Foaming pressure

In the high pressure process, a resia melt containing a chemical blowiag ageat is iajected iato an expandable mold under high pressure. Foaming begias as the mold cavity expands. This process produces stmctural foam products with very smooth surfaces siace the skin is formed before expansion takes place. 

High-pressure structural foam products have generally been found to require little or no postfinishing. Although high-pressure foam products may exhibit visual splay, their surface smoothness is maintained and no sanding or filling is required. 

Several surfactants were studied in ambient-pressure foam tests, including alcohol ethoxylates, alcohol ethoxysulfates, alcohol ethoxyethylsulfonates, and alcohol ethoxyglycerylsuUbnates [210]. Surfactants that performed well in the 1-atm foaming experiment were also good foaming agents in site cell and core flood experiments performed in the presence of CO2 and reservoir fluids under realistic reservoir temperature and pressure conditions. 

Subsurface Method. The subsurface method requires a high back-pressure foam maker and forces this foam through a pipe into the bottom of the tank. This pipe may be the existing product line or a line installed specifically for... 

Using the coinjection procedure, a solid melt is injected to form the solid, smooth skin against the cavity surface. Simultaneously a second short shot melt with blowing agent is injected to form the foamed core. With a full second shot, the mold can incorporate pins or a mold that opens similar to high-pressure foam molding. 

Structural-web molding is a low pressure foam molding method. It is the phrase usually used to identify the gap between structural foam (SF) molding and injection molding. Its surface does not have the usual SF characteristic swirl pattern. It can produce very large, lightweight parts with smooth surfaces like conventional injection molded parts. 

Fig. 6.3. Kinetic curves of the decrease in water content of a foam at different capillary pressures foam...

The kinetics of establishing equilibrium pressure in a foam shows that the time needed is much shorter (about 6-7 times) than the time for foam destruction. Thus, with respect to pressure, foam destruction can be considered to occur under equilibrium conditions. 

The initial expansion ratio and dispersity of polyhedral foams are related through the quantitative dependence, given by Eq. (4.9). There at Ap > 103 Pa the content of the liquid phase in the films can be neglected. Thus, the connection of the structure parameters n, a and r can be expressed by the simple relation in Eq. (4.10). It follows from it that under given foaming conditions a definite expansion ratio can be reached by changing the border pressure, foam dispersity and surface tension of the foaming solution. 

Larger values of the accumulation ratio can be reached in dry foams [24,25,47,73,74,76-78]. Kruglyakov and Kuznetsova [47,71] have studied the effect of capillary pressure, foam expansion ratio and dispersity on / mjn. The foam was prepared from NaDoBS and NP20 solutions. The accumulation ratio //m,n increased directly proportional to the expansion ratio (at a = const) and inversely proportional to the parameter a (at n = const) (Fig. 10.4). The maximum degree of accumulation in a NaDoBS solution (0.3 g dm 3 + 0.4 mol dm 3 NaCl) which could be achieved was = 1050 at Ap = 102 kPa. Further increase in... 

CD mix starch and water cook under pressure foam by pressure relief (T) shape and cut foam toast surface of foam dry the snacks (7) cool the snacks... 

The first studies of CO2 dispersions at pressures around 10 MPa (1,500 psi) were reported in 1978 (48,49). Before that time virtually all experiments were performed on true foams (i.e., near atmospheric pressure on dispersions of a low-density gas in a continuous liquid phase). For this historical reason, the literature on FOR often refers to high-pressure dispersions as "foams, even though the phase, physical, and flow properties of a dispersion in which both phases have a liquid-like density and compressibility cannot always be assumed similar to those of a true foam (66). For many (but not all) mechanistic studies it may be appropriate to employ a foam, and atmospheric pressure emulsions are appropriate stand-ins for high-pressure emulsions of the same chemical composition. However, atmospheric pressure foams cannot be used when the correct answer depends on replicating all of the physical properties of a dispersion that exists only at high pressure. 

CO2 floods at pressures above 10 MPa (49). Only flooding experiments were used to choose surfactants in this first extension of low-pressure foam flooding to high-pressure, C02-miscible flooding. 

Foam-Kon. [LNP ICI Advanced Materials] Thermoplastic structural foam cone. for high pressure foam systems, inj. molding compds. 

Texture. Foam texture is an important parameter that affects the rheology of the foam fluid. Texture of a foam is a means of classifying a foam according to its bubble size, shape, and distribution within the foam matrix. Texture is a description of the manner in which the gas bubbles are distributed throughout the liquid phase of the foam. This property not only influences the foam s rheology but also its fluid loss, proppant transport, and cleanup properties. The texture of a foam is a qualitative rather than a quantitative value, and therefore a number cannot be used to describe it a physical description will be used. Factors that effect the texture of foams are quality, pressure, foam generating technique, and chemical composition. 

Certain methods of calculating friction pressures involve the use of pressure charts that are in the form of pressure drop per length of pipe versus the flow rate of the foam. These types of charts incorporate foam quality and tubular geometry but may neglect consideration of one or more of the parameters such as temperature, pressure, foam texture, polymer or surfactant type, and concentration. Each of these parameters is often unspecified but drastically affects the friction pressures of foams. Information derived from such charts should be taken only as a guideline. 

Determination of bottomhole pressures for conventional fracture fluids such as gelled oil or water are relatively simple compared to foam bottomhole pressure calculations. However, when compressible fluids such as foams are used, more rigorous calculations are required to determine bottomhole pressures. Foam density, foam quality, and injection rates are functions of temperature and pressure. 

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