Polymers foam stabilization

In most cases, these active defoaming components are insoluble in the defoamer formulation as weU as in the foaming media, but there are cases which function by the inverted cloud-point mechanism (3). These products are soluble at low temperature and precipitate when the temperature is raised. When precipitated, these defoamer—surfactants function as defoamers when dissolved, they may act as foam stabilizers. Examples of this type are the block polymers of poly(ethylene oxide) and poly(propylene oxide) and other low HLB (hydrophilic—lipophilic balance) nonionic surfactants. 

The interest in this type of copolymers is still very strong due to their large volume applications as emulsifiers and stabilizers in many different systems 43,260,261). However, little is known about the structure-property relationships of these systems 262) and the specific interactions of different segments in these copolymers with other components in a particular multicomponent system. Sometimes, minor chemical modifications in the PDMS-PEO copolymer backbone structures can lead to dramatic changes in its properties, e.g. from a foam stabilizer to an antifoam. Therefore, recent studies are usually directed towards the modification of polymer structures and block lengths in order to optimize the overall structure-property-performance characteristics of these systems 262). 

Choose macromolecular compounds like water-soluble polymers and proteins over surfactants and electrolytes as foam stabilizers for products with enhanced skin feel and skin mildness. 

Foams have a large variety of applications. Solid foams are widely used as insulating materials. Due to the presence of air bubbles they have a low thermal conductivity. Polyurethane foams and Styrofoam are examples. Styrofoam is also used as a packing material. The light weight of polymer foams makes them attractive as filling materials to stabilize otherwise hollow structures. A natural solid foam is pumice stone. Metal foams are used in the automotive and aerospace industry as light and stable materials [567], Ceramic foams are developed for electronic applications as piezoelectric transducers and low dielectric constant substrates [568],... 

Williams, M. K., Holland, D. B., Melendez, O., Weiser, E. S., Brenner, J. R., and Nelson, G. L. Aromatic polyimide foams Factors that lead to high fire performance, Polym. Degrad. Stabil. 2005, 88, 20-27. 

The study of the foam lifetime versus concentration for the widely used foaming agents Volgonate (at Ap = 10 kPa) indicates that foam stability decreases visibly at concentrations less than 0.1%. The rate of diffusion bubble expansion gradually decreases, starting from concentrations -1%. Additional rise in foam stability is obtained with addition of various additives (electrolytes, water soluble polymers, fatty alcohols, etc.). 

The formation and preservation of the uniform cell structure of either the solid polymer or frozen foam depend on the properties of the initial foam, i.e. on its expansion ratio and stability. On the one hand, the former two processes are determined mainly by the rates of drainage and internal foam collapse. On the other hand, however, they are affected by the rate of polymerisation and the increase in strength of the foam material. That is why optimisation of the processing properties of polymer foams can be achieved by decreasing both the rate of microsyneresis and drainage, and the rate of internal foam collapse. Along with that precise control of the rate of solidification, reduction of the water content and introduction of plastifiers are needed. 

FOAMING. The foaming of Quatrlsoft IN 200 was studied by the conventional cylinder shake test. While the Immediate foam height of Quatrlsoft IM 200 was much higher than that of Polymer JR (30 ml vs. 10 ml), the foam decay results of Figure 5, show that the foam stability of the former polymer Is also much greater. 

We have already mentioned in Sect. 6.2, 6.3 that the physicochemical conditions of the foaming process and the foam stability criteria determine the upper and lower limits of cell sizes so that, depending on the polymer type, composition, and foaming process conditions, the upper limit of size may be as large as a few millimeters 36,83-85) recently, it was believed that the minimum size of a plastic foam cell cannot be less than several dozens of microns (Table 2). However, by the application of scanning electron microscopy and the mercury penetration method, plastic foam structures were found to incorporate gas voids whose minimum dimensions were fractions of a micron, i.e. 2 or 3 orders of magnitude smaller than could be observed earlier in cellular polymers... 

Surfactants for urethane and related polymer foams are usually silicone-surfactants. These surfactants generally are copolymers of poly(dimethylsiloxane) [-Si(CH3)2-0-] , oxyalkylene chains, e.g., polyethylene oxide chain (EO) , and polypropyene oxide chains, (PO) . The copolymers can be linear, branched or pendant types. The surfactants have different functions, i.e., emulsifying, foam stabilizing, and cell-size control. 

Salinity was found to decrease foam stability. The surfactant concentrations in which foaming ability increased with concentration were 0 to 0.5%. The optimum polymer molecular weight for foaming ability was around 17 million. Core flood tests showed that ASPF incremental oil recovery factor over ASP was above 10% because the ASPF sweep efficiency was higher than the ASP efficiency. 

U.S. 4,576,744 (1986) Edwards et al. (Lever Brothers) Polymers Enhanced foam stability and increased viscosity... 

U.S. 4,490,279 (1983) Schmolka (BASF) Nonionic block polymer surfactant with an amine oxide High foaming and good foam stability... 

Fatty alkanolamides are mainly used as foam stabilizers, but they can also have a large effect on the viscosity of an LDLD formulation, usually increasing it. Other viscosity modifiers include hydrotropes such as alcohol, SXS, SCS, urea, and water-soluble polymers. However, not all of these have the same magnitude of effect, which depends on the surfactant system in the product. 

Perhaps the petroleum industry s most widely recognized advantage to using foam as a stimulation fluid is its ability to cleanup the liquid load fluid used to perform the fracture. Upon completion of the fracture treatment, the fracture fluid, after it has broken , should ideally be completely removed from the well. This step ensures that no residual polymers, fines, or unbroken gel will hinder the conductivity of the fracture. Also, a quick cleanup in order to bring the well back onto production is important. Fracture cleanup is accomplished by back-flowing the fluid from the formation to the surface. As the surface pressure is released, the gas within the foam expands, the foam stability is diminished, and the gas—liquid interface weakens. Further release of pressure at the surface will cause a... 

Improvements in chemical research and development have increased the stability of foams by improving gellants and stabilizers. Thickening of the continuous phase increases the difficulty for gas bubbles to coalesce. Although relatively high qualities are required to achieve stability, qualities of less than 52% can maintain dispersion of the gas phase. Further improvements in foam stability can be accomplished by cross-linking the polymers in the aqueous phase. To date, foams have been established with qualities less than 40% (5). The use of low-quality foams is advantageous if viscosity or fluid loss control is a primary concern. If the formation sensitivity or fluid flow-back is important, low-quality foams are not desirable because of the reduced gas volume and increased fluid volume. 

Those factors that were previously mentioned that produce finer-textured foams also produce more stable foams. Factors such as surfactant type, concentration, increasing pressure, and higher inputs of mechanical energy generate more stable foams. For higher temperatures such as those that exist downhole, dynamic foam stability relies upon surfactant type and concentration rather than the addition of thickeners (polymer stabilizers). It is not known what rates are necessary to maintain dynamic stability in fractures, or whether those conditions typically exist. 

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