Foam cells definition

The edges of this dodecahedron sized a - 8.5 cm. When the volume of the rubber balloon at inflation became bigger than the volume of the sphere inscribed in the dodecahedron, the balloon was deformed by the dedecahedron faces and took a shape close to the respective shape of a bubble in a monodisperse dodecahedral foam with a definite expansion ratio. The expansion ratio of the foam was determined by the volume of liquid (surfactant solution or black ink in the presence of sodium dodecylsulphate) poured into the dodecahedron. An electric bulb fixed in the centre of the balloon was used to take pictures of the model of the foam cell obtained. The film shape and the projection of the borders and vertexes on the dodecahedron face are clearly seen in Fig. 1.10. 

Cell Structure. A complete knowledge of the cell stmcture of a cellular polymer requires a definition of its cell sizes, cell shapes, and location of each cell in the foam. 

Microcellular elastomers16 bridge the gap between solid elastomers and low-density foams. Although they may appear to be noncellular, these materials have a microscopic cell structure and so are by definition high-density foams, with densities between noncellular solids and standard foams. The most commercially important applications include shoe soles, carpet backing, chair armrests,... 

After the measuring cell is filled with foam to a specified level it is covered with the lid in order to ensure a vapour saturated atmosphere. Then the space under the filter is connected through a glass cock with the buffer in which a definite reduced pressure is created and controlled by the vacuometer. The liquid draining from the foam is collected in trap 7. Thus a definite reduced pressure in the Plateau borders is established. 

The probability of formation of polyhedra (cells) of a definite shape was studied with the methods of statistical mechanics applying two variants of calculations [52], These theoretical considerations were done for a monolayer of a polydisperse foam. Both variants gave a probability curve the maximum of which was at 6 side faces of the polyhedron. The theoretical dependence fits well with the curve of probability for distribution of cell faces in a real foam monolayer [53],... 

Fig. 3.76 presents an analogous P(h) isotherm of foam films obtained from system n. Here stratified foam films were also observed. At constant p0 (measuring cell A), seven metastable states of the films (in the various experiments) with thicknesses ranging from 82.1 to 45.2 nm were distinguished. The latter thickness was the lowest that could be realised by a spontaneous stepwise thinning. Spontaneous and forced transitions followed upon pressure increase, similar to those shown in Fig. 3.75. The final thickness reached was about 5.6 nm, i.e. a bilayer film. Therefore, on imposing a definite pressure on the films of both systems,...

By definition at an expansion ratio variable by height, the total foam resistance in Eq. (4.32), appears to be its harmonic mean value. That is why the experimental expansion ratio (Eq. 4.32) at its equilibrium distribution along the height of the cells is compared to the calculated harmonic mean ng value A2Al... 

A schematic presentation of one of the most convenient modifications of these cells is given in Fig. 8.2. It represents a glass cuvette 1 (internal dimensions 5x3 cm and 7 x 1.7 cm), made of transparent optical glass, sintered glass filters 2 for creating a definite capillary pressure and electrodes 3 for measuring foam electrical conductivity. 

The losses with the filtrate were determined under static conditions a foam with a known volume was prepared from a definite liquid volume in a separate cell this foam was then dried in the same cell by increasing the pressure to Ap = 1.6 kPa [25,67]. Variations in... 

For a few decades now cellular and porous systems have been classified in morphological terms by simulating the real systems by one or another imaginary, and always simplified, geometrical or stereometrical scheme using an artificially ordered-structure model. Such classifications have always been based on the concept that in any cellular or porous system it is possible to isolate a structural element (cell or pore). However, the diversity of pore and cell types even in small-sized real foamed systems does, in most cases, not permit a definition by only one single geometrical structural parameter, as for other types of solids (type and volume of elementary cell, interplanar or interatomic distances, etc.)... 

Acoustic absorption in open-cell foams is very useful in quieting reflected noise. High thermal and high electrical insulation are due to the very low conductivity of the ubiquitous gas phase, and are definitely best at lowest density even choice of the... 

Microcellular foams are solids composed of relatively small cells. It is difficult to identify a universally accepted definition of the term "microcellular. Defining this term as "relatively small" is hardly quantitative. Aubert (1988) has defined microcellular foams as "foams whose cell or pore size is much smaller than that obtained in conventional foams." This is a subjective definition. The assertion is that traditional methods of foam formation can be used to produce foams with cells approximately 50 to 100 pm in diameter. This range in cell size serves as Aubert s basis for comparison. Aubert then defines microcellular foams as foams with cell diameters smaller than this, i.e., in the range of 10 pm or below. One author s attempt at defining "microcellular" illustrates this term s nebulous character. To provide a... 

Poly (styrene-co-acrylonitrile). See Styrene/acrylonitrile copolymer Poly (styrene-co-allyl alcohol). See Styrene/allyl alcohol copolymer Poly (styrene-co-butadiene). See Styrene/butadiene polymer Poly (styrene-co-divinylbenzene). See Styrene/DVB copolymer Poly (styrene-co-maleic anhydride). See Styrene/MA copolymer Poly (styrene-co-methyl methacrylate). See Styrene/methyl methacrylate copolymer Poly (styrene-co-a-methylstyrene). See Styrene/a-methyl styrene resin Poly (styrene-divinylbenzene). See Styrene/DVB copolymer Polystyrene, expandable Synonyms EPS Expandable polystyrene Expanded polystyrene XPS Definition Amorphous PS beads contg. pentane as a blowing agent and coated with a lubricant the polymer is converted to foamed articles with a closed cell structure by applic. of steam Properties Beads (0.4-1.5 mm diam.)... 

Definition Types include flexible, semirigid, and rigid foams, open- or closed-cell foams, and high-... 

While these previous studies offered valuable insights, demonstrating the continuous extrusion process of PLA foamed with supercritical CO2, the morphology achieved in foamed PLA failed to satisfy the definition of microcellular foam due to lower cell population density (less than 10 cells/ cm ) with cells being larger than 60 m in average size. Distinctions between these features and microcellular foam... 

FIGURE 2.9 Measurement of disjoining pressure isotherms of air-liquid-air foam films, (a) Porous frit film holder located inside hermetically sealed cell subject to applied gas pressure, Pg. Bulk liquid pressure is Pl (= Pi + PhS hyd text for definition of terms)... 

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