Cotton fiber is heated to 350 ℃ thermal decomposition, it is easy to produce combustible pyrolysis and gasification, such as H ·, CO, etc. If there is sufficient oxygen is present, it will catch fire and burn. Cotton fibers to produce a limiting oxygen index (LOI value) of 18-20% combustion. The polyester fiber is a thermoplastic fr fabrics fiber, its softening temperature is 238 to 240 ° C, the melting point is 255 - 260 ° C, heated to 420 ~ 447 ℃ thermal decomposition. The limiting oxygen index of the polyester fabric on the glass foil is 20 - 22% is 25%, in the suspended state. Polyester fabric in the suspended state of the combustion process occurs first heat-shrinkable, and then produce a molten, further molten droplets dripping into the ground, the heat away, thereby producing the self-extinguishing effect.
The combustion of the polyester-cotton blended fabric, is not equal to the polyester-cotton fiber component flammability added cotton fabric in the combustion process, the molten polyester component covers the surface of the pyrolyzed cotton fibers (carbon shape), while the thermal solution the cotton of carbon status architecture prevents thermal shrinkage of the polyester firefighters suit fiber, and thus will not automatically dripping out of the combustion heat source. In fact, the fibrous carbon shaped coke only bracket molten polyester, but also put a molten polyester wick combustion heat source, the increase in the supply of fuel in the ignition zone, this situation, known as "skeleton" effect. Much stronger than people expected, precisely because of the role of such a "skeleton" polyester cotton blended fabric flammability.
Polyester-cotton blended fabric, and other fuels, in the pyrolysis reaction can be generated with the oxygen in the air, and by the disproportionation reaction:
H · + O2 → HO · + O · (1)
O · + H2 → HO · + H · (2)
So that the flame spread. In the combustion flame, the main exothermic reaction is:
HO · + CO → CO2 + H · (3)
Thereby providing the majority of the heat required to maintain combustion. Therefore, to achieve the flame-retardant purposes, must be strongly inhibit the disproportionation reaction (1) and (2) is carried out.