Solid dispersion system effect

The same group also reported a disperse system consisting of N-oxyl-immobilized polyethylene particles as disperse phase and aqueous NaHC03-NaBr as disperse medium [19]. N-Oxyl-immobilized poly(p-phenylenebenzobisthiazolc) network polymer particles (PBZTNT-N-oxyl) have also been developed. The polymer is effective for the anodic oxidation of alcohols to afford the corresponding ketones, aldehydes, and/ or carboxylic adds [20]. These achievements nicely demonstrate the potential of liquid-solid disperse systems for eledroorganic synthesis. 

Summer MR Evener RP (1977) Effect of primidone concentration on glass transition temperature and dissolution of solid dispersion system containing of primidone and citric acid. J Pharm Sci 66 825-828... 

Chiou and Riegelman reviewed the pharmaceutical applications of solid dispersion systems. These authors found complete and rapid absorption of griseofulvin dispersed in polyethylene glycol 6000 for both capsule and tablet dosage forms, in contrast to irregular and incomplete absorption from commercially available micronized drug. Munzel reviewed various formulation variables which can influence drug action. Kakemi and co-workers studied the effects of buffer components, osmotic... 

This is because the effect of the dispersed solid, rather than the dispersing medium, is usually more significant. However, the latter should not be ignored. Many industrial problems involving unacceptably high viscosities in dispersed systems are solved by substituting solvents of lower viscosity. 

The stabilizing function of macromolecular surfactants in solid-liquid systems is exercised through protective colloid action. To be effective, they must have a strong solution affinity for hydrophobic and hydrophilic entities. In liquid-liquid systems, surfactants are more accurately called emulsifiers. The same stabilizing function is exercised in gas-liquid disperse systems where the surfactants are called foam stabilizers. 

In this equation, viscosity is independent of the degree of dispersion. As soon as the ratio of disperse and continuous phases increases to the point where particles start to interact, the flow behavior becomes more complex. The effect of increasing the concentration of the disperse phase on the flow behavior of a disperse system is shown in Figure 8-41. The disperse phase, as well as the low solids dispersion (curves 1 and 2), shows Newtonian flow behavior. As the solids content increases, the flow behavior becomes non-Newtonian (curves 3 and 4). Especially with anisotropic particles, interaction between them will result in the formation of three-dimensional network structures. These network structures usually show non-Newtonian flow behavior and viscoelastic properties and often have a yield value. Network structure formation may occur in emulsions (Figure 8-42) as well as in particulate systems. The forces between particles that result in the formation of networks may be... 

Figure 8-41 Effect of Increasing the Concentration of the Disperse Phase on the Flow Behavior of a Disperse System. 1—continuous phase, 2— low solids content, 3—medium solids content, 4—high solids content.

It has been found that for pigments in solvents, a high dielectric constant leads to a more dispersed system. In general, polar liquids disperse polar solids and non-polar liquids disperse non-polar solids. For polar solids suspended in non-polar liquids, it is possible to use the difference in polarity to anchor a stabilizing molecule to the powder surface. The effectiveness is characterized by the heat of wetting, which can be determined by calorimetry. 

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