## 3 Results and Discussion
### Thermal Stability and Crystallinity of P3 HB Nanocomites  
Figure 9 presents the TGA and DTGA curves of extruded P3 HB and representative nanocomposites prepared via USM. All samples exhibited thermal stability up to a common onset temperature of 195 \({}^{\circ}\)C, though the decomposition rates varied significantly depending  
Figure 8: (**a**) TEM micrographs at decreasing magnification from top to bottom of P3 HB/C20 (left) and P3 HB/C116 (right) nanocomposites with a clay content of 5 wt%; (**b**) SEM micrographs of P3 HB/C20 (left) and P3 HB/C116 (right) nanocomposite cross-sections. The clay content was 5 wt% and the samples were processed using USM technology. Dashed ellipsoids point out the presence of exfoliated clays. on the type of clay incorporated. The DTGA peak temperatures followed a sequential trend: P3 HB/C116 < P3 HB/C20 < neat P3 HB. This sequence contrasted with typical stabilization effects reported for other nanoclays, such as C25 and Nanofil 757 [17]. The earlier weight loss observed in P3 HB/C116 nanocomposites compared to P3 HB/C20 can be attributed to the physicochemical differences between the clays. Cloisite C116 is a natural bentonite that lacks the organic surface modifications present in Cloisite C20. These untreated surfaces in Cloisite C116 can act as catalytic sites for thermal degradation, leading to rapid decomposition. In contrast, Cloisite C20, which is modified with quaternary ammonium salts, exhibits better interfacial compatibility with the P3 HB matrix. This modification promoted stronger interfacial interactions, reducing the mobility of polymer chains near the clay surface, thereby inhibiting thermal degradation and delaying weight loss. The narrow gap between the melting and onset degradation temperatures for P3 HB/C116 further highlighted the challenges associated with processing this nanocomposite. The USM process produced homogeneous nanocomposites, as evidenced by the minimal differences in thermal stability between distal and proximal parts of P3 HB/C116 specimens. Additionally, the char yield at 420 \({}^{\circ}\)C correlated directly with clay content, confirming accurate clay loading (5 wt% and 8 wt%). Figure 10 displays DSC traces (first heating and cooling) for P3 HB/C20 and P3 HB/C116 nanocomposites at varying clay contents. Although changes in melting and crystallization behavior were subtle, specific trends were observed. First, the melting enthalpy decreased slightly with increasing clay content, from 47 J/g for neat P3 HB to 44 J/g and 39 J/g for 8 wt% of C20 and C166 nanocomposites, respectively. This suggested that the exfoliated nanoclay structures slightly inhibit crystallization, though the effect remained minor due to the inherent strong crystallization ability of P3 HB. The DSC traces also revealed complex melting peaks with distinct transitions around 165 \({}^{\circ}\)C and 171 \({}^{\circ}\)C. These differences are attributed to the reordering of thin lamellae influenced by the clay type and content. For instance, P3 HB/C116 nanocomposites exhibited a predominant melting peak at 171 \({}^{\circ}\)C, indicating significant reordering effects. Conversely, P3 HB/C20 nanocomposites showed a less pronounced effect, with a shoulder around 171 \({}^{\circ}\)C appearing only at 8 wt% clay content. The cooling traces demonstrated slightly hindered crystallization as clay content increased, evidenced by lower crystallization temperature and enthalpy value. This effect was more pronounced in P3 HB/C166 nanocomposites, suggesting a stronger influence of C116 on the crystallization process. Figure 9: (**a**) TGA and (**b**) DTGA curves of extruded P3 HB (green) and different USM-processed samples: distal (black) and proximal (pink) parts of nanocomposites with 5 wt% of Cloisite C116, proximal part of the nanocomposite with 5 wt% of Cloisite C20 (blue) and proximal part of the specimen with 8 wt% (illac) of Cloisite C116.