HOW IS PVC MANUFACTURED?

Step 1 Producing Ethylene Dichloride

Chlorine is extracted from sea salt via electrolysis, and ethylene is derived from hydrocarbon raw materials. These are reacted to produce ethylene dichloride (1,2-dichloroethane) according to the reaction:

C2H4 + Cl2 = C2H4Cl2
ethylene + chlorine = ethylene dichloride

Step 2 Producing Vinyl Chloride Monomer

The ethylene dichloride is then decomposed by heating in a high temperature furnace, according to the reaction:

C2H4Cl2 = C2H3Cl + HCl
ethylene dichloride = vinyl chloride monomer + hydrogen chloride

The hydrogen chloride is reacted with more ethylene in the presence of oxygen (a reaction known as oxychlorination) to produce further ethylene dichloride. The ethylene dichloride so produced is decomposed according to the above equation, and the hydrogen chloride again returned for oxychlorination.

2HCl + C2H4 + ½ O2 = C2H4Cl2 + H2O
= C2H3Cl + HCl2 + H2O

The overall reaction can be shown by adding together the above equations to give:

2C2H4 + Cl2 + ½ O2 = 2C2H3Cl + H2O
ethylene + chlorine + oxygen = VCM + water

Click on the diagram below for an outline of the process.

Step 3 Manufacturing Polyvinyl Chloride

PVC is made by a process called addition polymerisation. This reaction opens the double bonds in the vinyl chloride monomer (VCM) allowing neighbouring molecules to join together creating long chain molecules.

nC2H3Cl = (C2H3Cl)n
Vinyl chloride = polyvinylchloride

In Australia, only the polymerisation step is carried out, the PVC resin being made from imported VCM. Around 65% of Australia's demand for PVC resin is met by domestic production.