Thermal protection principle of flame retardant thermal protective clothing

Heat sources that cause injury to the human body are: flames (convective heat), contact heat, radiant heat, sparks and molten metal jets, high temperature gases and hot vapors, and high heat from electric arcs. In high temperature environments, wearing thermal protective clothing can reduce the rate of warming of human skin and provide the wearer with time to react and escape to avoid or mitigate the injury of heat sources to the human body.

The thermal protection performance of thermal protective clothing also has a lot to do with the way heat is transferred from the heat source. Usually, the ways of heat transfer are heat convection, heat conduction, heat radiation and a combination of the above three ways.

(1) Heat convection. It means that heat is transferred by various high temperature gases and hot steam. Fabric against heat convection performance is mainly closely related to the weight, density, breathability, etc. of the fabric. Increase the weight of the fabric can improve the time required to cause skin burns. At the same time, multi-layer fabrics also have better anti-heat convection effect than single-layer fabrics.

(2) heat conduction. It refers to the heat to sparks, molten metal jets, etc. as a carrier, contact clothing and heat transfer through the clothing to the body, thus causing injury to the body. Increase the temperature of the heat source and the pressure of the heat source in contact with the fabric, will reduce the thermal protective clothing against heat transfer performance.

(3) Thermal radiation. It means that heat is radiated outward from the object along a straight line. The essence of thermal radiation is the object due to the temperature of the heat radiation, its size is proportional to the four times the temperature of the heat source, thermal radiation is one of the main forms of heat transfer that causes injury to the victim. Fabric thermal radiation performance and fabric weight, thickness, density, and fabric surface conditions have a direct relationship. In the fiber surface aluminum plating, in the fabric interspersed with some broken aluminum foil, or in the fabric surface compound aluminum foil, so that the fabric surface has a high reflectivity and good electrical conductivity, can greatly improve the thermal radiation performance of the fabric.

In a word, flame retardant protective clothing is mainly through heat insulation, reflection, absorption, carbonization isolation and other shielding effects to achieve the purpose of protection.