The results of an extensive study of percolation to verify some theor. predictions about percolation crit. indexes for changes in static and dynamic dielec. properties of a microemulsion a a function of temp. and frequency are presented. The dynamic behavior of the microemulsions was also studied to reveal the mechanisms that are responsible for dielec. polarization of the system. The measurements were made by the time domain dielec. spectroscopy method in the frequency range 105-1010 Hz and at 10-40°. Crit. indexes for cond. and dielec. permittivity have the values s ≈ 1.2 below and t ≈ 1.9 above the percolation threshold. The value for the crit. index s is in agreement with a dynamic percolation picture. This confirms the idea that the mechanism responsible for the temp. dependence of cond. and permittivity has the same origin. The numerical value of t indicates a percolation picture above the threshold; however, it does not provide information about the nature of percolation. The data treatment for the dynamic behavior of the microemulsions was carried out in the time domain in terms of dipole correlation functions. The correlation functions exhibit complex nonexponential relaxation behavior in the percolation region and must be deconvoluted into normal modes and represented as the sum of the simple exponential exp(-t/$\tau$) and nonexponential terms exp[-(t/$\tau$)$\beta$]. The frequency scaling parameters m, p, and u, as well as the stretched parameters in the time window $\beta$, provide information about the microstructure and dynamics of the system. The anal. of their temp. dependence shows the existence of spatial, temporal, and energetic disorder assocd. with anomalous diffusion of charge carriers in the percolation clusters. From a detailed anal. of the time relaxation data spectrum, the mol. dynamic mechanism of dielec. polarization in the percolation region was suggested. [on SciFinder(R)]

Calcium oxalate dihydrate (CaC2O4.(2+x)H2O; COD; x less than or equal to 0.5) does not readily crystallize from electrolytic solutions but appears as a component in crystalluria. In this paper, we review in vitro studies on the factors responsible for its nucleation and growth with special attention given to the role of surfactants. The following surfactants were tested: dodecyl ammonium chloride (cationic), octaethylene mono-hexadecylether (non-ionic), sodium dodecyl sulfate (SDS, anionic), dioctyl sulphosuccinate (AOT, anionic), and sodium cholate (NaC, anionic). The cationic and some of the anionic surfactants (SDS, AOT) induced different habit modifications of growing calcium oxalate crystals by preferential adsorption at different crystal faces. In addition, the anionic surfactants effectively induced crystallization of COD at the expense of COM, the proportion of COD in the precipitates abruptly increasing above a critical surfactant concentration, close to, but not necessarily identical with the respective CMC. A mechanism is proposed, whereby crystallization of COD in the presence of surfactants is a consequence of the inhibition of COM by preferential adsorption of surfactant hemimicelles (two-dimensional surface aggregates) at the surfaces of growing crystals.

The BSO (V. Bansal, D. Shah, and J. O'Connell, 1980) equation was derived as an empirical condition for max. H2O solubilization in microemulsions stabilized by anionic surfactants, in relation to the cosurfactant (alc.) and oil chain lengths. The present study examines, for the 1st time, the applicability of this equation for nonionic microemulsions. By constructing pseudo-ternary phase diagrams and measuring the area of the single phase regions as well as the H2O contents at the boundary, the authors find the solubilization capacity is related directly to the alc. chain length only if the alc. soly. in both the aq. and oleic phases is limited. In addn., the authors try to integrate the concept of chain length compatibility with the competition between the natural curvature and the crit. radius of the interface. The attempt to unify the exptl. results may serve as a guideline for optimization of microemulsion systems. [on SciFinder(R)]

In search for tomorrow's technol. for water-based coatings, Decora Manufg. and The Hebrew University of Jerusalem, have initiated an intensive research program for designing, developing and manufg. new coatings based on crosslinked, room-temp.-cured silicone-epoxy resins. The new water-borne coatings have most exciting characteristics such as: non-stick properties, effective release, high lubricity, corrosion protection and abrasion resistance. The coatings are environmentally friendly and easy to use. These coatings are ideal for marine, agricultural, industrial and maintenance applications. This paper brings quant. measurements related to the dispersion technol. (particle size, stability, shelf-life), to the non-stick properties (deicing, low surface energy, easy-release and non-stick), lubricity, adhesion to substrates, viscosity, dynamic and static friction coeffs. and environmental impact (low VOC, non-toxicity, low-leaching). The coating was tested in various industrial coating systems and was found to exhibit excellent non-stick and release properties. Special attention was given to Zebra Mussels, Quagga Mussels, and other bacterial and algal bioforms. The coating proved to be efficient as foul-release coating with very low biofouling adhesion. The low adhesion applied to many other substances in which foul-release means easy-clean and low wear. [on SciFinder(R)]

A process for the removal of a cholesterol from liq. or liquefiable edibles, by hydrocolloid extractants, preferably galactomannose, is disclosed. [on SciFinder(R)]

The invention provides a water-in-oil microemulsion having a high fire resistance, consisting of mineral oil; at least 50% water; and at least one polyethoxylated nonionic alc. surfactant, the alc. having 12-18 carbon atoms and having attached thereto between 2 and 25 ethoxy groups. [on SciFinder(R)]

Fenugreek saponins have improved properties as compared to soybean saponins when used as emulsifiers. Thus, comestible products may contain emulsifying fenugreek saponins selected from tigogenin, neotigogenin, gitogenin, neogitogenin, diosgenin, yamogenin, yuccagenin, and lilagenin. [on SciFinder(R)]

A polymorph of aspartame, designated APM II, characterized by X-ray diffraction powder patterns, an IR diffraction pattern, and differential scanning calorimetric patterns, was prepd. Thus, aspartame was crystd. from a pH 5.3 buffer prepd. from potassium hydrogen phthalate and NaOH in H2O at 21° to give APM II. Sweetening compns. contg. APM II are claimed. [on SciFinder(R)]

Cationic guar gums of varying molar mass and charge d. were synthesized and tested as flocculants for bentonite suspensions. The gums were fragmented using ammonium persulfate as a degrading agent, followed by pptn. of the products with ethanol. Cationic charge was added to the guar mol. by reacting it with 2,3-epoxypropyltrimethylammonium chloride. Flocculant performance was assessed by detg. the extent of polymer adsorption, by measuring both residual turbidities of the resulting supernatants and the changes in the particles' electrophoretic mobility (EM). Increasing the flocculant charge d. causes the optimal flocculation concn. (OFC), as well as the efficient flocculant concn. range, to be reduced. Above this range restabilization occurs. The OFC (for highly modified guar) is also the concn. at which the particles' EM is zero. It was found that decreasing the mol. wt. of the guar (at the same charge d.) increases the OFC and decreases the electrophoretic mobility of the clay particles in the overdose range. [on SciFinder(R)]

Silicone based surfactants were used as stabilizers for W/O/W double emulsions with unusual mech. stability. W/O/W multiple emulsions contg. several markers were prepd. The entrapped markers were: (1) halide salts, (2) a typical drug, ephedrine hydrochloride, and (3) KNO3 (water sol. fertilizer). Good solute trapping (95% yield of prepn.) with slow release rates through the liq. oil membrane (60% release after 30 days), were obtained. The halides, with the exception of iodide, showed almost the same typical slow release rates to the outer water phase. The release rates of the ephedrine hydrochloride and KNO3 were faster than that of the halides. The results suggested that multiple emulsions based on silicone surfactants can be used as slow release systems for agricultural applications. Up to 20 wt% of the total concn. of the hydrophobic silicone-based emulsifier (E1 - the inner emulsifier) was replaced by Span 80. As a result, water was entrapped in the oil phase, suggesting formation of reverse micelles in the presence of Span 80, explaining, in part, the release kinetics of the halides. The release seems to be composed of three sep. stages: lag time, fast release and "no release". The release mechanism seems to comply, in part, with a transport mechanism involving "reverse micelles" and is also dependent on the hydrophobicity of the marker. The more hydrophobic markers (the drug and iodide) seem to be released also by "direct diffusion of the mol. through the oil" in addn. to their release through the reverse micelles. [on SciFinder(R)]

The dielec. behavior of a microemulsion prepd. from dodecane, butanol, H2O and polyoxyethylene (10) oleyl alc. (Brij 97) was studied by time domain dielec. spectroscopy over the frequency range 105-1010 Hz for temps. between 10 and 40° with varying H2O content. Several dielec. dispersion regions with the typical characteristic relaxation times of the order of nanoseconds and tens of picoseconds are obsd. They are analyzed in time domain in terms of macroscopic dipole correlation functions and are attributed to the relaxation mechanisms of the different chem. compds. within the microemulsion. The appearance and intensity of the peaks for the relaxation processes depend on the H2O content. The types of motion of different kinetic units that can be manifested as local relaxation processes are proposed. The dielec. properties of microemulsions depend on the underlying phase behavior and on the consequent morphol. in these systems. The results suggest that changes in the microstructure of polarization and relaxation mechanisms occur in the H2O fraction content intervals of 5-10, 10-35, and 35%. [on SciFinder(R)]

The influence of sodium dodecyl sulphate, SDS, dodecyl ammonium chloride, DDACl and octaethylene glycol mono-n-hexadecyl ether, C(16)EO(8), On the crystallization of calcium oxalate from 0.3 molar sodium chloride solutions is discussed. Under the given experimental conditions the thermodynamically stable monohydrate, COM was the predominant crystal form. Both ionic surfactants inhibited growth and aggregation of COM and, by preferential adsorption at different crystal faces, induced different habit modifications. In addition, micellar solutions of SDS promoted crystallization of the metastable calcium oxalate dihydrate, GOD. The nonionic surfactant, C(16)EO(8), Stimulated nucleation and/or initial crystal growth of COM, most probably by providing active centers for heterogeneous nucleation.

The influence of SDS and octaethylene glycol mono-n-hexadecyl ether (I) on the crystn. of Ca oxalate from 0.3 M NaCl solns. is discussed. Under the given exptl. conditions the thermodynamically stable monohydrate (II) was the predominant crystal form. SDS inhibited growth and aggregation of II and, by preferential adsorption at different crystal faces, induced different habit modifications. In addn, micellar solns. of SDS promoted crystn. of the metastable calcium oxalate dihydrate. I stimulated nucleation and/or initial crystal growth of II, most probably by providing active centers for heterogeneous nucleation. [on SciFinder(R)]

The stability of w/o/w emulsions has been significantly improved by using a blend of nonionic surfactant (Span 80) and bovine serum albumin (BSA) as an interfacial complex in the inner phase. Improved stability was obtained by replacing the common nonionic hydrophilic monomeric emulsifier by BSA in the outer phase. Optimum stability and droplet size of double emulsion was achieved with 0.2 wt% BSA + 10 wt% Span 80 as emulsifier I and 5.0 wt% Span 80-Tween 80 (2:3) or 0.1 wt% BSA as emulsifier II. Significant slow release of NaCl was obtained. The results were examd. in view of Higuchi mechanism and it was found that one can account for the thickness of the inner interfacial complex from the plot of B (diffusion parameter correlated to the fraction of electrolyte release) vs. time. It can be clearly seen that in the inner phase the surfactant and the BSA act synergistically (active interfacial complex), and enhance stability and reduce release. In the outer phase BSA has mainly a stabilizing effect with a limited release retardation effect. Effective diffusion coeffs. for each BSA concn. in the inner and outer phase have been calcd. and evaluated in a view of the diffusion controlled mechanism and the thickness of the viscoelastic film which is formed. [on SciFinder(R)]