Molding of Powders

Injection molding of powder-liquid mixtures at temperatures below the freezing point of the liquid and freeze drying of the frozen parts. 

Rotational molding of vinyl plastisols is similar to the rotational molding of powder or liquid plastics (Chapter 13). Plastisol is placed in the mold and heated while the mold is being rotated. Molded products can include tanks, volleyballs, basketballs, doll heads and bodies, and various automobile parts. 

Thus, FO are acting as adhesion promoters and corrosion inhibitors, whose mechanism can be explained as follows. In the course of thermal molding of powder polymer coatings filled by FO the oxides enter into physical-chemical interactions with the polymer melt. As a result, the oxides are reduced in the surface layer of the particles to metals. This fact is confirmed by... 

Other things being equal, normally, at the same glass concentration the direct molding of powder blended with glass is less expensive than molding glass-reinforced pellet concentrate with unreinforced pellets. This is because the pellet concen-... 

This involves molding of powdered alloy flux (somewhat like plasticine) to damaged areas of a component (blades and vanes typically) and use of elevated temperatures to make that flux integral with the parent material. Some sophisticated repair shops develop their own equivalent process and do the work under license to OEMs or sell the OEM (and other facilities) the rig t to use the process. 

More complex shapes can be made by cold isostatic pressing (CIP). CIP uses deformable mbber molds of the required shape to contain the powder. The appHcation of isostatic pressure to the mold suspended in a pressure transfer media, such as oil, compacts the powder. CIP is not as easily automated as uniaxial pressing, but has found wide appHcation in the preparation of more complex shapes such as spark plug insulators (26). 

Slip casting of metal powders closely follows ceramic slip casting techniques (see Ceramics). SHp, which is a viscous Hquid containing finely divided metal particles in a stable suspension, is poured into a plaster-of-Paris mold of the shape desired. As the Hquid is absorbed by the mold, the metal particles are carried to the wall and deposited there. This occurs equally in all directions and equally for metal particles of all sizes which gives a uniformly thick layer of powder deposited at the mold wall. 

EngrDesHndbk, Rotational Molding of Plastic Powders , AMCP 706-312(1975) 48) Anon,... 

Polyvinyl chloride is also widely used. Rigid polyvinyl chloride is introduced to the mold in powder form. The material is chosen for durable constructions because of its chemical resistance and ease of processing. It incorporates functional additives and demolds easily. Plasticized polyvinyl chloride can be used to produce flexible parts such as balls and soft toy parts. The polyvinyl chloride is introduced to the mold as either a plastisol or powder. A plastisol is a suspension of granules in a plasticizing agent. When heated, the polymer granules absorb the plasticizer and fuse to form a cohesive, flexible material. 

Uses. Production of polymethyl methacrylate polymers for use in acrylic sheet and acrylic molding, extrusion powder, acrylic surface coatings, printing inks, and adhesives used in surgery and dentistry... 

Another important aspect is the proximity of particle layer and thin or thick films, whereby the border between thin and thick films remains ambiguous. Conventional processing of particle assemblies comprises molding of the particle mass, like dry compression or wet casting. In the case of nanoparticles, to form a film is much more rational than conventional powder processing. In a dry procedure, production of nanoparticles and film formation in most cases take place simultaneously. An assembly of nanoparticles can also be formed in a wet procedure by precipitation on the templates or even by simple dip or spin coating from a sol containing nanoparticles. 

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