Thermal degradation kinetics parameter estimation

The increase in the thermal degradation temperatures of the PEN/CNT nanocomposites with the incorporation of the CNT m be explained by the decrease in the evolution rate of volatile degradation products in the polymer nanocomposites. The thermal degradation temperatures and degradation kinetic parameter are in common use to estimate the thermal... 

The FDS5 pyrolysis model is used here to qualitatively illustrate the complexity associated with material property estimation. Each condensed-phase species (i.e., virgin wood, char, ash, etc.) must be characterized in terms of its bulk density, thermal properties (thermal conductivity and specific heat capacity, both of which are usually temperature-dependent), emissivity, and in-depth radiation absorption coefficient. Similarly, each condensed-phase reaction must be quantified through specification of its kinetic triplet (preexponential factor, activation energy, reaction order), heat of reaction, and the reactant/product species. For a simple charring material with temperature-invariant thermal properties that degrades by a single-step first order reaction, this amounts to -11 parameters that must be specified (two kinetic parameters, one heat of reaction, two thermal conductivities, two specific heat capacities, two emissivities, and two in-depth radiation absorption coefficients). 

Pyrolysis kinetics of all the selected lignocellulosic wastes is properly described over the wide thermal degradation range 25°C 900°C by a model that considers an increasing dependence of the activation energy on the temperature and waste conversion with the process course. Appreciable differences in the estimated kinetic parameters are found. 

In many polymer pyrolyses, the TGA trace follows a relatively simple sigmoidal path. Thus, the sample weight decreases slowly as the reaction begins, then decreases rapidly over a comparatively narrow temperature range, and finally levels off as the reactant becomes spent. The shape of the trace depends primarily upon the kinetic parameters involved, i.e., upon reaction order ( ), frequency factor (A), and activation energy ( ). The values of these parameters can be of major importance in the elucidation of mechanisms involved in polymer degradation [7, 8] and in the estimation of thermal stability [9]. 

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