Compaction speed

The compaction process can be described by a variety of force (or pressure)-displacement profiles, such as force versus time, force versus tablet porosity, and force versus tablet properties (hardness, friability, dissolution, etc.). The effect of compaction speed on a variety of tablet properties can also be studied. 

Force measurements made without displacement values are still useful in identifying the dependency of tablet hardness (and other associated characteristics) on compaction force, and also the effect of the tablet press compaction speed on tablet strength (influence of dwell time/effective... 

The Bib and BI are defined as shown below in Equations (2) and (3), respectively. Both indices describe the bonding ability of the tablets by using the ratio of tensile strength and indentation hardness. However, Bib is determined at low-indentation speed (Hq) and BIw is determined at high speed (Hio). Hence, BI is considered more indicative of actual tableting conditions, whereas Bib relates to slower compactions speeds typical of development or roller compaction processes. 

Force measurements made without displacement values are still useful in identifying the dependency of tablet hardness (and other associated characteristics) on compaction force, and also the effect of the tablet press compaction speed on tablet strength (influence of dwell time/effective contact time). Dwell time dependency is an important scale-up factor for the tableting process, and evaluation of the sensitivity of a formulation to dwell time at small scale is useful, although the actual commercial dwell time is not always achievable on instrumented, small-scale tablet presses. 

In what follows, we will use the mechanical, rather than functional, definitions because they serve as an objective material-independent measure of compaction speed. 

In consideration of LC as an on-line sensor, ideal device characteristics would be compactness, speed, very low maintenance, self-containment and low solvent consumption. Compactness is not a given here, albeit the fact that the chips themselves are very small. It is the peripheral system surrounding the chip to which attention needs to be paid in order to minimize footprint. Unlike liquid handling for CE and CEC microchips, hydrodynamic flow components involve pumps and valves, for which more effort is required to miniaturize. We have touched on current advances in these areas already, but extensive development in miniaturization and integration of hydrodynamic fluid handling components is still forthcoming. The following is envisioned. 

Of course, the deformation of granular materials is typically rate dependent. In this case, a family of curves collected at different compaction rates may be necessary to folly characterize a given material over of range of conditions. In the case of very fast rates of compaction, the test apparatus may impose limitations, either via physical control of the compaction cycle, or by the rate of data collection. On the other hand, the method is typically well suited to lower compaction speeds of the magnitude of 0.1 to 1 mm/s. 

Immersion-type extractors have been made continuous through the inclusion of screw conveyors to transport the soHds. The Hildebrandt immersion extractor (18) employs a sequence of separate screw conveyors to move soHds through three parts of a U-shaped extraction vessel. The helix surface is perforated so that solvent can pass through the unit in the direction countercurrent to the flow of soHds. The screw conveyors rotate at different speeds so that the soHds are compacted as they travel toward the discharge end of the unit. Alternative designs using fewer screws are also available. 

Consumer Products. Laser-based products have emerged from the laboratories and become familiar products used by many millions of people in everyday circumstances. Examples include the supermarket scaimer, the laser printer, and the compact disk. The supermarket scanner has become a familiar fixture at the point of sale in stores. The beam from a laser is scaimed across the bar-code marking that identifies a product, and the pattern of varying reflected light intensity is detected and interpreted by a computer to identify the product. Then the information is printed on the sales sHp. The use of the scanner can speed checkout from places like supermarkets. The scanners have usually been helium—neon lasers, but visible semiconductor lasers may take an impact in this appHcation. 

Fig. 6. Effects on the pressed compact of (a) speed, where A is low and B, high speed compacting (b) powders, where A is soft and B, hard powders (c) dimensional change after sintering and (d) sintering temperatures, where A is high, B, medium, and C room temperature.

Decrease load to reduce wear Lower-formulation density. Decrease hed-agitation and compaction forces (e.g., mixer impeller speed, fliiid-hed height, bed weight, fluid-hed excess gas velocity, drum rotation speed). 

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