# Attempts to Obtain Material Based on Polyvinyl Alcohol with Barrier Properties against Water Vapor
## 1 Introduction
It is easy to process, highly polar, and forms strong hydrogen bonds in the presence of hydroxyl groups. Although it has low oxygen permeability [16] it exhibits high WVP. Reducing the WVP of PVA-based films can be achieved by combining the biopolymer with other materials [17], adding multiple functional constituents [18; 19] such as cross-linking agents or plasticizers [20], or applying various methods such as grafting, etherification, phosphorylation, acetylation, freezing, heat treatment, or irradiation [21; 22]. The transfer of water between food and the environment influences the shelf life of food leading to its alteration. For this reason, many researchers have devoted their attention to improving this barrier property by mixing PVA with other biopolymers or using various chemical or physical methods [23]. A packaging material with a low permeability prevents water from penetrating the food, thus preventing the growth of microorganisms on or within its surface [24]. Hydrophobic films and coatings can reduce the rate of water molecule transfer acting as effective barriers against moisture. Mixing waves into the polymer matrix can also be a viable strategy for improving water vapor barrier properties due to their hydrophobic character. The type and amount of wax and emulsifiers, as well as different preparation conditions (such as temperature and homogenization conditions) are important factors that influence the stability, structure, and properties of the film. For a more homogeneous dispersion of wax in the film matrix, its melting point should be as low as possible helping to obtain small droplets facilitating the formation of emulsion. [PERSON] et al. [25] tested three types of wax (beeswax (BW), candleilla wax (CL), and carnauba wax (CB)) for reducing the hydrophilicity of edible starch/gelatin films prepared by extrusion blowing. By incorporating BW and CL into the matrix, the film surface became rougher and more irregular, thus improving the surface hydrophobicity of the film. Films containing BW showed the stronger thermal stability and the lowest permeability to water vapor. The authors of this study recommended BW for obtaining edible films with low water vapor permeability. BW is commonly used to produce hydrophobic films or coatings. It has a complex composition, containing various constituents including long-chain hydrocarbons, fatty acids, free acids and esters, alcohols. Beeswax has a melting point of 63-65 \({}^{\circ}\)C, is insoluble in water, and has a yellowish color. The superhydrophobic nature of BW is attributed to the methylene [int-(CH\({}_{2}\))] carbons in the internal chain of which more than 95% is present [26]. [PERSON] et al. [27] prepared agar/maltodextrin-beeswax (A/M-BW) pseudo-bilayer films and studied drying temperatures and homogenization conditions to increase the hydrophobicity of the films. The best results were obtained at 80 \({}^{\circ}\)C and 8000 rpm for 1 min. Composite films based on PVA/polyacrylic acid (PAA) were prepared by [PERSON] et al. [28] who studied the effect of wax content on the formation of solutions. The analysis results showed that excessive wax content led to the separation of solution phases, resulting in non-homogeneous structures due to the clumping of BW. The best results were achieved with a film containing 10% BW, which improved the properties against water, oxygen and oil. Emulsifiers are amphiphilic substances that determine the interaction between lipids and matrices and contribute to their homogeneous dispersion in the film matrix. They can reduce the size of droplets in the emulsion thus increasing the number of drops in it [29]. [PERSON] et al. [30] prepared PVA and starch films, then added coconut shell extract (CSE) in different mass proportions (3, 5, 10, and 20%) and sepiolite clay to obtain a material with antioxidant properties for food packaging. The mechanical and thermal properties of the films improved by adding CSE and sepiolite clay to the matrix due to the formed hydrogen bonds.