Function of emulsifier

The kinetic mechanism of emulsion polymerization was developed by Smith and Ewart [10]. The quantitative treatment of this mechanism was made by using Har-kin s Micellar Theory [18,19]. By means of quantitative treatment, the researchers obtained an expression in which the particle number was expressed as a function of emulsifier concentration, initiation, and polymerization rates. This expression was derived for the systems including the monomers with low water solubility and partly solubilized within the micelles formed by emulsifiers having low critical micelle concentration (CMC) values [10]. 

The function of emulsifier in the emulsion polymerization process may be summarized as follows [45] (1) the insolubilized part of the monomer is dispersed and stabilized within the water phase in the form of fine droplets, (2) a part of monomer is taken into the micel structure by solubilization, (3) the forming latex particles are protected from the coagulation by the adsorption of monomer onto the surface of the particles, (4) the emulsifier makes it easier the solubilize the oligomeric chains within the micelles, (5) the emulsifier catalyzes the initiation reaction, and (6) it may act as a transfer agent or retarder leading to chemical binding of emulsifier molecules to the polymer. 

The Data Analysis portion of RSM perforins a statistical analysis to validate the experimental results obtained in the COED designed program. A set of contour maps is then produced to illustrate how the dependent variable "Performance" varies as a function of Emulsifier A and Emulsifier B concentration. The variable AI is held constant. The program calculated that 99.6% variability could be explained. 

AU discussions of particle nudeation start with the Smith-Ewart theory in which Smith and Ewart (1948) in a quantitative treatment of Harkins micellar theory (Harkins, 1947, 1950) managed to obtain an equation for the particle number as a function of emulsifier concentration and initiation and polymerization rates. This equation was developed mainly for systems of monomers with low water solubility (e.g., styrene), partly solubilized in micelles of an emulsifier with low critical micelle concentration (CMC) and rseeited to work well for such systems (Gerrens, 1963). Other authors have, however, argued against the Smith-Ewart theory on the grounds that (i) particles are formed even if no micelles are present, (ii) the equation for the... 

It does not follow from Eqp. (I) and (2) that the polymerization rate being a function of emulsifier concentration also depends on the emulsifier activity in the given polymerization system. It has been shown in several studies, however, that emulsifier activity at the water-organic phase interface is determined by the structure of the emulsifier molecule and the... 

The number of particles is a function of emulsifier type and concentration and initiator level, although for monomers that obey Case 1 kinetics such as vinyl chloride and vinyl acetate, is almost independent of initiator level (Ugelstad et al, 1969 Friis and Nyhagen, 1973). The calculation of iVp for various reactor operations will he discussed later. The monomer concentration in the polymer particle [Mp] can he obtained using a simple mass balance. Assuming the monomer and pdymer volumes are additive, one obtains the following relationship for the conversion interval,... 

Fig. 6. Number of polymer particles as a function of emulsifier and fnitiator levels for a single CSTR. Case 2 kinetics.

Figure 6. Number of particles formed as a function of emulsifier concentration in polymerization of styrene...

In summary, tensiometry and surface rheology give complementary information about emulsifier adsorption and interactions at fluid interfaces as a function of emulsifier concentration, aqueous phase composition, and the scale of adsorption time. 

The thermodynamics of spread films at the air-water interface can be expressed by the tt-A isotherm, obtained in a Langmuir- or Wilhelmy-type film balance (Figure 14.4a). From the tt-A isotherm, different structures can be deduced for emulsifier monolayers as a function of emulsifier, temperature, and surface density or surface pressure. A phase diagram... 

Figure 4.1 Logarithmic plot of (A) the Interval II rate and (B) the final number of latex particles formed per dm water in the emulsion polymerization of styrene at 60 C as a function of emulsifier (potassium decanoate) concentration. Monomer water mass ratio 1 3. Initiator 0.2% potassium persulfate [57]...

The melting properties are of crucial importance to the technical functionality of emulsifiers, in addition to their amphiphilic properties. Most food and feed emulsifiers are based on natural fat sources, thus giving different melting properties. The consequences of the melting properties can be expressed as the Krafft temperature (i.e. the temperature at which the solubility is above the critical micelle concentration) or as the transition temperature (chain melting temperature, i.e. the melting temperature of the fatty acids in a semicrystaline bilayer). The transition temperature in an emulsifier water system forming a lamellar liquid crystalline phase... 

For initiation in micelles, the emulsifier concentration must exceed the cmc. The classical concept of the cmc is that it represents that concentration at which micelles form at higher concentrations, more micelles form, and at lower concentrations, no micelles are present. The cmc is usually determined by the inflection point in some physical property measured as a function of emulsifier concentration. Figure 1 shows a schematic illustration of the variation of conductivity k, turbidity t, equivalent conductivity X, surface tension y, and osmotic pressure tt with sodium dodecyl sulfate concentration (18). All five parameters show an inflection point at ca. 8mM, which is the most common value of the cmc, and all five curves are consistent with the concept of micelles forming above ca. 8mM and not forming at lower concentrations. Recent measurements of the partial specific volume of sodium lau-ryl sulfate solutions (19), however, suggest that aggregates of lauryl sulfate ions are present of concentrations well below the cmc. 

Reactor comparisons based on SE kinetics will not necessarily be valid when other kinetic schemes are functional. If particle nucleation in a batch reactor is a strong function of emulsifier content, however, one would expect fewer particles to be formed in a CSTR for the reasons cited above. If particle concentration is an important factor in product performance, a continuous pilot unit should be employed in the product and process development work before a commercial continuous system is designed. 

The slight variation of ionic groups in polymers with different initiator types and concentrations (potassium peroxodisulfate or other initiators carrying no ionic groups) was taken as an evidence of an active role of the emulsifier in the chain transfer or termination events. This behavior was a function of emulsifier type. For example, the fraction of emulsifier fragments in the polymer molecule increased in the following order of emulsifiers used ... 

Figure 12.1 Casein is the protein that has the function of emulsifier in milk. Without the casein (milk s "natural polymer"), the milk would be destabilized, since the fat globules, via coagulation or coalescence, would result in destruction of the colloidal dispersion. Reprinted from Walstra et al. f / 984), with permission from John Wiley Sons, Ltd...

Figure 36 Volume of rolls as a function of emulsifier dosage and fermentation time with Panodan 10 (DATAE) in Danish flour.

Emulsifiers are classified by the hydrophilic—lipophilic balance (HLB) system. This system indicates whether an emulsifier is more soluble in water or oil, and for which type of emulsion (water-in-oil or oil-in-water) it is best suited. Emulsifiers having alow HLB value are more oil soluble, and are better suited for water-in-oil appHcations such as margarine. Conversely, emulsifiers having a high HLB value are more water soluble, and function more effectively in oil-in-water emulsions such as ice cream (34). The use of this system is somewhat limited because the properties of emulsifiers are modified by the presence of other ingredients and different combinations of emulsifiers are needed to achieve a desired effect. The HLB values of some common emulsifiers are given (35). 

The basic constituents of all commercial emulsion polymerization recipes are monomers, emulsifiers, and polymerization initiators. Other common components are modifiers, inorganic salts and free alkaH, and shortstops. The function of these different components and the mechanism of emulsion polymerization have been described (43,44). 

A recent trend in the baking industry is to produce bakery foods with either no or reduced fat, to achieve perceived nutritional benefits (25). The functions of fat are achieved, to a degree, with materials such as maltodextrins and modified starches in combination with gums and emulsifiers (see Fat replacers). 

Emulsion breakers (dewatering agents) These functional materials are water-in-oil emulsion breakers that permit the separation of emulsified water. The water accumulates in the tank bottom and... 

The viscosity function of the natural gums is utilized in both oil in water and water in oil emulsions. Often the gums are referred to as emulsifying agents. They are considered not so much as emulsifiers, but rather as emulsion protectors or stabilizers. To a large extent, the function is to increase the viscosity of the aqueous phase so that it approaches, or slightly exceeds, that of the oil hence, there is less tendency for the two phases, once emulsified, to separate by mechanical slippage. 

Emulsifiers assist the stabilizing hydrocolloids in controlling crystal structure. They accentuate the function of the homogenizer in reducing the size of the fat globules. They also reduce the interfacial tension between the fat and water phases of the mix. The result is smaller ice particles and air cells when the mix is frozen and a smoother and creamier finished product. 

Levonantradol (8.4) was synthesized with the intention to introduce a basic amino function into the heterocycle in the hope of obtaining water-soluble salts. Although the solubility of the hydrochloride is not good it was possible to get stable aqueous micellar solutions with the aid of emulsifiers [145] and the compound made its way as an injectable into clinical trials, but never was approved. 

Shinoda, K. and Saito, H. (1969) Thestability of O/W type emulsions as functions of temperature and the HLB of emulsifiers the emulsification by PIT-method. Journal of Colloid and Interface Science, 30, 258-263. 

As with solubility, Kow is a function of the presence of electrolytes and for dissociating chemicals it is a function of pH. Accurate values can generally be measured up to about 107, but accurate measurement beyond this requires meticulous technique. A common problem is the presence of small quantities of emulsified octanol in the water phase. The high concentration of chemical in that emulsion causes an erroneously high apparent water phase concentration. 

Fig. 6. Amount of coagulum as a function of the emulsifier concentration in 1,4-DVB polymerization. Polymerization temperature = 50 °C,water/monomer volume ratio = 6.25 (0),and 12.5 ( ). [Reproduced from Ref. 79 with permission, Hiithig Wepf Publ., Zug, Switzerland].

Fats are used as ingredients in bakery products because they perform some function. As fats are generally more expensive than most other ingredients, commercial pressure would have eliminated them otherwise. In some cases the function of a fat can be either partially or completely replaced by some other ingredient, typically an emulsifier. 

Several emulsions were prepared with SMO as the emulsifier of the primary emulsion, at constant concentration Ci in the oil phase, and SDS at various concentrations Ch in the external aqueous phase. Figure 6.10 shows the quantity of salt released (expressed in relative percentage) as a function of time for all the plots, the globule diameter, the initial droplet volume fraction, and the globule volume fraction were the same. For Ch < CMC, the release is quite slow, occurring over a characteristic time scale of several days. The rate decreases when Ch increases, being minimal around 1 CMC. When the process is achieved (nearly 100% has been released), it appears via microscopy that the water droplet... 

Because of their similarity to the composition of human bile, which consists mainly of bile salts, phospholipids, and cholesterol, of interest for pharmaceutical studies are mainly binary bile salt micelles (BS/PL) (32,33). The function of the bile is to emulsify lipids in food and to dissolve the fission products of lipids as well as fat-soluble vitamins. The spontaneous formation of micelles is a necessary prerequisite to a contact of the lipophilic fission products with the intestinal wall. For affinity measurements, micellar sys-... 

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