Emulsions continued photomicrograph

Studies on the kinetics of carbon black dispersion in various rubbers have been reported using a Brabender mixer fitted with cam-type rotors [110]. Dispersion rating, determined by visual inspection of photomicrographs, was found to depend strongly on mixing time. For an SBR emulsion, it was observed that there was an initial delay period where the carbon black agglomerates were thought to be fractured and incorporated into the rubber. Subsequently, the process of dispersion continued for a considerable time thereafter. 

Just as with emulsions and foams, suspensions can exist with additional dispersed phases present. They may contain, in addition to solid particles and a continuous liquid phase (and possibly a stabilizing agent), emulsified droplets and/or gas bubbles. Figure 2.4 (in Section 2.2.1) shows photomicrographs of a practical suspension that contains suspended oil droplets in addition to the particles. The terminology used to describe such systems can become confusing. Consider an aqueous dispersion of solid particles and emulsion droplets. If the solid particles are adsorbed on the emulsion droplets then it is an emulsion that also contains solids. If, however, the particles and droplets are not mutually associated then the system is at once a suspension and an emulsion. Which term is used becomes a matter of choosing the most appropriate context frequently one or the other is considered to be the primary dispersion while the other phase is considered to be an additive or a contaminant. 

Figure 3 shows a representative photomicrograph of the Huntington Beach crude oil-alkaline emulsion taken at 400 magnification in a continuous aqueous phase. The emulsion contained one part by volume of oil phase to twenty parts aqueous phase. 

In many surface separation processes there will occur three distinct phases or process streams, an oil product stream, which may contain emulsified water, an aqueous tailings stream, which may contain emulsified oil, and an interface or rag layer emulsion stream, which may contain emulsified oil and/or water. The interface emulsion layer may build up to a certain level in a process, continuously reform and break in the separator and never cause operational problems. On the other hand, the interface emulsion layer may build to such an extent that it requires removal and treatment. Knowledge of the nature of the dispersed phase will be required to determine an effective treatment. Figure 3 Ulustrated the simultaneous presence of W/O and O/W/O emulsion. Mikula shows (Figure 1 in reference [132]) a photomicrograph of a quite stable interface emulsion (rag layer emulsion) in which one can clearly observe the simultaneous occurrences of both O/W and W/O emulsions in different regions of the same sample. 

Figure 6.11 Photomicrographs showing monodisperse W/O/W emulsion droplets obtained in straight-through MC emulsification process at the pressure difference across the channels of 1.3 kPa and continuous phase cross-flow velocity of 1.2 mm/s. The concentration of internal droplets in the outer drops ranged between 0 and 30 vol% and the channel dimensions were 42.8 x 13.3zyxonetwothreexyzm.

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