There is two evaluation of fire retardant fabric:
Fabric combustion requires oxygen, oxygen index is the flame retardant fabric required for the expression of oxygen, so by determining the oxygen index can determine the fire retardant fabric properties. The higher the oxygen index, the higher the oxygen concentration required to maintain the combustion, which means that the more difficult to burn. The index can be expressed as the minimum volume percentage of the oxygen required to keep the sample in the nitrogen and oxygen mixture. Theoretically, the oxygen index of the textile material is greater than 21% (the volume of oxygen in the natural air), which is self-extinguishing in the air. According to the size of the oxygen index, the textile is usually divided into flammable (LOI <20%), combustible(LOI = 20% ~ 26%), fire retardant (LOI = 26% ~ 34%) and nonflammable (LOI> 35% Four grades. In fact, almost all conventional textile materials (fibers) are flammable or combustible.
2, Burning rate.
Keep fire retardant fabric in contact with the flame for a certain amount of time, then remove the flame, to determine the burning time of with/without flame, and the extent of flame retardant fabric damage. The shorter the burning time of with/without flame, the lower the degree of damage, then the better fire retardant performance; otherwise, the fire retardant performance is poor.