Polyvinyl alcohol is a synthetic water-soluble and thermoplastic polymer. This substance is synthesized due to the exchange reaction of alcoholysis and alkaline hydrolysis. Polyvinyl alcohol was first discovered in 1924. The substance was created by German chemists Wolfram Gonel and Willy Herman.
Polyvinyl alcohol: preparation
Unlike many vinyl polymers, this substance is formed not by polymerization of the corresponding components. The monomer of this product is found only in the form of a tautomeric form of acetaldehyde. Polyvinyl alcohol is obtained by complete or partial hydrolysis of a substance such as polyvinyl acetate. This method allows the removal of ethyl acetate groups from the final alcohol.
As for the industrial production of polyvinyl product, there are several ways. In this case, the saponification of the substance in an alcoholic medium or in an aqueous medium in the presence of bases and acid occurs.
Under the leadership of AA Kuznetsov in 2002, a more effective way of obtaining the product was developed. In this case, it was made without a gel method. This method has many advantages over previous ones. First of all, it is necessary to allocate relatively low cost, short-term synthesis and high productivity.
What properties does the substance possess?
Polyvinyl alcohol is widely used in many areas. This can be explained by its basic properties. This substance has gluing, emulsifying and film-forming properties.
In addition, PVA (polyvinyl alcohol) perfectly tolerates the effects of solvents, fats and oils. The substance has no odor and is completely non-toxic. The polymer has a high tensile strength and flexibility. It should be noted that the composition of polyvinyl alcohol is very much oxygen.
However, it should be noted that these properties of the product directly depend on some factors, among which humidity. With this increase, the substance begins to absorb water. It also acts on the polymer as a plasticizer. As a result, polyvinyl alcohol loses its strength. In some cases, the substance completely disintegrates, and then dissolves in water.
What is this substance - polyvinyl alcohol? Its application is wide enough. So, what you need to know about the product:
- Molecular formula - C2 H4 ABOUTx .
- The temperature at which the substance boils: 228 ° C.
- Density - 1,19 - 1,31 g / cm 3.
- The temperature at which the substance melts is 200 ° C.
The use of a substance for the preparation of polymers
Most often, polyvinyl alcohol is used to produce other polymers, for example:
- Acetal is polyvinyl. This substance is formed as a result of the interaction of polyvinyl alcohol with aldehydes.
- Polyvinyl nitrate is an ester of polyvinyl alcohol and nitric acid.
As what is used and where
Due to its properties, polyvinyl alcohol is used as a modifier and thickener in the composition of polyvinyl acetate adhesives. In China, this substance is used as an emulsion polymerization stabilizer, and also as a protective colloid in the process of manufacturing polyvinyl acetate dispersions.
Often, the product is used in the textile industry. In North Korea and Japan, polyvinyl alcohol has become widespread in the production of fibers.
In what sectors is the substance used
Polyvinyl alcohol has long been used in completely different areas and industries. It produces:
- Covering paper for liners.
- Barrier layer in polyethylene terephthalate tanks for carbon dioxide.
- Water-soluble film for the production of detergent powders in special capsules.
- Lubricant for solid contact lenses, it is also added to eye drops.
- A clamp necessary to collect samples.
- Fibers for reinforcing elements in concrete mortar.
- Agent embolization during medical procedures.
- Adhesive substance and thickener in the production of all kinds of shampoos, as well as latex.
- Emulsifier in many branches of the food industry.
- Embolic agent in the treatment of cancer without surgery.
Medical and food industry
Polyvinyl alcohol is a physiologically neutral substance. That is why it is often used not only in the medical, but also in the food industry. As a rule, this product is used as a glazing, water-retaining and film-forming additive. She was given the international name - E1203.
Thanks to polyvinyl alcohol, after all possible treatments in products, it is possible to keep moisture in the right amount. It should be noted that the E1203 additive is often used to make the glaze, which covers many seafood.