Science Fair Project Encyclopedia
Poly vinyl pyrrolidone
PVP (polyvinyl pyrrolidone, povidone, polyvidone) is made from the monomer n-vinyl pyrrolidone:
The monomer is carcinogenic and is extremely toxic to aquatic life. However its polymer PVP in its pure form is so safe that not only is it edible by humans, it is used as a blood plasma expander for trauma victims.
PVP is soluble in water and other polar solvents. In water it has the useful property of Newtonian viscosity. When dry it is a light flaky powder, which readily absorbs up to 18% of its weight in atmospheric water. In solution, it has excellent wetting properties and readily forms films. This makes it good as a coating or an additive to coatings.
The uses to which PVP has been put are very wide.
It is used as a binder in many pharmaceutical tablets; being completely inert to humans, it simply passes through.
PVP binds to polar molecules exceptionally well, owing to its polarity. This has led to its application in coatings for photo-quality ink-jet papers and transparencies, as well as in inks for ink jet printers.
A very similar polymer - polyvinyl polypyrrolidone (PVPP) - is used to bind impurities to remove them from solutions. Basically, PVPP is a more highly cross-linked version of PVP, which makes it insoluble in water. This means that it can be used to extract impurities by filtration. This polymer is used to filter bitter compounds from drinks and can even be taken as a tablet to absorb compounds causing diarrhoea.
PVP is also used in personal care products, such as shampoos and toothpastes, in paints, and adhesives that you have to moisten, such as old-style postage stamps and envelopes. It has also been used in contact lens solutions and in steel-quenching solutions.
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