摘要:

The synthesis of new water soluble nonylphenol poly(ethylene carbonate) surfactants derived from nonylphenol ethoxylated (NP(EO)10), ethylene oxide (EO), and carbon dioxide was carried out in high yields in the presence of K2SnO3as a basic catalysts. Synthesis reactions were carried out in a stainless-steel reactor at 175°C at an initial pressure of 800 psi for a 24 h-period. Surfactants were characterized by FTTR,1H- and13C-NMR. The percentages of carbon dioxide incorporation obtained were between 5.8 and 10.9, depending on the starting molar ratio of NP(EO)10:EO:CO2. CMC values, as well as cloud points decreased with the molar ratio CO2/EO, indicating a reduction of hydrophilic character of the surfactants due to the addition of carbonate groups, O-C(=O)-O, into the ethoxylated chains. Also, the area per molecule at die interface increased when molar ratio CO2/EO increased, indicating a two site anchoring model for both hydrophobic moieties, poly(ethylene carbonate) chain and nonylphenol. Finally, nonylphenol poly(ethylene carbonate) surfactants showed good emulsification properties for stabilizing sunflower oil in water emulsions.

ISSN:0193-2691    

DOI:10.1080/01932699708943713

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The stability of pesticide emulsions has been studied with respect to HLB values of surfactant blends. Calcium alkylbenzene sulfonate was used as the anionic surfactant and nonylphenol ethoxylates with different number of ethylene oxide units were used as nonionic surfactants. Mixed micelle formation studies were carried out to correlate mixed micelle formation with the stability of emulsion. Emulsion formation was observed to be spontaneous. Studies regarding spontaneity were carried out photographically.

ISSN:0193-2691    

DOI:10.1080/01932699708943714

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Polymerization systems of vinyl acetate that retain the homogeneity regardless of the ratio organic/aqueous phases were studied. The organic phase consisted of 30/70 monomer/alcohol solutions and the aqueous one of solutions of nonyl phenol etoxylated with 25 moles ethylene oxide in 33% water. Ethanol was used in homopolymerization and n-propanol in copolymerization. Copolymerization was performed with di-2-ethyl-hexyl maleate. In the homogeneous systems obtained, the surfactant complexes the initiator, ammonium persulfate, while the cosurfactant modifies the initial structure of water. Owing to these phenomena, the structure of the reaction medium changes according to the ratio of phases. The rate of initiator decomposition and of polymerization depends on the ratio of phases. In presence of soluble initiator in the organic phase, AIBN, the rate of copolymerization is proportional to the content of the comonomers if the final system rest homogeneous.

ISSN:0193-2691    

DOI:10.1080/01932699708943715

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Oil-in-water microemulsions regions in systems of indometha-cin, isopropyl myristate, polysorbate 80, sorbitol and water have indicated an optimum polysorbate:sorbitol mass ratio for micro-emulsion formation of 1:2.5. The time-average light scattering technique results for this system have shown a linear increase of droplet size with an increase of oil content. An equation contained the partition coefficient of the drug between dispersed and continuous phase was used to estimate the permeation of the drug from microemulsions through a hydrophilic-lipophilic barrier. An increase of total polysorbate and sorbitol concentration from 32% to 44% w/w caused an increase of the permeability coefficient of indomethacin from 0.9 to 2.1 10−5cm/min.

ISSN:0193-2691    

DOI:10.1080/01932699708943716

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The adsorption of sodium polystyrene sulfonate (PSSNa) on TiO2in aqueous dispersion has been investigated in pure water and in the presence of different concentrations of sodium sulphate. The stability of TiO2dispersions in PSSNa and Na2SO4solutions has also been studied. Correlation between adsorption isotherms,zeta potential data and stability measurements has shown that the specific adorption of sulphate anions influences the adsorption of PSSNa and then the stability of the dispersions. The adding of proper amounts of Na2SO4increases the stability of TiO2dispersions in PSSNa solutions.

ISSN:0193-2691    

DOI:10.1080/01932699708943717

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The perturbation flow field that appears as a result of the presence of a spherical solid inside a boundary layer along a plate is quantitatively analyzed. The problem of the hydrodynamic interaction is reduced to the solution of a partial differential equation for the longitudinal disturbance velocity. The results are presented in an analytical form. A general overview of the disturbance flow field is presented as a function of the increasing effective dimensions of the particle. It was established that there exists an optimum range of particle's dimensions $ where a significant reduction of the background flow is observed. The theoretical predictions are illustrated by numerical calculations and are discussed in the light of the existing experimental data.

ISSN:0193-2691    

DOI:10.1080/01932699708943718

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The disturbance of the bounary layer on a plate by tiny solid spheres is studied. The range of the particle dimensions is $ (Lbeing the length of the plate andReiis the background Reynolds number). Two model cases are analysed -- viscous and inertial-viscous. The forces that act on the solids inside the layer flow are calculated. The trajectories of particles with different radii are presented. The basic result is that fine solids are retained inside the boundary layer. This entrapment is maximal for particles whose dimensions are in the interval

ISSN:0193-2691    

DOI:10.1080/01932699708943719

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0193-2691    

DOI:10.1080/01932699708943721

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor