What is The Thermal Protection Theory for FR Thermal Insulation Protection Clothing?
2016-03-21 08:23 | writer: admin
The heat sources harmed human body including flame(convection heat), thermal contact, thermal radiation, spark, molten metal ejecta high-temperature gas, and high heat caused by hot steam and arc etc. In high temperature condition, with heat protective clothing can help to lower the heating rate of human skin, and offer enough time to reaction and escape for wearer, which can avoid or reduce the injury from heat recourse.
The thermal protective performance of heat protective clothing has a lot to the heat transfer method of heat source. In general, the heat transfer methods including heat convection, heat conduction, thermal radiation and the combination of these three methods.
(1)Heat convection: it means the heat transfer is according to various high temperature gas and super heated steam. The textile anti heat convection performance is closely related to the weight, density, and air permeability of textile. The fabric weight increase can help to improve the time to caused skin burn, at the same time, multilayers fabric has better anti heat convection effect than single fabric.
(2)Heat conduction: it is the heat takes the spark, molten metal ejecta as carrier, touch the garment and transfer the heat to human body by garment and damage body. Increase the pressure of the heat source temperature and heat source in contact with the textile will lower the anti heat convection performance of heat protective clothing.
(3)Thermal radiation: It refers that the heat radiates outward by objects in a straight line. The nature of thermal radiation is heat radiation caused by the temperature, it’s size is proportional to heat source absolute temperature to the fourth power. The mainly heat transfer form caused victim injury is the thermal radiation. There is a direct relationship between the fabric anti thermal radiation performance and the weight, thickness, density, and the surface appearance of fabric. With aluminizing on the fiber surface and some aluminium foils on fabric, or recombine aluminium foil on the fabric surface, makes the fabric surface have higher reflective rate and good electrical conductivity, which can greatly improve the fabric anti thermal radiation performance.
On the whole, flame retardant protective clothing achieve the protection aim through thermal insulation, reflection, absorption, carbide segregation etc shielding effect.