Foams thinning

Our objective in this study is to elucidate the complex phenomena occurring during the process of three phase foam thinning, to identify the interaction mechanisms between the oil droplets, the thinning foam film and the Plateau-Gibbs borders and the role of surface and interfacial tension gradients in foam stability, and to examine the implications upon crude oil displacement by foam in pourous media. 

During the process of three phase foam thinning, three distinct films may occur foam films (water film between air bubbles), emulsion films (water between oil droplets) and pseudoemulsion films (water film between air and oil droplets) (Figure 1). To study the behavior of these films and particularly the oil droplet-droplet, oil droplet-air bubble and oil droplet-foam frame interactions it is necessary to utilize numerous microscopic techniques, including transmitted light, microinterferometric, differential interferometric and cinemicrographic microscopy. 

Abbas MN, El-Assy NB, Abdel-Maniem SH. 1989. Determination of traces of mercury(II) and phenylmercury by direct polyurethane foam thin-layer spectrophotometry. Anal Lett... 

Gas Liquid Foam, thin films, froth, fire extinguisher foam... 

The application area of surface and colloid science has increased dramatically during the past decades. For example, the major industrial areas have been soaps and detergents, emulsion technology, colloidal dispersions (suspensions, nanoparticles), wetting and contact angle, paper, cement, oil recovery (enhanced oil recovery [FOR] and shale oil/gas reservoir technology), pollution control, fogs, foams (thin liquid films), food industry, biomembranes, membranes, and pharmaceutical industry. 

METHOD 52 - DETERMINATION OF TRACES OF 2,4- AND 2,6-DIAMINOTOLUENES IN FLEXIBLE POLYURETHANE FOAMS. THIN-LAYER CHROMATOGRAPHY-FLUORIMETRIC METHOD... 

The constant C, which can be obtained by fitting the experimental data to the equation, accounts for the cell shape. For example, C takes a value of 3.46 for pentagonal dodecahedrons and a value of 3.35 for tetracaidecahedra. The other way to estimate the cell shape is by doing a permanganate etching to the foam. Thin cell walls are removed, and the shape of the cells can be observed directly with a microscope (Fig. 6). Pentagonal dodecahedrons and tetracaidecahedra are usually observed. 

There were some studies on preparation of nanocellular foams with self-assembled bloek copolymers. Recently, Yokoyama et al. [4,5], Li et al. [6] and Taki et al [7] reported the preparation of nanocellular foamed thin film with 10-nm size cells using a block copolymer and carbon dioxide. The concept of their nanocellular foaming is to use the block copolymer... 

The importance of the thin film between the mineral particle and the air bubble has been discussed in a review by Pugh and Manev [74]. In this paper, modem studies of thin films via SFA and interferometry are discussed. These film effects come into play in the stability of foams and froths. Johansson and Pugh have studied the stability of a froth with particles. Small (30-/ m), moderately hydrophobic 6c = 65°) quartz particles stabilized a froth, while more hydrophobic particles destabilized it and larger particles had less influence [75]. 

There appear to be two stages in the collapse of emulsions flocculation, in which some clustering of emulsion droplets takes place, and coalescence, in which the number of distinct droplets decreases (see Refs. 31-33). Coalescence rates very likely depend primarily on the film-film surface chemical repulsion and on the degree of irreversibility of film desorption, as discussed. However, if emulsions are centrifuged, a compressed polyhedral structure similar to that of foams results [32-34]—see Section XIV-8—and coalescence may now take on mechanisms more related to those operative in the thinning of foams. 

Exerowa and co-workers [201] suggest that surfactant association initiates black film formation the growth of a black film is discussed theoretically by de Gennes [202]. A characteristic of thin films important for foam stability, their permeability to gas, has been studied in some depth by Platikanov and co-workers [203, 204]. A review of the stability and permeability of amphiphile films is available [205]. 

Cross-linking of polyethylene can be accomphshed either chemically or by high energy radiation. Radiation cross-linking is usually accomphshed by x-rays (44) or electrons (45,46). Chemical cross-linking of polyethylene is accomphshed with dicumyl peroxide (47), d4-tert-huty peroxide (48), or other peroxides. Radiation cross-linking (49) is preferred for thin foams, and chemical cross-linking for the thicker foams. 

Low deasity polyethyleae foam products (thin sheets, planks, rounds, tubes) ia the range of 32—160 kg/m (2—10 lbs/ft ) have beea prepared by an extmsion technique usiag various gaseous fluorocarboa blowiag ageats (100,101). The techniques are similar to those described earlier for produciag extmded polystyreae foam planks and foam sheets. 

The insulating value and mechanical properties of rigid plastic foams have led to the development of several novel methods of buUding constmction. Polyurethane foam panels may be used as unit stmctural components (220) and expanded polystyrene is employed as a concrete base in thin-sheU constmction (221). 

The combination of stmctural strength and flotation has stimulated the design of pleasure boats using a foamed-in-place polyurethane between thin skins of high tensUe strength (231). Other ceUular polymers that have been used in considerable quantities for buoyancy appHcations are those produced from polyethylene, poly(vinyl chloride), and certain types of mbber. The susceptibUity of polystyrene foams to attack by certain petroleum products that are likely to come in contact with boats led to the development of foams from copolymers of styrene and acrylonitrUe which are resistant to these materials... 

J. A.F. Plateau, who first studied their properties. It is the Plateau borders, rather than the thin Hquid films, which are apparent in the polyhedral foam shown toward the top of Figure 1. Lines formed by the Plateau borders of intersecting films themselves intersect at a vertex here mechanical constraints imply that the only stable vertex is the one made from four borders. The angle between intersecting borders is the tetrahedral angle,... 

Fig. 4. Schematic representation of a two-dimensional model to account for the shear modulus of a foam. The foam stmcture is modeled as a coUection of thin films the Plateau borders and any other fluid between the bubbles is ignored. Furthermore, aH the bubbles are taken to be uniform in size and shape.

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