# Attempts to Obtain Material Based on Polyvinyl Alcohol with Barrier Properties against Water Vapor
## 1 Introduction  
The growing concern for environmental pollution and the widespread accumulation of huge amounts of plastic waste, which remains in the environment for a long time and has a negative impact on resource depletion as well as human health, have led many institutions to adopt Sustainable Development Goals to reduce the impact of these materials on the environment. Under the influence of several factors, these plastics break down into very small particles, so-called microplastics (smaller than 5 mm), which can be ingested by animals, birds and marine fauna and pose a threat to all trophic levels [1]. Traditional plastics are used in many industries, with some materials having a longer lifespan, such as those used in construction, lasting about 35 years, and others, like packaging materials, having a shorter lifespan of about 6 months. In contrast, biodegradable materials degrade in shorter periods of time, about 1-2 months, compared to traditional materials that can remain in the environment for centuries or even longer [2]. The current trend is to find viable and environmentally friendly solutions to replace non-degradable petroleum-based plastics with sustainable, renewable, hydrophobic and biodegradable materials that can be recycled and compost. This aims to reduce fossil fuel dependence and greenhouse gas footprint in the environment and promote more efficient use of renewable resources [3, 4]. Biodegradable polymeric materials have been the subject of numerous studies due to their unique benefits, such as: excellent film-forming properties, good mechanical, optical and thermal properties, corrosion resistance, low weight and high hardness, and excellent oxygen barrier properties. However, these materials also have some disadvantages, suchas high water vapor permeability (WVP). Despite the efforts of by many researchers, due to these limitations, there are few biodegradable polymers that meet the requirements of modern society's packaging needs [2; 5]. There are various studies in the literature on obtaining hydrophobic surfaces for potential packaging materials, but obtaining environmentally friendly and sustainable hydrophobic materials remains a major challenge. The water vapor barrier performance of biomaterials can be influenced by various factors such as sample preparation methods (casting, biaxial orientation, annealing), test conditions (temperature, humidity), and micro-morphology (crystallization, phase separation) [6; 7]. Under high humidity conditions, the biopolymer matrix should be cross-linked to ensure the integrity. Cross-linking refers to the reactions that lead to the formation of bonds between polymer chains [8]. Polyvinyl alcohol (PVA) is a biodegradable synthetic polymer widely studied by researchers. It is applicable in many industries, such as: biomedicine, cosmetics, and pharmaceutical industry, in the paper, textile, and paint industries, in construction. Recently, there has been growing interest in obtaining packaging biomaterials for use in the food industry, either as a film [9], as a layer in biocomposites, or as a coating [10]. PVA can be completely broken down by appropriately acclimatized microorganisms [11]. Its biodegradation can occur under aerobic or anaerobic conditions. Under appropriate environmental conditions (pH and temperature), selected microorganisms grow rapidly, resulting in the rapid degradation of the polymer. This process should be completed in a minimum of 6 and a maximum of 12 weeks [12].The biodegradability of PVA has been demonstrated since the early 1930s. Biodegradation occurs through hydrolysis or enzymatic cleavage of the polymer matrix [1; 13]. PVA is one of the most commonly used biopolymers for the production of bioplastics. It is a biodegradable synthetic polymer obtained by the hydrolysis of poly(vinyl acetate) under alkaline conditions [14]. PVA is non-toxic, water-soluble, exhibits excellent biocompatibility, and good mechanical and thermal properties [15].