Aqueous surface tensions, fluorinated

Fluorinated surfactants lower the surface tension of stimulation fluids more than hydrocarbon surfactants and are stable in aqueous stimulation fluids at 100°C. Drainage of salt solution (2% KCl) from sand packs is inversely related to the surface tension. Fluorinated surfactants enhance drainage more than hydrocarbon surfactants. Flow rates of fluids through sand packs or low-permeability sandstone cores were unaffected by the fluorinated surfactant, indicating that formation blockage by a fluorinated surfactant is improbable. Aqueous fluorinated surfactant solutions do not form emulsions of kerosine. 

Depression of the surface tension of their aqueous solutions and other surface-active properties are given in Chap. 4. When fluorine is changed for hydrogen in the alkyl chain of a phosphonate the compound becomes less heat-sensitive. Often the surface tension of aqueous solutions of these compounds is very low. 

The aqueous films stabilized with fluorine containing surfactants on organic substrates are an exception since they have very low surface tension (- 10 mM m 1). However, there are no literature data about them. 

Generalizations from the aqueous-solution surface tensions in Table IX are risky, because values are as dependent on the hydrophilic-lipophilic balance (HLB) as on the intrinsic surface activity of the hydrophobe. The data in Table IX are consistent with earlier observations that longer per-fluorinated groups are most effective in producing low surface tensions (in this case CF3(CF2)5-) and that a terminal CF2H- is detrimental. 

Table 1. Aqueous Phase Critical Micelle Concentrations (erne s), Limiting Surface Tensions yeme s and Microemulsion Stability Pressures for Fluorinated Surfactants.

At low concentrations fluorinated surfactants are capable of lowering effectively the surface tension of aqueous solutions and non-aqueous liquids and work well in acidic, alkaline and electrochemical media as well as at elevated temperatures. Their destruction may be bound up just with the decomposition of polar groups, e.g. polyoxyethylene chain. Adsorbing with the... 

There is large body of data on the surface and interfacial tensions of aqueous surfactant solutions. This data show that the structure of the surfactant molecule has a pronounced effect on its ability to reduce these tensions. As the length of the alkyl or fluorinated alkyl chain increases, the CMC decreases and the surface excess concentration increases, causing a drop in the interfacial tension at a fixed surfactant concentration. At low surfactant concentrations the reduction in surface tension (or increase in surface pressure O = yo - y) is linear with the molar bulk solute concentration c (in the case of the dilute solution)... 

SHA Sharma, S.C., Acharya, D.P., Garcia-Roman, M., Itami, Y., and Kunieda, H., Phase behavior and surface tensions of amphiphilic fluorinated random copolymer aqueous solutions, Coll. Surfaces A, 280, 140, 2006. 

Abstract Fluorinated surfactants have been conunercially available since the 1950s. The first available were perfluoroalkyl sulfonic acids. The unique properties e.g., surface tension lowering in aqueous systems, high chemical and thermal stability of these acids and their derivatives when used at low concentrations resulted in their widespread use in industrial processes and consumer uses. The most common commercially produced peifluorinated surfactants are the perfluoroalkyl acids. 

Kunieda H, Shinoda K (1976) Krafft points, critical micelle concentrations, surface tension, and solubilizing power of aqueous solutirats of fluorinated surfactants. J Phys Chem 80 (22) 2468-2470... 

Dams RJ, Terrazas MS (2008) Aqueous compositions of fluorinated surfactants and coating/ cleaning use on surfaces and reducing surface tension of liquids. World Appl 2,008,147,796. 3M Innovative Properties Company, USA... 

Schagerlof, H., Johansson, M., Richardson, S., Brinkmalm, G., Wittgren, B., and Tjemeld, F., Substituent distribution and clouding behavior of hydroxypropyl methyl cellulose analyzed using enzymatic degradation. Biomacromolecules, 7, 3474, 2006. Shartna, S.C., Acharya, D.P., Garcia-Roman, M., Itatni, Y., and Kunieda, H., Phase behavior and surface tensions of amphiphilic fluorinated random copolymer aqueous solutions, Colloids Surfaces A, 280, 140, 2006. 

As lubricants, low-surface-tension perfluorinated liquids (e.g., DuPont Krytox oils) that are nonvolatile and are immiscible with both aqueous and hydrocarbon liquids can be used. Kim et al. (2012) reported the development of lubricant infosed structured surfaces fabricated on aluminum substrates. Polypyrrole was initially electrodeposited on the surface of aluminum samples, which was then followed by the subsequent fluorination of the structured coating and infiltration with lubricant. The resulting water contact angle measurements showed that these surfaces were characterized by low contact angle hysteresis (A0= str,R H7°-115° = 2°) and... 

The minimum surface tension achievable is also much lower for fluorinated surfactants than for nonfluorinated surfactants. The minima of the surface tensions of surfactants with a hydrocarbon hydrophobe are in the range 25-35 mN/m [51-53], whereas those of fluorinated surfactants are as low as 15-20 nM/m or even lower [54]. The surface tension of aqueous solutions above cmc varies only slightly with surfactant concentration. Surface tension above cmc decreases with increasing fluorocarbon chain length and depends on the counterion (Table 4.1). 

Table 4.7 Surface Tension of Aqueous Solution of Fluorinated Surfactants C7Fi5CON(R)CH2CH2CH2 CH2S03Na at 30°C...

Fig. 4.28 Effect of surfactant concentration on the dynamic surface tension of aqueous solutions of an anionic fluorinated surfactant Zonyl FSA. (From Ref. 76. Reproduced by permission of Elsevier Science Publishers.)...

In aqueous solutions of nonfluorinated surfactants, the lowest surface tensions are attained by covering the surface with a close-packed monolayer of vertically oriented hydrocarbon chains forming a continuous layer of —CH3 groups exposed to air [89]. By analogy, the surface tension of a solution of a fluorinated... 

The fluorinated surfactant-hydrocarbon surfactant mixtures have unique properties. In two-phase systems of water and a hydrocarbon solvent, the fluorinated surfactant reduces surface tension and the hydrocarbon surfactant decreases the interfacial tension. For example, an aqueous foam of mixed surfactants spreads on a hydrocarbon solvent because the fluorinated surfactant adsorbs preferentially at the air-water interface, whereas the hydrocarbon surfactant adsorbs at the water-oil interface (see Chapter 8, Fire-fighting Foams). 

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