Compaction bond mechanisms

Nystrom, C., Alderborn, G., Duberg, M., and Karehill, P-G. (1993), Bonding surface area and bonding mechanism—Two important factors for the understanding of powder compactability, Drug Dev. Ind. Pharm., 19, 2143-2196. 

Tribasic calcium phosphate is widely used as a capsule diluent and tablet filler/binder in either direct-compression or wet-granulation processes. The primary bonding mechanism in compaction is plastic deformation. As with dibasic calcium phosphate, a lubricant and a disintegrant should usually be incorporated in capsule or tablet formulations that include tribasic calcium phosphate. In some cases tribasic calcium phosphate has been used as a disintegrant. It is most widely used in vitamin and mineral preparations as a filler and as a binder. It is a source of both calcium and phosphorus, the two main osteogenic minerals for bone health. The bioavailability of the calcium is well known to be improved by the presence of cholecalciferol. Recent research reports that combinations of tribasic calcium phosphate and vitamin D3 are a cost-effective advance in bone fracture prevention. ... 

Fig. 5. Protein folding. The unfolded polypeptide chain coUapses and assembles to form simple stmctural motifs such as -sheets and a-hehces by nucleation-condensation mechanisms involving the formation of hydrogen bonds and van der Waal s interactions. Small proteins (eg, chymotrypsin inhibitor 2) attain their final (tertiary) stmcture in this way. Larger proteins and multiple protein assembhes aggregate by recognition and docking of multiple domains (eg, -barrels, a-helix bundles), often displaying positive cooperativity. Many noncovalent interactions, including hydrogen bonding, van der Waal s and electrostatic interactions, and the hydrophobic effect are exploited to create the final, compact protein assembly. Further stmctural...

In sintering, the green compact is placed on a wide-mesh belt and slowly moves through a controlled atmosphere furnace (Fig. 3). The parts are heated to below the melting point of the base metal, held at the sintering temperature, and cooled. Basically a solid-state process, sintering transforms mechanical bonds, ie, contact points, between the powder particles in the compact into metallurgical bonds which provide the primary functional properties of the part. 

Sintering. Basically a soHd-state process, sintering transforms compacted mechanical bonds between the powder particle into metallurgical bonds (23,34—38). 

The success of compression agglomeration depends on the effective utilization and transmission ofthe applied external force and on the ability of the material to form and maintain interparticle bonds during pressure compaction (or consolidation) and decompression. Both these aspects are controlled in turn by the geometiy of the confined space, the nature of the apphed loads and the physical properties of the particulate material and of the confining walls. (See the section on Powder Mechanics and Powder Compaction.)... 

ITMs provide a valuable service to all phases of tablet manufacture, from research to production and quality control [109 111]. As a research tool, ITMs allow in-depth study of the mechanism of tablet compaction by measuring the forces that develop during formation, ejection, and detachment of tablets. ITMs can also provide clues about how materials bond,... 

The mechanism of densification begins with individnal particle motion at low pressnre before interparticle bonding becomes extensive. At higher pressures, the compact... 

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