## 3 Results & Discussion
### TGA--Thermograimetric Analysis  
The thermal stability of the nanocomposite materials was evaluated through TGA. The temperature corresponding to the onset of decomposition (T onset) for the samples studied is essential for evaluating their thermal stability and is shown in Table 3.  
In addition, the appearance of volatile traces in the first section of the DTG was evaluated. Theoretically, high amounts of some identified volatiles that might be found in the neat matrices, may have been released during the extrusion-compounding of the bio-nanocomposites due to the temperature profile reached during the material development (over 150 \({}^{\circ}\)C) [21; 32]. However, the release rate is unknown and there is not a clear perception of volatile release. Nevertheless, the DTG range \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Materials** & **T\({}_{\text{onset}}\) [\({}^{\circ}\)C]** & **T\({}_{\text{max}}\) [\({}^{\circ}\)C]** & **T\({}_{\text{50}}\) wt \% [\({}^{\circ}\)C]** & **FR [\%]** \\ \hline PHA1005 & 268.13 & 278.33 & 279.62 & 9.45 \\ PHA1005\_T1 & 267.94 & 275.51 & 278.89 & 12.93 \\ PHA1005\_T2 & 265.75 & 278.33 & 278.52 & 13.56 \\ PHA1005\_T3 & 263.20 & 278.33 & 277.25 & 13.27 \\ \hline PHA3002 & 290.01 & 307.67 & 305.34 & 8.39 \\ PHA3002\_T1 & 287.46 & 307.67 & 305.61 & 11.71 \\ PHA3002\_T2 & 283.63 & 302.33 & 300.23 & 10.93 \\ PHA3002\_T3 & 284.73 & 299.67 & 298.95 & 11.26 \\ \hline PHB226 & 275.97 & 386.87 & 297.00 & 403.70 & 293.84 & 2.73 \\ PHB226\_T1 & 283.63 & 384.31 & 299.82 & 411.67 & 301.50 & 5.61 \\ PHB226\_T2 & 278.52 & 383.03 & 297.00 & 407.30 & 296.40 & 5.83 \\ PHB226\_T3 & 272.14 & 347.29 & 291.49 & 382.86 & 287.46 & 6.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Thermal results obtained by TGA. T\({}_{\text{onset}}\) %, T\({}_{\text{max}}\) %, and T\({}_{\text{50}}\) % represent the temperature of the initial degradation, the maximum degradation rate of decomposition, and 50 wt % loss of the samples, respectively. FR represents the final residue and DTG first derivative. between 100 and 220 \({}^{\circ}\)C was studied trying to observe substantial peaks. The signal noise of the apparatus seems too high compared to the amount of volatiles released in order to be able to obtain reliable results. Therefore the correct volatile analysis is left for the accurate technique HS-SPME and authors will focus the TGA results to study the thermal stability and the non-organic residue. The degradation of PHA 3002 occurred in one step while PHA 1005F shows a smooth second step at higher temperatures which may correspond to a greater amount of inorganic fillers. Several steps occurred for the PHB226 sample too, distinctly exhibiting two decomposition platforms. This behaviour has been previously reported in the literature for some pure P3 HB polymers and for different P3 HB-_co_-P4 HB co-blends. According to literature, pure P3 HB thermally decomposes at around 270 \({}^{\circ}\)C, above its melting point (around 180 \({}^{\circ}\)C). However, a short exposure of PHB to temperatures near its melting point induce a severe degradation producing degraded products such as olefinic and carboxylic acid compounds due to the random chain scission reaction that takes place [37]. [PERSON] et al. studied the thermal degradation of P3 HB-_co_-P4 HB composites [38]. The results showed that thermal degradation of P3 HB occurs almost exclusively by random chain-scission involving a six-member ring formation while P4 HB decomposes through intermolecular ester exchange reaction and generates a decomposition product Y-butyrolactone. Therefore, P4 HB crystals are thermally more stable than P3 HB. In addition, in a previous analysis carried out by the authors for these composites, the presence of PBA was corroborated in the NMR and DSC analyses for PHB226 [30].