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  • Author or Editor: A. Schiraldi x
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Abstract  

Traditional phenomenological kinetics describes the process rate in terms of the progress degree (mass fraction which has already undergone the change), a, and with a monomial function (or combination of monomial functions for multistep processes) of (1-a), without any connection to the underlying mechanism at the molecular level. The approach proposed in the present work aims at the direct treatment of the experimental data, like DSC records, without suggesting any specific reaction mechanism and excluding any Arrhenius like behaviour. Formal expressions are proposed that include the thermodynamic constraints for any spontaneous process, viz. a negative drop of the Gibbs function throughout the process, and describe the process rate as the result of the effects of a thermodynamic driving force, identified with the drop of the Gibbs function, and of the medium hindrance.

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Abstract  

Water states and displacements can be investigated with thermogravimetry (TG) either in its classical or in the Knudsen version (where standard pans are replaced with Knudsen cells). The case of wheat flour dough is considered in various steps of bread making, namely, mixing, proofing, baking, staling. The split of DTG signals into various components (gaussian functions) support the assumption that the overall dough water is partitioned into various fractions. Few comments are devoted to water displacements during freezing.

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Epoxy polymers

Use and misuse of non-isothermal DTA and DSC in the study of the curing process

Journal of Thermal Analysis and Calorimetry
Authors: A. Schiraldi and P. Baldini

The current use of non-isothermal DTA or DSC for the investigation of polymers is based upon assumptions which allow a number of conclusions supported only by data drawn from the DTA or DSC traces of prepolymer samples.

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Polymorphous transitions in cocoa butter

A quantitative DSC study

Journal of Thermal Analysis and Calorimetry
Authors: D. Fessas, M. Signorelli, and A. Schiraldi

Summary  

Large experimental evidence was collected on polymorphous transitions of triacyl glycerols (TAG) in cocoa butter by means of DSC investigations. The cooling treatment (in conditions close to those of the industrial practice) and the annealing temperature significantly affect the overall crystal fraction and the distribution of the various polymorphs. These data allowed a quantitative, although purely phenomenological, kinetic parameterization of polymorphous transitions of cocoa butter. The evaluation of the relevant kinetic constants and their dependence on the temperature allowed prediction of the yield in every polymorph after a given thermal history. Similar evidences were attained for cocoa liquor and dark chocolate where TAG are sided by other ingredients. These results can be the basis for an industrial exploitation.</o:p>

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The correlation between the glass transition temperature,T g, and the cure degree, α, of epoxy polymers has been analysed on the basis of an extension of the Vogel-Tamman-Fulcher equation for the viscosity of polymers and glasses.

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