Polyvinyl chloride, better known as PVC, is a polymer made from vinyl chloride monomers. Polymerization is triggered by the addition of a peroxide under the appropriate reaction conditions. Because of the chemistry of this reaction, PVC has a very regular structure with a chlorine attached to every second carbon atom in the chain. Its structure imparts a number of desirable properties.
Plasticizers and Colorants
By itself, PVC is hard and somewhat brittle. It's fairly easy to add colorants and plasticizers, however, since these mix well with PVC. Plasticizers are typically chemicals called "carboxylic acid esters." Commercial PVC typically contains these ingredients, which improve its strength and flexibility. It's a viscoelastic material, meaning it can be gradually deformed, although its susceptibility to so-called "creep deformation" is less than that of plastics such as polyethylene. Thanks to the structure of this material, designs can be printed on it, so it's sometimes used in clothing or fashion design.
Chemical Reactivity
One of PVC's most important properties is its resistance to chemical degradation. It is resistant to acid, base and most inorganic chemicals. That's why you can pour drain opener down your drain without dissolving the trap. It does swell or dissolve in various organic solvents including ketones, however. It's resistant to oxidation and thus has a long lifespan. It should be noted, however, that polypropylene and polyethylene also exhibit very good resistance to chemical degradation, and polytetrafluoroethylene is of course even more inert than any of these others.
Flammability
When PVC burns, it releases the toxic gas hydrogen chloride. These same hydrogen chloride fumes, however, make it much less likely to burn, because the hydrogen chloride slows the progress of the combustion reaction. Consequently, PVC is difficult to ignite. Polypropylene, nylon, polyethylene and polyethylene terephthalate are all much more flammable chemicals than PVC. As you would expect given its structure, it's also a very poor conductor of electric current --- even more so, in fact, than nylon or polyester.
Other Properties
PVC is highly waterproof --- one of the characteristics that made it popular with fashion designers making vinyl clothing items and accessories. While it's unsuitable for injection molding, it can be used for extrusion molding to make housing materials, and it can also be processed to make sheets and films. It's also suitable for surface treatments that impart it a chosen texture such as enamel gloss or delustered suede.
