Particle size powders

During the preformulation stage, the chemical and physical properties of the dmg moiety are studied exhaustively to ensure stabdity, safety, bioavadabdity, and therapeutic efficacy. Tablets are produced directly by compression of powder blends or granulations, which include a small percentage of fine, particle-sized powders. 

Direct Compression. This process is relatively simple and time saving. AH the ingredients are blended and then compressed into the final tablet. This is an excellent method, but encumbered by a number of problems. Not all substances can be compressed directly, necessitating a granulation step. Likewise, the flow properties of many blends of fine, particle-sized powders are not such as to ensure even filling of the die cavities of tablet presses. In addition, air entrapment can occur. 

Chemically Synthesized Powders. Chemical synthesis provides a means of produciag powders for manufacturiag advanced ceramics. Disadvantages of chemically synthesized raw materials are expense and difficulties ia scale-up and availabihty. Additionally, ultrafine particle-size powders produced by chemical synthesis pose some unresolved processiag problems ia the areas of handling and mixing. 

The sample format used for XRF measurement is typically compressed fine particle size powder (2-10 mm thick, 20-50 diameter), moulded film or... 

Borates, through their ability to act as glass network formers, can act as excellent char formers and drip suppressants in fire retardant applications. In many cases this involves processing into polymeric materials, leading to specific requirements for thermal stability and particle size. Most common borate materials, however, exhibit relatively low dehydration temperatures and may be unsuitable for use in many polymer systems. Zinc borates are often used because they have unusually high dehydration onset temperatures and can be produced as small particle size powders. 

British Standards Methods for the Determination of Particle Size Powders. Part I, Subdivision of Gross Sample Down to 0.2 ml BS3406, Part 1 London, 1961. 

As one can see, the densification of the powder with the smallest particles size (powder A) is completed during lower temperatures (1400-1600 C), meanwhile the density of A and B powders increases monotonically with an increase of the temperature up to 1800-1900°C. Samples sintered from B powder under the temperatures higher than 1400°C have the highest density (about 99%). 

Metallurgical grade silicon is marketed in a coarsely crushed form or as a finely ground powder in different particle sizes. Powders with increased purity due to acid washing, particularly for the removal of metallic impurities, are specialty products. They are utilized, for example, in the manufacture of silicon nitride powder or reaction-bonded silicon nitride ceramic components and are therefore the starting materials for engineering ceramic specialties. 

Oral solids Solubility, dissolution, polymorphism, chirality, particle size, powder flow, chemical stability, photostability, compressibility, hygroscopicity, and excipient interactions. 

A number of other studies can be performed on a candidate drug to determine other important solid-state properties, for example, particle size, powder flow and compression and polymorphism. Therefore, when a sample undergoes initial preformulation testing the following parameters should be noted particle size, true, bulk and tapped density, surface area, compression properties and, powder flow properties. Some of these factors will be discussed in this chapter others, however, are dealt with in more detail in Chapter 11 on Solid Oral Dosage Forms. 

Tor powder synthesis a large variety of methods is available, for example mixed-oxide solution precipitation or emulsion precipitation. Figure 8.11 shows as an example a (Y,Gd)202 powder prepared by three different precipitation techniques. The powders obtained ate different in particle morphology as well as in particle size. Powders prepared by the citrate and the oxalate precipitation techniques are strongly agglomerated [14], From powders derived in this way, compacts are formed. These powder compacts demonstrate total luminescent properties, but have still low light output due to the high porosity of about 50 vol.%. 

Sintering materials (metals, polymers, ceramics and their mixtures) solvent free easy and rapid precise control on macro- and micro-porosity pore interconnectivity laser spot and particle size Powder material No biomolecules or cells can be incorporated due to high temperature for particle sintering... 

The particle size powders consisting of many small particles tend to show a poor flow. 

Standard particle size powders are typically used as a feedstock for processes such as extrusion and compression moulding. There are... 

This process exploits an imusual effect of the difference in solubility of acrylic acid monomer and polyacrylic acid in specific solvents. When products based on the process were first developed [4] and made commercially available, benzene was used as the polymerisation medium. The polymerisation reaction is initiated in a system containing a mixture of acrylic acid monomer and a cross-linking monomer (typically a multi-allyl ether derivative of sucrose or pentaeryrthritol) and, as the polymer network grows, the solubility in the solvent decreases until precipitation of the polymer network occurs in the form of a small particle size powder. The use of a cross-linking monomer results in a 3D network of... 

The reactive dispersions (CD-627, CD-628, PRO 1825) are experimental materials developed by Sartomer Company for evaluation in this study. They are proprietary products that consist of a metallic coagent dispersed at various concentrations in different acrylic monomers. A viscous solution or paste is formed which can be used in place of an adhesive to form adhesive bonds during the curing step of the rubber compoimd (peroxide cure only). They contain no solvents and are 100% reactive. The metallic coagent is a small particle-size powder that is not soluble in monomers, but does form a stable dispersion. 

Description Fine particle size powder grade. 

As the particle size of the molding powder is increased, a longer fusion time is required to obtain a surface smoothness equivalent to that of a smaller particle size powder. The likely cause of less efficient heating is the reduced contact surface area between the wall of the mold and the powder. 

Gravimetric analysis was performed on Pr-powders precipitated from solvated Pr Oj and PrC030H and PitOH)j to determine the effects of particle size/powder preparation on the solubility of each species (Fig. 6.6). The Pr-powder precipitated at atmospheric conditions at 85 °C was the most soluble followed by the powder precipitated in the presence of at ambient temperature, and Ar at 85 °C, which were not statistically different as calculated by a t-test. The Pr-powder precipitated with COj at ambient temperature, Ar at ambient temperature, at 85 °C, CO ... 

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