Precise Kinetic Analysis of PHB Thermal Degradation

The degradation of PHB (1 K-min ) in Fig. 9.5 is initially faithful to a simulation plot of random degradation (L = 2). The L value was actually measured to be around 2 (crotonic acid) or 3 (dimer) by Py-GC/MS analysis. Thereafter, the observed curve gradually diverges from the random (L = 2) simulation with an associated rise in L value (L 6). 

Plots in Fig. 9.6 show the integral analysis of the observed data (1 K-min ) and the model reaction plots with parameter values E = 120 kj-mol and A = 1.0 x 10 s . Interestingly, the observed plots gradually decreased in weight similar to the random degradation process in the initial period, and thereafter the weight loss curve showed a linear relationship between w and A9 in parallel to the 0 -order simulation plot. 

According to Flynn and Wall [89], if the total material may be volatilized by two alternative degradation paths, for which the respective Arrhenius parameters are al and Ai for path 1, and and A2 for path 2, and if the two paths are expressible by a combined function/[w], then the integral function will be given by Eq. 9.4. 

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