Fire

All plastics are combustible, producing noxious fumes and smoke (Table 10.1). Carbon monoxide is produced by most organic materials, but in addition, plastics containing nitrogen, such as polyurethane foam, generate hydrogen cyanide and PVC produces hydrochloric acid. Some plastics, particularly acrylics and expanded polystyrene have a high surface spread of flame and produce burning droplets; however, others when treated with fire retardant are difficult to ignite and some are self-extinguishing.

Table 10.1 Behaviour of common building plastics in fire

Material

Behaviour in fire

Thermoplastics

Polythene /

Melts and burns readily

Polypropylene

Polyvinyl chloride

Melts, does not burn easily, but emits

smoke and hydrogen chloride

PTFE / ETFE

Does not burn, but at high temperatures

evolves toxic fumes

Polymethyl methacrylate

Melts and burns rapidly, producing

droplets of flaming material

Polystyrene

Melts and burns readily, producing dense

black smoke and droplets of flaming

material

ABS copolymer

Burns readily

Polyurethane

The foam burns readily producing highly

toxic fumes including cyanides and

isocyanates

Thermosetting plastics

Phenol formaldehyde

Resistant to ignition, but produce noxious

Melamine formaldehyde

fumes including ammonia

Urea formaldehyde

Glass-reinforced polyester

Burns producing smoke, but flame-

(GRP)

retarded grades are available

Elastomers

Rubber

Burns readily producing black smoke and

sulfur dioxide

Neoprene

Better fire resistance than natural rubber

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