Emulsions emulsion films

The diversity of release products and the wide range of release problems make classification difficult. One approach is by product form, with subdivisions such as emulsions, films, powders, reactive or iaert sprays, reactive coatings, and so on. Another approach is by appHcation, eg, metal casting, mbber processiag, thermoplastic iajection mol ding, and food preparation and packagiag. 

Indirect type, batch or continuous operation for pharmaceuticals such as peniciUin and blood plasma. Expensive. Used on beat-sensitive and readily oxidized materials under Liquids under Liquids under Liquids used on pharmaceuticals and related products which cannot be dried successfuby by other means. Applicable to fine chemicals under Granular solids cial cases such as emulsion-coated films under Granular solids... 

Film-bildschicht, /. Photog.) film emulsion, film layer, film coat, -schicht, /. film layer. 

The past decade has seen a dramatic increase in the number of reported applications of neural computing in pharmaceutical formulation [29-32]. Applications now cover a variety of formulations—for example, immediate and controlled release tablets, skin creams, hydrogel ointments, liposomes and emulsions, and film coatings. The following examples are by no means exhaustive, but they show where neural computing has been used successfully in modeling formulations. 

Stripping film adheres less firmly than a layer of liquid emulsion, thus film can be displaced from specimen during development Presence of the gelatin layer above the emulsion may yield staining problems, as gelatin can become stained, obscuring view of specimen... 

The identity of methoprene photoproducts has been studied from aqueous emulsions, thin films on glass or silica gel, and in methanolic solution (Figures 3 and 4, 40). As a thin film (0.1 ym) on glass, the half-life of methoprene was about 6 hr. After 93% degradation of parent, more than 50 photoproducts were observed, only five of these present in 3% or higher yield 7-methoxycitronellic acid (4%), 7-methoxycitronellal (4%), the 4,5-epoxide of methoprene (6%), a C12 methyl ketone (3%), and 14C02 (6%). Similar products were encountered on photolysis of a 100 ppm aqueous emulsion of methoprene, except that methoxy-citronellal was isolated only as its dimethyl acetal (9% yield), a presumed artifact of work-up. In addition to the same products identified from thin film studies, at least forty-six other discrete products were detected, but not identified (40). 

Initially devised to measure interactions in single soap films (air/water/air) [8], the TFB technique has been progressively improved and its application has been broadened to emulsion films (oil/water/oil) [ 12] and asymmetric films (air/water/oil or air/water/solid) [13,14]. In a classical setup, a thin porous glass disk is fused on the side to a capillary tube and a small hole is drilled in the center of the disk. The liquid solution fills the disk, part of the capillary, and a thin horizontal film is formed across the hole. The disk is enclosed in a hermetically sealed box, with the capillary tube exposed to a constant reference pressure Pr. Under the effect of the pressure difference AP between the box and the reference, the... 

This technique allows measuring interparticle forces as small as 10 N, corresponding to the minimum force required for forming chains. One advantage of this particular experiment is the built-in averaging over extremely large number of emulsion films. 

Figure 2.22. (a) Disjoining pressure vs. thickness isotherm for an emulsion film stabilized by 0.1% BSA, ionic strength of 10 mol/1 NaCl, oil phase = hexadecane. The dots are the experimental data, dashed line is the double-layer contribution to the total disjoining pressure, and the solid line is the best fit done supposing additivity of the double-layer and steric forces, (b) Force vs. distance profiles for ferrofluid emulsions stabilized with mixed BSA-Tween-20 adsorption layers. The total concentration of the Tween-20 is kept constant = 5CMC, pH = 5.8. (Adopted from [78].)... 

Rgure 2.26. Six consecutive steps in shrinking of an emulsion film stabilized with 0.1 wt% BSA. Oil phase is hexadecane the ionic strength is 10 mol/1. The bar corresponds to 100 j,m. The local adhesion on aggregates is evident. Arrows indicate some of the points of adherence at the interfaces. (Adapted from [87].)... 

V. Bergeron Stability of Emulsion Films. In Proceedings of the Second World Congress of Emulsions 4, 247, Bordeaux, France (1997). 

T.D. Dimitrova, F. Leal-Calderon, T.D. Gurkov, and B. Campbell Disjoining Pressure vs. Thickness Isotherms of Thin Emulsion Films Stabilized by Proteins. Langmuir 17, 8069 (2001). 

As another example of utilizing platy forms of twinned crystals, we should mention a recent remarkable increase in the photosensitivity of photographic film. Photographic emulsion film consists of minute AgBr crystallites, with octahedral or cubo-octahedral Habitus. The photosensitivity is determined by the area... 

Marinova, K., Gurkov, T., Velev, O., Ivanov, I., Campbell, B., Borwankar, R. (1997). The role of additives for the behaviour of thin emulsion films stabilized by proteins. Colloids and Surfaces A Physicochemical and Engineering Aspects, 123-124, 155-167. 

Silver halides employed in emulsions are the chloride, the bromide and the iodide. Negative emulsions are composed of silver bromide with a small amount of silver iodide. Positive emulsions for films and paper contain silver chloride, or mixtures of silver chloride and silver bromide in varying amounts, according to the tone, speed, and contrast desired. 

A similar technique can be used to study the rheological properties of liquid films. Figure 4 shows the formation of a W/O/W emulsion film with two, identical aqueous phases (such as in water-in-oil emulsions) at the tip of the capillary. A pre-requisite of the experiment is that the surface of the capillary must be well wetted by the film phase, i.e., it should be hydrophobic in this case. First, an aqueous drop is formed inside the oil (film liquid) and the aqueous phase is in the bottom of the cuvette. Then, the level of the aqueous phase is slowly increased. As the oil/water interface passes the drop, a cap shaped oil film, bordered by a circular meniscus, covers the drop. This film can be studied in equilibrium and in dynamic conditions, similar to the single interfaces (See above). The technique can be used to study films from oil or aqueous phase which can be sandwiched between identical or different liquid or gas phases. 

The film is observed by a microscope using reflected light The film holder and the objective are immersed in air in the case of foam (i.e., air/liquid/air) film and in the oil phase, in the case of an O/W/O emulsion film, respectively. The film thickness can be determined by measuring the intensity of the light reflected from the film surfaces [9]. Further details of the technique will be discussed in Chapter 2. 

Emulsion Film Emulsion Flotation Emulsion Test... 

Bergeron, V., An Introduction to Forces and Structure in Individual Foam and Emulsion Films in Foams and Emulsions, Sadoc, J.F. Rivier, N. (Eds.), NATO ASI Ser., Ser. E, Kluwer Academic Publishers Boston, 1999, pp.45-72. 

Slow, thin emulsion films, such as Kodak Technical Pan or Ilford Pan-F, developed in high-definition developers such as Windisch Extreme Compensating Developer or POTA, will produce negatives, even from 35 mm, of extremely high acutance with the ability to enlarge to mural size. The trade-off is an extremely low EL... 

The fixing process involves a series of chemical reactions in which the silver bromide is converted into complex argentothiosulfates, which are then dissolved by contact with fresh fixer and finally washed out of the film or paper. Upon immersing an emulsion (film or paper unless otherwise noted) into fixer, the first reaction is the conversion of unused silver bromide into an insoluble but not very stable compound. This compound can be seen by looking at negatives (not prints) after only a few seconds in the fix. They will appear milky in appearance. If fixation is not continued and the compound not completely dissolved, the negatives will rapidly degenerate. 

Develop conventional emulsion films for 3 minutes in each solution do not rinse in-between. Develop T-grain films for 4 minutes in each bath. Use continuous agitation in both baths. 

NOTE This formula may cause dichroic fog on some modern emulsion films. Testing is advised. 

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