The technological revolution, starting in the second half of the 19th century and continuing at an even greater pace today, has resulted in a huge surge in power requirements for public buildings and private homes.

The increasing need for more power is not only for the use of household appliances but also due to elevators, heating systems and other structural features in modern buildings. This growth in electric installations has brought with it a greater risk of fire. The sheer volume of cabling in any modern building poses an enormous risk due to the flammability of the insulating material, the potential for short circuits from overheating and electrical faults.

Figure 1. Advances in modern day electrical cabling 

Growing Fire Hazards

Inside a building, the large amount of electrical or communication cables extending out to different rooms are generally hidden out of view behind the walls.

• these cables are all thickly bunched together in columns, sometimes running vertically from one floor to another and so pose a particularly high fire risk.
• they are not all required to comply with the same flammability standards, if one type of wire causes a fire, it can affect all of them.
• they are not easily accessible for safety checks and maintenance as they are lodged inside the walls of the building which makes it even more important to ensure their resistance to fire

It is essential, therefore, that wires are well protected from any chance of their catching fire. Cables are therefore typically coated with insulating plastic materials that contain flame retardants to prevent any spark or flame from spreading along the jacketing of electrical or communication cables (Figure 1 above).

Use of Flame Retardants

Fire safety of cables can be achieved by different methods depending on the degree of fire resistance required for the given application, and the electrical insulating and mechanical properties of the cable :

• intrinsically poorly flammable materials can be used for cable insulation and sheathings (e.g. PVCv)
• or PVC plus flame retardants for higher fire safety requirements
• or appropriate flame retardants can be used to ensure the fire safety of other insulating polymers (polyethylene, polyolefins)
• polymer-flame retardant combinations can be used to obtain ‘low smoke flame retardant’ cables.

The aromatic phosphate esters, which include the aryl and bisphosphate range, combine flame retardancy with plasticizing properties and have many applications in the flame retarding of plastics, particularly PVC (aryls).

Fine precipitated Aluminium trihydroxide (ATH) and Magnesium Hydroxide (MTH) are used in melt compounding and extrusion of thermoplastics for cable PVC or polyolefin for cables, they are often coated with organic materials to improve their compatibility with the polymer.

Brominated flame retardants are also used in wire and building cable installations, switches and connectors. TBBPA is used as an additive flame retardant in ABS plastics.

Flame retardants used for cable fire safety