Solid dispersions definition

A disperse system is defined as a heterogenous, two-phase system in which the internal (dispersed, discontinuous) phase is distributed or dispersed within the continuous (external) phase or vehicle. Various pharmaceutical systems are included in this definition, the internal and external phases being gases, liquids, or solids. Disperse systems are also important in other fields of application, e.g., processing and manufacturing of household and industrial products such as cosmetics, foods, and paints. 

In areas such as miscible liquid blending, the formation of emulsions, solid dispersions such as paints, and dry powder mixing, it is understandable, therefore, that several criteria have been developed to assess mixture quality . It is unfortunate that of the many definitions presently available for mixture quality, in solid or liquid mixtures, none is universally applicable. In the case of powder mixing, further details may be found in Chapter 2, while for liquid mixing more information is presented in Chapters 8 and 10 for mechanically agitated vessels. Chapter 9 for Jet mixers and Chapter 12 for in-line static mixers. 

Amorphous solid dispersions are leveraged at varying stages in development for a number of reasons. For extruded dispersions, a limited number of polymer systems summarized in Table 6.3 form the backbone of the compositional definition. In early development, they are most commonly used to support elevated exposures necessary for preclinical assessment and/or assure phase stability when a crystalline form is not readily isolated. At this stage of development, the amount of material available for development will be restricted. As discussed previously, this constraint can challenge the utility of extruded systems where minimum batch sizes are significantly larger than for development of spray-dried dispersions or coprecipitated material. 

It should be noted that this is quite an unusual law, since in other known cases durability of solids is expressed by stronger laws, namely, exponential or power laws. Thus, in the given example we cannot give a unified definition of yield stress. The work cited is the only published observation of the durability of a filler s structure in dispersion systems. Therefore at present it is difficult to say how much such phenomena are typical for filled polymers, but we cannot exclude them. 

The rubber may be natural, in which case the latex is produced by the rubber tree. Latex of the main synthetic rubbers is produced by the technique of emulsion polymerisation. The term latex has been broadened in recent years and a general definition is now a stable dispersion of a polymeric substance in an aqueous medium . Latices may be classified as natural (from trees and plants), synthetic (by emulsion polymerisation) and artificial (by dispersion of the solid polymer in an aqueous medium). They may also be classified according to the chemical nature of the polymer, e.g., SBR, nitrile, polychloroprene, etc. 

Graham s definitions were expanded, and the concept of a colloidal state of matter evolved. According to this view, a substance could occur in a colloidal state just as it could occur under various conditions as a gas, liquid, or solid. If a colloidal solution was, at that time, defined as a solution in which the dispersed particles were comprised of large molecules, the ascertion would have been more acceptable. 

The methods of disintegration rely entirely upon increasing the dispersity of a solids which process can, at least theoretically, be stopped at any instant resulting in the formation of a suspension of definite dispersity but one that is not necessarily stable. The processes of suspension formation by methods of condensation on the other hand are more complicated, owing to the fact that unless the resulting colloidal suspension possesses at least some degree of stability the process of condensation once set in operation will not cease but proceed until the transformation to the macrocrystalline structure is complete. 

Not only a zinc-copper couple, but also a zinc-lead couple forms a gem-dimetal species from diiodomethane, according to the 1975 Nysted patent5. He also insisted that treatment of dibromethane with a zinc-lead couple in THF at 80 °C forms a characteristic gem-dizinc species 1 (equation 3). However, there was no further evidence concerning the structure except H NMR data, which was not enough for the complete structural determination. The obtained compound was definitely a gem-dizinc species, but the written structure 1 was not fully characterized. The white solid 1 is obtained as a dispersion in THF, and does not dissolve in DMF and DMI (l,3-dimethyl-2-imidazolidinone). This THF dispersion is commercially available from Aldrich Co. as Nysted reagent. Nysted also showed that this dizinc compound is effective for the methylenation of a-hydroxy ketone moiety in steroid derivatives5. 

Norbert Berkowitz. I suggest that initial reaction data cannot justify the author s rather definite conclusions since a diffusion-controlled component of the overall reaction would be relatively slow compared with an initial surface reaction and therefore more or less completely masked by it. Moreover, if the oxidation reaction were carried out in a liquid medium, swelling and dispersion of the solid reactant would accompany it, and in a dry (gaseous) medium, oxidation is known to cause some eating out of pores, etc. In both cases, therefore, continuous changes in reactant geometry accompany the reaction, and the critique applying to Hill et al. applies to Kapo. 

Definitions. Colloids are solid particles with diameters of 1 100 nanometers, A sol is a dispersion of colloidal particles in a liquid. A gel is an interconnected rigid network of sub-micrometer dimensions. A gel can be formed from an array of discrete colloidal particles (Method I) or the 3-D network can be formed from the hydrolysis and condensation of liquid meial alkoxide precursors (Methods 2 and 3). shown in Fig. 11. The metal alkoxide precursors used in Methods 2 and 3 are usually Si(OR)4 where R is CHj. C-Hj. or C3H7. The metal ions can be Si, Ti. Sn. Al, and so on,... 

Commercial Plastisols, Accdg to definition given in Ref 2, a plastisol is a liquid dispersion of finely divided resin in a plasticizer. It is usually 100% solid with no volatiles when volatile content exceeds 5% of the total wt it is called organosol. When the plastisol is heated, the plasticizer solvates the resin particles, and the mass gels. With continued application of heat the mass fuses to become a conventional thermoplastic material... 

A system of solid particles dispersed in a liquid. Suspensions were previously referred to as suspensoids , meaning suspension colloids. Aside from the obvious definition of a colloidal suspension, a number of operational definitions are common in industry, such as any dispersed matter that can be removed by a 0.45 pm nominal pore-size filter. 

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