Surfactant-polymer incompatibility

Reduction of the brine salinity reduces the size of the microemulsion particles and therefore should suppress polymer/surfactant incompatibility. Indeed, core floods with a reduced salinity... 

Several examples of polymer-polymer incompatibility in aqueous solution are given in Reference 3, whereas de Hek and Vrij (4) recently described a phase separation in a solvent in which both polymer and colloidal spheres were dissolved. Ph se separation can be suppressed by reducing the molecular weight of the polymers. Reduction of the salinity reduces the size of the surfactant micelles and indeed also the polymer-surfactant incompatibilities (5,6). Actually, reduction of the salinity of the polymer drive, even without direct reference to polymer/surfactant incompatibilities, has recently become a favorable recipe for successful micellar floods (7-9). 

It is speculated that the effect of temperature on the critical electrolyte concentration is similarly related to the effect of temperature on the structure of aqueous solutions. An increase in temperature has been shown to extend the range of micellar solutions to a higher salinity in anionic surfactant systems (31). Hence, polymer-aggregate incompatibility would be less when the temperature is increased. However, addition of alcohol or change in temperature... 

The copolymer of acrylamide and ammonium acrylate is used to build viscosity in rinse cycle fabric softeners. This polymer is compatible with nonionic and most cationic surfactants that are used in fabric softener formulations. The polymer is incompatible with anionic surfactants and strong oxidizing agents, and it is sensitive to electrolytes. An example of other cationic polymers useful as thickeners for aqueous acid solutions is described in patent application EP 395282 [24],... 

There also exists a need to avoid surfactant aggregate structures such as lamellar liquid crystals which exhibit high viscosity (29-32). System parameters should be such that mixing between the fluids in the surfactant, oil and polymer slugs does not occur. A dispersion of surfactant and oil would form an undesired emulsion, while a dispersion of surfactant and polymer, if incompatible, could lead to phase separation, which would decrease the effectiveness of the process. Other points to take into account are (i) the mass transfer of surfactant to the oil bank can change the interfacial tension, and (ii) surfactant-polymer incompatibility leads to a phase separation, which would reduce the efficiency of the process (30, 31). 

Figure 20.15. Because of the high molecular weight of a micelle we expect a mixed polymer-surfactant solution, in the absence of significant attractive interactions, to display the incompatibility typical of polymer mixtures (a), i. e. segregate into one polymer-rich and one micelle-rich solution (b)...

Usually polymeric substances of appropriate chemical structure and morphology which promote the miscibility of incompatible materials. Block copolymers are especially useful surfactants at the polymer/polymer interface because the two blocks can be made up from molecules of the individual polymers to be mixed. Typical compatibilisers in polymer blends are LDPE-g-PS in PE/PS CPE in PE/PVC acrylic- -PE, -PP, -EPDM in polyolefin/PA and maleic-g-PE, -PP, -EPDM, -SEBS in polyolefin/polyesters. 

Cellulose derivatives Microcrystalline cellulose (and derivatives such as CMC) Nonionic 1-5 Insoluble in water 5-7 Plastic/ thixotropic Incompatible with strong oxidizing agents. Small amounts of electrolyte, cationic polymers and surfactants may flocculate MCC... 

Xanthan gum Anionic 0.3-3 Readily soluble in either hot or cold water 2-13 Plastic or pseudoplastic Incompatible with cationic surfactants, polymers and preservatives CMC sodium and oxidizing agents... 

Macromonomers afford a powerful means of designing a vast variety of well-defined graft copolymers. These species are particularly useful in the field of polymer blends as compatibilizers and/or stabilizers (surfactants). When macromonomer itself is an amphiphilic polymer, then its polymerization in water usually occurs rapidly as a result of organization into micelles. In copolymerizations, important factors for macromonomer reactivity are the thermodynamic repulsion or incompatibility between the macromonomer and the trunk polymer and its partitioning between the continuous phase and the polymer particles [4,5]. 

It is a common misunderstanding that silicones and silicone surfactants are incompatible with hydrocarbon oils this is only partly correct. Small silicone surfactants, such as the trisiloxanes, are very compatible with organic oils. For example, aqueous solutions of the trisiloxane surfactants give very low interfacial tension against alkane oils. The incompatibility between polymeric silicones and some hydrocarbon oils is due more to the polymeric nature of the silicone block rather than to strong phobicity such as that between fluorocarbon and hydrocarbon groups. The compatibility between two species, such as a polymer and a... 

Here, again, we start from compressible SCFT formalism described in Section 2.2 and consider a model system in which bulk polymer consists of "free" matrix chains (Ny= 300) and "active" one-sticker chains (Na= 100). Flory-Huggins interaction parameters between various species are summarized in Table 1. This corresponds to the scenario in which surfactants, matrix chains, and functionalized chains are all hydrocarbon molecules (e.g., surfactant is a C12 linear chain, matrix is a 100,000 Da molecular weight polyethylene, and functionalized chain is a shorter polyethylene molecule with one grafted maleic group). The nonzero interaction parameter between voids and hydrocarbon monomers reflects the nonzero surface tension of polyethylene. The interaction parameter between the clay surface and the hydrocarbon monomers, Xac= 10 (a = G, F, A), reflects a very strong incompatibility between the nonpolar polymers and... 

Drop stabilization methods rely on the immediate stabilization of drops by encapsulation with thin polymer films or surfactants [219-221] a photomicrographic method has been employed usually after encapsulation of drops. However this method cannot always be used due to incompatibility of the encapsulating materials with some systems. The method also has the disadvantage of the influence of the chemical treatment on drop size. A special sampling apparatus has been developed to withdraw a sample of dispersed phase from the mixing vessel to stabilize drops with a surfactant and to force the dispersed sample through a capillary with a photometer assembly to measure both droplet size and concentration [222]. 

Incompatibility of surfactant and polymer that is used in the micellar slug or chase fluid can occur because polymer may not be incorporated readily into micelles. Use of alcohols mitigates this difficulty. 

Rgure 8.5 Representative polymer-polymer phase behaviour with different molecular architectures. Microphase separation (a) results when thermodynamically incompatible linear homopolymers are mixed. The covalent bond between blocks in a diblock copolymer leads to microphase segregation (c). A mixed architecture of linear homopolymers and the corresponding diblock copolymer produces a surfactant-like stabilized intermediate-scale phase separation (b). 

It was observed that the formulations consisting of ethoxylated sulfonates and petroleum sulfonates are relatively insensitive to divalent cations. The results show that a minimum in coalescence rate, interfacial tension, surfactant loss, apparent viscosity and a maximum in oil recovery are observed at the optimal salinity of the system. The flattening rate of an oil drop in a surfactant formulation increases strikingly in the presence of alcohol. It appears that the addition of alcohol promotes the mass transfer of surfactant from the aqueous phase to the interface. The addition of alcohol also promotes the coalescence of oil drops, presumably due to a decrease in the interfacial viscosity. Some novel concepts such as surfactant-polymer incompatibility, injection of an oil bank and demulsification to promote oil recovery have been discussed for surfactant flooding processes. 

The mixing of surfactant and polymer in the porous medium occurs due to both dispersion and the excluded volume effect for the flow of polymer molecules in porous media, which in turn could lead to the phase separation. Figure 16 illustrates the schematic explanation of the surfactant-polymer incompatibility and concomittant phase separation. We propose that around each micelle there is a region of solvent that is excluded to polymer molecules. However, when these micelles approach each other, there is overlapping of this excluded region. Therefore, if all micelles separate out then the excluded region diminishes due to the overlap of the shell and more solvent becomes available for the polymer molecules. This effect is very similar to the polymer depletion stabilization (55). Therefore, this is similar to osmotic effect where the polymer molecule tends to maximize the solvent for all possible configurations. ... 

Figure 16. Schematic illustration of surfactant-polymer incompatibility leading to phase separation in mixed surfactant-polymer systems.

The effect of polymers on microemulsions phase behavior has been reported by Hesselink and Faber (8). They have described the surfactant-polymer phase separation in terras of the incompatibility of two different polymers in a single solvent, considering the microemulsion as a pseudo-polymer system. The effect of polymers on the phase behavior of micellar fluids has been recently studied by Pope et al. (9) and others (10,11). 

There is another phenomenon that is called polymer inaccessible pore volume (IPV). Laboratory data indicate that inaccessible pore volume is usually greater than the adsorption loss for polymers following a micellar solution (Trushenski et al., 1974). The competitive adsorption and IPV may make polymer penetrate the surfactant slug ahead of it. Therefore, surfactant-polymer interaction or incompatibility occurs not only in the surfactant-polymer process where the surfactant and the polymer are injected in the same slug, but also in the surfactant-polymer process where surfactant is injected before the polymer slug. 

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