## 3 Results and Discussion  
### Thermal Characteristic of Urea-Based Mixtures  
Before using the U-based mixtures as plasticizers, their thermal properties i.e., phase transitions (T\({}_{\mathrm{g}}\)--glass temperature, T\({}_{\mathrm{m}}\)--melting temperature, T\({}_{\mathrm{deg}}\)--decomposition temperature) were investigated via the DSC technique and thermal stability was assessed via TGA. Results are presented in Table 1. The DSC results present temperatures of phase transitions for the cooling and second heating run. For mixtures with CC, increasing urea content led to an increase in T\({}_{\mathrm{g}}\) and T\({}_{\mathrm{m}}\) as well as to a decrease in the thermal stability of the DESs (Table 1, Figure 1). A similar trend was obtained when [PERSON] and coworkers studied DESs made with betaine and urea [28]. In Figure 1, it can be noticed that, for the DESs with higher U content, degradation runs in two steps. The first, main weight loss at range (180-200 \({}^{\circ}\)C), can be related to the degradation of a dissolved urea due to its lower thermal stability in the eutectic mixture [38; 39]. Comparing two types of betaines monohydrate (Bh) is more thermally stable than anhydrous betaine (Ba) (Supplementary Information; Figure S1). Mechanical Test Results for the Films Obtained via Thermocompression as Well as via Extrusion and Thermcompression  
Table 2 lists results of the tensile test for the films. For choline chloride and anhydrous betaine-based plasticizing mixtures, the higher the U content in the DES is, the lower TS and YM and the higher EB values will be. It means that the higher content of urea leads to more elastic films. Generally, U-based DESs lead to highly elastic TPS films with lower TS and higher EB than starch films plasticized with a conventional plasticizer like glycerol or polyol-based DESs [5,12]. Similar results were obtained also in the work where mixtures of urea and glycerol were used as starch plasticizers [22,32]. In the case of BhU eutectics, there is decrease in mechanical properties with the increase in U content in the plasticizer. This could be caused by the lower thermal stability of these systems (Table 1). Comparing the type of ammonium compound, films with Ba-based DESs exhibited slightly better mechanical properties. This can be caused by Ba forming stronger interactions with the polymer matrix than CC. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Ammonium** & \multicolumn{2}{c}{**DSC**} & \multicolumn{2}{c}{**TGA**} \\ \cline{2-6}  & **Compound: U** & **Molar Ratio** & **Tf**[\({}^{\circ}\)**C] & **Tdeg**[\({}^{\circ}\)**C] & **Tdeg** & **DTAmax** \\ \hline TPS/CCU 1:2 & 1:2 & T\({}_{\text{g}}\) -67; T\({}_{\text{m}}\) 5; & 169 & 182 & 260 \\ TPS/CCU 1:3 & 1:3 & T\({}_{\text{g}}\) -48; T\({}_{\text{m}}\) 12 & 168 & 144 & 254 \\ TPS/CCU 1:4 & 1:4 & T\({}_{\text{g}}\) T\({}_{\text{m}}\) 62; T\({}_{\text{cc}}\) -14 & 186 & 138 & 250 \\ TPS/CCU 1:5 & 1:5 & T\({}_{\text{g}}\) -11; 86; T\({}_{\text{c}}\) 31 & 171 & 125 & 244 \\ \hline TPS/BaU 1:2 & 1:2 & T\({}_{\text{g}}\) -19; T\({}_{\text{m}}\) 106, T\({}_{\text{cc}}\) 37 & 167 & 180 & 254 \\ TPS/BaU 1:3 & 1:3 & T\({}_{\text{g}}\) -22; T\({}_{\text{m}}\) 100; T\({}_{\text{cc}}\) 51 & 166 & 150 & 245 \\ TPS/BaU 1:4 & 1:4 & T\({}_{\text{g}}\) -30; T\({}_{\text{m}}\) 88 T\({}_{\text{cc}}\) 55 & 166 & 148 & 241 \\ TPS/BaU 1:5 & 1:5 & T\({}_{\text{g}}\) -20; T\({}_{\text{m}}\) 107; T\({}_{\text{cc}}\) 57 & 168 & 131 & 237 \\ \hline TPS/BhU 1:2 & 1:2 & T\({}_{\text{m}}\) 91 & 147 & 177 & 246 \\ TPS/BhU 1:3 & 1:3 & T\({}_{\text{g}}\) -22; T\({}_{\text{m}}\) 76 & 130 & 161 & 245 \\ TPS/BhU 1:4 & 1:4 & T\({}_{\text{g}}\) -24; T\({}_{\text{m}}\) 88 & 136 & 155 & 245 \\ TPS/BhU 1:5 & 1:5 & T\({}_{\text{g}}\) -18; T\({}_{\text{m}}\) 101 & 139 & 144 & 247 \\ \hline \hline \end{tabular} T\({}_{\text{c}}\)—crystallization temperature, T\({}_{\text{cc}}\)—cold crystallization temperature, T\({}_{\text{g}}\)—glass temperature, T\({}_{\text{m}}\)—melting temperature.  
\end{table}