Polyvinyl alcohol (PVA) is a water-soluble polymer, characterized by good compactness, high crystallinity, strong adhesion, thin film flexible and smooth, oil resistance, solvent resistance, abrasion resistance, good gas permeability, and the special treatment of water resistance, widely used.
Polyvinyl alcohol is non-toxic, tasteless, harmless to the human body, with good affinity to the natural environment, no accumulation, no pollution.
Polyvinyl alcohol film is a green functional material with polyvinyl alcohol as the main body, adding modifier and other additives, which can be completely degraded by microorganism in the soil by special process processing. It can degrade into carbon dioxide and water in a short period of time and has the effect of improving land.
The biggest advantage of PVA film is water solubility, and the biggest drawback is water resistance. Water resistance is due to the hydrophilic hydroxyl (OH) in its molecule. The water resistance of PVA film can be improved if the hydroxyl group is properly closed and the water resistance groups are grafted on. PVA contains hydroxyl, which can occur all typical reactions of polyols, the appropriate condensation is selected, in the case of small amount of addition, it can be made with the hydroxyl in PVA, so that PVA forms a strong three-dimensional structure, stabilizes the air tightness of PVA under wet condition, and enhances the water resistance. In practice, the water solubility and moisture absorption of polyvinyl alcohol films can be controlled by adjusting the raw materials, recipes and processes to meet the needs of different use purposes.
Polyvinyl alcohol films are divided into the following categories according to dissolution characteristics:
Ambient temperature soluble Film (NT type, rapid-soluble film, cold film): Dissolution temperature 25 ℃
Medium-Temperature soluble film (IT type, also known as medium-soluble film, hot-melt film): Dissolution temperature 65 ℃
High-temperature soluble film (HT type, also known as refractory film, soluble film): Dissolution temperature 85 ℃
Special film: According to the specific use of the design formula and technology, to meet the requirements of special use.