Particles flowability

For particulate systems, the key characteristics are the surface area per unit volume (as shown in Fig. 1.2), the diameter of the particles (related to a commonly used method called Mesh size), the void volumes for a packed bed of particles and parameters to measure dry particle flowability. 

Prolonged Action Parenterals Injections. Intramuscular injections have been developed to achieve prolonged therapeutic effects. This can be accompHshed by suspension of dmg particles in oils or flowable gels, from which the dmg slowly diffuses. Aqueous suspensions can also provide such therapeutic response. In these cases, the soHd dmg crystals generally are quite water insoluble and of a controlled particle size and crystallized form. 

Plow chaiacterlstic.s. Angle of repose and flowability are measurable charac teristics for which standard tests are available (e.g., ASTM Test B213-48, Flow Rate of Metal Powders, etc.). A steeper angle of repose would indicate less flowability. The term Hubricity has sometimes been used for solid particles to correspond roughly to viscosity of a fluid. 

Age appears to improve the flowability of certain materials. This is probably the result of particle-surface oxidation, more even moisture distribution, and the rounding of particle corners caused by handhng. 

Moisture can significantly affect loose materials, particularly their flowability. Low temperatures, particle bridging, and caking can alter interparticle void fractions and cause dramatic changes in bulk density. Moisture becomes bound to solids because of mechanical, physicochemical, and chemical mechanisms. Moisture retained... 

Manufacture of highly water-absorbent polymers with uniform particle size and good flowability can be carried out by reverse phase suspension polymerization of (meth)acrylic acid monomers in a hydrocarbon solvent containing crosslinker and radical initiator. Phosphoric acid monoester or diester of alka-nole or ethoxylated alkanole is used as surfactant. A polymer with water-absorbent capacity of 78 g/g polymer can be obtained [240]. 

Natural sand is a major component of most flowable fill mixes. Ferrous spent foundry sand can be used as substitute for natural sand (fine aggregate) in flowable fill.48 49 Spent sands from nonferrous foundries and foundry baghouse dust can contain high concentrations of heavy metals that may preclude their use in flowable fill applications. Some of the engineering properties of spent foundry sand that are of particular interest when foundry sand is used in flowable fill applications include particle shape, gradation, strength characteristics, soundness, deleterious substances, and corrosivity. 

In the pharmaceutical industry, surface area is becoming more important in the characterization of materials during development, formulation, and manufacturing. The surface area of a solid material provides information about the void spaces on the surfaces of individual particles or aggregates of particles [5], This becomes important because factors such as chemical activity, adsorption, dissolution, and bioavailability of the drug may depend on the surface on the solid [3,5]. Handling properties of materials, such as flowability of a powder, can also be related to particle size and surface area [4],... 

Compressibility is indirectly related to the relative flow rate, cohesiveness, and particle size of a powder. A compressible material will be less flowable, and powders with compressibility values greater than 20-21% have been found to exhibit poor flow properties [69]. 

The influence of mixed coupling on the properties of Cl Pigment Yellow 12 has been studied recently [12]. Carboxy- or sulpho- substituted derivatives of acetoacetanilide were evaluated as co-coupling components and analysis revealed that the state of the crystal and the particle size were changed and new diffraction peaks were observed. When these modified pigments were treated with a fatty amine such as stearylamine, the hydrocarbon chains enclosed the anionic groups in the co-coupler so that properties such as flowability, wettability and dispersibility in nonpolar solvents were greatly improved. 

An important application of granulation is in improving the flowability of very fine (submicron) particles which stick together because of the large surface forces acting in materials with very high surface/volume ratios. 

Once manufactured, small particles present another challenge. At small particle size diameters, gravity ceases to be the major force exerted on the particles and interparticle forces become more prominent. The resultant increase in the cohesive and adhesive nature of the particles produces problems such as poor flowability, fillability, and dispersibility. These problems are typically minimized by blending with larger. 

The floodability index was calculated from the dispersibility, cohesion, angle of fall, and flowability index parameters. The values for this property ranged from 55 to 76. The most floodable material was lot 4405K5, and the least floodable material lot was the instant sorbitol, which is in agreement with the flow index and the particle size data. The... 

Because particle size is so intimately intertwined with powder performance, it is one of the prime considerations in selecting excipients to develop or improve a formulation. This is particularly important with direct compression formulations where excipient flowability and compaction performance are critical. Typically, excipients for these applications exhibit narrow size distributions with moderate-to-coarse particle size, having a mean size from 100 to 200 pm. 

Early data collection of prototype-blend experiments could be an invaluable tool to successful scale-up. Physical characteristics such as particle size distribution, bulk and tapped density, and flowability and functional characteristics (mainly compactability) are key indicators of possible downsteam scale-up problems. If, for example, the active drug substance has a mean particle diameter... 

Particle-Size Distribution. Particle size, crystal shape, and distribution of vanillin are important and greatly affect parameters such as taste, flavor, solubility, case of dispersion in solvent, flowability of the powder, caking effect, and production of dust. 

P. Maijanovic, D. Geldart, J.L.R. Orband, Techniques for assessing powder flowability - a comparison, Proceedings of the World Congress on Particle Technology 3, Brighton, UK, July 1998. 

A major interest in using this new process [8] is the value of the temperature at which seeding can be done with the cocoa butter particles supercritically generated. At 305 K the chocolate is less viscous, this is advantageous in term of flowability and energy consumption. An additional advantage lies in the fact that the time needed to obtain a well-tempered chocolate is shorter (about 5 min). Moreover, the overall quantity of seeds to temper the chocolate is very small. Therefore, a scaling-up of this process to an industrial scale appears feasible. 

In addition, a new type of new biocide (designated FIBCIDE-KF), this time a water-based flowable product in which the inclusion complex (FIBCIDE-K58) has been ground into fine particles of 10 xm or less, in an aqueous solvent, has been manufactured using the process shown in Figure 8 [6],... 

---