## 3 Results and Discussion
### Microscopy (SEM)  
Figure 4 shows 1000\(\times\) transverse cross-sectional SEM images of the various TPS/PBAT and TPS/PBAT-PBSA composite formulations. In the micrographs corresponding to TPS/PBAT and TPS/PBAT-PBSA without additives, a relatively homogeneous structure with a smooth surface can be observed, although there are some starch granules that were not fully broken during the extrusion process.  
In contrast, the formulations containing Vinnex (TPS/PBAT-V and TPS/PBAT-PBSA-V) exhibit a rougher surface. This increased roughness could be attributed to the interaction between Vinnex and the polymer matrix, suggesting that compatibility between the components is not fully achieved. While Vinnex enhances interfacial adhesion and improves dispersion, the incomplete miscibility between the starch and polyester phases may lead to localized phase separation. This results in heterogeneities at the interface which manifest as increased surface roughness. Such behavior is common in partially compatibilized polymer blends, where molecular interactions are insufficient to achieve full homogeneity [62].  
The images of the formulations with Joncryl (TPS/PBAT-J and TPS/PBAT-PBSA-J) also show an increase in roughness, although it is less pronounced compared to the Vinnex formulations. The surface texture appears more controlled, which could indicate better compatibility between Joncryl and the polymer matrix.  
Finally, the formulations combining both additives (TPS/PBAT-V/J and TPS/PBAT-PBSA-V/J) exhibit the highest surface roughness, with a clearly more irregular structure. However, no pronounced interfaces between the phases are observed, suggesting that, despite the roughness, the additives are well integrated into the polymer matrix. This integration could enhance certain mechanical properties, as a rougher surface can improve adhesion between phases and potentially distribute stress more effectively, leading to better mechanical performance [63].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Coiling**} & \\ \hline
**Reference** & **Tc**, **PBSA (\({}^{\circ}\)C)** & **\(\Delta\)hc**, **PBSA (J/kg)** & **Tc**, **PBAT (\({}^{\circ}\)C)** & **\(\Delta\)hc**, **PBAT (J/kg)** \\ \hline PBAT [61] & - & - & 88-91 & 35–50 \\ PBSA [56] & 73–78 & 40–60 & - & - \\ TPS/PBAT & - & - & 86 & 7.8 \\ TPS/PBAT-V & - & - & 83 & 6.5 \\ TPS/PBAT-J & - & - & 89 & 8.4 \\ TPS/PBAT-V/J & - & - & 87 & 8.5 \\ TPS/PBAT-PBSA & 32 & 3.9 & 78 & 8.2 \\ TPS/PBAT-PBSA-V & 28 & 4.3 & 86 & 9.7 \\ TPS/PBAT-PBSA-J & 33 & 4.2 & 91 & 9.6 \\ TPS/PBAT-PBSA-V/J & 31 & 4.0 & 87 & 6.3 \\ \hline \hline  & \multicolumn{2}{c}{**Second Heating**} & \\ \hline
**Reference** & **Tg Polymer (\({}^{\circ}\)C)** & **Tm**, **PBSA (\({}^{\circ}\)C)** & **\(\Delta\)hm**, **PBSA (J/kg)** & **Tm**, **PBAT (\({}^{\circ}\)C)** & **\(\Delta\)hm**, **PBAT (J/kg)** \\ \hline PBAT [61] & –30 & - & - & 120–125 & 35–50 \\ PBSA [56] & –35 & 90–95 & 40–60 & - & - \\ TPS/PBAT & –31.0 & - & - & 124 & 3.7 \\ TPS/PBAT-V & –34.0 & - & - & 123 & 4.1 \\ TPS/PBAT-J & –32.6 & - & - & 124 & 3.8 \\ TPS/PBAT-V/J & –31.7 & - & - & 125 & 3.1 \\ TPS/PBAT-PBSA & –34.0 & 89 & 4.6 & 121 & 4.4 \\ TPS/PBAT-PBSA-V & –28.0 & 86 & 5.0 & 125 & 4.4 \\ TPS/PBAT-PBSA-J & –31.0 & 85 & 4.9 & 121 & 4.7 \\ TPS/PBAT-PBSA-V/J & –30.7 & 86 & 4.8 & 122 & 3.0 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Differential scanning calorimetry (DSC) results for TPS/PBAT and TPS/PBAT-PBSA formulations (note that error intervals are not shown for the sake of clearness and lie in the 1–3% range.).