Halogens (which means “to form salt”) include the chemical elements chlorine (Cl), bromine (Br), fluorine (F), and iodine (I). When manufacturing cables, these are used to make certain core insulation and sheathing materials flame retardant. This is where chlorine (which is a component of PVC plastic or chloroprene rubber) and fluorine (which is found in the high-temperature materials FEP, PTFE, and ETFE) come into play. Even bromine is used in flame retardants for cables and wires.
The problem is that halogens burn extremely aggressively and emit noxious fumes when ignited.
They produce halogen halides which turn into acids when they come into contact with moisture and can cause acid burns in the respiratory tract. Furthermore, the acids that are released can cause metal parts to corrode, damaging machines and even the rebar reinforcements of concrete in buildings. This can result in the need for time-consuming and costly decontamination efforts.
The flame retardancy of cables and wires is, of course, an important criterion for fire prevention measures. There are also a number of applications that explicitly require halogen-free products, which means cables and wires consisting of materials that are free of chlorine, bromine, fluorine, and iodine. Should these cables be ignited, they produce much less acid and smoke, and are less toxic, which substantially reduces the consequential damages to people, buildings, and machines. Poisonous gases such as carbon monoxide are, however, still emitted when halogen-free cables are ignited.
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