A7.2 Burning Plastics

If a plastic burns completely in a good oxygen supply, complete oxidation will result in carbon dioxide and water vapour.
Burning of polyvinyl chloride releases HCl gas and incomplete hydrocarbon combustion products (and also dioxins – see below*). Hydrogen chloride (HCl, toxic and corrosive) is released by the combustion of plastics like PVC (polyvinyl chloride, polychloroethene) which contain chlorine.
For large scale incineration of plastics, HCl is easily and safely neutralised using an alkaline scrubber.
Ideally, an incineration process oxidises all carbon to carbon dioxide and converts all chlorine to hydrogen chloride (HCl).
*However if the combustion temperature is too low (400-700°C) it is possible for toxic dioxins to be formed and released into the atmosphere. High temperature incineration is essential to avoid this.
House fires can release many toxins into the atmosphere due to plastics (electrical cables, shower curtains, etc).
The use of “Low smoke zero halogen” for the insulation of electrical cables reduces the amount of toxic and corrosive gas emitted during combustion. This reduces the chance of toxic gases accumulating in these areas should the wires be damaged by fire or a short circuit fault.
Burning some polymers can cause depolymerisation.
A common example is polystyrene which releases molecules of the monomer styrene (phenylethene). Styrene gas can be easily absorbed and styrene can damage the eyes and mucous membranes. Long term exposure to styrene can affect the central nervous system, causing headaches, fatigue, weakness, and depression.