Kinetic analysis, Flynn method

The decomposition kinetic analysis of the mass loss curves was carried out using standard TGA kinetics software that is based on the Flynn-Wall method (Flynn and Wall 1966a,b) and described in Section 3.5.5. In this technique a plot of the logarithm of the heating rate (log q) against the reciprocal of the absolute temperature [see. Eq. (3.23)] was made where the conversion or mass loss equaled 4%, 5.5%, 8%, 12%, 18% and 26%. From the slope of this plot (Fig. 3.32) the activation energy for decomposition E) was calculated from Eq. (3.32), which is based on Eq. (3.23) ... 

Similar to studies reported by Litwinienko and co-workers discussed above, a recent report (Dunn, 2006b) demonstrated that non-isothermal (conventional) DSC, static mode P-DSC and dynamic mode P-DSC may be employed to study kinetics of the oxidation of SME. OT results obtained at ambient pressure for DSC and P = 2000kPa for P-DSC and with varying p = 1-20 °C/ min were analyzed by the Ozawa-Flynn-Wall method to calculate activation energies and rate constants. This work concluded that rates of the oxidation reaction could be calculated at any temperature based on accurate measurement of kinetic parameters from analysis of non-isothermal dynamic mode P-DSC scans. 

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]. 

Fibonacci Leonardo of Pisa (-1170-1230) It. math., best known for his book of Abacus, putting thus end to old Roman system of numerical notations, his series are now called Fibonacci s Pick Adolf Eugen (1829—1901) Ger. physiol, who made important discoveries in every branch of psychology, well-knownfor the Law of difftision (Ann. Phys. 94(1855)59) named after him Flynn Joseph Henry (1922-) US phys., known for Flynn kinetic evaluation method Fourier Jean Baptiste Joseph (1768—1830) Fr. math., evolved mathematical series knovm by his name and important in harmonic analysis, providing source of all modem methods in mathematical physics, originated Fourier s theorem on vibratory motions... 

Reaction kinetics from DSC, DTA or TGA, have been used to examine the stability of a limited number of pharmaceutical materials. Various models have been used including the Power Law, Avarami-Erofeev and Prout-Tomkins models [72]. These methods are also based on the Kissinger [73], ASTME 698 [74] or Ozawa [75] methods [8]. Most frequently, they have been applied to the dehydration of various materials such as theophylline monohydrate [76], phenobarbitone monohydrate or hemihydrate [77], phenylbutazone [78], oxazepam [23] and trazodone tetrahydrate [79]. The uses are limited for pharmaceutical systems, not least because dehydration is particle size dependent. Thermal analysis, especially DSC, DTA and TG, has been used outside the pharmaceutical area in the prediction of reaction kinetics as described elsewhere in this handbook. Methods used include those by Borchart and Daniels [80], Kissinger [73], Freeman and Carroll [81] and Flynn and Wall [82]. Although these techniques are well established and, if used properly, can give pertinent information, their use in pharmaceutical arenas is restricted to dehydration and decomposition. 

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