Poly(vinyl alcohol) (PVA) is a white, stable, non-toxic water-soluble polymer made from vinyl acetate by polymerization and alcoholysis. It is a solid in powder, flake or flocculent form. Polyvinyl alcohol contains many alcohol groups, has polarity, and can form hydrogen bonds with water, so it can dissolve in polar water. It is also soluble in hot hydroxy solvents such as glycerol, phenol, etc., and insoluble in methanol, benzene, acetone, gasoline and other general organic solvents.
What is PVA material ?
Polyvinyl alcohol (PVA) is a widely used water-soluble polymer whose properties are between plastic and rubber. PVA is a soft, biodegradable polymer that is highly sensitive to water. When exposed to water, PVA actually dissolves, which makes it a very useful support structural material for 3D printing.
PVA characteristics:
1. Solubility: PVA powder can be dissolved in water. The polyvinyl alcohol resin (PVA) with an alcoholysis degree of less than 95% can be dissolved in room temperature water, and the polyvinyl alcohol resin (PVA) with an alcoholysis degree of more than 99.5% can only be dissolved in hot water above 95℃.
2. Thermal stability: polyvinyl alcohol will soften when heated, there is no significant change below 40℃, glass transition temperature :75~85℃, heating to more than 100℃ slowly discoloration, embrittlement. Above 160℃, long-term heating will gradually color, dehydration etherification, loss of solubility; Above 220℃, decomposition occurs and water, acetic acid, acetaldehyde and butenal are formed. Above 250℃ becomes a polymer containing conjugated double bonds.
3. Chemical resistance: PVA is almost unaffected by weak acids, weak alkalis or organic solvents, and has high oil resistance.
4. Storage stability: PVA is a low viscosity polymer, and its aqueous solution is stable at room temperature. The aqueous solution will not deteriorate during storage.
5. Film formation: Due to the high adhesion between PVA molecules, PVA is easy to form a film, the formed film is colorless and transparent, has good mechanical strength, the surface is smooth and not sticky, and the solubility is good. The molecular film has good light transmittance, high moisture transmittance, no electricity, no dust suction and good printability.
What are PVA used for?
1.PVA can be used for coating, printing and dyeing of textiles, which can improve the fastness, wrinkle resistance and softness of textiles. In addition, PVA can also be used as a binder for textiles to form a protective film on the surface of the fabric to increase the durability and stability of the textile.
2. PVA also plays an important role in building materials. PVA can be used as an additive to cement and mortar to enhance its bond and durability. It can improve the fluidity and crack resistance of concrete, improve the compressive strength and durability of components. In addition, PVA can also be used in the production of binders, coatings and sealing materials to improve the adhesion and water resistance of materials and extend the service life.
3. PVA also has important applications in the packaging and food industry. Due to its excellent processing properties and solubility, PVA can be used to make a variety of packaging materials, such as plastic bags, plastic wrap and packaging film. Its stability and water resistance make PVA an ideal choice for food packaging. In addition, due to its compatibility with other substances, PVA can also be used in the production of stabilizers, emulsifiers and thickeners in food processing, improving the quality and taste of products.
4. PVA is a kind of polymer material, which has a moisturizing effect, can keep the water of the skin from losing, and can also make the skin more elastic. If the skin is relatively dry, the appropriate use of polyvinyl alcohol can be improved, so as to achieve the moisturizing effect. Pva has a hydrating effect, which can keep the water of the skin from being lost, and can also make the skin become more elastic, suitable for people with dry skin.
5.PVA can also be used in the field of medicine, common in life are medical gauze, bandages, etc. Its main function is to absorb water in blood and tissue fluid, and has a certain wetness.
In short, as an important synthetic resin, polyvinyl alcohol plays an important role in various fields. From the textile industry to building materials, to the packaging and food industries as well as the pharmaceutical and cosmetic industries, PVA plays an irreplaceable role in improving the performance and quality of products. With the continuous development of science and technology, the application prospect of PVA will be broader.
