Flynn-Wall-Ozawa

The Flynn-Wall-Ozawa method [142, 143] has been used to determine the activation energy from dynamic tests by plotting the logarithm of heating rate as a function of the inverse of the temperature, at different conversions. Being integrated with the initial condition of a = 0 at r= To, the equation (24) can be arranged as follows ... 

The variation of the activation energy for thermal degradation (Ea) of the PEN/CNT nanocomposites under nitrogen and air estimated from the Flynn-Wall-Ozawa analysis are presented in Tables 13 and 14, respectively. 

Table 13. Activation energy E and correlation coefficient (r ) of the PEN/CNT nanocomposites with the CNT content under nitrogen from the Flynn-Wall Ozawa...

PEN/CNT nanocomposites induced by the incorporation of the CNT may be explained by the function of the CNT as an effective physieal barrier to retard the thermal degradation of volatile components and to prevent the diffusion out of the deeomposed polymeric molecules in the PEN/CNT nanocomposites [145, 146], Based on the Flynn-Wall-Ozawa analysis, it can be deduced that the Ea values of the PEN/CNT nanocomposites calculated from Flyim-Wall-Ozawa method exhibited good reliance on describing the thermal degradation kinetics of their nanocomposites, which was confirmed by the fact that the values of the correlation coefficient (r2) were greater than 0.99. 

To evaluate the apparent activation energy, the isoconversional methods are use as suitable analysis procedures. These methods are based on the assumption that at a constant extent of conversion degree (a), the decomposition rate da/dt is a function only of the temperature. In methods developed by Friedman and Flynn-Wall-Ozawa, linear functions are obtained from which slopes the apparent activation energy at constant conversion a is achieved. In the free kinetic method set by Kissinger is calculated from the slope of the linear function takes into consideration the relationship between the heating rate and peak temperature of the first-derivative thermogravimetric curve [97]. 

Where a is the extent of decomposition, Z is a pre-exponential factor, E is the activation energy, R the universal gas constant (8.3154 Jmol K 0> and f(a) depends on the decomposition mechanisms. E, Z, and a) are commonly called the kinetic triplet [28]. There are different kinds of methods to obtain the kinetic triplet reported in the scientific literatme among which are those reported by Flynn-Wall-Ozawa [29], Friedman [30], Kissinger [21], or Coats-Redfem [31], with different proposed equations presented to solve Eq. (7.1). 

Workers in India [18] have also blended both waste plastic and waste rubber. In this instance they took scrap computer plastics (e.g., acrylonitrile-butadiene-styrene and styrene-acrylonitrile) and blended them with waste NBR powder. The blends were analysed by TGA in a nitrogen atmosphere and their activation energies of decomposition determined using Friedman and Flynn-Wall-Ozawa methods. 

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