Foams cationic surfactants

Good foaming, cationic surfactant for hair and bath preparations. 

Surfactants used as lubricants are added to polymer resins to improve the flow characteristics of the plastic during processing they also stabilise the cells of polyurethane foams during the foaming process. Surfactants are either nonionic (e.g. fatty amides and alcohols), cationic, anionic (dominating class e.g. alkylbenzene sulfonates), zwitterionic, hetero-element or polymeric (e.g. EO-PO block copolymers). Fluorinated anionic surfactants or super surfactants enable a variety of surfaces normally regarded as difficult to wet. These include PE and PP any product required to wet the surface of these polymers will benefit from inclusion of fluorosurfactants. Surfactants are frequently multicomponent formulations, based on petro- or oleochemicals. 

Cationic surfactants show a high affinity for negatively charged surfaces making them suitable for industrial applications and as components for consumer products where they are used as disinfectants, foam depressants, and first and foremost as textile softeners [23], Due to the possible formation of ion-pair associates they are usually not formulated together with anionic surfactants. 

Even if this class covers the smallest market segment, amphoteric surfactants still remain useful because of their unique properties, which justifies their comparably high manufacturing costs. Since they have partial anionic and cationic character, they can be compatible, under specific conditions, with both anionic and cationic surfactants. They can function in acid or basic pH systems and, at their isoelectric point, they exhibit special behaviour. Many amphoteric surfactants demonstrate exceptional foaming and detergency properties combined with antistatic effects. 

The common gangue material quartz (silica) is naturally hydrophilic and can be easily separated in this way from hydrophobic materials such as talc, molybdenite, metal sulphides and some types of coal. Minerals which are hydrophilic can usually be made hydrophobic by adding surfactant (referred to as an activator ) to the solution which selectively adsorbs on the required grains. For example, cationic surfactants (e.g. CTAB) will adsorb onto most negatively charged surfaces whereas anionic surfactants (e.g. SDS) will not. Optimum flotation conditions are usually obtained by experiment using a model test cell called a Hallimond tube . In addition to activator compounds, frothers which are also surfactants are added to stabilize the foam produced at the top of the flotation chamber. Mixtures of non-ionic and ionic surfactant molecules make the best frothers. As examples of the remarkable efficiency of the process, only 45 g of collector and 35 g of frother are required to float 1 ton of quartz and only 30 g of collector will separate 3 tons of sulphide ore. 

Fatty Acid—Sarcosine Condensates. These surfactants are prepared by the reaction of fatty acid chlorides with methyl glycine sodium lauroyl sarcosinate [137-16-6] is an example of this group. They are most effective at pH 5.5—6.0 for foaming activity in soft to moderately hard water. The action of these deteigents is gready reduced under severe hard water conditions. The sarcosinates exhibit compatibility with cationic surfactants and have been suggested for use in formulation of conditioning shampoos (7). 

The cationic surfactant reduces the capillary forces already at concentrations far below the erne. This may be a great advantage since problems occurring at concentrations around the cmc like melting of the photoresist structures [15] or defect creation by foaming [17] can be avoided. 

A great advantage of the cationic surfactant rinse is that the minimum of the capillary forces is obtained already at concentrations far below the erne. Low amounts of surfactant are needed and problems as melting of the structures or foaming occurring at high surfactant concentration are avoided. 

Thus, one may conclude that the above-described features of foam films from aqueous solutions of a cationic surfactant clearly indicate a charge reversal at the air/water interface. Such a charge reversal should be material to the behaviour of both foam and wetting films in the case, where cationic surfactants are present. In particular, data for wetting films from aqueous solutions of cationic surfactants are remarkably consistent with the effect of charge reversal at the air/solution interface [207,208]. 

The 9(Cei) dependence has been studied with microscopic foam films from other surfactants [324], For instance, films from cationic surfactants exhibit the same course of the dependence. It has to be noted, however, that the metastable region of such films lays within a... 

Antifoams can be divided into two groups. The first group includes substances, for which the principle of defoaming action is based on the interaction with the foaming agent resulting in formation of insoluble or poorly soluble compounds. For instance, if soluble calcium or aluminium salts (chlorides) are added to the foaming solution of sodium or potassium salts of fatty acids, or cationic surfactants to anionic surfactants solution, insoluble compounds are formed and the foam is destroyed [6]. The less soluble compound formed, the more efficient the antifoam is. 

For this group of antifoams an effective way of application is in the form of foams [7]. For example, a foam stabilised by cationic surfactants is introduced in the foam to be destructed, obtained from an anionic surfactant solution. The cationic surfactant solution usually contains a considerable amount of calcium or aluminium salts. The large consumption of substances should be considered as a disadvantage of this group of antifoams. Furthermore,... 

Catalytic action of cationic surfactants (quaternary pyridinium chlorides) in the hydrolysis of 2,4-dinitrochlorobenzene and in the reaction with aniline in a foam has been observed as well [109,110]. For example, in the presence of quaternary pyridinium bases, the rate constant of the hydrolysis in a foam increased from 1.4210 7 (without the surfactant) to 2.7 1 O 2 m3 mol 1 s 1 (with surfactant) which is greater than in the case of catalysis in micelles (8.3-10 6 m3 mol 1 s"1). A similar acceleration of acid hydrolysis occurs also in the presence of anionic surfactants [112,113]. 

To be a promising candidate for CO2 foam, the surfactant loss by adsorption, partitioning and emulsion formation must be low. In general, anionic surfactants have low adsorption on sandstones and high adsorption on carbonates, whereas the reverse is true for nonionics ( ). Cationic surfactants are not considered because of their high adsorption on many surfaces. 

In the context of a study of foam flotation of powdered activated carbon (PAC), Zouboulis et al. [143] noted large and different pH effects when an anionic surfactant was used instead of a cationic one. For the cationic surfactant, best recovery (at low surfactant concentration) was achieved at the highest pH, in agreement with electrostatic arguments (see Section IV.B.l) for the anionic surfactant, an intermediate pH was the best. The authors also measured the zeta potential of the carbon in the presence and absence of the surfactants and concluded that the specific chemical nature and the dissociation of each surfactant. 

Sheiham and Pinfold (81) have attempted to remove a cationic surfactant, hexadecyl-trimethylammonium chloride, by both solvent sublation and foam fractionation. A comparison (81) between the rates of surfactant removal by the two separation techniques shows that the separation of the cationic surfactant from 10 M solutions by solvent sublation into 2-octanol is slower but preferable if the foams are unstable. 

In acid solutions, the amino group is protonated and acts as a cationic surfactant, whereas in neutral or alkaline solution the amine oxides are essentially nonionic in character. Alkyl dimethyl amine oxides are water-soluble up to Cj, alkyl chain. Above pH 9, amine oxides are compatible with most anionics, but at pH 6.5 and below some anionics tend to interact and form precipitates. In combination with anionics, amine oxides can be used as foam boosters (e.g., in shampoos). 

Other useful effects of solubilization are the binding of organic acids soluble in lubricating oils to the cations of metal sulfonate detergents in these oils, thereby decreasing the corrosion of metals by these acids (Bascom, 1958) and the solubilization of foamicidal oils by foam-producing surfactants, leading to increased foam life. 

The situation is very different for the more rigid polyelectrolyte xanthan. The foam films made with DTAB solutions are very unstable. When using DTAB or CTAB which alone give stable foam films, the incorporation of the polymers in the solutions also leads to unstable films. This behaviour is particular to the cationic surfactants indeed stable foam films can be made with nonionic surfactants and all the polymers. The data of Figure 8 for xanthan were obtained in this way.29 We have seen that in the case of cationic surfactants, mixed poly-... 

The interfacial behavior of block copolymers is of interest in several fields like stabilization of emulsions, foams, and wetting control [154]. Gerdes et al. [155] studied the wetting behavior of aqueous solutions of triblock copolymers on silica. The experimental approach was based on the use of a Wilhelmy force balance and direct images of contact angle. Their results show that the three-phase contact line advances in jumps over the surface when it is immersed at constant speed into the copolymer solution. Apparently the stick-slip spreading mechanism is the same as has been proposed for short chain cationic surfactants. 

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