The main characteristics of PVA film are as follows:

(1) Biodegradability

The biological oxygen demand (BOD) of PVA is much smaller than that of starch. After 5 days of biodegradation of Airvol's PVA products by the American Air Products Company, the measured BOD amount was less than 1% of the initial total BOD amount. PVA has been proven non-toxic through biological experiments.

In terms of degradation mechanism, PVA materials have two degradation properties: hydrolysis and biodegradation. Firstly, it dissolves in water to form a gel that seeps into the soil, which can increase the soil's cohesiveness, permeability, and water retention, making it particularly suitable for soil modification. PVA materials in soil can be decomposed by bacteria in the soil, ultimately degrading into carbon dioxide and water.

(2) Water solubility

Water is the solvent for PVA, but the water solubility of PVA is affected by the degree of alcoholysis and polymerization. Especially when the alcoholysis degree is below 88%, it is almost completely soluble in water. As the degree of alcoholysis increases, the solubility decreases significantly, and the fully alcoholized PVA dissolves very little in water. The water solubility of PVA film is also related to the film thickness and water temperature. Taking a 25 micron thick film as an example, the dissolution time is less than or equal to 300s at 20 ℃; The dissolution time is less than or equal to 50 seconds at 30 ℃, and less than or equal to 30 seconds at 40 ℃,

(3) Strength and weather resistance

PVA film has excellent mechanical properties, good toughness, high tensile strength, and ranks first in terms of tear resistance among various films (tear force 30-100kg/cm). Its biaxial tensile strength is superior. Good weather resistance and long service life. The mechanical properties of various thin films are shown in the table below.

(4) Transparency and glossiness

The transparency and glossiness of PVA film are superior to other films.

(5) Moisture permeability

The moisture permeability of PVA is similar to that of cellophane, and it is a thin film with extremely high moisture permeability. It does not produce fog droplets when packaging hot and wet items. The data measured according to JIS-Z1503 is shown in the table below.

(5) Barrier property

PVA film has excellent oxygen resistance under dry conditions, and its oxygen permeability coefficient is the lowest among various resin films. The blocking rate of oxygen under atmospheric pressure is about 1000 times that of PE film and 300 times that of PP film. The use of PVA film can effectively maintain the components and odor of the packaged product. It has superior barrier properties for nitrogen, hydrogen, helium, argon, and carbon dioxide.

But PVA membrane has strong permeability to water and ammonia. There are a large number of hydroxyl groups on the PVA molecular chain, which are prone to hydrogen bonding with water molecules in a humid environment, leading to changes in the aggregation structure of PVA and loss of barrier properties. As the relative humidity increases, the oxygen permeability significantly increases.

(6) Printing performance

PVA film has excellent water color and ink printability, which is an unparalleled advantage of existing plastic films that can only be printed with ink. Can be used for water transfer printing. Used for color printing on irregular surfaces such as glass, ceramics, electrical enclosures, automotive components, etc. At the same time, the polarity of PVA film is strong, and there is no need for electric spark treatment during printing. It is widely used in special printing industries, such as water transfer film substrates.

(7) Heat sealing performance

PVA water-soluble packaging film has good heat sealing performance, suitable for resistance heat sealing and high-frequency heat sealing. The heat sealing strength is related to temperature, humidity, pressure, time and other conditions, and generally does not exceed 200g/cm2.

(8) Oil and solvent resistance

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

(9) Fragrance retention and sublimation prevention

The fragrance retention and anti sublimation performance of PVA film are excellent. The use of PVA film packaging not only effectively maintains the fragrance of the packaging, but also prevents the packaging from being affected by external odors. The fragrance retention test table is as follows.