Sodium dodecyl sulphate stability

Effect of hexadecane as additive In a series of papers Hallworth and Carless (7,8,9,TO) have investigated the effect of the nature oT the internal phase on the stability of oil in water emulsions as well as the effect of addition of long chain fatty alcohols with sodium dodecyl sulphate or sodium hexadecyl sulphate as the ionic emulsifier. They found that light petroleum and chlorobenzene emulsions prepared only with sodium hexadecyl sulphate were much less stable than those produced using the longer chain paraffins, white spirit and light liquid paraffins. 

The object of this study was to clarify some aspects of the mechanism of shear-induced flocculation in colloidal dispersions. Vinyl chloride homopolymer and copolymer latices were prepared by emulsion polymerization using sodium dodecyl sulphate as emulsifier. Agglomeration behavior in these latices was studied by measuring the mechanical stability using a high speed stirring test. The latex particle size was measured by an analytical centrifuge. Molecular areas of emulsifier in the saturated adsorption layer at the surface of homopolymer and copolymer latex particles were estimated from adsorption titration data. 

Several investigations were carried out to study the above transitions from CF to common black film, and finally to Newton black film. For sodium dodecyl sulphate, the common black films have thicknesses ranging from 200 nm in very dilute systems to about 5.4 nm. The thickness depends heavily on the electrolyte concentration, while the stability may be considered to be caused by the secondary minimum in the energy distance curve. In cases where the film thins further and overcomes the primary energy maximum, it will fall into the primary minimum potential energy sink where very thin Newton black films are produced. The transition from common black films to Newton black films occurs at a critical electrolyte concentration which depends on the type of surfactant... 

For the evaluation of the foamability of a surfactant the bulk concentration is used at which the relative rate of foam collapse is equal to 50% of its formation (cw °). The cw ° values determined from foam formation isotherms of a number of products are given in Table 6.1. As it is seen, typical representatives of anionics (sodium dodecyl sulphate), cationics (cetyl trimethyl ammonium bromide) and nonionics (ethoxylated alkylphenols) give bubble foams at very low concentrations, and the foam stability of ionic surfactants does not differ much from that of nonionics. For anionics, the highest concentrations are required for soaps of higher carboxylic acids. 

The stability improvement of Ti02 suspensions is important not only for water-based paints, but also for paints based on non-polar or low-polar solvents. It is shown in [208] that Ti02 powders modified with an anionic surfactant, e.g. sodium dodecyl sulphate, are dispersed to smaller sizes, and their sedimentation stability increases. The production of water-alkyd emulsions is inhibited due to low mechanical stability. These emulsions can easily break when exposed to shear forces such as those produced by pumps, and when intensively agitated during dispersion. [209] demonstrates that most stable emulsions can be obtained with alkyds showing high acid numbers, as well as with highly polymerised alkyds of low viscosities. 

Sperry et al. found that the addition of either the anionic surfactant sodium dodecyl sulphate or the nonionic surfactant Triton X-405 completely desorbed any hydroxyethyl cellulose from the surface of the latex particles. This meant that, even in the presence of free hydroxyethyl cellulose in the continuous phase, none of the flocculating polymer was attached to the surface. The latex particles in the presence of the sodium dodecyl sulphate (0-5%) were thus electrostatically stabilized whereas the nonionic Triton surfactant conferred steric stabilization. 

The carbohydrate moiety of j3-D-fructofuranosidase of Candida utilis was suggested to be localized at certain sites of the enzyme protein. The oxidation of the sugar moeity with periodate to a certain extent had no effect on the enzyme activity, but the stability of the enzyme was decreased. This partially oxidized enzyme bound hide powder or nylon powder and the enzyme activity was retained. The enzyme was shown to be divided into glycoprotein sub-units of a similar molecular size when heated in the presence of sodium dodecyl sulphate. The enzyme did not dissociate upon treatment with reducing agent such as mercaptoethanol. 

Earlier, oleic-acid- or sodium dodecyl sulphate (SDS)-stabilized ferrofluid encapsulation with EGDM was reported, where 4,4-azobis (4-cyanovaleric acid) (ACVA) was used as initiator and particles were further functionalized with MA... 

The polymerisation of styrene in miniemnlsions stabilised with anionic sodium dodecyl sulphate or nonionic Lntensol AT50 results in stable polymer dispersions with particle diameters between 30 and 480 nm and narrow particle size distributions. Steady-state mini-emulsification results in a system with critical stability , i.e. the droplet size is the prodnct of a rate equation of fission by ultrasound and fusion by collisions, and the mini-droplets are as small as possible for the timescales involved. The droplet growth by monomer exchange, or the T1 mechanism, is effectively suppressed by addition of a very hydrophobic material, whereas droplet growth by collisions, or the T2 mechanism, is subject to the critical conditions. The growth of the critically stabilised miniemulsion droplets is usually slower than the polymerisation time therefore, in ideal cases, a 1 1 copy of droplets to particles is obtained, and the critically stabilised state is frozen. 6 refs. 

The objective of this work was to characterise the sodium dodecyl allyl sulphosuccinate (Eliminol JS-2) stabilised poly(butyl acrylate) (PBA) lattices produced in a semibatch reactor. The PBA latex particles were prepared using a semibatch pulsion polymerisation process. It was found that the concentration of JS-2 or sodium dodecyl sulphate present in the initial reactor charge is very important in determining the final latex particle size. The higher the particle size polarity is, the larger is the saturated particle surface area covered by one JS-2 molecule. It was also found that at a common surfactant concentration, the JS-2 stabilised latex displays reduced chemical stability than the sodium dodecyl sulphate stabilised latex. The results of such research should be useful to tape and label manufacturers. 3 refs. 

Colloid Polymer Science 278, No.9, Sept. 2000, p.821-9 MICROEMULSION POLYMERISATION OF STYRENE STABILIZED BY SODIUM DODECYL SULPHATE AND DIETHYLENE GLYCOL MONOALKYL ETHER Chem C S Liu C W... 

Diethylene glycol monoalkyl ether was used as a cosurfactant in the formation of an oil-in-water styrene microemulsion. Sodium dodecyl sulphate was used as a surfactant. The pseudo three-component phase diagram, macroemulsion, microemulsion and lamellar gal phases, was constructed for the cosurfactants. A smaller number of latex particles nucleated than there were microemulsion droplets initially present. The diethylene glycol monoalkyl ether group of CiEj enhances the latex stability and the CiEj more effectively stabihses the styrene microemulsion and subsequent polymerisation compared with CiOH cosurfactants used as a comparison. 15 refs. 

The hydrodynamic particle size distribution of samples was measured by dynamic light scattering (DLS-700, Otsuka Electronics) for the sample-redispersed aqueous suspension containing a small amount of sodium dodecyl sulphate as a dispersion stabilizer. The... 

Because of this dual character of its molecules association colloids are of great practical utility. Most of them are surface-active substances. Examples of this class are the soaps and detergents like sodium dodecyl sulphate. While some are excellent solubilizers of various types of organic compounds in water, others are good dispersion stabilizers. 

Conditions for the maximum yield of extracellular a-amylase from Bac-teroides amylophilus have been reported. Isoelectric focusing and polyacrylamide gel electrophoresis demonstrated the presence of six isoenzymes one of these was purified by ion-exchange chromatography and gel filtration. This enzyme (pH optimum 6.3, temperature optimum 43 °C, pH stability range 5.8—7.5, p7 4.6, mol. wt. 9.2 x 10 by sodium dodecyl sulphate-polyacrylamide gel electrophoresis) was inhibited by cyclo-hexa and hepta-amyloses, phenyl a-D-glucopyranoside, and Hg + whereas Ca + and Co were strong activators. The relative rates of hydrolysis of amylose, soluble starch, amylo-pectin, and dextrin were 100, 97, 92, and 60%, respectively (Am values 18.2, 18.7, 18.2, and 16.7 [xmol D-glucosidic bonds 1, respectively). 

The hydrodynamic interface of the droplets has been shown to contain a significant amount of the continuous phase and a quantity of co-surfactant which increases as the amount of solubilizate increases [176]. Small-angle neutron scattering indicates that there is a portion of the interfacial film, 0.9 nm thick, which is not penetrated by the continuous phase [176] in water-in-cyclohexane microemulsions stabilized by sodium dodecyl sulphate and 1-pentanol. 

Table 8.7 Residual viscosity (%) and compliance (Jo) of liquid parafiin-in-water emulsions stabilized by 4.5 % long-chain alcohol and 0.5% sodium dodecyl sulphate [196].

The stability of the non-ionic surfactant, sucrose monolaurate, below and above its CMC has been studied. Below the CMC first-order kinetics are observed for its hydrolysis to lauric acid, but this is not so above the CMC. In buffered systems at a pH when the lauric acid is ionized, the product of hydrolysis appears to form mixed micelles with the sucrose monolaurate, producing negatively charged micelles which appear to protect the ester from attack and thus reduce rates of hydrolysis [155]. Sodium dodecyl sulphate is more stable to hydrolysis in alkaline solutions above its CMC than in acid solutions where the rate of hydrolysis is proportional not only to the hydrogen ion concentration, but also to the concentration of the detergent itself [156]. This agrees with the observation of Kurz [157] that the proton-catalysed rates of hydrolysis of mono-... 

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