Fireproof sheets

Fire retardants are added to polymeric compounds to prevent polymer burning and improve safety. One method to measure flammability is the Limiting Oxygen Index (LOI) under the ASTM 2863-00 standard.

Fireproof polycarbonate sheets

LOI is defined as the oxygen level in the atmosphere that allows combustion under standard conditions. A higher LOI indicates the greater resistance of the polymer against flame; hence, becoming self-extinguishing. There are a variety of fire retardants with different chemical structures; the mechanism of them depends on the nature of a given polymeric compound.

Fire extinguishing mechanisms

Fire retardants extinguish the fire by several mechanisms:

Formation of a carbon layer: by forming a carbon layer on the surface by the fire retardant, this additive isolates the polymer and reduces combustion and inhibits combustion gases.
Cooling: another class of hydrated mineral fire retardants promotes the formation of water molecules and polymer cooling, hindering combustion through an endothermic reaction in the presence of fire.
Vapor phase prevention: fire retardants react with the burning polymer and produce free radicals that extinguish the flame. This mechanism usually occurs in halogenated polymers.