Authors:E. Stepkowska, J. Bijen, J. Perez-Rodriguez, A. Justo, P. Sanchez-Soto, and M. Aviles
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.
Authors:C. Barba, M. Martí, A. Roddick-Lanzilotta, A. Manich, J. Carilla, J. L. Parra, and L. Coderch
that watersorption of wool is well documented [ 8 ], there are few data on watersorption 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
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.
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
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.
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
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.
Authors:C. Barba, M. Martí, A. Roddick-Lanzilotta, A. Manich, J. Carilla, J. Parra, and L. Coderch
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.
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.
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 (aw)
between 0.11–0.90. Samples with aw>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 aw>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(Tg