Particle size, controlling

In addition to graft copolymer attached to the mbber particle surface, the formation of styrene—acrylonitrile copolymer occluded within the mbber particle may occur. The mechanism and extent of occluded polymer formation depends on the manufacturing process. The factors affecting occlusion formation in bulk (77) and emulsion processes (78) have been described. The use of block copolymers of styrene and butadiene in bulk systems can control particle size and give rise to unusual particle morphologies (eg, coil, rod, capsule, cellular) (77). 

Some pioneering work has been done on the effect of particle size on mouthfeel and texture perception (31). When particles of food materials are smaller than 0.1 ]lni they impart no sense of substance and the consumer calls the product watery. Particles of 0.1—3.0 ]lni are sensed as a smooth rich fluid, but when the particles exceed 3 ]lni the food is perceived as chalky or powdery. By controlling particle size, deskable creaminess can be obtained (32). 

Bubble size control is achieved by controlling particle size distribution or by increasing gas velocity. The data as to whether internal baffles also lower bubble size are contradictory. (Internals are commonly used in fluidized beds for heat exchange, control of soflds hackmixing, and other purposes.)... 

Property Technical grade Controlled particle size (CPS) " CPS-ultrafine (UF) usp"... 

Size reduction (qv) or comminution is the first and very important step in the processing of most minerals (2,6,10,20—24). It also involves large expenditures for heavy equipment, energy, operation, and maintenance. Size reduction is necessary because the value minerals are intimately associated with gangue and need to be Hberated, and/or because most minerals processing/separation methods require the ore mass to be of certain size and/or shape. Size reduction is also required in the case of quarry products to produce material of controlled particle size (see Size measurement of particles). In some instances, hberation of valuables or impurities from the ore matrix is achieved without any apparent size reduction. Scmbbers and attritors used in the industrial minerals plants, eg, phosphate, mtile, glass sands, or clay, ate examples. 

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. 

Common names have been given to sodium sulfate as a result of manufacturiag methods. In rayon production, by-product sodium sulfate is separated from a slurry by filtration where a 7—10-cm cake forms over the filter media. Thus rayon cake was the term coiaed for this cake. Similarly, salt cake, chrome cake, phenol cake, and other sodium sulfate cakes were named. Historically, sulfate cakes were low purity, but demand for higher purity and controlled particle size has forced manufacturers either to produce higher quaUty or go out of busiaess. Sodium sulfate is mined commercially from three types of mineral evaporites thenardite, mirabilite, and high sulfate brine deposits (see Chemicals FROMBRINe). 

Barium carbonate of finely controlled particle size reacts in the soHd state when heated with iron oxide to form barium ferrites. Magnetically aligned barium ferrite [11138-11-7] powder can be pressed and sintered into a hard-core permanent magnet which is used in many types of small motors. Alternatively, ground up magnetic powder can be compounded into plastic strips which are used in a variety of appHances as part of the closure mechanism. 

Electrolyte is added to the recipe to help control particle size of the latex produced. Materials like sodium carbonate or trisodium phosphate are commonly used. 

Kobayashi et al. [508] developed an effective method to control particle size and fluoride content in granular tantalum oxide and niobium oxide. The resultant powders are suitable for application in the manufacturing of ceramics, single crystals, optical glass, etc. 

A method of the preparation of polylactic acid microcapsules of controlled particle size and drug loading, J. Microencapsul.,... 

The synthesis of nanoparticles has been intensively pursued not only for their fundamental scientific interest, but also for many technological applications [1]. For many of these applications, the synthesis of monodisperse nanoparticles (standard deviations a < 5%) with controlled particle sizes is of key importance, because the electrical, optical, and... 

The ability to produce threads, discs and spheres of defined size and structure will be of great importance when the very promising initial results from catalytic studies are applied on a larger scale. Processes using heterogeneous catalysts require the ability to control particle size and shape in order to ensure good mixing of all the reaction components, and separations after reaction. 

From the above description it will be appreciated that the efficiency of release of nutrients from ingested plant material is dependent upon the ease with which the digestive enzymes can penetrate the cell wall to release the nutrients so that they can diffuse out of the structure to be absorbed. Thus tissue maturity, cooking, macerating, mastication and mode of tissue failure, all of which control particle size, cell wall softening or cell disruption, are key features which regulate nutrient release. 

Particle size and the method of nanoparticle preparation (including the capping agent used) determine the physical and electronic properties of the quantum dots produced. This gives chemists the unique ability to change the electronic and chemical properties of a semiconductor material by simply controlling particle size and preparative conditions employed. There are various methods for the preparation of nanoparticles however, not all methods work well for the preparation of compound semiconductor nanocrystallites. 

Fuertes A.B. Template synthesis of mesoporous carbons with a controlled particle size, J. Mater. Chem. 2003 13 3085-8. 

Most examples discussed so far made use of amorphous inorganic supports or sol-gel processed hybrid polymers. Highly disperse materials have recently become accessible via standard processes and, as a result, materials with various controlled particle size, pore diameter are now available. Micelle-templated synthesis of inorganic materials leads to mesoporous materials such as MCM-41, MCM-48, MSU, and these have been extensively used as solid supports for catalysis [52]. Modifications of the polarity of the material can increase the reactivity of the embedded centre, or can decrease its susceptibility to deactivation. In rare cases, enhanced stereo- or even... 

Generally, particle attrition is unwanted. However, at times controlled attrition is desirable. For example, in coking units where agglomeration due to wet particles is frequent, jets are used to attrit particles to control particle size [Dunlop, Griffin, and Moser, J. Chem. Eng. Prog. 54 39-43 (1958)]. 

Ultrasonic sprays produced via horns are also finding use in spray drying installations where there are clear advantages in producing minimal particle velocity with a controlled particle size through a non-clogging nozzle. 

The importance of tobacco includes both those constituents in smoke that may interact with nicotine directly, as well as those that indirectly influence a smoker s perception and behaviors. For example, some tobacco smoke constituents may alter the site of absorption of nicotine, such as bronchodilators (e.g., cocoa, licorice), which allow deeper inhalation and subsequent deposition of constituents in more highly permeable areas of the respiratory tract. Likewise, product changes to alter or control particle size, or to provide particulate carriers for vapor-phase smoke constituents, also could facilitate changes at the site of absorption (Ingebrethsen 1993). This would also include the use of acids or bases to alter the form of nicotine and basicity of smoke. Again, a wide range of relevant findings is indicated by internal documents (Ferris Wayne et al. 2006 Keithly et al. 2005 Pankow 2001). 

Transition-metal nanopartides are of fundamental interest and technological importance because of their applications to catalysis [22,104-107]. Synthetic routes to metal nanopartides include evaporation and condensation, and chemical or electrochemical reduction of metal salts in the presence of stabilizers [104,105,108-110]. The purpose of the stabilizers, which include polymers, ligands, and surfactants, is to control particle size and prevent agglomeration. However, stabilizers also passivate cluster surfaces. For some applications, such as catalysis, it is desirable to prepare small, stable, but not-fully-passivated, particles so that substrates can access the encapsulated clusters. Another promising method for preparing clusters and colloids involves the use of templates, such as reverse micelles [111,112] and porous membranes [106,113,114]. However, even this approach results in at least partial passivation and mass transfer limitations unless the template is removed. Unfortunately, removal of the template may re-... 

Calcium chloride has several industrial applications. The major applications of this compound are in deicing of roads, dust control, imparting stability to roads and buildings, and to improve traction in tractor tires. It is mixed with ice to make freezing mixtures. Hexahydrate mixed with crushed ice can lower the temperature of the cooling bath to below -50°C. It also is used as a desiccant for dehydrating gases and liquids. It is added to cement in various proportions to manufacture different types of concrete. Other uses are in adhesives, to lower gel temperatures, and as a calcium source in liquid feed supplements for dairy cattle. Also, the compound is used to control particle size development and reduce coalescence in plastics. 

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