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Journal of Thermal Analysis and Calorimetry
Authors: B. Ormsby, G. Foster, T. Learner, S. Ritchie, and M. Schilling

Abstract  

After improvements were made to a modified Polymer Labs MkIII DMTA instrument to facilitate repeatable controlled humidity (RH) experiments using isothermal and thermal scanning conditions, the viscoelastic properties of titanium white pigmented artists’ acrylic emulsion films were measured in tensile mode. The effects of temperature, relative humidity and accelerated ageing regimes on two brands of titanium white paints were explored. These paints are highly responsive to changes in temperature and relative humidity, formulation differences affect properties slightly, and while light ageing had a negligible effect, thermal ageing resulted in decreased storage modulus and increased film density.

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Abstract  

A new liquid emulsion membrane (LEM) process for uranium extraction from either dihydrate 28-30% P2O5 (DH) or hemi-dihydrate 42-45% P2O5 (HDH) wet process phosphoric acid is proposed. In this process, the organic component of the LEM is composed of a synergistic mixture of 0.1M di-2-ethyl hexyl phosphoric acid (DEHPA) and 0.025M trioctyl phosphine oxide (TOPO) with 4% Span 80. The internal or the strip acid phase is composed of 0.5M citric acid. The prepared LEM was proved to be stable in 42-45% P2O5 acid concentration range and can, therefore, be applied to the phosphoric acid produced by the hemi-dihydrate process. After breakdown of the loaded emulsion, the uranyl citrate in the internal strip phase is separated by adding methanol followed by its calcination to the orange oxide. Most of the reagents used are recycled. The proposed process is characterized by simplicity, practically closed operation cycle in addition to lower capital and operating costs.

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Abstract  

Samples of water based commercial acrylic resin paints were spread in a film form on slides, dried at room temperature and exposed to solar radiation for up to eight months. The characterization and quantification of resins and charges in the white paint emulsion were carried out for the thermal decomposition. Besides this, X-ray diffractometry was used to identify CaCO3 as charge and TiO2 (rutile phase) as pigment. It was observed through thermal techniques similar behavior to the samples even though with varied exposure time. Kinetic studies of the samples allowed to obtain the activation energy (E a) and Arrhenius parameters (A) to the thermal decomposition of acrylic resin to three different commercial emulsion (called P1, P2, P3) through non-isothermal procedures. The values of E a varied regarding the exposition time (eight months) and solar radiation from 173 to 197 kJ mol−1 (P1 sample), from 175 to 226 kJ mol−1 (P2 sample) and 206 to 197 kJ mol−1 (P3 sample). Kinetic Compensation Effect (KCE) observed for samples P2 and P3 indicate acrylic resin s present in these may be similar in nature. This aspect could be observed by a small difference in the thermal behavior of the TG curves from P1 to P2 and P3 sample. The simulated kinetic model to all the samples was the autocatalytic Šesták-Berggreen.

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Abstract  

Comparative studies between column and batch liquid emulsion membrane techniques based on HDEHP/HCl system were carried out to develop a system for isolation of234Th from natural uranium. For column investigations a spray column was constructed and used with two different modes. In the first mode the feed solution was circulated through the membrane while in the second mode the membrane phase was circulated through the feed solution. The results showed that, kinetically, the equilibrium for thorium separation using batch technique is faster than the continous column system. Quantitative permeation of thorium was achieved within one minute of mixing whereby the permeation of uranium reached equilibrium after 3 minutes with a permeation percentage less than 6%. A procedure was developed to separate234Th from natural uranium with high radiochemical purity of more than 98%.

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Abstract  

The main component of an emulsion explosive is a water-in-oil emulsion consisting of a supersaturated ammonium nitrate (AN) water phase, finely dispersed in an oil phase. Quantitative determination of nearly all the components in a W/O emulsion is possible using thermogravimetry (TG) and differential scanning calorimetry (DSC). Isothermal TG measurements enable determination of water content, while cycled DSC measurements allow the amount of ammonium nitrate to be determined. In the case that sodium nitrate (SN) is also added to AN as an oxidizing agent, it is necessary to quantitatively separate both salts from organic matter with diethyl ether. On the basis of the TG curve of the precipitated salts, the amount of AN can then be calculated, and that of SN is obtained from TG measurement of the original sample.

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Abstract  

-Irradiated KCl, KBr and KI are dissolved separately in the emulsion of water and aniline. Halogens as radiolytic products are extracted in aniline forming stable halogen-aniline complexes. Hole species from V2 and V3 centers and free halogens trapped in crystalline salts are solvated first in water phase during dissolution and immediately form complexes with aniline. A typical vibrational structure of absorption bands around 300 nm is observed. The yields of halogens and thereby complexes are found to depend upon the concentration of F and hole centers and the mesh of the salt.

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Abstract  

An emulsion liquid membrane (ELM) containing di-2-ethylhexylphosphoric acid (D2EHPA) as the carrier extractant and SPAN 80 as the surfactant was used to pre-concentrate Am3+ from dilute acid solutions. Effects of various factors such as: external phase pH, internal phase conditions, equilibration time, D2EHPA concentration, SPAN 80 concentration, etc. on Am3+ mass transfer were investigated. Emulsion was broken by the addition of solvents such as acetone and the actual mass transfer obtained after breaking the emulsion agreed well with that obtained by the difference method.

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Herein, an optimized microfluidic device for manufacturing encapsulating water-in-oil-in-water (w/o/w) double emulsions is reported. The adjustability of the microfluidic device allows on-demand formation of oil shells with different thicknesses during the w/o/w double emulsion formation while maintaining the same core size. This was achieved by manipulation of the separation distance between the cylindrical tubes constituting the flow-focusing part of the device, the middle flow rate of the middle phase, and the outer flow rate of the continuous phase, all at the same time. By incorporating lipids in the oil shell, the w/o/w double emulsions serve as templates for the formation of monodisperse encapsulating liposomes. Thus, liposomes with different shell properties can be generated after evaporation of the oil that can be collected either separately or pooled together in a single sample batch using only one experimental step. The w/o/w double emulsions are highly monodisperse, generated with a throughput of more than 10 Hz, having water core diameters ranging from 130 to 290 μm and different oil shell thicknesses varying from 5 to 13 μm. Moreover, double emulsions with diameters down to 10 μm are reported; however, at this size, the dispersity is less controllable. The microfluidic device is composed of commercially available parts with only minor modifications required, thus, facilitating the manufacturing of encapsulating w/o/w double emulsions.

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Abstract  

A micro DSC analyzer fitted with special high-pressure vessels was used to investigate the kinetics of methane hydrate formation in the water phase dispersed as a stable emulsion in deep offshore drilling fluids. At high sub-cooling conditions, the peak of hydrate formation is perfectly visible and regular-shaped, and could be fitted by a Gaussian law. The average time for hydrate crystallization of the water droplets’ population was represented as a logarithmic function of the inverse of absolute temperature. At low sub-cooling conditions, the formation appears confused with the baseline; the amount of hydrate formed was thus measured from its enthalpy of dissociation, after periods of formation of variable duration.

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Abstract  

Emulsion counting, more correctly known as colloid counting, is the most widely practised technique for the radioassay of aqueous sample types by the liquid scintillation technique. The double ratio technique can be used to determine whether or not radioactivity is being counted with true solution efficiency, and was applied to a range of systems consisting of deionised water, Triton X-100 and toluene (containing3H-water,3H-toluene or14C-toluene). Some hypotheses were developed in an attempt to explain the double ratio values obtained for the various systems studied.

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