Surfactant chemical stability

Surfactant Chemical Stability. Two approaches were used in assessing surfactant degradation over time. The first consisted of monitoring the pH of surfactant solutions that were in contact with pieces of reservoir rock over several months. Because only commercially available surfactants were tested and almost all of them contained secondary components, the pH data were rather inconclusive. The fact that reservoir solids have some buffering capacity made the interpretation of pH trends even more difficult. 

The high thermal and chemical stability of fluorocarbons, combined with their very weak intermolecular interactions, makes them ideal stationary phases for the separation of a wide variety of organic compounds, including both hydrocarbons and fluorine-containing molecules Fluonnated stationary phases include per-fluoroalkanes, fluorocarbon surfactants, poly(chlorotrifluoroethylene), polyfper-fluoroalkyl) ethers, and other functionalized perfluoro compounds The applications of fluonnated compounds as stationary phases in gas-liquid chroma... 

The chemical stability of Toyopearl HW-40 resin to organic eluents allows this material to be used for a variety of applications, including the purification of synthetic functionalized surfactants, polyphenolics, and phenolic glycosides (50,51). 

Emulsions and Emulsion Technology (in three parts), edited by Kenneth J. Lissant Anionic Surfactants (in two parts), edited by Warner M. Linfieid see Volume 56) Anionic Surfactants Chemical Analysis, edited by John Cross Stabilization of Colloidal Dispersions by Polymer Adsorption, Tatsuo Sato and Richard Ruch... 

Of these surfactants, two classes are worthy of further note. The alpha-olefin sulfonates have been found to possess good salt tolerance, chemical stability at elevated temperatures, and appear to exhibit good oil solubilization and low interfacial tension over a wide range of temperatures (438,465). While being less salt tolerant, alkylaromatic sulfonates exhibit excellent chemical... 

Public information about the specific chemical identity of the surfactants and stabilizers in use is scant(353-355) (Figure 11). Performance of foamed fluids is heavily dependent upon the size and distribution of the individual foam cells that are present, therefore the generator, testing apparatus, pressure and procedures employed are critical parts of the evaluation and the observed results. Contaminants (salts, acids, alkalies, etc) in the liquid phase also can cause drastic changes in foam performance. 

The solid matrix of SLN protects the drug from hydrolysis and oxidation. Chemical stability of tocopherol and retinol improves considerably [17,39], with tocopherol improving by 57% compared with an aqueous dispersion. The degree of retinol stabilization depends on the nature of lipid and surfactant [39]. For each drug, the optimal preparation has to be defined individually. 

The properties of a latex depend on the nature of polymers in the latex, particularly the monomer ratio in copolymers and the type and amount of plasticizers. The monomer ratio affects the strengths of the latex modified mortars to the same extent as the polymer-cement ratio [87, 92]. Mechanical and chemical stability, bubbling and coalescence on drying all depend on the type and amount of surfactants and antifoamers and the size of dispersed polymer particles. It is important that the use of selected antifoamers and surfactants as stabilizers or emulsifiers produces no adverse effect on cement hydration. 

Surfactants enable the polymer particles to disperse effectively without coagulation in the mortar and concrete. Thus, mechanical and chemical stabilities of latexes are improved with an increase in the content of the surfactants selected as stabilizers. An excess of surfactant, however, may have an adverse effect on the strength because of the reduced latex film strength, the delayed cement hydration and excess air entrainment. Consequently, the latexes used as cement modifiers should have an optimum surfactant content (from 5 to 30% of the weight of total solids) to provide adequate strength. Suitable antifoamers are usually added to the latexes to prevent excess air entrainment increased dosages causes a drastic reduction in the air content and a concurrent increase in compressive strength [87, 92-94]. 

Amendments may include surfactants, electron acceptors, lubricity enhancers, or chemical stabilization agents. Support mechanisms, such as pumping or fracturing technologies, may also be used. 

The chemical stability of the amide bond is high. When the surfactant containing an amide bond was subjected to 1 M sodium hydroxide during five days at room temperature, only 5% of the amide surfactant was cleaved. The corresponding experiment performed in 1 M HCl resulted in no hydrolysis. The amide bond was, however, found to be slowly hydrolyzed when lipase from Candida antarctica or peptidase was used as catalyst. Amidase and lipase from Mucor miehei was found to be ineffective. Despite the very high chemical stability, the amide surfactant biodegrades by a similar path in the... 

A related system is that of the lipid-bilayer corked capsule membranes which are formed from ultrathin (about 1 pm thick), spongy, 2.0- to 2.5-mm-diameter, more-or-less spherical nylon bags in which multiple bilayers are immobilized (Fig. 43) [343-345]. They were considered to combine the advantages of mechanical and chemical stabilities of polymeric membranes with the controllable permeabilities of surfactant vesicles. Polymerization of the bilayers, in situ,... 

The purpose of this paper is to summarise results which have recently been obtained for the effects of various soaps and surfactants upon the mechanical and chemical stability of natural rubber latex, and to indicate the inferences which have been drawn in the course of endeavouring to interpret these observations. 

The ability of a soap or surfactant to enhance the chemical stability of natural rubber latex was assessed by ascertaining its effect upon the mechanical stability of natural rubber latices whose stabilities had been reduced by various chemical modifications. Natural rubber latices of reduced stability were produced in three different ways as follows ... 

Effects of added sulphate and sulphonate surfactants upon the mechanical and chemical stability of natural rubber latex (8)... 

As a group of surfactants, ADPODSs all show very good chemical stability and high solubility, generally better than LAS. They are sold as per cent active solutions, the Dowfax series being the best known. 

As a class of surfactants, sulphosuccinates differ from most other sulphonates in their chemical stability and, due to the presence of the ester linkages, sulphosuccinates will hydrolyse at extremes of pH and with elevated temperature. Monoesters are more sensitive than diesters, with optimal stability of pH 6-8, whilst diesters are more stable and will tolerate pH of 1-10 at room temperature. This allows the use of diesters in a much wider range of environments, particularly under moderately acidic conditions. 

Sulphates are the second most important class of anionic surfactants in terms ofvolumes and range of application and share many features with sulphonates in that they are manufactured in the same way. However, there is one very important difference between the two that is the chemical stability of the sulphate group compared to the sulphonate. 

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