Agglomerate strength, compression/compaction

The success of the compaction operation depends pardy on the effective utilization and transmission of appHed forces and pardy on the physical properties and condition of the mixture being compressed. Friction at the die surface opposes the transmission of the appHed pressure in this region, results in unequal distribution of forces within the compact, and hence leads to density and strength maldistribution within the agglomerate (70). Lubricants, both external ones appHed to the mold surfaces and internal ones mixed with the powder, are often used to reduce undesirable friction effects (71). For strong compacts, external lubricants are preferable as they do not interfere with the optimum cohesion of clean particulate surfaces. Binder materials maybe used to improve strength and also to act as lubricants. 

These processes complement spray drying, especially when larger particles are needed. Compaction results in a compressed product with low porosity, i.e. more strength. Agglomeration, in contrast, produces a fluffy powder with high porosity, ideally suited for applications that which call for instant dissolving. 

Figure 5 The microlevel processes of compressive agglomeration, or compaction. These processes combined control compact strength, hardness, and porosity.

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