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Abstract  

This article is a review about the ways in which solidification and the melting may occur within emulsions submitted to steady cooling and heating performed in a differential scanning calorimeter. Simple, multiple and mixed emulsions are considered. Due to nucleation phenomena creating supercooled and supersaturated liquids, the DSC curves obtained during cooling and heating are quite different. The influence of a solute in the disperse phase is described in detail. Some implications about the instabilities of emulsions due to mass transfer phenomena are described.

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Abstract  

Fat fractions composed by different proportions of low (LMT) or high (HMT) melting temperature triacylglycerols were used, alone or in mixture with α-tocopherol for the preparation of oil-in-water protein stabilised nano-emulsions. Addition of α-tocopherol to the LMT or HMT fat fractions was accompanied by different changes in the emulsion characteristics such as fat droplet size distributions, under-cooling and polymorphic transitions, in parallel with different extent of α-tocopherol degradation reactions. Our results showed higher immobilisation pattern of α-tocopherol molecules and higher protection against degradation when incorporated in higher size fat droplets, which presented 2Lα → 2Lβ′ polymorphic transitions under cooling and re-heating cycles.

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Abstract  

This article is a review of some of the results we have obtained by studying various kinds of emulsions using techniques from the simplest one, a home-made differential thermal analysis to elaborated ones such as differential scanning calorimetry commercial devices. These techniques were used not only to determine energetic values but also essentially to show and quantify physical chemical phenomena such as undercooling, freezing, melting, mass transfer between droplets and solid formation involved in hydrate formation.

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Abstract  

A batch pertraction (liquid membrane extraction, MX) of cobalt has been studied, with industrial reagent LIX 64N and ABF (USSR) as a carrier. The influence of cobalt, reagents and acid concentration has been searched. The kinetic and hydrodynamic characteristics of the emulsion were optimized. In one batch pertraction process it is possible to reach 100-fold cobalt preconcentration with 93–98% yield from 1 dm3 sample volume.

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Abstract  

The stability of emulsions, containing tri-n-octylamine and di-n-octylamine salts in the organic phase and nitric acid in the aqueous phase has been studied. Optimal conditions for the extraction of Am(III) and Am(IV) phosphorus tungstate complexes with such emulsions have been determined. Emulsion membrane extraction is shown to be more effective for this purpose than conventional liquid extraction.

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Abstract  

The effect of emulsion process formulation ingredients on the morphology, structure, and properties of polyvinyl chloride (PVC) powder has been considered in this study. PVC powder was extracted with ethanol and films were obtained by solvent casting from tetrahydrofurane. Characterization of powders, films, and ethanol extract was performed through FTIR spectroscopy, DSC, AFM, SEM, EDX analysis, methylene blue, and nitrogen adsorption. PVC powder was composed of spheres of a large particle size range from 10 nm to 20 μm as shown by SEM. The specific surface area of the PVC powder was determined as 16 and 12 m2 g−1 from methylene blue adsorption at 25 °C and from N2 adsorption at −196 °C, respectively. AFM indicated the surface roughness of the films obtained by pressing the particles was 25.9 nm. Density of PVC powder was determined by helium pycnometry as 1.39 g cm−3. FTIR spectroscopy indicated that it contained carbonyl and carboxylate groups belonging to additives such as surface active agents, plasticizers, and antioxidants used in production of PVC. These additives were 1.6% in mass of PVC as determined by ethanol extraction. EDX analysis showed PVC particles surfaces were coated with carbon-rich materials. The coatings had plasticizer effect since, glass transition temperature was lower than 25 °C for PVC powder and it was 80 °C for ethanol extracted powders as found by using differential scanning calorimetry. These additives from polymerization process made PVC powder more thermally stable as understood from Metrom PVC thermomat tests as well.

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Journal of Flow Chemistry
Authors: Viktor Misuk, Andreas Mai, Yuning Zhao, Julian Heinrich, Daniel Rauber, Konstantinos Giannopoulos, and Holger Löwe

Fast mixing is essential for many microfluidic applications, especially for flow at low Reynolds numbers. A capillary tube-in-tube coaxial flow setup in combination with a glass microreactor was used to produce immiscible multiphase segments. These double emulsion segments are composed of an organic solvent as the shell (outer) phase and a completely fluorinated liquid (Fluorinert® FC-40) as the core (inner) phase. Due to the higher density of the core droplets, they are responsive to changing their position to the force of gravity (g-force). By gently shaking or jiggling the reactor, the core drop flows very fast in the direction of the g-field without leaving the shell organic phase segment. Furthermore, by shaking or jiggling the reactor, the inner droplet moves along the phase boundary of the shell segment and continuous phase. Computational fluid dynamics (CFD) calculations show an enhancement of the internal circulations, i.e., causing an exceptional mixing inside of the shell segment. For reactions which are limited by mass transfer, where the conversion significantly increases with improved mixing, these recirculation zones are decisive because they also accelerate the mixing process. With a common phase-transfer catalytic (PTC) etherification of phenol with dimethyl sulphate, a remarkable increase of yield (85% gas chromatography [GC]) could be achieved by applying active mixing within a segment in continuous flow.

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Abstract  

Crystallization of fat droplets in complex emulsions, which differed only by the initial structure of proteins, was studied by differential scanning calorimetry, before and after application of a whipping process. Upon cooling at 5 or 1°C min–1, the temperature needed to initiate fat crystallization was lower, and one more distinguishable crystallization peak was detected in emulsions containing caseins, in comparison with the emulsion containing pure whey proteins. Furthermore, the whipping process was accompanied by more protein depletion from the fat droplet surface, less resistance to coalescence, and a lower supercooling effect in the emulsion based on pure whey proteins.

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Abstract  

Issues encountered with dynamic mechanical analysis of artists’ acrylic emulsion paint films are presented alongside modifications to improve controlled relative humidity (RH) experiments using isothermal and thermal scanning conditions. Free films of titanium white (PW6) artists’ acrylic emulsion paints were cast as free films and their viscoelastic properties measured using the tensile mode of the dynamic mechanical analyser (DMA). Artists’ acrylic emulsion paints are within their glass transition temperature region at room temperature and are highly responsive to changes in ambient temperature and relative humidity, hence controlling relative humidity during analysis is vital to the successful analysis of these paints.

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Journal of Thermal Analysis and Calorimetry
Authors: Anita Kovács, I. Csóka, Magdolna Kónya, E. Csányi, A. Fehér, and I. Erős

The properties of the inner and the external aqueous phases, were studied in w/o/w multiple emulsions with light microscopic image analysis and differential scanning calorimetry (DSC). The importance of multiple emulsions lies in the presence of these aqueous phases, making them available for sustained, controlled drug delivery systems. Differentiation of these two aqueous phases, studying the effect of manufacturing technology on droplet structure, quantitative determination of phase volumes and any changes occurring during storage are essential when planning w/o/w emulsions. The present study uses microscopic observations combined with DSC measurements in order to identify the formed structure, at developmental stage in case of different components, preparation methods, and stirring rates. These tools are beneficial during manufacturing as in process controls, or to ensure product quality.

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