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
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.
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.
Authors:D. Fessas, M. Signorelli, and A. Schiraldi
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>
The correlation between the glass transition temperature,Tg, 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.