## 3 Results and Discussion
### WVP Analysis  
To assess the moisture barrier properties of the films, the water vapor transmission rate (WVTR) and water vapor permeability (WVP) were measured. Since the WVTR value is influenced by the film thickness, WVP was used to ensure a more accurate comparison across different specimens [53]. The analysis is reported in Figure 6.  
The results indicate that the pure PW exhibited the highest WVP at \(2.4\times 10^{-12}\) g/(Pa-cm-s), suggesting poor moisture barrier properties. This can be attributed to the structural characteristics of the PW matrix, which contains cavities and inherent porosities in the structure of the film matrix. Unlike high-performance homogenizers, such as microfluidizers or high-shear mixers, the ball mill grinding process used in this study did not achieve ultra-fine particles, leading to insufficient integration of PW-derived starch and cellulose components and thereby facilitating moisture diffusion. Figure 6: Water vapor permeability (WVP) for PW, PW/SA (PAlv, PAhv), and crosslinked PW/SA films (PAlvx, PAhvx). The inclusion of SA significantly enhanced moisture barrier properties by reducing the WVP factor. The addition of lvSA and hvSA resulted in a WVP reduction of 1.83 \(\times\) 10\({}^{-12}\) and 1.63 \(\times\) 10\({}^{-12}\) g/(Pa\(\cdot\)cm\(\cdot\)s), indicating decreases of 24% and 32%, respectively. This improvement is attributed to SA's excellent film-forming ability, which fills the gaps in the PW matrix, creating a denser and more cohesive structure that restricts moisture diffusion [54]. Additionally, the PAhv composite exhibited greater moisture resistance compared to PAlv, probably due to its longer polymer chains and higher carboxyl group content, which enhance hydrogen bonding interactions with water molecules [55]. The presence of carboxylic functional groups not only increases hydrophilicity but also strengthens the polymer network, further improving the film's barrier efficiency [56]. Crosslinking further improved the moisture barrier properties of the composites. Upon crosslinking, the WVP values decreased to 1.66 \(\times\) 10\({}^{-12}\) and 1.58 \(\times\) 10\({}^{-12}\) g/(Pa\(\cdot\)cm\(\cdot\)s) for PAlvx and PAhvx, respectively, corresponding to an additional 9% and 3% improvement. This enhancement can be attributed to two primary factors. Firstly, crosslinking reduces the hydrophilicity of the compound, thereby enhancing its water barrier performance [57]. Secondly, the crosslinking produces a more interconnected and compact structure, which effectively limits water vapor diffusion [58]. Table 3 presents a comparison of WVP values for the PAhvx composite in this study and those reported in similar studies, with all values converted to g/(Pa\(\cdot\)cm\(\cdot\)s) for consistency. The results indicate that PAhvx exhibits a notably lower WVP than most composites containing PW powder, suggesting superior moisture barrier properties. While there are no previous studies on the combination of PW with SA, the composites of SA and starch were selected for comparison. The WVP of the SA/starch/montmorillonite composite reported by [PERSON] is similar to that of the current study. In contrast, the addition of ground coffee powder to starch/SA films in other studies resulted in higher WVP values compared to the composites in this work. This difference is likely due to the heterogeneity introduced by the coffee powder, which adversely affects barrier performance. Overall, the composites developed in this study demonstrate lower and more promising WVP values than most previously reported materials. This suggests that the addition of SA, regardless of its viscosity, does not compromise the barrier properties and makes these composites strong candidates for packaging applications requiring high moisture resistance.