## 3 Results and Discussion
### The Thickness and Mechanical Properties  
Table 3 shows the effect of modifying PBS with sea buckthorn extract on the thickness and mechanical properties of the films. The addition of extracts had no statistically significant effect (\(p\) > 0.05) on the thickness of the films, but the tensile strength (TS) test of the films with PBS varied depending on the type and concentration of sea buckthorn extract. The control PBS sample achieved a strength of 6.16 \(\pm\) 1.70 MPa, as a point of reference. The addition of Chl extract (0.01 g/1 g PBS) increased the value to 6.86 \(\pm\) 2.23 MPa, but this result was not statistically different from neat PBS (\(p\) > 0.05). However, increasing the concentration of Chl extract to 0.05 g/1 g of PBS resulted in a significant decrease (\(p\) < 0.05) in strength to 3.95 \(\pm\) 1.26 MPa, which may have been the result of a weakening of the structure in response to the higher amount of additive. In the case of the scCO\({}_{2}\) extract, the TS was 5.93 \(\pm\) 1.34 MPa at 0.01 g/1 g of PBS concentration and 4.15 \(\pm\) 0.61 MPa at 0.05 g of extract per 1 g of PBS, suggesting a lesser effect on the change in TS value, as both results are not significantly different from the control (\(p\) > 0.05). These results indicate that the addition of sea buckthorn extract can modify the mechanical properties of the films; higher concentrations of both extracts weaken the material. This may be important in material design, where the balance between mechanical strength and other functional properties is important.  
In the elongation at break (EB) test, the PBS films showed relatively stable values, regardless of the presence or type of plant extract. The control PBS sample achieved an elongation of 14.48 \(\pm\) 2.54%, which was the highest value among all samples. The addition of 0.01 and 0.05 Chl extract resulted in a slight decrease in values to 13.95 \(\pm\) 2.59% and  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Sample** & **MC (\%)** \\ \hline PBS & 1.47 \(\pm\) 0.30 \({}^{\mathrm{c}}\) \\ PBS-Chl 0.01 & 1.73 \(\pm\) 0.61 \({}^{\mathrm{a,c}}\) \\ PBS-Chl 0.05 & 2.55 \(\pm\) 0.45 \({}^{\mathrm{a,b}}\) \\ PBS-CO\({}_{2}\) 0.01 & 2.54 \(\pm\) 0.47 \({}^{\mathrm{a,b}}\) \\ PBS-CO\({}_{2}\) 0.05 & 3.34 \(\pm\) 0.58 \({}^{\mathrm{b}}\) \\ \hline \end{tabular} Values are presented as the mean \(\pm\) standard deviation. Means with different lowercases are significantly different at \(p\) < 0.05.  
\end{table}
Table 2: Moisture content (MC) of neat and modified PBS films.  
14.02 \(\pm\) 2.99%, respectively, but these results were not statistically different from the control (\(p\) > 0.05), indicating that this additive had no effect on the material's ability to deform before breaking. In the case of the scCO\({}_{2}\) extract, the values were 13.17 \(\pm\) 1.93 and 13.74 \(\pm\) 2.64% for PBS-CO\({}_{2}\) 0.01 and PBS-CO\({}_{2}\) 0.05, respectively, also indicating that this additive had no effect on the mechanical parameter studied. The results suggest that both the type and concentration of the sea buckthorn extracts did not significantly affect the elongation at break of the PBS films, indicating the stability of this parameter independent of the amount and type of extract. Such properties may be advantageous in applications in which it is necessary to preserve the material elasticity while modifying other functional characteristics. Additionally, the lack of an EB increase shows that the extract does not have a plasticizing effect within the polymer. Similar results were observed by the authors [10], who observed that the tensile strength and the tensile modulus of the PBS film containing carvacrol in the matrix decreased with the addition of carvacrol beyond 4 wt%. Meanwhile, PBS could elongate more in the presence of carvacrol; the maximum elongation at 19% was noted when carvacrol was added at 10 wt%. However, PBS modified with carvacrol was developed by the authors via melt compounding.