Thermal protection principle of flame-retardant and heat-insulating protective clothing
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Thermal protective clothing flame retardant and heat insulation
The heat sources that cause harm to the human body include: flame (convection heat), contact heat, radiant heat, sparks and molten metal jets, High temperature gas and hot steam, high heat generated by arc, etc. In high-temperature environments, wearing thermal protective clothing can reduce the heating rate of human skin and provide the wearer with time to react and escape, so as to avoid or reduce the damage caused by heat sources to the human body.
Thermal protective clothingThe thermal protection performance is also closely related to the way heat is transferred from the heat source. Usually, the methods of heat transfer include heat convection, heat conduction, heat radiation, and a combination of the above three methods.
(1) Thermal convection. It refers to the transfer of heat by various high-temperature gases and hot steam. The thermal convection resistance of fabrics is mainly related to the weight, density, air permeability, etc. of the fabric. Increasing the weight of the fabric increases the time required to cause skin burns. At the same time, multi-layer fabrics also have better thermal convection protection than single-layer fabrics.
(2) Heat conduction. It means that heat uses sparks, molten metal jets, etc. as carriers to contact clothing and transfer the heat to the human body through the clothing, thereby causing harm to the human body. Increasing the temperature of the heat source and the pressure when the heat source is in contact with the fabric will reduce the thermal conductivity of the thermal protective clothing.
(3) Thermal radiation. It means that heat is radiated outward from an object in a straight line. The essence of thermal radiation is the heat radiation caused by the temperature of an object. Its size is proportional to the fourth power of the absolute temperature of the heat source. Thermal radiation is one of the main forms of heat transfer that causes harm to victims. The thermal radiation resistance of fabrics is directly related to the fabric weight, thickness, density, and fabric surface condition. Plating aluminum on the surface of the fiber, mixing some broken aluminum foil into the fabric, or compounding aluminum foil on the surface of the fabric makes the surface of the fabric have high reflectivity and good conductivity, which can greatly improve the thermal radiation resistance of the fabric.
In general, flame-retardant protective clothing mainly achieves protection purposes through shielding functions such as heat insulation, reflection, absorption, and carbonization isolation.
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