Surfactants perfluorooctanesulfonate

In addition to the electrolytic preparation of fluorine, the electrochemical fluorination of carboxylic acid and sulfonic acid derivatives have also become important industrially. The Simons process (Ni anodes, HF as solvent) has been realized industrially by 3 M 69). The most important products are perfluorooctanecarboxylic and perfluorooctanesulfonic acids, which are used as surfactants and for surface treatments. 

Moody, C. A., Herbert, G. N., Strauss, S. H., Field, J. A. Occurrence and persistence of perfluorooctanesulfonate and other perfiuorinated surfactants in groundwater at a fire-... 

Selectivity differences for the alkane sulfates and sulfonates are not particularly sensitive to changes in the identity of the counterion or the alkyl chain length [204,209]. Sodium dodecyl sulfate is representative of this group. On the other hand, the perflu-orooctanesulfonate and N-alkyl-N-methyltaurine surfactants afford different selectivity to sodium dodecyl sulfate [197,202,208]. Lithium perfluorooctanesulfonate has differ-... 

As shown in Figure 18.2, the majority of the perfluorooctanesulfonyl fluoride was converted onsite by the 3M Company through the sulfonamide into A-methyl or A-ethyl perfluorooctanesulfon-amidoethanol. These two compounds (and most of the other intermediates shown in Figure 18.2) were primarily used as intermediates for the preparation of fluoropolymers in protective treatments for carpets, upholstery, apparel, and leather products. Several of the other compounds derived from perfluorooctanesulfonyl fluoride were used for the production of surfactants. For example, the... 

The excellent chemical stability of perfluorinated alkanoic and alkanesul-fonic acids to acids, oxidants, and alkali [5,13,17] allows their application under conditions too severe for hydrocarbon-based surfactants. Gramstad and Haszel-dine [14] did not detect fluoride when they heated potassium perfluorooctanesulfonate (0.9 g) in water (5 mL) at 300°C for 8 h. However, when potassium perfluorooctanesulfonate was heated in 10% aqueous potassium hydroxide for 8 h at 270°C, 8% of the theoretical amount of fluoride was liberated. Perfluorooctane-... 

Commercial fluorinated surfactants are usually mixtures and the relationship between structure and melting point is less clearly defined. For the tetraethy-lammonium salt of perfluorooctanesulfonic acid a broad melting range, about 170-190°C, has been reported [15]. The parent acid of the salt was a mixture of isomers, formed by the electrofluorination process. The mixture consisted of the normal-chain isomer (70%) and branched isomers (30%). 

The kinetics of surfactant adsorption depend on the surfactant structure. Fluorination of the hydrophobe increases the rate (dyldt) of surface tension decrease, but the time needed to attain equilibrium may not be affected considerably. The surface tensions of sodium perfluorooctanesulfonate and its hydrocarbon-... 

Changes in zeta potential and turbidity of iron(III) oxide hydrate sols flocculated with lithium perfluorooctanesulfonate (LiFOS) are shown in Fig. 5.11. The nonionic surfactants NF7 and NP7.5 redispersed the sols. However, the anionic hydrocarbon surfactant LiDS (lithium dodecyl sulfate) had no significant effect. Accordingly, sols flocculated by LiDS were redispersed by a nonionic surfactant, NF7, but not by the anionic surfactant LiFOS (Fig. 5.12). 

The exchange of surfactant monomers between the micellar and the monomeric state is diffusion controlled for monomers with hydrophilic counterions. The exchange rate is slower for monomers with hydrophobic counterions. For lithium and substituted ammonium salts of perfluorooctanesulfonic acid [76], the values of the micellar distribution curve, a ln, increased with increasing hy-drophobicity of the counterion or with a decrease of temperature. Both the association rate constant, k /n, and dissociation rate constant, k /n, decreased with increasing counterion hydrophobicity. The increase in k /n values was larger than the decrease in cmc values, suggesting that hydrophobic counterions form a barrier to the monomer exchange process. 

The pseudophase model (see Section 6.2) for micellar solutions makes it possible to establish a partitioning coefficient for the partitioning of the solubilizate between the aqueous solution and the micellar pseudophase. Treiner et al. [206-208] studied partitioning of alcohols and phenol in an aqueous solution of a fluorinated surfactant or of mixed anionic hydrocarbon and fluorocarbon surfactants. The fluorinated surfactants used in their studies were potassium or sodium perfluorooctanoate and lithium perfluorooctanesulfonate. 

Chemical relaxation techniques [21-23] have been utilized to determine the aggregation numbers for salts of perfluorooctanesulfonic acid [21,22]. The aggregation numbers have been calculated from the kinetic data, based on the assumption that the micellar distribution curve obeys a Gaussian distribution function. This procedure was validated with aggregation numbers for hydrocarbon-type surfactants, which were in agreement with those obtained from light-scattering data. 

The structures and surface tensions of some Fluorad fluorinated surfactants, produced by electrochemical fluorination, are shown in Table 8.1. 3M has discontinued the production of Flourad fluorinated surfactants based on perfluo-rooctanesulfonic and perfluorooctanesulfonic acid (see Chapter 10). The structures and surface tensions of Zonyl fluorinated surfactants, produced by telomer-ization. are shown in Table 4.4. 

Flourinated surfactants aie used as wetting agents in etch baths because of their low surface tension and stability in strong acids. Glass articles are polished and etched with solutions containing sulfuric acid, HF, and a fluorinated surfactant (e.g., tetraethylammonium perfluorooctanesulfonate or potassium perfluorooc-tanesulfonate). Fluorinated surfactants increase the speed of etching, acid polish-... 

Fluorinated surfactants, such as lithium perfluorooctanesulfonate, potassium perfluoroalkanesulfonate, and an amine perfluoroalkanesulfonate, are effective wetting agents in etching solutions for plastics. 

Kato et al. [310] studied emulsion polymerization of styrene in the presence of sodium dodecyl sulfate and lithium perfluorooctanesulfonate. The fluorinated surfactant decreases the polymerization rate and the molecular weight of the polymer formed. 

Tamori et al. [290] used electric birefringence to estimate the micellar size and shape in mixed-surfactant solutions containing hexaoxyethylene glycol dode-cyl ether and lithium perfluorooctanesulfonate or lithium dodecyl sulfate. 

The intrinsic toxicity of some fluorinated surfactants has been related to their exceptionally high surface activity. The acute oral toxicity of tetraethylam-monium perfluorooctanesulfonate has been reported to be considerable [LD50 = 190 mg/kg (Wistar rat)] although the surfactant does not irritate mucous membranes and is not a bactericide. At low concentrations, the surfactant is not toxic... 

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