# Structural Features and Properties' Characterization of
## 3 Results and Discussion  
### Crystallization Analysis  
The DSC analysis was used to evaluate the thermophysical properties of the tested samples. Figure 1 shows DSC thermograms of the studied samples, for which the temperatures of characteristic thermal transitions and the estimated crystallinity are presented in Table 1.  
Many researchers have noted the absence of a shift in the PLA glass transition temperatures when mixed with the NR [26], or that the shift is small and about 3-4 \({}^{\circ}\)C [27]. In our case, based on the PLA glass transition temperature, it can be concluded that the addition  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Samples** & **Tg.**\({}^{\circ}\)**C** & **Tc,**\({}^{\circ}\)**C** & **Tm,**\({}^{\circ}\)**C** & **X, \%** \\ \hline M0 & 59.4 \(\pm\) 0.1 & 108.6 \(\pm\) 0.1 & 151.7 \(\pm\) 0.1 & 8.5 \(\pm\) 0.4 \\ M5 & 54.9 \(\pm\) 0.1 & 98.9 \(\pm\) 0.1 & 151.2 \(\pm\) 0.1 & 8.3 \(\pm\) 0.4 \\ M10 & 52.6 \(\pm\) 0.1 & 109.8 \(\pm\) 0.1 & 150.1 \(\pm\) 0.1 & 8.2 \(\pm\) 0.4 \\ M15 & 51.0 \(\pm\) 0.1 & 98.6 \(\pm\) 0.1 & 150.2 \(\pm\) 0.1 & 6.1 \(\pm\) 0.5 \\ M20 & 50.9 \(\pm\) 0.1 & 101.8 \(\pm\) 0.1 & 148.8 \(\pm\) 0.1 & 6.2 \(\pm\) 0.5 \\ \hline \end{tabular}
\end{table}
Table 1: The samples’ thermal characteristics.  
Figure 1: The samples’ differential scanning calorimetry (DSC) thermograms.  
of ESO results in the thermoplastic phase plasticization. This is confirmed by a significant decrease in the PLA Tg from 59.4 \({}^{\circ}\)C (no oil) to 50.9 \({}^{\circ}\)C (20 mass parts of oil).  
Researchers also pay close attention to the PLA's crystallization behavior. It was demonstrated earlier [14] that the introduction of elastomers promotes greater mobility of PLA chains. In our case, the introduction of ESO additionally resulted in PLA Tc decrease. This fact can be explained by a decrease in the mobility of PLA molecules and an acceleration in the crystallization process [26]. This effect is especially pronounced in the M20 sample, where the greatest Tc shift toward low temperatures is recorded; thus, the corresponding peak is the highest of all the samples studied.  
With an increase in the ESO content, the temperature of endothermic transitions corresponding to PLA melting, also shifted, as expected, towards a lower temperature range. The appearance of double peaks in M15 samples, and even more pronounced in the M20 sample, should be noted. In earlier studies, the authors [26] associated the appearance of PLA double melting peaks in the thermoplastic phase with the presence of a more ordered crystalline structure (high-temperature peak) and a less ordered, more defective structure (low-temperature peak). In our case, the appearance of a second peak at a lower melting point in the M15 and M20 samples can be explained by the formation of excessive ESO content areas, where the PLA component is characterized by a lower melting point.  
The degree of crystallinity in the PLA phase decreased with an increase in the ESO content. This is due to interaction enhancement for both biopolymers that leads to the segmental mobility retardation of PLA and the reduction of crystallization ability. The analogous situation was observed for the series of PLA/poly(3-hydroxybutyrate) plasticized with PEG in the work [28].