Dispersion homogeneous

Table 2 Hsts the four main groups of compounds most commonly used as dye carriers. In order for these compounds to act effectively as carriers, they must be homogeneously dispersed in the dyebath. Because the carrier-active compounds have Httie or no solubiUty in water, emulsifiers are needed to disperse these compounds in the dyebath (see Emulsions).

For many laboratoiy studies, a suitable reactor is a cell with independent agitation of each phase and an undisturbed interface of known area, like the item shown in Fig. 23-29d, Whether a rate process is controlled by a mass-transfer rate or a chemical reaction rate sometimes can be identified by simple parameters. When agitation is sufficient to produce a homogeneous dispersion and the rate varies with further increases of agitation, mass-transfer rates are likely to be significant. The effect of change in temperature is a major criterion-, a rise of 10°C (18°F) normally raises the rate of a chemical reaction by a factor of 2 to 3, but the mass-transfer rate by much less. There may be instances, however, where the combined effect on chemical equilibrium, diffusivity, viscosity, and surface tension also may give a comparable enhancement. 

In order to be effective in imparting various chosen characteristics, all additives employed in a blend must be homogeneously dispersed throughout the blend. The two most commonly employed pieces of equipment for blending rubber and additives are rubber mills and a special type of mechanical mixer known as the Banbury mixer. A typical rubber mill consists of two rolls which rotate toward each... 

Figure 9 The schematical representation of dispersion polymerization process, (a) initially homogeneous dispersion medium (b) particle formation and stabilizer adsorption onto the nucleated macroradicals (c) capturing of radicals generated in the continuous medium by the forming particles and monomer diffusion to the forming particles (d) polymerization within the monomer swollen latex particles, (e) latex particle stabilized by steric stabilizer and graft copolymer molecules (f) list of symbols.

We also studied the effect of initiator on the dispersion polymerization of styrene in alcohol-water media by using a shaking reactor system [89]. We used AIBN and polyacrylic acid as the initiator and the stabilizer, respectively. Three different homogenous dispersion media including 90% alcohol and 10% water (by volume) were prepared by using isopropanol, 1-butanol, and 2-... 

The small metal particle size, large available surface area and homogeneous dispersion of the metal nanoclusters on the supports are key factors in improving the electrocatalytic activity and the anti-polarization ability of the Pt-based catalysts for fuel cells. The alkaline EG synthesis method proved to be of universal significance for preparing different electrocatalysts of supported metal and alloy nanoparticles with high metal loadings and excellent cell performances. 

Figure 1. Graphical model for the generation of size-controlled metal nanoparticles inside metallated resins, (a) Pd is homogeneously dispersed inside the polymer framework (b) Pd is reduced to Pd (c) Pd atoms start to aggregate in subnanoclusters (d) a single 3 nm nanocluster is formed and blocked inside the largest mesh present in that slice of polymer framework (Reprinted from Ref [5], 2004, with permission from Wiley-VCH.)...

The particles in a disperse system with a liquid or gas being the dispersion medium are thermally mobile and occasionally collide as a result of the Brownian motion. As the particles approach one another, both attractive and repulsive forces are operative. If the attractive forces prevail, agglomerates result indicating an instability of the system. If repulsive forces dominate, a homogeneously dispersed or stable dispersion remains. 

Description Homogeneous dispersion of solid drug in a polymer mix... 

Description A homogeneous dispersion of drug in an erodible matrix... 

Matrix diffusion-controlled system in which the drug is homogeneously dispersed in a hydrophilic polymer diffusion from the matrix controls release rate Nitrodur (nitroglycerin key). 

Summary Materials containing uniform, nanometer-sized metal particles homogeneously dispersed in a Si02 matrix, with a variable metal loading, were prepared by the sol-gel processing starting from metal salts, alkoxysilanes of the type X(CH2)nSi(OR)3 and, optionally, Si(OR)4. 

Table 18.2 lists 30 of the molecules used in this study that are known to be substrates for active transport or active efflux. The mechanistic ACAT model was modified to accommodate saturable uptake and saturable efflux using standard Michaelis-Menten equations. It was assumed that enzymes responsible for active uptake of drug molecules from the lumen and active efflux from the enterocytes to the lumen were homogeneously dispersed within each luminal compartment and each corresponding enterocyte compartment, respectively. Equation (5) is the overall mass balance for drug in the enterocyte compartment lining the intestinal wall. 

Scanning electron microscopy indicated that the zeolites crystals are homogeneously dispersed in the surface and the core of the composites. Figure 2 presents micrographs of cross-sections of the chitosan-zeolite spheres and shows that the morphology of the zeolite crystals has not been affected by the gelling of chitosan. 

SEM indicated that the zeolite crystals were homogeneously dispersed inside the gel. The crystals of zeolite A inside the polymer are represented in figure 3. 

When describing erosion of and drug release from surface erodible polymers, it is often implicitly assumed that the matrix erodes uniformly, thus resulting in a uniform release profile for a homogenously dispersed drug. While this may be a valid assumption for some homopolymer systems, neglecting the effects of crystallinity, some multicomponent... 

Alternatively, lipospheres might be prepared by a solvent technique. In this case, the active agent, the solid carrier, and the phospholipid are dissolved in an organic solvent such as acetone, ethyl acetate, ethanol, or dichloromethane. The solvent is then evaporated and the resulting solid mixed with warm buffer solution, and mixing is continued until a homogeneous dispersion of lipospheres is obtained. 

In 1996, Liu et al. reported the selective hydrogenation of cinnamaldehyde, an a,/ -unsaturated aldehyde, to cinnamyl alcohol, an a,/ -unsaturated alcohol, by means of PVP-protected Pt/Co bimetallic colloids prepared by the polyol process [111]. The colloids were obtained as a dark-brown homogeneous dispersion in a mixture of ethylene glycol and diethylene glycol, and characterized by TEM and XRD. These authors prepared different samples of nanoparticles with Pt Co ratios of 3 1 and 1 1, the mean diameters of which measured 1.7 and 2.2 nm, respectively. These colloidal systems were also compared with the single metal-... 

Stabilizers Substance which makes it possible to maintain the physicochemical state of a foodstuff stabilizers include substances which enable maintenance of a homogenous dispersion of two or more immiscible substances in a foodstuff and include also substances which stabilize, retain or intensity an existing colour of a foodstuff... 

Solvent methods are similar to in situ polymerizations. During the first stage, the nanomaterial is dispersed in a solvent. In some cases a surfactant can be used as a bridge between the nanomaterials and the matrix (Fig. 4.9). This reaction occurs in a liquid or gel form in the presence of a solvent such as toluene, chloroform, acetonitrile, water, acetone, etc. The solution of modified nanoparticles is then added to a polymeric solution under agitation (at room or elevated temperatures) in order to ensure a homogeneous dispersion of the nanomaterials in the matrix. Finally, the polymer composite... 

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