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Journal of Thermal Analysis and Calorimetry
Authors: E. Stepkowska, J. Bijen, J. Perez-Rodriguez, A. Justo, P. Sanchez-Soto, and M. Aviles

Abstract  

A simple water sorption/retention (WS/WR) test, followed by stepwise static heating, was applied to the study of cement quality and the reactivity of its grain surface. The physically bound water and hence the specific surface both in the unhydrated and in the hydrated state were estimated as a function of the hydration time. Rehydration after heating at 220°C and contact with air was different inWS from that inWR samples, which indicates a difference in microstructure. XRD proved the formation of portlandite during the sorption test and eventual heating at 200°C, and its transformation into carbonates on contact with air, especially on heating at 400°C. The contents of these compounds were estimated from the mass difference between 400 and 800°C, which was compatible with the mass change between 220 and 400°C and this indicates surface reactivity. The test may serve for the routine study of cement.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Barba, M. Martí, A. Roddick-Lanzilotta, A. Manich, J. Carilla, J. L. Parra, and L. Coderch

that water sorption of wool is well documented [ 8 ], there are few data on water sorption of human nails. The amount of water in a sample may be expressed in terms of either regain or moisture content. Regain is the mass of adsorbed water over

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Abstract  

An understanding of the mechanisms by which water molecules are held within a substance or at its surface, either by physical or chemical processes, is of importance in the formulation, preparation and storage of a wide variety of substances. The traditional experimental techniques which have been used to make measurements on samples exposed to specific levels of relative humidity, (e.g. using desiccators containing saturated salt solutions), are slow, laborious, inaccurate, and provide a limited amount of data. This paper describes the conception, operation, and facilities of a new system which by employing recently developed electronic components and transducers, significantly advances the performance capability for moisture sorption analysis.

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Abstract  

The CISORP Water Sorption Analyser has been used to characterise a selection of solid samples at relative humidities from 0 to 100% and at ambient pressure. The analysis reveals many interesting features about the samples and shows the scope of the equipment. Hysteresis due to porosity and differences in the physical properties of similar chemical samples show up clearly in isotherm curves. Kinetic curves reveal features such as the level of stability of dehydrated food products, changes in the hydration states of salts, and the effect of adding powdered excipient on the water sorption behaviour of a pharmaceutical compound. Kinetic curves were also used to compare the water sorption behaviour of two types of wood found inside a pine cone, and to determine equilibrium moisture sorption by calculation. It was shown that many samples take up moisture irreversibly under the experimental conditions such as amorphous sucrose and other freeze-dried samples, as well as unstable crystalline forms of compounds. Wet samples such as soaked brick and archaeological wood from a well dry out irreversibly even at 100% RH. Recording isotherms at different temperatures allows the calculation of enthalpies of water sorption. If these are compared with the enthalpy of water condensation the two processes can be compared quantitatively.

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Abstract  

The technique of gravimetric water sorption was used to identify samples which appear to interact with water as a chemical reagent. These were distinguished from those which take up moisture purely physically. In the latter case water acts as a probe which aids the characterization of the sample surfaces and their hydration states. After identifying the features in the sorption behavior which allow this distinction to be made, we drew the following conclusions: 1. Few if any of the samples investigated interact chemically with water. 2. The demonstration of chemical interaction of a sample with water and other vapors by sorption studies alone is not always straightforward. 3. Chemical interaction of water with samples appears to be relatively rare. The major problems associated with high humidity in the production, storage and handling of samples therefore seem to be due to physical rather than chemical degradation.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Barba, M. Martí, A. Roddick-Lanzilotta, A. Manich, J. Carilla, J. Parra, and L. Coderch

Abstract  

Most beauty care products and treatments primarily affect the cuticle layers of hair fibers. The resulting damage has an adverse effect on hair water absorption. Water changes a wide variety of properties of human hair and is therefore of fundamental interest. Wool proteins are mild, natural, biodegradable, and sustainably produced with multiple functionalities and potential for use in the personal care and detergent market. In this study, the effect on hair water sorption of two types of keratin samples obtained from wool is investigated. Modifications of hair water sorption due to a bleaching treatment have been demonstrated, with lower values of water sorption capacity and an increase of the fibers permeability. Applications of keratin peptides and proteins to bleached hair improved the water sorption properties of the fibers and reduced their permeability.

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Abstract  

Several lactose samples containing various amounts of amorphicity were studied with an isothermal microcalorimetric technique, which allow to detect the heat and the quantity of water sorption simultaneously. As interaction with vapor is characteristic of different surfaces, the samples were easy to be discriminated from each other by studying sorption behavior. With the crystalline lactose samples, the amount of sorbed water was too minor to be detected reliably with the technique, but differences were found when the energy values (J g−1) were compared. In the future work, the measurement set-up will be improved so that sorption rates less than 0.1 nmol s−1 can be measured repeatably and reliably.

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Abstract  

Differential scanning calorimetry (DSC) was used to determine phase transitions of freeze-dried camu-camu pulp in a wide range of moisture content. Samples were equilibrated at 25°C over saturated salt solutions in order to obtain water activities (a w) between 0.11–0.90. Samples with a w>0.90 were obtained by direct water addition. At the low and intermediate moisture content range, Gordon–Taylor model was able to predict the plasticizing effect of water. In samples, with a w>0.90, the glass transition curve exhibited a discontinuity and T g was practically constant (–58.8°C), representing the glass transition temperature of the maximally concentrated phase(T g ).

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