How is PVC made?

The basic raw materials are derived from salt (sodium chloride (NaCl)) and oil.

The electrolysis of brine (sodium chloride dissolved in water) produces chlorine (and also hydrogen and sodium hydroxide). The chlorine is then combined with ethylene that has been obtained from oil.

The resulting element is ethylene dichloride, which is converted at very high temperatures to vinyl chloride monomer (VCM).

PVC is produced by polymerising vinyl chloride monomer (VCM) at very high temperatures. This method is referred to as the ethylene process or ethylene route.

Notes:
- Ethylene is a gas which has to be pressurised before transportation.
- VCM is a gas at ambient temperature, but is usually stored in liquid form under pressure.
- PVC is often supplied as an odourless white powder.

The raw materials (feedstocks) are supplied by upstream industries. These include basic petrochemical producers which supply ethylene, and the chloralkali (caustic soda) industry, which supplies chlorine.

Step 1
Chlorine is extracted from brine (common salt and water) through the process of electrolysis.
2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH

Step 2
The chlorine is added to ethylene to make ethylene dichloride (EDC).
H2C=CH2 + Cl2 → ClCH2-CH2Cl

Step 3
EDC
is broken down into vinyl chloride monomer (VCM) and hydrogen chloride (HCl).
This part of the process is called thermal cracking.
ClCH2CH2Cl → CH2=CHCl + HCl

Step 4
Many single molecules of VCM are added together to form long chains of polyvinyl chloride (PVC). This is called polymerisation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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