantages of injection moulding are:
1) There is no special requirement for powder, and parts with large size and complex shape and wall thickness can be prepared; 2) The mold can choose a variety of materials, short molding cycle; 3) High strength of wet and dry billet, can be machined, low content of organic matter in billet, good uniformity of performance of billet and sintered body, easy to control process, process and operation is relatively simple; 4) Simple equipment, low cost.
Injection process flow chart
The preparation process of the injection type is well understood, there are not too many complex steps, but the complexity is that the solvent required in the injection type technology will greatly affect the preparation process.
1, Depending on whether the required solvent is an aqueous solution
Gelatinized gel systems are usually divided into two main systems: non-water-based gel system and water-based gel system.
Alcohols, hydrocarbons, ethers, ketones and other organic solvents are commonly used in non-aqueous gel systems. The system has its own low viscosity and low vapor pressure at the temperature of cross-linking reaction. The main disadvantage is that organic solution will cause environmental pollution, which is not conducive to environmental protection. Water-based gel system, which is mainly acrylic ester system and acrylamide (AM) system at present, has become one of the most active ceramic injection molding methods in recent years because of the simple operation of water-based injection molding process, low raw material cost and environmental protection.
However, the neurotoxicity level of AM is level 4, and it has strong water solubility and can enter the human body through the skin and mucous membranes. Therefore, it is urgent to develop a low toxicity or non-toxic injection type system.
2, According to the organic polymerization method
(1) free radical reaction system: In the free radical polymerization reaction, oxygen has the effect of hindering polymerization, resulting in spalling on the green surface, so there are certain requirements for the atmosphere. (2) Nucleophilic addition reaction system: effectively prevent the surface stripping phenomenon caused by oxygen hindering free radical polymerization, which is an important factor in the casting of ceramic hydrogels under air conditions. (3) Natural gel system: Environmental protection issues are increasingly attracting attention, and natural gel systems have been developed.