Dynamic foam tests

The first method is quite difficult to reproduce due to the strong influence on the results that small contaminations or vibrations can have. The latter two are also difficult to reproduce since the foam generation and collapse is not always uniform, yet these methods are very commonly used. The dynamic foam tests are most suitable for evanescent foams since their lifetimes are transient. For more stable foams the static foam tests are more commonly used. 

The foaming capability and foam stability obtained from sparkling wines is usually tested by a dynamic foam stability method, as discussed in Section 2.6.2. Because these foams are evanescent and not really very stable, at least compared with the foams found in other industries, dynamic rather than static foam tests are the most suitable. In one version of the dynamic foam test, the Mosalux method, the foam heights are automatically measured using infrared beams and sensors [848],... 

A measure of the persistence of a foam (the time an average bubble exists before bursting). Ideally independent of the apparatus and procedure used, and characteristic of the foaming solution being tested. See also Dynamic Foam Test. 

Any of several methods for assessing foam stability in which one measures the rate of collapse of a (static) column of foam. See also Dynamic Foam Test, Foaminess. 

Results of the Dynamic Foam Tests. Typical plots of pressure drop vs. time for the dynamic foam tests are given in Figure 3. The initial sharp rise in... 

Dynamic foam tests and the displacement tests are needed to complete the screening of the candidate surfactants. Good correspondence was obtained between the two tests. 

In a typical dynamic foam test, foam is generated by flowing gas through a porous orifice into a test solution, as shown in Figure 15. The steady-state foam volume maintained under constant gas flow into the column is then measured. There are many variations of this kind of test (4, 40), including an ASTM standard test (41). This technique is frequently used to assess the stability of evanescent foams. 

Figure 2.17 Illustration of a dynamic foam stability test apparatus in which foam is generated by flowing gas through a porous diffuser. Not drawn to scale.

In either the dynamic or static foam tests, but especially the static tests, one should bear in mind the many changes in a foam that may occur over time, including gas diffusion and changing bubble size distribution. 

Tertiary oil was increased up to 41% over conventional CO2 recovery by means of mobility control where a carefully selected surfactant structure was used to form an in situ foam. Linear flow oil displacement tests were performed for both miscible and immiscible floods. Mobility control was achieved without detracting from the C02-oil interaction that enhances recovery. Surfactant selection is critical in maximizing performance. Several tests were combined for surfactant screening, included were foam tests, dynamic flow tests through a porous bed pack and oil displacement tests. Ethoxylated aliphatic alcohols, their sulfate derivatives and ethylene oxide - propylene oxide copolymers were the best performers in oil reservoir brines. One sulfonate surfactant also proved to be effective especially in low salinity injection fluid. 

Apparatus and Procedure. It was necessary to design more definitive tests to further evaluate the better candidate surfactants. This was accomplished by means of a multi-phase dynamic-fiow test that consists of a small packed bed through which surfactant solution can be passed followed by gas to produce in situ foam. The pressure drop through the column is measured as the fiuid is drawn through the column at a constant volumetric fiow rate. From the recorded data, relative mobilities of the liquid and gas phases may be calculated. The change in gas mobility due to the presence of the surfactant is very closely related to the effectiveness of that surfactant for mobility control in oil core studies. A schematic drawing of the apparatus is shown in Figure 2. 

Experimental Assessment of Foam Stability. Usually foam stability has been tested by one of three methods (4, 6, 13) (1) the lifetime of single bubbles (2) the steady-state (dynamic) foam volume under given conditions of gas flow, shaking, or shearing or (3) the rate of collapse of a (static) column of foam generated as described. 

Ample evidence suggests that crude oil can have an effect on foams applied to enhanced oil recovery. Rendall et al. (21) investigated the behavior of several commercial surfactant-stabilized foams in the presence of crude oils. On the basis of dynamic bulk foaming tests, gas mobility reduction factors measured in reservoir cores, and observations in a micro-... 

The durability of a flexible foam may be determined by using a shear or a pounding force on the foam. Tests described here are designed to assess the suitability of foam for use in upholstery and are therefore primarily aimed at cellular latex or polyether urethane types of foam. A dynamic fatigue test using a roller shear at constant force is described in ASTM D 3574, Test U. However a much more popular fatigue test for cellular upholstery materials is determined by constant load pounding. 

Table 1.22 shows the dynamic fatigue test results for Lyondell and Dow cushion foams tested for 80,000 cycles and 60 minute recovery time. Results indicate that equivalent dynamic fatigue values are ohtainahle with use of the new non-fugitive and cell opening catalysts, based on nominal test error of 3. 

Static and dynamic property The uses of these foams or porous solids are used in a variety of applications such as energy absorbers in addition to buoyant products. Properties of these materials such as a compressive constitutive law or equation of state is needed in the calculation of the dynamic response of the material to suddenly applied loads. Static testing to provide such data is appealing because of its simplicity, however, the importance of rate effects cannot be determined by this one method alone. Therefore, additional but numerically limited elevated strain-rate tests must be run for this purpose. 

There is good correlation between the concentration giving the maximum surface dilatational viscosity and that giving the best foam performance. The nonylphenol 10 EO is a low-foaming nonionic surfactant with a maximum foam height of 150 ml in this test, whereas AOS produced 670 ml of foam. Figure 12 clearly shows that there is an optimum surfactant concentration for a dynamic process such as foam generation. 

Also, other dependent variables associated with CO2-foam mobility measurements, such as surfactant concentrations and C02 foam fractions have been investigated as well. The surfactants incorporated in this experiment were carefully chosen from the information obtained during the surfactant screening test which was developed in the laboratory. In addition to the mobility measurements, the dynamic adsorption experiment was performed with Baker dolomite. The amount of surfactant adsorbed per gram of rock and the chromatographic time delay factor were studied as a function of surfactant concentration at different flow rates. 

Various polymeric materials were tested statically with both gaseous and liquefied mixtures of fluorine and oxygen containing from 50 to 100% of the former. The materials which burned or reacted violently were phenol-formaldehyde resins (Bakelite) polyacrylonitrile-butadiene (Buna N) polyamides (Nylon) polychloroprene (Neoprene) polyethylene polytriflu-oropropylmethylsiloxane (LS63) polyvinyl chloride-vinyl acetate (Tygan) polyvinylidene fluoride-hexafluoropropylene (Viton) polyurethane foam. Under dynamic conditions of flow and pressure, the more resistant materials which binned were chlorinated polyethylenes, polymethyl methacrylate (Perspex) polytetraflu-oroethylene (Teflon). 

The static modulus and dynamic storage modulus were investigated for some open-celled PE foams by static compression tests and dynamic viscoelastic measurements in compression mode. Experimental data were compared with theoretical predictions. 8 refs. 

The mechanical response of polypropylene foam was studied over a wide range of strain rates and the linear and non-linear viscoelastic behaviour was analysed. The material was tested in creep and dynamic mechanical experiments and a correlation between strain rate effects and viscoelastic properties of the foam was obtained using viscoelasticity theory and separating strain and time effects. A scheme for the prediction of the stress-strain curve at any strain rate was developed in which a strain rate-dependent scaling factor was introduced. An energy absorption diagram was constructed. 14 refs. 

Polymer Testing 20,No.3,2001,p.253-67 IMPROVEMENT OF THE MEASUREMENT PROCESS USED FOR THE DYNAMIC MECHANICAL CHARACTERISATION OF POLYOLEFIN FOAMS IN COMPRESSION Rodrignez-Perez, M A Almanza O del Valle JL Gonzalez A de Saja J A Valladolid,Universidad Colombia,University... 

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