Annual Production

diagram: PVC polymer

Poly(chloroethene), commonly referred to as PVC (polyvinylchloride) has been in commercial production since 1933, and now accounts for about 20% of all plastic made, second only to poly(ethene). World production is in the region of 30 million tonnes, with UK producing 500,000 tonnes.

The structure of the polymer molecule is very similar to poly(ethene), with one hydrogen on alternate carbon atoms substituted by a chlorine atom. The much higher relative atomic mass of chlorine means that chlorine makes up 56.8% of the pure polymer mass.

Click to find out more about the structure of PVC

Pure poly(chloroethene) is unstable when exposed to visible light or ultra violet, and also needs its properties modifying to make it suitable for various different applications. Most polymers will in fact contain many other materials to modify properties. For PVC these may include:

Anti-oxidants and other stabilisers Slow down the rate at which the polymer will be degraded by oxygen, heat, visible light or UV radiation
Compatibilisers Enable PVC to be blended with other plastics with which it would not normally mix (also used to help mixed plastic recycling)
Flame retardants Reduce flammability of plastic
Pigments Colour the plastic
Plasticisers Make the PVC more flexible and easier to mould for specific applications
Impact modifiers Help plastic mouldings absorb shock without damage
Fillers Inexpensive, inert materials that simply add bulk to the plastic

A PVC product may therefore consist of up to 60% additives.

The use of plasticisers leads to two basic types of PVC:

  • Rigid PVC (used for window frames) - PVC-U or uPVC ("unplasticised")
  • Flexible PVC (used for flexible medical tubing)

PVC is such a versatile plastic because of its compatibility with many different additives, though the use of some additives has been a source of environmental concern

diagram: the action of plasticisers

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