摘要:

Due to the multiplicity of parameters governing emulsion stability, existing theories generally cannot quantitatively predict the phase separation in oil/water systems. In this work, an artificial neural network, which is known to have a strong nonlinear mapping ability, was used to “learif” the correlation between the factors influencing emulsion stability (phase ratio, surfactant concentration and comonomer concentrations) and the magnitude of phase separation. This has been applied to the water-in-oil copolymerizations of acrylamide with quaternary ammonium cationic monomers. It was found that the ANN can accurately predict the subset of the stability state (stable, metastable, unstable), along with the extent of oil separation for metastable systems.

ISSN:0193-2691    

DOI:10.1080/01932699808913199

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The hydrolysis of tetraethylsilane can be carried out and using chloral hydrate as the source of water. The first step of the hydrolysis, formation of triethoxysilanol is the rate determining step. The hydrolysis thus resembles that of aectals, ketals and orthoesters. In unbuffered media the reaction is sufficiently slow to follow the decrease of Si(OEt)4, and changes in concentrations of Si(OEt)3(OH) and Si(OH)4by29Si NMR The most rapidly formed dimeric species has two OH groups on a given Si atom. Formation of oligomers involves one or more hydrolyzed momoners. In solutions acidified by HCI and containing small amount of water, both hydrolysis and formation of oligomers by condensation occurs faster. The intermediate Si(OEt)2(OH)2is also detected, indicating that the rate of the first step of hydrolysis increase with increasing acidity more than that of the second step.

ISSN:0193-2691    

DOI:10.1080/01932699808913200

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The alkaline hydrolysis of dimethylformamide has been studied at 40°C In mixed micelles of surfactants (CTAB—Brij35, SD6 — Brij35, CTAB — BHMI, SDS —BHMI, Brtj35—BHMI) and functional molecule 1—benzyl—2—hydroxymethylimidazole (BHMI) solutions with analog thermogram method of thermokinetics. The kinetic parameters kmIn micellar pseudophase, rate constant kein functional molecular solution, and the association constant of reactant with micelle Ki, with functional molecule K, have been calculated from kinetic equations of mixed micellar catalysis in the case of [S]>[M]. The results indicate that all the researched systems exhibit catalytic effect on the reaction. Polarity and local concentration effect were employed to explain these phenomena. A mechanism of catalysis of BHMI and mixed micelles of a surfactant and BHMI was proposed.

ISSN:0193-2691    

DOI:10.1080/01932699808913201

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Solubilization of water and aqueous NaCl solutions in mixed reverse micellar systems of anionic surfactant AOT and nonionic surfactants in n-heptane was studied. It was found that the maximum solubilization capacity of water was higher in the presence of certain concentrations of NaCl electrolyte, and these concentrations increased with the increase of nonionic surfactant content and their EO chain length. Soluibilization capacity was enhanced by mixing AOT with nonionic surfactants. The observed phenomena were interpreted in terms of the stability of the interfacial film of reverse micellar microdroplet and the packing parameter of the surfactant that formed mixed reverse micelles.

ISSN:0193-2691    

DOI:10.1080/01932699808913202

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Fe(NO3))-SiO2glasses were prepared by hydrorlyzing silicon alkoxides with various amount of ferric nitrate hydrate following the sol-gel process. The gel glasses were allowed to dry completely at room temperature then several thermally treatments were done. The thermal transition was studied with differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The structural features of the glassy materials were analyzed by means of infrared (IR) spectroscopy and X-ray diffraction (XRD). The samples with a higher concentration of 30 % mole of iron existed in the crystalline structure; the thermal transitions did not affect the crystalline structure of these mixed samples as indicated by the X-ray diffraction. The IR spectra indicated the existence of Si-O-Fe bond. The thermal analysis indicated similar heat transitions for the glass as the pure iron nitrate with some modification due to the interactions with the silica network.

ISSN:0193-2691    

DOI:10.1080/01932699808913203

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0193-2691    

DOI:10.1080/01932699808913204

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Electrophoretic light scattering (ELS) is used to determine the zeta potential of O/W emulsions of five commercial cutting oils. AlCl3, MgCl2, CaCl2and NaCl were added as electrolytes to the emulsions at concentrations varying from 10−4mol/dm3to 10−1mol/dm3in order to study the influence of electrolyte concentration and cation charge on the zeta potential of the emulsions and to explain their stability.

ISSN:0193-2691    

DOI:10.1080/01932699808913205

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In a model emulsion system consisting of 10% w/w of methyl linoleate and 0.5% w/v of Tween 20 as an emulsifier in a 0.05 M sodium acetate buffer (pH 4.0) with polysaccharide, locust bean gum, xanthan and glucomannan considerably inhibited oxidation, as proved by the change in peroxide value. Carrageenan and chitosan had no or only a small effect on oxidation. There was no evidence of organic radical scavenging activity as shown by ESR, but oxidation inhibiting polysaccharides manifested an iron binding activity.

ISSN:0193-2691    

DOI:10.1080/01932699808913206

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0193-2691    

DOI:10.1080/01932699808913207

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor