## 3 Results and Discussion
### Thermophysical Characteristics of PHB-Cmitosan and PLA-Cmitosan Compositions  
The thermal behavior and thermal stability of PLA, PHB, and their compositions with chitosan, as well as the compositions PLA-chitosan and PHB-chitosan with absorbed Fe\({}^{3+}\) ions was investigated by the DSC method in the temperature range of 30-400 \({}^{\circ}\)C.  
Figures 1 and 2 show the typical DSC thermograms obtained for plain PLA, PHB, chitosan, PLA-chitosan (50:50) wt. %, PHB-chitosan (50:50) wt. %, as well as for the same compositions containing absorbed Fe\({}^{3+}\) ions in the amounts of 0.89 and 2.20 wt. %, correspondingly. Table 2 summarizes the main DSC parameters: glass transition T\({}_{\rm g}\), peak temperatures for cold crystallization T\({}_{\rm cc}\) and melting T\({}_{\rm m}\), characteristic enthalpies associated with cold crystallization \(\Delta\)H\({}_{\rm cc}\) and melting \(\Delta\)H\({}_{\rm m}\), as well as the degree of crystallization (\(\chi\), %, Equation (1)) (Supplementary Materials, Calculation of the thermophysical parameters obtained by DSC). From the PLA data presented in Figure 1 and Table 2, a glass transition can be observed at 65 \({}^{\circ}\)C, as well as two melting peaks with temperatures of 146.0 \({}^{\circ}\)C and 163.3 \({}^{\circ}\)C, related to \(\alpha^{\prime}\) (imperfect) and \(\alpha\) (perfect) crystalline forms of PLA, respectively. The absence of a cold crystallization peak on the DSC curve should be noted, which indicates a relatively high degree of crystallinity of the initial PLA (\(\chi\) = 43.2%) (Table 2). In contrast to plain PLA, the glass transition temperature of PLA in composition with chitosan decreases by 2 \({}^{\circ}\)C, and the melting peaks related to \(\alpha^{\prime}\) (imperfect) and \(\alpha\) (perfect) PLA crystalline forms are 154.0 \({}^{\circ}\)C and 161.5 \({}^{\circ}\)C, respectively, and the crystallinity degree (\(\chi\), %) is lower by 43% (from 43.2 to 24.6). In this regard, one can conclude that, in the process of producing a PLA-chitosan composition in the solution, the original \begin{table}
\begin{tabular}{c c c c c c c} \hline \multicolumn{6}{c}{**Concentration of**} & \multicolumn{6}{c}{**Time of Sorption, h**} \\ \cline{2-7} \multicolumn{1}{c}{**FeCl\({}_{3}\), Solutions, mol/L**} & **0.5** & **2** & **4** & **8** & **16** & **24** \\ \hline \multicolumn{6}{c}{PHB–Cmitosan} \\ \hline
0.002 & 0.10 & 0.19 & 0.36 & 0.41 & 0.40 & 0.42 \\
0.005 & 0.22 & 0.48 & 0.97 & 0.97 & 1.31 & 1.24 \\
0.008 & 0.39 & 0.75 & 1.32 & 2.08 & 2.20 & 2.30 \\ \hline \multicolumn{6}{c}{PLA–Cmitosan} \\ \hline
0.002 & 0.03 & 0.07 & 0.09 & 0.13 & 0.15 & 0.11 \\
0.005 & 0.03 & 0.06 & 0.08 & 0.56 & 0.48 & 0.51 \\
0.008 & 0.05 & 0.12 & 0.37 & 0.85 & 0.89 & 0.66 \\ \hline \end{tabular}
\end{table} 
Table 1: The concentration of sorbed Fe\({}^{3+}\) ions (wt. %) by the film compositions PHB–chitosan (50:50) wt. %. Figure 1: DSC heat flow curves of PLA: (1) PLA–chitosan (50:50) wt. % and (2) PLA–chitosan (50:50); wt. % compositions containing sorbed Fe\({}^{3+}\) ions (3) and original chitosan (4). Figure 2: DSC heat flow curves of PHB (1), PHB–chitosan (50:50) wt. % (2) and PHB–chitosan (50:50) wt. % composition containing sorbed Fe\({}^{3+}\) ions (3). This DSC analysis of the PLA-chitosan composition containing sorbed Fe\({}^{3+}\) shows a slight decrease in the values of T\({}_{\rm g}\), T\({}_{\rm cc}\), and T\({}_{\rm m}\), as well as an increase in the enthalpy of \"cold crystallization\" \(\Delta\)H\({}_{\rm cc}\) = 12.6 J/g as compared to the initial composition PLA-chitosan. As a result, the degree of PLA crystallinity absorbed in the composition PLA-chitosan with Fe\({}^{3+}\) slightly decreases (Table 2).