Degradation Reaction Mechanisms - Criado Method

The activation energy of a solid-state reaction can be determined, no matter the mechanism of degradation, by isothermal or dynamic methods. After determining the E, the 

For the P(x) function, Senum and Yang s [43] proposed different rotational degree expressions to assess the accuracy of the Arrhenius integral and ensure a margin of error precisely controlled. The rotational expressions, to the 8 degree, are illustrated in Table 21.2. Using the expression of the 4 degree, for example, one can assume that for X 20 the expression results in errors of less than 10 % [43]. 

Equation (21.12) allows the determination of the thermogravimetric master curves represented by the g(a) and a) functions as shown in Table 21.3. To confront the theoretical curves shown in Table 21.3, it is possible to superimpose the experimental data 

Equation (21.12) is used to plot the master Z(a) versus a curves for the different models hsted in Table 21.3, whereas Equation (21.13) is used to represent the experimental curve. The activation energy values in Equation (21.13) are usually obtained through the FWO method [38, 39]. The Criado method uses reference theoretical ctnves obtained from Equation (21.12) that are derivatives of the (a) and a) functions represented in Table 21.3 (called master curves) which are compared to experimental data for determination of the mechanism of a solid-state process [35,42]. These mechanisms represent how the sohd-state degradation process occurs. The algebraic expressions that represent the theoretical mechanisms are separated into four main groups, and F, as can be seen in Table 21.3. These mechanisms describe the 

As can be seen at Equation (21.12), the shape of the theoretical master plot is entirely determined by the shape of the a) function because A is a constant. However, because 

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