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There are 4 main flame retardant technologies:
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Phosphorus -
reacts when heated to create a char, inhibiting the pyrolysis
process. Suitable for use with textiles and plastics materials,
it may be mixed in and chemically bound to the plastics matrix
at polymerisation or made into a solution and then impregnated
into textiles. This chemistry is the basis of all Firestop
products.
Halogenated FRs -
release bromine or chlorine as free radicals which react with
hydrocarbon molecules (flammable gases) to slow or prevent
the burning process. Antimony trioxide may be combined with
halogenated FRs to act as a synergist.
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Nitrogen - used
in conjunction with other FR chemicals (phosphorus), nitrogen forms
cross-linked molecular structures which are stable at high temperatures,
both inhibiting the decomposition of materials to flammable gases
and diluting flammable gases.
Inorganic FRs -
include aluminium trihydrate (ATH), magnesium hydroxide, boron,
zinc borate and other zinc and tin compounds. Suitable for use with
organic coatings, relatively low efficiency inorganic FRs, are commonly
used in conjunction with other types of FR.
Additionally, there is a group of FRs known as intumescents, which
offer fire resistance as opposed to flame retardancy. Intumescent
FRs are applied as a coating to the surface of steel structures
and wood, expanding to form an insulating and fire resistant char
when subjected to heat.
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