Type, foam properties related

Foam properties related to seed type. Soybean flour suspensions produced thick egg white-type foams at all pH levels tested except at 4.0 (Figure 14 47). Although the increase in capacity of suspensions at pH values 6.5 and 4.0 was identical, a medium thick foam was produced by the latter. At pH 4.0, the level of soluble protein in the suspension was significantly lower than at the higher pH values the latter three percentages of protein were similar. A decline in foaming capacity at pH... 

Foam films are usually used as a model in the study of various physicochemical processes, such as thinning, expansion and contraction of films, formation of black spots, film rupture, molecular interactions in films. Thus, it is possible to model not only the properties of a foam but also the processes undergoing in it. These studies allow to clarify the mechanism of these processes and to derive quantitative dependences for foams, O/W type emulsions and foamed emulsions, which in fact are closely related by properties to foams. Furthermore, a number of theoretical and practical problems of colloid chemistry, molecular physics, biophysics and biochemistry can also be solved. Several physico-technical parameters, such as pressure drop, volumetric flow rate (foam rotameter) and rate of gas diffusion through the film, are based on the measurement of some of the foam film parameters. For instance, Dewar [1] has used foam films in acoustic measurements. The study of the shape and tension of foam bubble films, in particular of bubbles floating at a liquid surface, provides information that is used in designing pneumatic constructions [2], Given bellow are the most important foam properties that determine their practical application. The processes of foam flotation of suspensions, ion flotation, foam accumulation and foam separation of soluble surfactants as well as the treatment of waste waters polluted by various substances (soluble and insoluble), are based on the difference in the compositions of the initial foaming solution and the liquid phase in the foam. Due ro this difference it is possible to accelerate some reactions (foam catalysis) and to shift the chemical equilibrium of some reactions in the foam. The low heat... 

Although in vivo a proportion of foam cells in lesions are demonstrated by immunohistochemical marking to be of smooth muscle cell origin, feeding smooth muscle cells in vitro with P-very low-density lipoprotein or chemically modified LDL does not, in contrast to the case with macrophages, lead to foam cell formation (Heinecke etal. 1991, Hoff et al. 1991, Huff et al. 1991). The reason for this differences in response relates in the types and properties of the hpoprotein receptors expressed in cultured macrophages and cultured smooth muscle cells. Smooth muscle cells, like fibroblasts (the cell type on which the classical studies were conducted), are typical LDL receptor cells (Goldstein and Brown 1977). 

This comprehensive chapter supplies a detailed analysis of the types of cellular material where the impact properties are the main reason for their use, such as foams used for protective purposes in packaging and other applications, e.g. protective helmets. The chapter includes detailed information and discussion on such aspects as macroscopic deformation geometry cell geometry and deformation mechanisms impact properties and the relation of impact properties to microstructure, packaging design and complex impacts. 36 refs. 

The studies discussed expand the use of the method for assessment of foetal lung maturity with the aid of microscopic foam bilayers [20]. It is important to make a clear distinction between this method [20] and the foam test [5]. The disperse system foam is not a mere sum of single foam films. Up to this point in the book, it has been repeatedly shown that the different types of foam films (common thin, common black and bilayer films) play a role in the formation and stability of foams (see Chapter 7). The difference between thin and bilayer foam films [19,48] results from the transition from long- to short-range molecular interactions. The type of the foam film depends considerably also on the capillary pressure of the liquid phase of the foam. That is why the stability of a foam consisting of thin films, and a foam consisting of foam bilayers (NBF) is different and the physical parameters related to this stability are also different. Furthermore, if the structural properties (e.g. drainage, polydispersity) of the disperse system foam are accounted for it becomes clear that the foam and foam film are different physical objects and their stability is described by different physical parameters. 

The theory indicates that the mechanical properties of the foam are dependent on the properties of the cell wall materials and their size and shape. By relating the density of the foam to its bulk mechanical properties, the slope of the fitted line (n) can give us information about the type of failure mechanism (Figure 20.19). This also indicates that the size and shape of the bubbles in a foam will have a predictable effect on the strength and fracture of the foam. Bread and extruded cereal foams have been considered as cellular solids using the Gibson and Ashby analysis, and have been shown to follow the Gibson and Ashby prediction (Keetels et al. 1996 Hayter etal. 1986). 

Edible ester-type surfactants can be based on glycerol, sorbitol, or propylene glycol. The foam stabilization and viscosity-thickening properties of diethanolamine-fatty acid condensates are related directly to their diethanolamide content on the other hand, solubility in water is shown only by the 2 1 condensate. 

An accurate formulation handling is extremely useful not only to make microemulsion and to adjust their properties such as their solubilisation ability, or to attain a low interfacial tension to ease emulsification or to enhance oil recovery. Formulation has been shown to be also directly linked with emulsion properties such as their type, stability, viscosity, drop size [6] and with the efficiency of the emulsification protocol [7]. The existence and persistence of foams are dependent on formulation too [8]. Solid surface wetting is also linked with formulation as well as with many related applications. This is why an accurate numerical treatment of formulation issues is paramount in industrial research and development. 

Flow Resistance of Foams in Porous Medium. Foam flows in the reservoir by making and breaking processes. Because of its dispersed nature, foam exhibits low flow mobilities depending on texture (bubble size and distribution) in relation to the imposed injection and reservoir conditions (27). To perform successfully, the foam must withstand a vast range of conditions and still maintain its integrity and flow resistance properties. For a given surfactant and reservoir type, therefore, it is important to consider a range of gas and liquid velocities, and liquid volume fraction (LVF). 

The test methods mostly follow British Standards, but some are more closely related to the ISO tests. Care must be taken to ensure that the correct sample size is u.sed. The determination of water absorption by diffusion is based on the Swiss Standard SIA 279 Part 5.07 [13] (see Section 2.6 below). Similarly the properties of extruded board are specified in BS 3837, Part 2, 1990 [14]. BS 3927, 1986 [15], specifies rigid phenolic foam for thermal insulation in the form of slabs and profiled sections. The material is classified as types A. B. and C. which differ principally in thermal conductivity, water vapor permeability and apparent water absorption. Thermal conductivity is measured by methods described in BS 4370, Part 2, Method 7 [16] or Appendix B of BS 874 [17]. ... 

The test methods developed for testing flexible cellular plastics are quite different from those developed for rigid foams. For rigid cellular plastics, separate test methods were developed for specific properties. No such separate test methods relating to specific properties are developed for flexible cellular plastics. Instead, a series of test procedures that describe a variety of physical properties of a particular type of material are commonly used to test flexible cellular plastics. 

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