Foam application methods

Additional benefits to be realized from the low wet pick-up foam application method include greater line speed (especially where the dryer represents a bottleneck in the pad process to be replaced), lower pollution abatement costs due to reduced volumes of effluent and exhaust gases and reduced water consunption. 

Some of the foam application methods are shown in Fig. 2.9 and Fig. 2.10. The one side applicators apply foam to only one side of the fabric, leaving open the possibility of two different finishes on different sides of the same fabric. The two side applicators, on the other hand, apply the same foam to both sides of the treated... 

Application is mainly by padding followed by curing at 150-180 °C, although minimum add-on techniques such as slop padding, spraying and foam application have been successful. They can also be applied by discontinuous methods, such as exhaust or dip-spin [501]. 

Foam Application Time—Chambers and Subsurface Methods... 

Two techniques allow determination of the compressibility of foam. The methods are related and the application dictates which method better defines the quality of the product. For example, for furniture cushions, indentation force deflection (IFD) is a more common test technique than compression force deflection. Both methods determine the amount of force required to compress a foam to a percentage of its thickness. In the IFD test, the plunger that compresses the foam is smaller than the foam sample. This presumably correlates to a person sitting in the center of a chair cushion. 

Adsorption can be measured by direct or indirect methods. Direct methods include surface microtome method [46], foam generation method [47] and radio-labelled surfactant adsorption method [48]. These direct methods have several disadvantages. Hence, the amount of surfactant adsorbed per unit area of interface (T) at surface saturation is mostly determined by indirect methods namely surface and interfacial tension measurements along with the application of Gibbs adsorption equations (see Section 2.2.3 and Figure 2.1). Surfactant structure, presence of electrolyte, nature of non-polar liquid and temperature significantly affect the T value. The T values and the area occupied per surfactant molecule at water-air and water-hydrocarbon interfaces for several anionic, cationic, non-ionic and amphoteric surfactants can be found in Chapter 2 of [2]. 

The volumetric add-on of foam can also be used to control the dry pick-up on the fabric when the application method Is knife coating, But for horizontal pad application, dry pickup Is best controlled by the blow ratio,... 

The upper and lower concentration limits of applicability of the foam separation method have been studied by Khaskova and Kruglyakov [67,70,84]. They found experimentally that accumulation from surfactant solutions with a concentration cl.q = 2-3 CMC is possible at //mm = 6-9 (for NaOL foams) or = 27-30 (for NaDoBS foams) [67,70]. Surely, the time needed to extract surfactants from concentrated solutions increases considerably (a prolonged air barbotage is necessary), and a substantial carry-away of the liquid phase is possible. For example, about 20 hours were needed to extract OP-10 from a solution with concentration 300 mg dm3 and to decrease its concentration to 10 mg dm 3 [72]. 

The lower concentration limit of the applicability of the foam separation method is determined by the lowest residual concentration and depends on the surface activity of the substances, the rate of establishing of the adsorption equilibrium, foam stability and the apparatus used in the process. During foam accumulation the surfactant is extracted from the solution, thus leading to a decrease in foam stability and expansion ratio. Finally, a concentration is reached at which the foam cannot be withdrawn from the apparatus and the accumulation ratio becomes close to 1. 

There are two main types of low wet picknp applicators. The first is the saturation-removal type where the fabric is completely satnrated with the finish liquid and then the excess liqnid is removed mechanically or with a vacnnm before drying. With the second type, a precise amount of finish liqnid is nniformly applied to the fabric using transfer roll, spray or foam techniqnes. Table 2.2 gives a snrvey on low wet pickup finishing application methods, some of which will now be discussed in more detail. 

One important application method for chemical finishes is the use of foam to apply the finish to the fabric. By replacing part of the water in the chemical... 

Mor-Flo CS-38-S1 is a polyurethane modified acrylic concrete sealer. A simple water dilution and the addition of a preservative will produce a ready-to-use product. Leveling and wetting on tightly troweled concrete or other extremely smooth surfaces can be improved by the addition of 0.5% Fluorad FC-129 (1% active solution). Foaming, which may be a problem depending on the application method, can be greatly reduced by adding 0.03% of an antifoam emulsion (2). 

Polyols based on sucrose or sucrose and a coinitiator are used primarily to make rigid urethane foams for a wide variety of end-uses. Following are some applications listed by application method. 

Due to the extensive research that has been conducted in the area of foam application in enhanced oil recovery, simulation of foam behaviour has become more feasible. Several methods of foam simulation have been developed population balance models [16, 17], fractional flow models [IS, 19], and models that alter the gas phase permeabilities [20, 21], Although the population balance models treat the foam generation mechanisms in a detailed fashion, they may be impractical to apply on large field scale simulations. Both the fractional flow model and the models that alter the gas phase permeabilities rely on history matching experimental data. The fractional flow model provides insight into onedimensional foam flow, but it may be more difficult to apply in three-dimensional situations. In the following section, the application of relative permeability alterations to model foam flow is investigated. 

For the pour-in place and foam technique, there is a group of characteristic rigid PU foam applications available, however, their largest consumption area is in the insulation of refrigerators and freezers, but not that much in the construction industry. Standard two-component formulations with special adaptations, or one-component systems that cure by reaction with the moisture existing in the atmosphere, are available. The method produces highly effective thermal and noise insulation as well as physical reinforcement, although the foams produced are less uniform than those produced in-plant. 

Refrigeration in Transportation. Styling is imimportant. The volume of insulation and a low thermal conductivity are of primary concern. Volume is not large, so application methods are not of prime importance. Low moisture sensitivity and permanence are necessary. The mechanical properties of the insulant are quite important owing to the continued abuse the vehicle imdergoes. Cost is of less concern here than in other applications. Polystyrene foam is widely used in this application. 

Nonstabilized foams are referred to as froths froth-bonded fabrics are similar in properties to some satnration-bonded nonwovens. Typical foams nsed as non woven binder solutions have a consistency similar to shaving cream. Application methods include knife-edge layering onto a horizontal web snrface followed by vacuum penetration, and saturation and penetration of a vertical web snrface... 

Foam and wave fluxing have given way to spray fluxing as the predominant flux application method. All three techniques are discussed here. 

Despite these limitations, Denkov et al. [50] have made some comparison with experiment. Here, for example, and were determined from foam volume against time plots for one method of foam generation. Assuming these constants are independent of foam generation method, they were then combined with an experimental value of t for another method of foam generation in an application of deductions from Equations 6.30 through 6.31. A reasonable estimate of VqIV, for that method of foam generation was obtained. 

Abstract The purpose of this paper is to review the most significant developments of the last 10 years in the field of crosslinked polyolefin foams. The methods to produce the foams, the relationships between structure and properties, and the main applications of these materials are briefly reviewed. Topics of possible future research are proposed. 

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