## 4 Conclusions  
This study developed sustainable biopolymer films from potato peel waste reinforced with sodium alginate (SA), achieving significant improvements in mechanical strength and moisture barrier properties through the use of high-viscosity SA (hvSA) and calcium chloride crosslinking. These composites demonstrated over a 100% increase in tensile strength and reduced water vapor permeability compared to pure potato peel films, indicating their promise as biodegradable alternatives for packaging and biomedical applications.  
Mechanical characterization revealed that pure PW films had poor performance, with a tensile strength of 3.17 MPa and 25% elongation at break. Incorporating SA improved these properties, with hvSA and its crosslinked form outperforming low-viscosity SA (lvSA).  
Figure 7: Cross-sectional SEM images of films: PW, PW/SA (PAlv, PAhv), and crosslinked PW/SA (PAlvx, PAhvx).  
The hvSA composite increased tensile strength by 68% (5.34 MPa), while its crosslinked version increased it by 104% (6.47 MPa). LvSA films showed greater elongation improvements, reaching 54%, which is more than double that of the pure PW film. WVP tests revealed poor moisture barrier performance in pure PW (2.4 \(\times\) 10\({}^{-12}\) g/(Pa\(\cdot\)cm\(\cdot\)s)). Adding SA improved barrier properties, with hvSA performing better than lvSA. Crosslinking further reduced permeability, with the crosslinked hvSA film achieving the lowest WVP (1.58 \(\times\) 10\({}^{-12}\) g/(Pa\(\cdot\)cm\(\cdot\)s)). The DMA results showed that pure PW had a Tg of 60 \({}^{\circ}\)C, which decreased with SA addition. Tg values dropped to 48 \({}^{\circ}\)C and 38 \({}^{\circ}\)C for lvSA and hvSA composites, respectively. TGA analysis indicated that SA-modified films degraded at lower temperatures than pure PW (peak at 290 \({}^{\circ}\)C), with a new peak near 225 \({}^{\circ}\)C. Crosslinking slightly enhanced thermal stability, shifting this peak to about 240 \({}^{\circ}\)C. SEM analysis confirmed that SA incorporation improved film structural integrity by filling voids caused by potato peel heterogeneity.  
By valorizing agricultural waste, this work advances the development of eco-friendly materials with practical potential to replace petroleum-based plastics for packaging or biomedical applications. Future efforts could focus on scaling up production and incorporating functional additives to tailor film properties for specific uses.  
Conceptualization, M.S.-S., S.E. and M.R.; validation, M.S.-S., S.E. and M.R.; Methodology, M.S.-S.; Formal analysis, M.S.-S.; Investigation, M.S.-S.; Resources, M.R. and S.E.; Data curation, M.S.-S.; Writing--original draft, M.S.-S.; Writing--review & editing, M.S.-S., S.E. and M.R.; Supervision, M.R. and S.E.; Project administration, M.R. and S.E. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
During the preparation of this work, the authors used ChatGPT-4o to check grammar and spelling. After using this tool, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} PW & Potato peel waste \\ SA & Sodium alginate \\ lvSA & Low-viscosity sodium alginate \\ hvSA & High-viscosity sodium alginate \\ PALv & Compound of PW/lvSA \\ PAhv & Compound of PW/hvSA \\ PALvx & Crosslinked compound of PW/lvSA \\ PAhvx & Crosslinked compound of PW/hvSA \\ \end{tabular}