摘要:

A series of highly carboxylated latices comprising methacrylic acid (MAA) (or acrylic acid (AA)), dodecyl methacrylate and methyl methacrylate was prepared and characterized. The reaction parameters include the monomer composition, the concentration of dodecyl mercaptan (used as the molecular weight regulator) and the type of carboxylic monomers. These carboxylated latices were then used as the seed for the subsequent semibatch surfactant-free emulsion polymerization of butyl acrylate (BA). The unneutralized seed latices are incapable of supporting the BA polymerization. On the other hand, the seed latices containing 50 wt% MAA or AA at pH 8-9 are very effective for this purpose due to the increased particle surface charge density. The seed latex containing 50 wt% AA should be a better candidate for producing latex products with a higher solid content due to the appropriate rheological properties.

ISSN:0193-2691    

DOI:10.1080/01932699808913157

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Vesicles were prepared by dilution with water of hydrotrope (sodium xylene sulfonate) solutions for a nonionic surfactant Laureth 4 (Brij® 30).

ISSN:0193-2691    

DOI:10.1080/01932699808913158

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Experimental determinations of apparent viscosity were used to investigate the rheological behaviour of easy-to-disperse (ETD) Carbopol 2001, 2020 and 2050 hydrogels, involving different polymer concentrations, degrees of neutralization, agitation times and shear rates. Mathematical expressions were obtained, based on the power law, to allow calculation of the viscosity of each system, for the different variables studied. These equations proved valid within the 5.5-7.5 pH range, i.e., the pH interval of greatest interest in pharmaceutics and cosmetics. The rheological behaviours of the three types of ETD hydrogels were investigated comparatively and with respect to Carbopol 940, i.e., one of the most widely utilized hydrogels.

ISSN:0193-2691    

DOI:10.1080/01932699808913159

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Emulsification of xylene was carried out using mixed surfactant system. HLB concept was used to select the right surfactant mixture. Variation in the stability of emulsion with respect to HLB was investigated by studying interaction between mixed surfactant. The interaction was quantified interms of interaction parameter β. Exact location and nature of the interaction was (hydrophilic / hydrophobic) studied by 1H NMR spectroscopy. Charge present on emulsion droplet was calculated by zetapotential measurement.

ISSN:0193-2691    

DOI:10.1080/01932699808913160

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Five novel zwitterionic surfactants with alkylbetaine structure incorporated by hydroxypropyl group have been prepared. The structure and composition of these compounds of high purity were identified by elemental analysis, IR,1H NMR, and13C NMR. Their isoelectric points have been determined by pH-titration method and lie in the range of 5.0-5.1. Surface tension experiment have demonstrated that these surfactants have higher surface activity than those without hydroxypropyl group. CMC, γCMC, free energy of micellization and area per molecule in micelles of each surfactants have also been studied. Plot of log CMC vs. the length of alkyl chain gives a straight line. The addition of Na+ions influences their CMCs slightly which is assignable to the inner salt-like structure of these molecules. All the surfactants prepared in this work have Krafft points below 0°C, possess calcium stability >1800 and good Lime Soap Dispersing Property and foam property. Biodegradability of them has also been tested suggesting that they can be used without any environmental problems.

ISSN:0193-2691    

DOI:10.1080/01932699808913161

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Monodisperse nickel boride catalysts are prepared from reversed micellar systems in situ and used directly as the catalysts of styrene hydrogenation. In order to investigate the influence of particle size and the effect of micellar components on the hydrogenating activity of nickel boride catalysts, the hydrogenation of styrene over nickel boride catalysts has been done, respectively, in ethanol solution, reversed micellar solution and various mixtures of reversed micellar solution with ethanol. The experimental results have shown that monodisperse nickel boride particles exhibit higher hydrogenation activity than those prepared in ethanol solution. On the other hand, the presence of a micellar system has an inhibiting effect on the hydrogenation activity of nickel boride particles, and the inhibiting effect is discussed in detail.

ISSN:0193-2691    

DOI:10.1080/01932699808913162

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dielectric spectroscopy is considered as an interesting method for determination quality parameters like density, viscosity and interfacial properties of petroleum fluids. In this paper are the mechanisms important for the dielectric properties of crude oils studied for development of new charaterising methods.

ISSN:0193-2691    

DOI:10.1080/01932699808913163

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Inorganic small particles were obtained by photochemical reaction of Fe(NO3)3and oxalic acid in aqueous solution, anionic AOT-water and cationic CTAB-hexanol-water liquid crystals, respectively. X-ray diffraction and IR spectra identified that the products obtained from these different systems have the same composition, β-FeC2O4. 2H2O, but have different shape and size of particles: rodlike for aqueous solution and needlike for liquid crystals. The size of the particles formed in the three systems followed the sequence: D(water)>D(CTAB-hexanol-water )>D(AOT-water). Varying the intensity of the incident light changed the growth rate of particles and affected the final particle size. The growth rate of the particles was enhanced by increasing the incident light intensity, but the largest average diameters were achieved with decreasing light intensity. This inverse relationship between final size and incident light intensity can be shown by comparing the average diameters of the particles formed in AOT liquid crystal under different conditions: D(weak light), D(moderate light) > D(strong light).

ISSN:0193-2691    

DOI:10.1080/01932699808913164

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0193-2691    

DOI:10.1080/01932699808913165

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor