Dispersed particles, size range

Many foods are oil-in-water or water-in-oil emulsions (o/w), with dispersed particle size range of 0.01-10 p.m (Rahalkar, 1992). Many of the equations discussed for food suspensions are also applicable to emulsions. In a dilute emulsion, the particles are far apart and the interparticle interactions are relatively weak. Skim milk is an example of a dilute emulsion with the concentration of fat droplets (dispersed phase) <1%. 

Phenolic Dispersions. These systems are predominantly resin-in-water systems in which the resin exists as discrete particles. Particle size ranges from 0.1 to 2 p.m for stable dispersions and up to 100 p.m for dispersions requiring constant agitation. Some of the earliest nonaqueous dispersions were developed for coatings appHcations. These systems consist of an oil-modified phenoHc resin complexed with a metal oxide and a weak solvent. 

Dispersion polymerizations of methyl methacrylate ntUizing poly(l,l,-dihydroper-fluorooctyl acrylate) as a steric stabilizer in snpercritical CO2 were carried out in the presence of helium. Particle size and particle size distribution were found to be dependent on the amonnt of inert helium present. Particle sizes ranging from 1.64 to 2.66 pm were obtained with varions amounts of helium. Solvatochromic investigations using 9-(a-perflnoroheptyl-p,p-dicyanovinyl)julolidine indicated that the solvent strength of CO2 decreases with increasing helium concentration. This effect was confirmed by calcnlations of Hildebrand solubility parameters (Hsiao and DeSimone, 1997). 

The emulsification is carried out in such a manner that part of the sulfur is dissolved in the asphalt and the remainder is dispersed in the continuous asphalt phase as molten sulfur droplets with a particle size range of 1-50 vm. 

In another system, miscible blends of PE and lauryl methacrylates (LMA) were in situ polymerized/crosslinked to yield submicrometer rubber particle sizes ranging from 70 to 400 nm [55]. Divinyl benzene (DVB) was used as a crosslinking system for LMA (rubber precursor). Typical TPV morphologies consisting of a crosslinked PLMA rubber dispersion (gel content >90%) in a PE matrix and, consequently, typical TPV solid-state properties are obtained. 

There remained the question of how to evaluate dye spectra in concentrated silver halide dispersions whose particle sizes ranged between 0.2-2.0 fi, and where multiple interparticle light scatter made it unfeasible... 

Commercial aqueous dispersions of FEP are supplied with 54 to 55% by weight of hydrophobic negatively charged particles with the addition of approximately 6% by weight of a mixture of nonionic and anionic surfactants based on polymer content. The particle size range is 0.1 to 0.26 pm. Nominal pH of the dispersion is 9.5 and the viscosity at room temperature is approximately 25 cP.6... 

The effects of liquid velocity (at least at low velocities), direction of flow and liquid properties are only minor for Newtonian fluids. Correlations on gas-liquid columns are given by Joshi [63], Field and Davidson [64] measured the dispersion in a large industrial column (de - 3.2 m, H — 19 m) and found agreement with the correlations of Dcckwer et al. [65] and Joshi [63] (Tabic 3). The influence of particles can be expected to be small, at least for low concentrations and small particles. This is confirmed by the early experiments of Kato et al. [15, 69], For particle sizes ranging from 63... 

The colloidal state of matter is distinguished by a certain range of particle size, as a consequence of which certain characteristic properties become apparent. Colloidal properties are in general exhibited by substances of particle size ranging between 0 2 /an and 5 nm (2 x 10"7 and 5 x 10"9 m). Ordinary filter paper will retain particles up to a diameter of 10-20/an (1-2 x 10" 5 m), so that colloidal solutions, just like true solutions, pass through an ordinary filter paper (the size of ions is of the order of 0-1 nm = 10 10 m). The limit of vision under the microscope is about 5-10 nm (5-10 x 10 9 m). Colloidal solutions are therefore not true solutions. Close examination shows that they are not homogeneous, but consist of suspension of solid or liquid particles in a liquid. Such a mixture is known as a disperse system the liquid (usually water in qualitative analysis) is called the dispersion medium and the colloid the disperse phase. 

It should be noted that although the above relation correlates the backmixing coefficient to the fluid properties, no experimental data on systems other than air or nitrogen and water have been reported in the literature. Kato et al.54 obtained data in 6.6-, 12.2-, and 21.4-cm-i.d. columns with particle sizes ranging from 63 through 177 pm and solid concentrations up to 0.2 g solid per cm- of slurry. They correlated the longitudinal dispersion coefficient of the liquid in the slurry by the following dimensionless relation ... 

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