# Attempts to Obtain Material Based on Polyvinyl Alcohol with Barrier Properties against Water Vapor
## 3 Results and Discussion
### PVA Film Modified with 0.75% CA, 0.4 g BW, CBS, 1.5% Gly, and 0.71% OEO, Thinner (PVA VI)  
The resulting mixture was not as homogeneous as with the PVA V film, as seen in Table 2, with agglomerations of lipid particles. The film was quite transparent, a slightly whitish, and the thickness of the film was 0.18 mm. The treatment of solution with ultrasounds resulted in particle conglomeration effect. The untreated film had a pleasant oregano smell, which was lost during heat treatment as essential oils had been shown to evaporate at high temperatures [41; 42]. However, this was added to the film with the intention of trapping part of it in the matrix network, thereby reducing the WVP of the film. The PVA VI film treated at 150 \({}^{\circ}\)C cracked during modeling and the WVTR of the film could not be determined. The WVTR values of the PVA VI film are shown in Figure 7, compared to those of the PE and pure PVA film. The best results were achieved with a PVA VI film heat treated at 125 \({}^{\circ}\)C, which had the lowest WVTR values, 0.74%, on day 34, compared to not thermally hardened PVA VI film, and to pure PVA film, the difference was 8.12%, on the same day. Compared to the PE film, the differences observed were smaller, with the untreated PVA VI film having 5.38% higher WVTR values and the PVA VI film treated at 125 \({}^{\circ}\)C showing even smaller differences on day 34, namely 4.64%. The addition of OEO to the modified BW film can be a good strategy to reduce the permeability of the pure PVA film, since the PVA VI film had almost the same WVTR values as the PVA V film, but possibly a better dispersion of both lipids in the film matrix would lead to even better results. Increasing the amount of added lipids to reduce the hygroscopicity of films was also confirmed by [PERSON] et al. [40] in their study by preparing trays made of thermoplastic starch materials (TPS) and PLA, obtained by extrusion and thermopressing, which covered with BW emulsion in different mass proportions (1, 2, and 3%), to lower their WVP. The authors demonstrated that the WVP of the trays obtained decreased with increasing the amount of wax from 7.9 \(\times\) 10\({}^{-11}\) to 0.2 \(\times\) 10\({}^{-11}\) g/m\(\cdot\)s\(\cdot\)Pa due to the hydrophobicity of BW. [PERSON]  
Figure 6: WVTR of untreated PE, PVA, PVA V films and PVA V film heat treated at 125 \({}^{\circ}\)C and 150 \({}^{\circ}\)C (the results were obtained in triplicate. The average of the three determinations was reported, with a maximum error of 5%). et al. (2018) also state that the aggregation and crystallization of BW during drying results in a rougher surface and subsequently in low WVP of the film. The difference between the WVTR values of the modified and heat-treated films and the PVA film is statistically significant at more than 99% (\(p<0.01\)) according to One-Way Anova, the Tukey model, which means that the WVP of the PVA film has been improved. PVA Film Modified with 0.75% CA and 1.5% Gly (PVA I) and PVA Film Modified with 0.75% CA, 0.4 g BW, CBS and 1.5% Gly (PVA V) (PVA VII Double Layer)  
The PVA VII double layer film is well homogenized, with glossy and transparent side and the other side slightly whitish, the combined biomaterials being compatible and making a very good grip. The thickness of the film was 0.5 mm and its image can be seen in Table 2. The WVTR values of PVA VII film subjected to heat treatment are shown in Figure 8 compared to those of the pure PVA film and the PE film. The heat-treated double-layer film became slightly stiffer and thicker, but did not break, while the film cured at 150 \({}^{\circ}\)C turned slightly yellow. Heat treatment of the double layer PVA VII film at 125 \({}^{\circ}\)C was found to be ineffective and gave WVTR values approximately equivalent to those of the untreated PVA VII film; however, compared to pure PVA, the WVTR was reduced by 5.57%. The PVA VII film cured at 150 \({}^{\circ}\)C was effective and reduced the WVTR of untreated double layer film by 1.36% on the 26 th day and by 1.06% on the 34 th day.