Chemical Processes - Isoconversional Kinetics of Thermally Stimulated Processes - page 203

Table 4.2 Parameters of Eq. 4.63 obtained [ 90 ] by its fitting to numerical f (α) data for equation
of random scission
Code L c n m

L2 2 1.204 1.119 0.4

L3 3 2.080 1.057 0.396

L4 4 2.929 1.039 0.394

L5 5 3.767 1.030 0.391

L6 6 4.597 1.024 0.389

L7 7 5.422 1.020 0.388

L8 8 6.242 1.017 0.386

(4.63)

m n

f () ααα = c ( 1 − ) .

Table 4.2 collects the fit parameters of Eq. 4.63.
The aforementioned approach has been tested by using data on the thermal deg-
radation of poly(butylene terephthalate) (PBT), the polymer that degrades via ran-
dom scission. Figure 4.32 presents the f ( ʱ ) plots reduced to ʱ = 0.5 for experimental
data as well as some theoretical models, including the models of random scission
(L2 and L8) and some solid-state reaction models. Clearly, the random scission
models provide much better fit to the experimental data than any of the solid-state
reaction models that makes a good case for the viability of the derived f ( ʱ ) models
of random scission.

Fig. 4.32 Comparison of the f ( ʱ ) data for the thermal degradation of PBT ( points ) against theo-
retical models ( lines ). L2 and L8 represent the random scission models with L equal to 2 and 8,
respectively. (Reproduced from Sanchez-Jimenez et al. [ 90 ] with permission of Elsevier)