Poly 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 for 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 it's own weight in atmospheric water. When in solution, it has excellent wetting properties, and will readily form films. This makes is good as a coating, or an additive to coatings.

The uses that PVP can, and has been put to are very wide.

You have probably eaten PVP, as it is used as a binder for many tablets; being completely inert to humans, it simply passes through.

PVP binds with polar molecules exceptionally well, owing to the polarity of the molecule. This has lead to its application in coatings for photo-quality ink-jet papers and transparencies, and ink-jet inks. A very similar polymer - poly vinyl poly pyrrolidone (PVPP), is used to bind with impurities to remove them from a solution. 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 steel quenching solutions.