Cold Isostatic Pressing

    Another variant of Isostatic pressing is the cold isostatic pressing (CIP). In isostatic compaction, a uniform pressure is applied to all external surfaces of the powder body simultaneously. However, when the isostatic pressing is performed at room temperature, it is referred as CIP. There are two main processing routes such as wet bag and dry bag isostatic pressing. In both techniques, the powder is sealed in an elastomeric mold, which is then pressurized by a liquid which makes the powder becomes set under (hydrostatic) pressure. Elastomers such as natural and synthetic, silicon rubber, polyurethane and poly vinyl-chloride prove to be good candidates for bag materials.

   Characteristic of CIP provides more uniform pressure distribution on the compact compared to density gradients obtained with die pressing. Thus, CIP produces high density and homogeneity of density distribution in compacts and is frequently applied for densification of ceramic powders. Pore size distribution in green bodies was noticed as the most important factor for sintering behaviour of the samples.

   Currently, wet bag process is widely used in the production of blanks which are shaped by conventional techniques either in their green or partially sintered states. Recent applications include dental zirconia milling blocks.