## 3 Results and Discussion
### Kinetic Parameters of the FR, KAS and FWO Models  
Table 1 shows the obtained kinetic parameters (activated energy and preexponential factor) using the different isoconversional kinetic models presented in Section 2.2.1. Regardless of the model, the kinetic parameters E and A decrease with an increasing heating rate; on the other hand, the reverse is true for the maximum degradation temperature (T\({}_{\text{m}}\)), since the lower the heating rate, the lower the temperature at which the sample exhibits greater degradation. Figures 4-6, below, show a comparison at each heating rate of the experimental DTG curves versus the DTG curves of the isoconversional kinetic models proposed. Figure 3: DTG curves of PLA at different heating rates of 5, 10 and 15 \({}^{\circ}\)C min\({}^{-1}\). Figure 2: PLA TGA curves at different heating rates of 5, 10 and 15 \({}^{\circ}\)C min\({}^{-1}\). In Figures 4 and 5, it is seen that the FR model curves are above those of KAS and FWO models and slightly below the experimental one. This occurs due to the different values obtained from the least squares method applied to each model. The closer to zero that the value is, the closer it is to the experimental value model. Additionally, it can be observed that, as the heating rate increases, the curve shifts to the right at a higher temperature due to thermal diffusion. Based on the correlation of the experimental and calculated data, the KAS and FWO models are the ones that fit the best with a value very close to 100% correlation, at the rate of 5 and 15 \({}^{\circ}\)C min\({}^{-1}\). These models included the temperature as adjusting parameter, to analyze the heating rate in the thermal degradation process. The present results are very close to those of the study by [PERSON] et al. [16]. The small difference that exists could be due to the fact that [PERSON] et al. worked with virgin PLA (activation energy 170 kJ/mol), while, in the present investigation, PLA was used that was thermally treated for its molding (activation energy 146 kJ/mol), showing lower activation energy due to its processing. The results at the rate of 15 \({}^{\circ}\)C min\({}^{-1}\) were within the same range as in [PERSON] & Tiwari, peak temperature 642 K and activated energy 113 kJ/mol [10]. According to [PERSON] & [PERSON], the KAS model is chosen due to the good agreement between the results obtained with this model and the experimental values; additionally, when using the maximum degradation temperature, this model allows for the calculation of thermodynamic parameters. However, it is important to mention that the three models \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Kinetic Model**} & \multicolumn{2}{c}{**Experimental Condition**} & \multicolumn{3}{c}{**Results**} \\ \cline{2-5}  & **Heating Rate \(\beta\) (\({}^{\circ}\)C min\({}^{-1}\))** & **T\({}_{\text{m}}\) (K)** & **E (kJ mol\({}^{-1}\))** & **A (s\({}^{-1}\))** & **R\({}^{2}\)** \\ \hline \multirow{4}{*}{**FR**} & 5 & 607.2 & 146.70 & \(1.192\times 10^{11}\) & 0.9840 \\ \cline{2-5}  & 10 & 624.8 & 130.94 & \(5.147\times 10^{9}\) & 0.9818 \\ \cline{2-5}  & 15 & 631.0 & 119.44 & \(5.224\times 10^{8}\) & 0.9453 \\ \hline \multirow{4}{*}{**KAS**} & 5 & 607.2 & 145.59 & \(8.958\times 10^{10}\) & 0.9909 \\ \cline{2-5}  & 10 & 624.8 & 128.27 & \(2.781\times 10^{9}\) & 0.9797 \\ \cline{2-5}  & 15 & 631.0 & 119.44 & \(5.224\times 10^{8}\) & 0.9663 \\ \hline \multirow{4}{*}{**FWO**} & 5 & 607.2 & 145.59 & \(8.958\times 10^{10}\) & 0.9909 \\ \cline{2-5}  & 10 & 624.8 & 128.28 & \(2.789\times 10^{9}\) & 0.9797 \\ \cline{2-5}  & 15 & 631.0 & 118.59 & \(4.353\times 10^{8}\) & 0.9663 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Kinetic parameters of PLA. Figure 4: Comparison of the FR, KAS and FWO models at 5 \({}^{\circ}\)C min\({}^{-1}\). are acceptable for the kinetic study of PLA since they presented just small variations with respect to experimental data, with the FR model being the simplest one compared to the KAS and FWO models which use a larger number of parameters.