## 3 Results and Discussion
### Mechanical Properties  
The impact of incorporating sodium alginate in low- and high-viscosity grades, as well as crosslinking, on the mechanical properties of PW-based films is presented in Figure 5. Table 2 summarizes the average values and standard deviations (SDs) for each material, representing the overall variability across five replicates. The analysis focuses on two key parameters: tensile strength (TS) and elongation at break (Eb). This poor mechanical performance can be attributed to its microstructure and composition. Scanning electron microscopy (SEM) revealed the presence of voids and microcracks, particularly at the interface between starch and cellulose, the primary components of potato peel waste [47]. These structural defects facilitate crack propagation during tensile testing, thereby reducing the film's mechanical properties. In addition to microstructural defects, the inherently low mechanical strength of starch further contributes to the poor mechanical performance of the pure PW film. Starch, which constitutes approximately 46% of potato peel waste mass [22], has lower tensile strength compared to SA. Since starch is the predominant component in the pure PW film, its inherent weakness explains the observed mechanical behavior. The incorporation of SA significantly improved the mechanical characteristics of the resultant films due to several factors. Firstly, SA possesses higher intrinsic tensile strength compared to the PW matrix [19]. Secondly, SA demonstrates excellent film-forming properties, which upon integration into the PW matrix, bridge the gaps within the PW structure [48]. This results in a more uniform film that prevents crack initiation and propagation while also enhancing stress distribution throughout the film when subjected to mechanical stress. Moreover, the formation of new hydrogen bonds between the carboxyl groups of SA and the hydroxyl groups of starch and cellulose further contributes to the enhanced mechanical performance [49]. The degree of improvement varied based on SA's viscosity. Compared to the pure PW film, lvSA incorporation increased TS by 44% and Eb by 116%, while hvSA incorporation led to a 70% increase in TS and a 76% increase in Eb. The higher TS in PAhv films can be attributed to the longer polymer chains of SA, which form stronger hydrogen bonds with starch and cellulose, facilitating more efficient stress transfer. However, this increased molecular interaction also restricts polymer mobility, leading to a lower Eb compared to the PAlv composite [50]. The crosslinking process further enhanced the TS of the composites while reducing their Eb. The TS of PAlvx and PAhvx increased by 19% and 13%, respectively, compared to their non-crosslinked counterparts. However, Eb decreased by 18% for PAlvx and 10% for PAhvx. This phenomenon can be attributed to the formation of an egg-box structure, wherein calcium ions (Ca\({}^{2+}\)) form a three-dimensional network with SA chains [51]. This structure restricts polymer chain mobility, leading to reduced elongation after crosslinking. The egg-box formation enhanced TS, which can be explained by the establishment of new bonds between the material structures [52]. \begin{table}
\begin{tabular}{c c c} \hline
**Composition** & **Tensile Strength (MPa)** & **Elongation at Break (\%)** \\ \hline Pure PW & 3.17 \(\pm\) 0.42 & 25 \(\pm\) 2.9 \\ PAlv & 4.55 \(\pm\) 0.28 & 54 \(\pm\) 2.3 \\ PAlvx & 5.4 \(\pm\) 0.4 & 44 \(\pm\) 5.6 \\ PAhv & 5.34 \(\pm\) 0.74 & 48 \(\pm\) 6.7 \\ PAhvx & 6.47 \(\pm\) 0.16 & 43 \(\pm\) 4.8 \\ \hline \end{tabular} All values are reported as mean \(\pm\) standard deviation (SD) based on five replicate measurements.  
\end{table} 
Table 2: Mechanical characteristics of PW, PW/SA (PAlv, PAhv), and crosslinked PW/SA films (PAlvx, PAhvx). Figure 5: Stress–strain graph for PW, PW/SA (PAlv, PAhv), and crosslinked PW/SA films (PAlvx, PAhvx). Among the untreated composites, the PAhv film exhibited the highest TS at 5.34 MPa.