The moisture permeability of PVA film is similar to that of cellophane. It is a film with extremely high moisture permeability. PVA is sensitive to hygroscopicity and has high moisture permeability. This is a shortcoming of PVA film as a packaging material. But on the other hand, it is not suitable for moisture after packaging. The advantage of steam items is that mist droplets will not condense inside the film. It is often used for packaging of finely processed fabrics whose temperature has not completely dropped after drying. Despite its high hygroscopicity, its film remains non-sticky and dry under high humidity

PVA has high barrier properties against many gases. The oxygen and helium permeability measured at 25°C of completely alcoholized PVA is almost 0, and the other two are 0.02g/m. Gas barrier products have good gas barrier properties. Under normal pressure, the oxygen barrier rate measured is 1,000 times that of plastic polyethylene film and 300 times that of polypropylene film. In addition, the barrier properties against carbon dioxide, nitrogen, hydrogen, chlorine, hydrogen and other gases are also very superior. It can preserve the ingredients and smell of packaged products intact, and is used in the packaging of dried and fresh products, cigarettes, medicines, etc. It can extend the freshness, fragrance and shelf life. It can also be used in the packaging of clothing, bedding, and textiles to block harmful substances in the air. Nitrogen to avoid fabric yellowing

The dissolution characteristics of PVA films are divided into several categories:

Normal temperature dissolving film (NT type, also known as fast dissolving film cold dissolving film): dissolving temperature 25°C

Medium temperature dissolving film (IT type, also known as medium dissolving film hot melt film): dissolving temperature 65°C

High temperature dissolving film (HT type, also known as difficult dissolving film, resistant dissolving film): dissolving temperature 85°C

PVA has a higher tensile strength than general plastics and can be used to make very strong and tear-resistant films. Its advantage is that the tensile strength, elongation at break, tear strength, hardness, etc. of the film or molded product can be adjusted by the amount of plasticizer, water content, etc. The tensile strength of the PVA film increases significantly during elongation. The film with an average tensile strength of 69MPa before orientation increases to 345MPa after being stretched to 5 times its original length. It has excellent biaxial tensile strength. It has good weather resistance and long service life. The mechanical properties of various films are shown in the following table

Main materials made from sustainable resources (natural starch and vegetable oil derivatives Free of PE/PP/PS/PET Low carbon footprint Can be recycled together with waste paper Compliant with EN13432 in terms of biodegradation and ecotoxicity Safe for animals, membrane Bag products can be consumed and digested by various animals without forming microplastics

Various plastics are highly charged, but PVA film has almost five charges like cellophane. PVA molecules contain a large number of hydroxyl groups and are highly hygroscopic, so they have excellent antistatic properties. Since it is uncharged, its products will not absorb dust in the air and have good printing adaptability and decoration properties, so they are often used for printing and bag making.

PVA film has excellent resistance to oil (vegetable oil, animal oil, mineral oil), organic solvents and carbohydrates, etc. However, strong alkali, strong acid, chlorine free radicals and other substances that can react chemically with PVA (such as borax, boric acid, certain dyes, etc.) are not suitable for packaging with PVA film.

PVA film has excellent fragrance preservation and the ability to prevent the sublimation of packaging materials. The use of PVA film for packaging can not only well maintain the fragrance of the packaging materials, but also prevent the packaging materials from being affected by external odors.

As is well known, starch can be metabolized by various microorganisms to form fermentation products that are easily degradable and renewable in plants. PVA is also prone to biodegradation, but the process is particularly slow. Moreover, the number of microorganisms that degrade PVA is very limited compared to the number of microorganisms that degrade aliphatic polyesters. Many researchers have studied the biodegradability of starch and PVA blends. It was found that the biodegradation rate of starch and PVA composite films is related to the content of PVA in the composite material. The blend degrades significantly faster than pure PVA. It was found that the starch glycerol sample could be degraded to a weight loss of up to 70% within 22 days, however, after the addition of PVA, the weight loss rate was only 59%, which also indicates that the addition of PVA slowed down the degradation process of the sample. The degradation process of thermoplastic starch and PVA under anaerobic conditions was studied, mainly simulating the exposure environment of household waste. The results showed that PVA was present throughout the degradation process, while starch was almost completely degraded. However, the content of PVA significantly affected the degradation rate of starch. The degradation process of modified starch and PVA blends was evaluated, and a bioactivity kinetic model was also established. The results showed that the degradation rate of PVA increased with the addition of starch. Based on the kinetic model, in the first order reaction process, the growth rate of microorganisms increases with the increase of starch content. et al. characterized the biodegradability of PVA, starch and cellulose films in the presence and absence of crosslinkers. The results showed that the composite films generally biodegraded within 30 days, while 50% to 80% of the minerals were obtained. The degradation rates of pure PVA and crosslinked blends were relatively slow.