Sodium Soaps Research Articles

Assembly of sodium soap fibers and fibrillar particles triggered by dissolution of sodium chloride crystals

Fatty acids in the presence of sodium ions are known to self-assemble into sodium soap fibers. Previous work has yielded these fibers only in the form of randomly entangled gels. Here, for the first time, we demonstrate a method to create discrete fibrillar particles from sodium soap fibers. Immersion of sodium chloride crystals in solutions of neutralized fatty acids causes the crystals to dissolve and release sodium ions. Release of sodium triggers the nucleation and assembly of fibers in the solution surrounding the dissolving crystal. This process ultimately yields fibrillar particles with brush layers of sodium soap fibers. The fibers are flexible ribbons that are 1 μm in width, 3 μm in height, and hundreds of microns in length. We extended our method to polystyrene microspheres by encapsulating them with thin shells of sodium chloride microcrystals. Microspheres coated with sodium chloride shells triggered the assembly of encapsulating fibrillar brush layers. Microspheres with such brush layers have dramatically increased surface areas and this property may be applicable to oral drug delivery systems.

Friction behavior of lubricated zinc phosphate coatings

The aim of the present work is to elucidate the influence of lubricants on the friction behavior of zinc phosphated coatings and provide an explanation for the results in terms of physical–chemical interactions between lubricant and phosphate. The friction behavior was studied through a sliding wear test, with a conventional ball-on-disc configuration. Discs, made of AISI 1006 low carbon steel, uncoated and coated with zinc phosphate, were tested against bearing steel balls. A stearate sodium soap, paraffinic oil and both soap and oil were used as lubricants. The sodium stearate soap was found to have the best seizure resistance. The nature of the interfacial forces between the lubricant and surface has an important role in determining the friction behavior.

Gel phase originating from molecular quasi-crystallization and nanofiber growth of - system.

Adding sodium salts to a dilute sodium laurate (SL) aqueous solution, slow phase transition was observed from the micelle solution to a gel phase. The phase-transition process has great resemblance to crystal salt-out. The observation by transmission electron microscopy (TEM) proved that the hydrogel is a network structure with interweaving fibers and ribbons, which can trap an aqueous solution. The images of high-resolution TEM (HR-TEM) indicated that each of the fibers and ribbons is composed of a bundle of parallel cylindrical nanofibers. Conductivity and in situ diffuse reflectance fourier-transform infrared (DR-FT-IR) spectroscopy measurements indicated that gel formation was induced due to a crystallization of rod micelles by Na+ ions bonding to the oxygen groups of salts of fatty carboxylates. Differential scanning calorimetry (DSC) showed that the increase of either the chain length of sodium soaps or the concentration of Na+ counter-ions promoted the growth of the nanofibers. We speculated that the phase transition from the micelle solution to the gel phase is a result of a crystallization of rod micelles induced by sodium ions.

Influence of sodium soap and ionic strength on the mesomorphic behavior and the α-gel stability of a commercial distilled monoglyceride

The lyotropic mesomorphic behavior of a commercial distilled monoglyceride based on fully hydrogenated palmstearin at a concentration of 25% was studied as a function of temperature. Polarized light microscopy and small angle X-ray scattering were used to determine the lamellar dispersion to bicontinuous cubic Im3m phase transition. The addition of sodium soap based on palm oil shifted this transition to higher temperatures. In contrast, by increasing the ionic strength of the water phase the formation of the cubic structure was promoted. Electrostatic interactions also played an important role in the stability of the α-gel that was obtained by cooling the lamellar dispersion. The stability of this metastable phase as expressed by the coagel-index determined by differential scanning calorimetry was positively and negatively influenced by increasing sodium soap concentration and ionic strength, respectively.

Chain-Length and Solvent Dependent Morphological Changes in Sodium Soap Fibers

Sodium soap fibers with varying alkyl chain lengths were studied by cryotransmission electron microscopy and differential scanning calorimetery in water and water-propylene glycol mixtures. The morphology of the lamellar fibers was found to be dependent on the chain length of the alkyl chain and the solvent polarity. Cryoelectron microscopy revealed that short-chain (C10-C14) sodium soaps have the bilayer plane perpendicular to the fiber width, which enables one to see the bilayer striations on the fibers, whereas long-chain (C16-C20) sodium soaps have bilayer planes parallel to the fiber width, and the bilayer striations are not visible. This change in morphology is accompanied by a change in dissolution enthalpy.

A tribo-testing method for high performance cold forging lubricants

A tribo-testing method based on inducing different deformation patterns at the tool–workpiece interface developed by the authors was used in rating the performance of high quality lubricants. Dies which can induce different levels of maximum surface expansion under localized rod drawing set up were used. The maximum local surface expansion induced ranged from 20 to 500%. The basic feature for this test lies under the assumption that the surface expansion is proportional to the lubricant thinning and breakdown at the tool–workpiece interface. The experimental set up is coupled with die heating facilities used to raise the temperature at the interface so that the influence of temperature on the performance of the lubricant is studied. The performance of several coating-based lubricants was studies under this method. One of the goals of screening the lubricant was to identify possible lubricant candidates for replacing zinc phosphate coating based lubricant for medium forging processes. The results have demonstrated that, the effectiveness of the lubricants varies considerably with changes in the maximum local surface expansion induced at the interface and the change in the interface temperature. Of the six lubricants studied, two lubricants based on calcium and sodium soap were found to be at the same performance level as the conventional zinc phosphate coating + metal soap.

Lubricating Grease: A Chemical Primer

This article provides an overview of the function, properties, composition, and preparation of lubricating grease. The function of grease is compared to that of a liquid lubricant. The properties of grease consistency and dropping point are delineated. The three major components of grease (the base oil, a thickener, and additives) are characterized. Important properties of base oil (its viscosity, cloud point, and pour point) are examined. The steps necessary to convert crude oil to base oil are outlined. The three categories of grease thickeners (soap, complex soap, and nonsoap thickeners) are described. A brief history of the evolution from calcium soaps to sodium soaps and finally lithium soaps is provided and the importance of lithium soaps to the creation of multipurpose greases is explained. The different categories of lubricant additives—antioxidants; metal deactivators and corrosion inhibitors; polymer additives; friction modifiers, anti-wear, and extreme pressure additives; and solid lubricants—a...

Preparation, amphiphilic properties and lyotropic phase behaviour of new surfactants based on sodium monoalkyl α,ω-dicarboxylates

New surfactants based on sodium monoalkyl α,ω-dicarboxylates H3C(CH2)n−1OC(O)(CH2)m−1CO2Na (CnCmCO2Na) with various chain lengths were prepared from succinic anhydride (m=3), azelaic acid (m=8) and dodecanedioic acid (m=11). Their physico-chemical properties (Krafft point, critical micelle concentration and kinetics of hydrolysis) were measured and their lyotropic aqueous phase behaviour was investigated by polarized light optical microscopy. To assess the influence of the ester function inside the hydrocarbon chain, sodium monoalkyl azelates and monoalkyl succinates were compared with sodium soaps (m=0) having a same carbon number. Insertion of an ester group within the surfactant alkyl chain considerably lowers the Krafft point and slightly delays the formation of the first mesophase. The methylene units localized between the ester and the carboxylate groups are equivalent to 0.5 methylene group in their effect on CMC. The rate of hydrolysis of those monoesters depends heavily on the pH and on the CMC. The kinetics is fast and pseudo-first order below the CMC and it is slow and pseudo-zeroth order above the CMC because the ester function is protected from hydrolysis when it is embedded within the micelle core.

Flotation of zinc and cadmium cations in presence of manganese dioxide

The subject of this paper is the flotation (foam separation) of zinc and cadmium cations in presence of manganese dioxide precipitate. The removal of zinc cations by adsorbing particulate (particles) flotation (with Tween 80) is higher than that of cadmium ones. It increases both with the increase of the concentration of manganese dioxide precipitate, and that of the nonionic surfactant (Tween 80). The removal of zinc cations by ion flotation (with sodium soaps) is lower than that of cadmium ones. It does not change with the increase of the manganese dioxide precipitate concentration. It increases, however, with the increase of the anionic surfactant (sodium laurate and stearate) concentration. The mechanism of foam separation was discussed on the base of the interaction: (a) between the surface of the manganese dioxide precipitate and the metal cations; (b) between the surface complexes of the precipitate–metal cations and Tween 80; (c) between the metal cations and the sodium soap.

Solubility of sodium soaps in aqueous salt solutions

The solubility of sodium soaps in dilute aqueous salt solutions has been systematically investigated by direct visual phase behavior observations. The added electrolytes, including simple inorganic salts and bulky organic salts, influence the solubility of sodium soaps in water, as represented by the varied soap Krafft point. Two inorganic salts, sodium chloride and sodium perchlorate, demonstrate a “salting-out” property. On the other hand, tetraalkylammonium bromides show an excellent ability to depress the soap Krafft point and enhance the soap solubility in water. With increasing the tetraalkylammonium ionic size, the degree of “salting-in” of soaps in water increases. However, solubility of pure tetraalkylammonium bromide in water decreases as the length of the alkyl chains increases. Furthermore, in the ternary water-tetrapentylammonium bromide (TPeAB)-sodium myristate (NaMy) system, we observed an upper cloud point phenomenon, which greatly shrinks the 1-phase micellar solution region in the phase diagram. This miscibility gap, together with the organic salt solubility limitation, restricts the use of tetraalkylammonium bromides with alkyl chains longer than 4 carbon atoms as effective soap solubility enhancement electrolytes. We also found that for sodium soap with a longer hydrocarbon chain, more tetrabutylammonium salt is required to reduce the soap Krafft point to room temperature.

Extraction of heavy metals and ammonium from waters by unsaturated fatty acids and their soaps

The process including heavy metals and ammonium extraction from waters by an extraction medium based on unsaturated fatty acids and their soaps, up-concentration of the extracted metals, and regeneration of the extraction medium was investigated. The process corresponds to current hydroxides-precipitating, coagulation and biotreatment processes. The two synergistically effective ways are described: the basic process with the pretreatment of feed water by sodium or calcium hydroxide and extraction with unsaturated fatty acids, and the advanced process exploiting the extraction through sodium and/or calcium unsaturated fatty acids soaps. Oleine as a commercially available extraction medium was used. High bonding capacity and metals removal efficiency, fast kinetics and selectivity for the extraction process, and the self-adjustment of the pH value after the extraction process, as well as the high up-concentration of the metals salts limiting to saturated solutions, and the complete regeneration of the extraction medium were reached. Heavy metals hydroxides precipitation behaviour was investigated. Chemical and hydrophobisation metals-bonding mechanisms for the extraction process were observed. Regeneration and up-concentration behaviour, Oleine stability and organics residues in the water phases were investigated.

Crystallization of silver stearate from sodium stearate dispersions.

Silver carboxylates, the common silver source used for photothermographic imaging materials, are normally obtained from the reaction between sodium soap (e.g., sodium stearate) and silver nitrate. They form platelet-like crystals with a lamellar structure in water at room temperature. Light microscopy investigations reveal that the formation of silver stearate (AgSt) crystals follows a diffusion-controlled mechanism. The reaction between the sodium soap and silver nitrate preferentially occurs in solution rather than on the soap fiber solid interface. Cryogenic transmission electron microscopy, together with an on-the-grid reaction technique, provides a useful tool to directly image silver stearate microstructures at the initial stages of AgSt precipitation. The AgSt reaction product first forms particles about 5 nm in size, which is similar to the d-spacing of final AgSt crystals. Those particles aggregate to produce larger and loosely packed embryonic crystals, the precursors to the ultimate silver stearate crystals.

Effect of palm kernel oil extraction method on the electrical conductance of Nigerian traditional soaps in alcohols

AbstractNigerian traditional soaps were prepared using two commercial samples of palm kernel oil (black and pale‐orange oils) that were extracted locally using two different traditional methods. The effect of the oil extraction method on the conductance of soaps in alcohols was then investigated. The conductance of the soaps prepared from the pale‐orange oil was higher than that prepared from the black type. The plots of concentration conductance vs. the square root of concentration for methanolic solutions of the pale‐orange oil soaps were linear, whereas the plots obtained for the black oil soaps were nonlinear. The plots of log10k vs. 1/T were linear for all the soaps in methanol and for potassium soaps in 1‐propanol, whereas they were nonlinear for sodium soaps in 1‐propanol. The activation energy terms for the soaps prepared from pale‐orange oil generally decreased with an increase in concentration, whereas the activation energies for the black oil soaps were less sensitive to changes in concentration. These observations suggest that the purity of the palm kernel oil can have a significant effect on the properties and quality of the traditional soaps and that the pale‐orange oil was probably purer than the black type.

New developments in the production of heavy soda-ash via compacting method

Sodium carbonate, also called soda, is mainly used in the glass industry, but also has its operative range in the chemical industry, i.e. for processing sodium phosphates, detergents and soaps. It is differentiated between light, calcined soda, which has a bulk weight of approx. 0.5 kg/l, and heavy soda with a bulk weight of 1.0–1.1 kg/l. One of the oldest methods for processing heavy soda from light soda is the monohydrate method, where by addition of water monohydrate is formed, from which subsequently, the crystal water is removed in a steam pipe calcining drum. As this method is very energy- and therefore cost-intensive, for reasons of reducing the operating costs in the last years, it was changed more and more to the method of compacting with subsequent crushing and following screening. However, due to mechanical screening, this method is limited to a minimum particle size of 200 μm. But as the international market demands today a multitude of particle sizes in the range between 75 and 1.180 μm and the particles have to be absolutely dust-free at the same time, a new method has been developed and turned into practice. In two plants of recent dates, with a capacity of 160.000 tons/year, the new demands of the market have been considered. The plant will be explained here in detail.

The electrical conductance and viscosity of Nigerian traditional soaps in alcoholic media

The electrical conductances and viscosities of Nigerian traditional soaps in alcohols have been measured. Potassium, sodium and potassium/sodium (50:1) soaps have been prepared from palm kernel oils using laboratory prepared reagent alkalis and their conductances have also been measured. While the conductances vary with the degree of purity of the soaps and the polarity of the solvents, the activation energy for conductance only varies with the change of solvents. The conductances of the laboratory prepared potassium soaps are higher than those of the sodium soaps, suggesting the metal ions to be the main charge carriers in solution. Plots of logarithm of conductivity against inverse temperature are linear for all the soaps in methanol and ethanol while such plots are non-linear in propan-1-ol in which the soaps are least soluble with lowest conductance values. However, the plot is linear for the laboratory prepared potassium soap in propan-1-ol. The conductivities of the commercial (traditionally prepared) soaps are found to be higher than those of the laboratory prepared ones, indicating the formation of soaps of many fatty acid constituents of palm kernel oil in the traditional process of soap preparation. The variations of the viscosities of the solutions with concentration, temperature and carbon chain length of the solvents are also discussed. The plots of log 10 η versus 1/ T for all the soap solutions are linear suggesting that the solutions are non-associated liquid systems in agreement with the conductance data. The variations of the activation energies obtained from these plots with concentration and molecular weights of the solvents are discussed. The viscosity data are also interpreted on the basis of Jones–Dole equation. The trend of the B-coefficient of this equation suggests that the soaps become less ideal with increase in the molecular weights of the alcohols. The erratic nature of the A-coefficient values is again related to the results of conductance measurement which indicate that the traditional method of soap preparation produces mixed soaps and that the soaps contain many trace metal ions.

Solution Phase Behavior and Solid Phase Structure of Long-Chain Sodium Soap Mixtures

Long-chain soaps are generally applied in industrial products as mixtures. For example, photothermographic materials often use a mixture of silver soaps consisting of silver stearate, arachidate, and behenate. Little phase information is available on long-chain soaps and none on soap mixtures, although the phase behavior and microstructure often have a direct effect on product properties. In the present study the Krafft solubility boundaries of sodium stearate, arachidate, and behenate in water were measured for low soap weight fractions. Data for the cmc showed that the observed Krafft boundary lies above the cmc in its entirety for each of the soaps. Therefore, the knee in the Krafft boundary cannot be identified with the formation of micelles. The Krafft temperature of mixtures of these three soaps was observed to have a minimum value at a high content of the shortest-chain soap. The nonlinear relationship between the soap solubility and the mixture composition can be fitted to a mixing rule based on the solid−liquid equilibrium thermodynamics. To determine if multiple solid soap phases were present, the structures of the solid phases were characterized by wide-angle X-ray scattering, FTIR, and DSC. It was found that a single mixed crystalline solid phase is formed over most of the composition range. The bilayer spacing of the soap crystals is close to that of the majority component, except when the weight fractions are roughly equal, in which case the solid phase is largely disordered. The water content of the soap crystals was found to increase continuously with increasing environmental humidity, indicating that soap hydrates are not stoichiometric.

Structure-related aspects on water diffusivity in fatty acid–soap and skin lipid model systems

Simplified skin barrier models are necessary to get a first hand understanding of the very complex morphology and physical properties of the human skin barrier. In addition, it is of great importance to construct relevant models that will allow for rational testing of barrier perturbing/occlusive effects of a large variety of substances. The primary objective of this work was to study the effect of lipid morphology on water permeation through various lipid mixtures (i.e., partly neutralised free fatty acids, as well as a skin lipid model mixture). In addition, the effects of incorporating Azone® (1-dodecyl-azacycloheptan-2-one) into the skin lipid model mixture was studied. Small- and wide-angle X-ray diffraction was used for structure determinations. It is concluded that: (a) the water flux through a crystalline fatty acid–sodium soap–water mixture (s) is statistically significantly higher than the water flux through the corresponding lamellar (Lα) and reversed hexagonal (HII) liquid crystalline phases, which do not differ between themselves; (b) the water flux through mixtures of Lα/s decreases statistically significantly with increasing relative amounts of lamellar (Lα) liquid crystalline phase; (c) the addition of Azone® to a skin lipid model system induces a reduction in water flux. However, further studies are needed to more closely characterise the structural basis for the occlusive effects of Azone® on water flux.

Surface activity of acylglycerol emulsifiers modified with carboxylates

The interaction of monoacylglycerols and sodium or potassium carboxylates in modified acylglycerol emulsifiers was investigated to find the influence of the product composition on the interfacial tension in paraffin oil/water systems. The modification of surface activity of the emulsifiers was obtained by programming sodium or potassium soap content and hydrocarbon chain length, as well as the length of the acyl in the monoacylglycerol. It was stated that the increase of carboxylate concentration in the emulsifier causes a decrease of the C.M.C. in the case of sodium and potassium soaps. The C.M.C. values of monoacylglycerols with sodium carboxylates are higher than for potassium salts. The effectiveness of interfacial tension reduction of the synthesised products was investigated.

Estimation of Dielectric Constants of Adsorbed Monolayers for Some Sodium Soap Solutions

The interfacial tensions of lauric and myristic acid sodium salt water solutions were measured at the air/water interface at 20°C and at the air/0.01 M NaOH water solution interface at 20° and 40°C. On the basis of these results the dependence of standard free energy of adsorption (ΔG0) on the interface coverage (Θ) was determined from the Blomgren–Bockris isotherm. According to these dependencies the interactions of adsorbed molecules were discussed and dielectric constants of the adsorbed monolayer were estimated.

The behaviour of modified monoacylglycerol emulsifiers in emulsion systems

Modified acylglycerol emulsifiers with programmed values of hydrophile-lipophile balance were synthesised in situ by esterification of glycerol with fatty acids in the presence of fatty acid soaps. The modification of the surface activity of the emulsifier was obtained by programming sodium or potassium soap content and hydrocarbon chain length, as well as the length of the fatty acid acyls in the monoacylglycerol. The effectiveness of the synthesised emulsifiers was investigated in model O/W emulsion systems. The influence of the phase volume ratio on emulsion inversion, stability and emulsion droplet size were studied.