Particulate solids properties

B. H. Kaye, Monitoring Particulate Solid Properties in Automatic Control Loops, Past, Present and Future, in Proceedings of the Conference on Instream Measurements of Particulate Solids Properties, Bergen. Norway, August 1978. Information from Chris Michelsen Institute, Bergen. 

R.VJ. Lines, J.G. Harfield, VJ.M. Wood and B.V. Miller, Intnl. Symp. "In Stream Measurements of Particulate Solid Properties", Bergen, August 22-23, 1978. 

PCA 16 is available as Beldene 161/164 (50/35% w/w solids), Acumer 4161 (50%), and Polysperse (50%). These are low-phosphorus content materials that have found application in boiler FW formulations because of excellent sludge conditioning and particulate dispersion properties. The number 16 represents a 16 1 w/w ratio of acrylic acid and sodium hypophosphite, giving PCA 16 a MW range of 3,300 to 3,900. PCA 16 is particularly effective for the control of calcium carbonate and sulfate deposition. It is usually incorporated with other polymers in formulations and is approved for use under U.S. CFR 21, 173.310. 

Mixing together of particulate solids, sometimes referred to as blending, is a very complex process in that it is very dependent, not only on the character of the particles — density, size, size distribution, shape and surface properties — but also on the differences of these... 

Elastomers, of which vulcanized natural rubber is the most important example, also undergo dramatic changes in mechanical properties when filled with particulate solids. In part, knowledge of this particular type of system has been developed empirically as the technology of car-tyre manufacture has advanced. 

In the present work, such a systematic approach to the physical characterization of pharmaceutical solids is outlined. Techniques available for the study of physical properties are classified as being associated with the molecular level (properties associated with individual molecules), the particulate level (properties pertaining to individual solid particles), and the bulk level (properties associated with an ensemble of particulates). Acquisition of this range of physical information yields a total profile of the pharmaceutical solid in question, whether it is an active drug, an excipient, or a blend of these. The development of a total profile is a requirement for successful manufacture of any solid dosage form. 

A bed of particulate solids through which a fluid passes, thus imparting liquid-like properties to the solids. The space between the surface of the dense phase and the gas exit. 

Scientific and engineering investigations into the properties and behavior of particulate solids date back to the early work of Coulomb, who in 1776 developed a theory on soil pressure and resistance, thus laying sound foundations for important engineering... 

In a column of particulate solids contained in a vertical bin, the pressure at the base will not be proportional to the height of the column because of the friction between the solids and the wall. Moreover, a complex stress distribution develops in the system, which depends on the properties of the particulate solids as well as the loading method. The latter affects the mobilization of friction, both at the wall and within the powder. Finally, arching or doming may further complicate matters. Hence, an exact solution to the problem is hard to obtain. In 1895, Janssen (18) derived a simple equation for the pressure at the base of the bin, which is still frequently quoted and used. The assumptions that he made are the vertical compressive stress is constant over any horizontal plane, the ratio of horizontal and vertical stresses is constant and independent of depth, the bulk density is constant, and the wall friction is fully mobilized, that is, the powder is in incipient slip condition at the wall. 

It was Wollaston (30) who in 1829 recognized the great pressures needed for compaction of dry powders—an observation that led to his famous toggle press. Since that time, compaction and deformation of powders and particulate systems have been extensively studied (31-35). There are many difficulties in analyzing the compaction process. Troublesome in particular are the facts that the properties of particulate solids vary greatly with consolidation, and that stress fields can be obtained, in principle, only in... 

Therefore in summary, for a particulate solid to be successfully transformed into tablets, three key properties need to be present ... 

Schwedcs J. Testers for measuring flow properties of particulate solids. Presented at Reliable Flow of Particulate Solids III, Posgrunn, Norway. 19. ... 

W. Pletch, "Granulate Dry Particulate Solids by Compaction and Retain Key Powder Particle Properties", Chemical Engineering Progress, April (1997), 24. 

As mentioned in Chap. 27, solids in chemical processes are most commonly in the form of particles, This section is concerned with the properties, modification, and separation of particulate solids. General properties, handling, and mixing are discussed in Chap. 28, size reduction in Chap. 29, and mechanical separations in Chap. 30. 

Depending on their flow properties, particulate solids are divided into two classes, cohesive and noncohesive. Noncohesive materials like grain, dry sand, and plastic chips readily flow out of a bin or silo. Cohesive solids, such as wet clay, are characterized by their reluctance to flow through openings. 

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