Direct compaction

The applicability of all aforementioned continuous optimization techniques depends very heavily on the simplified form of the objective function and constraints. They also suffer the common drawback that the solution must be rounded to the nearest standard pipe sizes, a procedure whose pitfalls must then be eliminated by a partially enumerative search. By contrast, the discrete merge method (C8) which is an enhancement of an earlier development by Rothfarb et al. (R5), is fast, direct, compact, and flexible. 

Bolhius GK, Chowhan ZT. Materials for direct compaction. In Alderbom G, Nystrom C, eds. Pharmaceutical Powder Compaction Technology. New York Marcel Dekker, Inc., 1996 419-500. 

Maarschalk KvdV, Bolhuis GK. Improving properties of materials for direct compaction. Pharm Technol 1999 23 34-46, 96. 

Briquetting of biomass can be achieved by different techniques, and by either using some kind of binder or by direct compacting without any binder. One example from a pilot plant is presented below. Bales of raw material are put on a conveyor, transported to a shredder and stored in a silo. The shredder cuts the material into particles ranging from microscopic to 15 mm. When the production of briquettes starts, material from the silos is transported through a mixer and a... 

Eissens AC, Bolhuis GK, Hinrichs WL, Frijlink HW. Inulin as filler-binder for tablets prepared by direct compaction. Eur ] Pharm Set 2002 15(1) 31-38. 

Bolhuis GK, Eissens AC, Adrichem TP, et al. Hollow filler-binders as excipients for direct compaction. Pharm Res 2003 20(3) 515-518. 

Muzikova J. A study of compressibility of directly compacting forms of lactitol. Ceska Slov Form 2003 52(5) 241-243. 

Sample preparation in direct compact sample analysis... 

Direct compacting. Direct compacting is applied for near-net shaping of parts. This means that the final hardmetal specimen after sintering already has the desired dimensions and only limited surface treatment is necessary afterward. For that purpose, semiautomatic or automatic mechanical or hydraulic presses are used. The pressure application is only from one direction, resulting in a slightly anisotropic density distribution in the green compact. 

Direct compacting is mainly used in producing mining tools, metal cutting inserts, and parts for construction applications. Around two-thirds of hardmetal production is compacted by this method. 

Similar behavior has been observed for noncrystallizing polymers. For example, the diffusivity of water in poly(vinylpyrrolidone) (PVP) (Oksanen and Zografi, 1993) has been shown to increase at water contents beyond the hydration limit. Additional reports have shovm that the hydration limit has physical significance for other polymer excipients. Microcrystalline cellulose and lactose for compression, for example, lose their direct compaction properties at water contents just below (Huettenrauch and Jacob, 1977), and gelatin capsules become brittle as the water content is reduced below Wm (Kontny and Mulski, 1989). Recently, the chemical stability of a model peptide in PVP matrices was shown to improve when the amorphous dispersion was stored below the polymer s hydration limit (Lai et al., 1999a Lai et al., 1999b Lechuga-Ballesteros et al., 2002). 

In comparison with die compaction, isostatic pressing can provide compacts with much less defects or flaws. However, delamination and fracture caused by springback could be present if the pressure is released too fast. In addition, isostatic pressing has been rarely used to directly compact ceramic powders, due to its difficulty in handling powder samples. In most cases, it is used to further increase the density of green bodies either before or after the calcination step. Usually, the increase in density after isostatic compaction is less than 10 %, but that is sufficient to promote the densification of green bodies of most transparent ceramics. 

Strydom SJ, Otto DP, Liebenberg W, Lvov YM, de Villiers MM. Preparation and characterization of directly compactible layer-by-layer nanocoated cellulose. Int J Pharm 2011 404(l/2) 57-65. Available from PM 21056645. 

TWRI system can test both undisturbed and remolded soil samples. Because the size limit of flow cell, local gravels lager than 2 mm were removed from the sliding zone soil sample. The remolded sample is directly compacted into the flow cell with original porosity 0.35. The shape of sample is a cylinder with base area of 60 cm and height of 3 cm. Before the test, ceramic stone and sample need to be fully... 

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