Flame retardants: what they are
We often talk about flame retardants in correspondence with polymeric materials to which they attribute this property. They are more generally indicated with the abbreviation FR (HFFR in the case of halogen-free products).
Flame retardants are additives that intervene during the combustion process of a material and that involve a certain type of chemical reaction to prevent or slow the spread of flame in the event of a fire.
Generally 3 types of flame retardants can be distinguished:
1 – Halogenated flame retardants
Halogenated flame retardants are appreciated for their versatility, for their low cost and availability, for their ability to maintain mechanical properties but, on the other hand, they can cause environmental damage. The fumes developed in the event of a fire are much more dangerous for humans.
2 – Inorganic Flame retardants
Among the most used inorganic flame retardants for this purpose we find magnesium and aluminum hydroxides, in general they are inorganic substances that fortunately do not create many environmental problems, do not cost much and are not difficult to find, however they must be used in very high dosages and they therefore compromise the final mechanical properties of the compound.
3 – Halogen-free flame retardants
These substances, during combustion, work with a mechanism called “char” and / or intumescence; they ensure that a carbonaceous “crust” is formed which is completely inert to combustion and which hinders or limits the meeting between oxygen and the polymer. The intumescence creates a swelling of the product which limits the spread of the flame. This kind of flame retardants are able to achieve excellent performance even with dosages that are not very high, so the mechanical properties of the polymer are not compromised. Furthermore, the absence of halogens reduces their danger compared to halogenated flame retardants.