Overview and classification of polyvinyl alcohol (PVA) film
1 Overview
Polyvinyl alcohol (PVA) is a water-soluble polymer characterized by good compactness, high crystallinity, strong adhesion, and the resulting film is flexible, smooth, oil resistant, solvent resistant, abrasion resistant, and gas barrier resistant. And the water resistance of special treatment has a wide range of uses.
Polyvinyl alcohol is non-toxic, odorless, harmless to the human body, has good affinity with the natural environment, does not accumulate, and is non-polluting.
The polyvinyl alcohol film is a green functional material which is mainly composed of polyvinyl alcohol, added with modifiers and other additives, and can be completely degraded by microorganisms in the soil after special processing. It degrades into carbon dioxide and water in a short period of time and has the effect of improving the land.
The biggest advantage of polyvinyl alcohol film is water solubility, the biggest disadvantage is poor water resistance. The reason why the water resistance is poor is due to the hydrophilic hydroxyl group (-OH) in the molecule. If the hydroxyl group can be properly blocked and the water resistant group is attached, the water resistance of the PVA film can be improved. PVA contains hydroxyl groups, and all typical reactions of polyols can be carried out. Appropriate polycondensates can be used to properly cross the hydroxyl groups in PVA in a small amount, so that PVA forms a strong three-dimensional structure. It stabilizes the airtightness of PVA under wet conditions and improves water resistance.
In practical applications, the water solubility and moisture absorption of the polyvinyl alcohol film can be controlled by adjusting raw materials, formulations and processes to meet the needs of different purposes.
2 classification
Polyvinyl alcohol films are classified into the following categories according to their solubility characteristics:
Normal temperature soluble film (NT type, also known as fast-dissolving film, cold-dissolving film): Dissolving temperature 25 °C
Medium temperature soluble film (IT type, also known as medium soluble film, hot melt film): Dissolving temperature 65 ° C
High temperature soluble film (HT type, also known as poorly soluble film, resistant film): Dissolving temperature 85 °C
Special film: The formula and process can be designed according to the specific application to meet the requirements of special use.
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