Foam performance

Dishwashing foam stability performance of an LAS-based light-duty liquid (LDL) is strongly affected by the carbon chain distribution, by water hardness, and, under some conditions, by phenyl isomer distribution. Foaming characteristics of C)2 phenyl isomer blends have been reported previously for conditions where LAS is the single anionic surfactant in the formulation (phosphate-built laundry powder) and the level of residual water hardness is low [30,31]. Under these conditions the internal phenyl isomers of C,2 LAS gave better foam performance than the 2-phenyl isomer. 

The LAS/AS and LAS/AS/AES combinations used in some U.S. spray-dried laundry powders for more than 30 years have provided good detergency with moderate to high foaming performance [39]. A typical example of a low-density, spray-dried, high-foaming laundry powder is shown below ... 

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. 

Public information about the specific chemical identity of the surfactants and stabilizers in use is scant(353-355) (Figure 11). Performance of foamed fluids is heavily dependent upon the size and distribution of the individual foam cells that are present, therefore the generator, testing apparatus, pressure and procedures employed are critical parts of the evaluation and the observed results. Contaminants (salts, acids, alkalies, etc) in the liquid phase also can cause drastic changes in foam performance. 

Troitzsch, J. How do foams perform under fire conditions . In Fire and Cellular Polymers, Buist, J.M., Grayson, S.J., Woolley, W.D., Eds. Elsevier Applied Science London, U.K., 1986 pp. 77-91. 

In the general case it is difficult to predict quantitatively the liquid carry-away with a foam. As mentioned in Chapter 5, analytical equations, describing the liquid distribution along the height of the foam column, have been derived only for a foam that is at hydrostatic equilibrium [57-59], Calculation of the liquid content in a non-equilibrium static foam, performed on the basis of the drainage model of Desai and Kumar [60], are given in [61]. 

Increasing the test pressure from one atmosphere to 2500 psig COj did not alter the effect of surfactant chemical structure on relative foaming performance. 

Hughes, P., Keeping a head optimizing beer foam performance, in Bubbles in Food, Campbell, G.M. et al., Eds., Eagan Press, St. Paul, MN, 1999, p. 129. 

Fillers affect foams in several ways they induce nucleation of gas bubbles and polymer crystallization, they destabilize liquid foam, they interfere with rate of chemical reactions and gas generation processes, they influence the viscosity of liquid premixes, they improve mechanical properties of foam, and foam durability. Care must be used in the selection of fillers for foams. They are used only sparingly in spite of the potential gains in foam performance which might be expected. 

The test methods discussed below are classified in five categories evaluation of cleaning performance evaluation of foam performance (volume and stability) evaluation of mildness evaluation of antibacterial efficacy and other tests. 

U.S. 4,537,709 (1985) Edge et al. (Lever Brothers) Particular chain length LAS and alkyl ether sulfates Improved foaming performance... 

Figure 11 shows all of these core-flood foam performance results plotted versus the logarithm of the lamella number. A strong correspondence is obtained with the logarithm of lamella number. That the trend between mobility reduction and lamella number is so consistent among the different systems is remarkable considering that the core-flood results... 

No universally accepted practices exist for selecting foam-forming surfactants for specific rock—fluid systems. In addition, information dealing with foam performance at brine salinities as high as those found in the pools mentioned previously is not readily available in the literature. The selection process is based on the following common sense criteria (2) ... 

In general, trends in MRF with surfactant concentration and foam quality are consistent for all surfactants, but the effects of brine salinity (Figure 4) and temperature (3) vary from surfactant to surfactant. Different surfactants are also affected to different degrees by the presence of an oil phase, as discussed in Chapter 4 of this book. The MRF increases with increasing permeability (Figure 5), as also noted by Lee and Heller (4) and described earlier in Chapter 5. This effect could be very beneficial to foam performance, because it leads to better mobility control in high-permeability zones. 

Because the surfactants described previously were selected for hydrocarbon-miscible flooding, the effect of hydrocarbon solvent on foam performance should be included in the surfactant screening process. Data on the characteristics of foams generated with light hydrocarbons as the gas phase are not readily available in the literature. Limited data comparing nitrogen foams with hydrocarbon solvent foams are shown in Table... 

Figure 9 illustrates typical order-of-magnitude differences in foam performance data obtained by this method (20). A data set from the vertical columns of Figure 2 is included, and this demonstrates that the effect of orientation is insignificant in this case. The data set in the lower right comer of the figure represents target performance at applicable conditions. 

Foam studies should not be done at atmospheric outlet pressure (37) because this introduces bubble expansion effects. We have found unpredictable differences between gas-blocking foams generated at atmospheric outlet pressure and outlet pressures of 5-6 bar (13). All our subsequent foam performance tests have been conducted at an elevated back pressure, even if reservoir conditions are not desired. We also attempt to limit the ratio between pressure drop and overall pressure, AP/P, to less than 20%... 

Finally, research the influence of concentration of foaming agent on foaming performance by change the concentration of foaming agent. The results are shown as Fig. 2. 

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